The urinary system serves to cleanse the blood of harmful products (mainly protein, salt metabolism, water) in the form of urine, remove it from the body and maintain a constant blood composition. The urinary organs include the kidneys, ureters, bladder and urethra. The kidneys are the urinary organs, and the rest make up the urinary tract. Over 80% of the final metabolic products are excreted from the body along with urine. The kidneys also perform an endocrine function. They synthesize a number of hormones: erythropoietin (stimulates erythropoiesis), prostaglandins and bradykinin (the main function of these hormones is the regulation of blood flow in the kidney), renin, etc.

STRUCTURE AND TYPES OF KIDNEYS

gene (perIgoya) - a paired organ, bean-shaped, dense consistency, red-brown in color. The kidneys are located in the abdominal cavity on the sides of the spinal column, in the lumbar region between the lumbar muscles and the parietal layer of the peritoneum. They lie in the region of the center of gravity of the third quarter of the animal’s body, and therefore are located in the center of relative rest (Fig. 6.1).

The kidney is covered with a dense fibrous capsule, which loosely connects with the parenchyma of the kidney, is surrounded on the outside by a fatty capsule, and on the lower side is also covered with a serous membrane - the peritoneum. On the inner surface there is a depression - the gate of the kidneys, through which vessels and nerves enter the kidneys, veins and ureters exit. In the depths of the hilum there is a renal cavity; the renal pelvis is located in it.

There are three zones in the kidneys: cortical (urinary), border (vascular) and medullary (urinary).

The cortical zone is dark red in color and located on the periphery. It contains convoluted urinary tubules - nephrons - the structural and functional units of the kidneys, where all processes of blood purification and urine formation take place. The renal corpuscle consists of a vascular glomerulus and a two-layer capsule, which passes into a convoluted tubule. The renal artery branches into interlobar arteries, from which the arcuate arteries arise. These arteries form

Rice. 6.1.

A- cattle; b- pigs; V- horses (with ureters and bladder);

• 1 - kidneys; 2 - adrenal gland; 3 - abdominal aorta; 4 - ureter;
• 5 - apex of the bladder; 6 - body of the bladder;
• 7 - mucous membrane of the bladder (the organ is opened); 8 - renal lobule; 9 - renal pyramid; 10 - urinary area;
• 11 - border zone; 12 - urinary drainage zone;
• 13 - renal papilla: 14, 15 - stems

[Pismenskaya V.N., Boev V.I. Workshop on the anatomy and histology of farm animals. M.: KolosS, 2010. P. 201]

the border zone, which in the form of a dark-colored strip separates the cortical zone. The radial arteries extend from the arcuate arteries into the cortical zone. Along them lie the renal corpuscles, the rows of which are separated from each other by the medullary rays. The terminal branches of the radial arteries form a network of arterial capillaries that form vascular glomeruli. The medullary zone lies in the center of the kidney, it is lighter in color and is divided into renal pyramids. The bases of the pyramids face the periphery. From them, the medullary rays exit into the cortical zone. The opposite ends of the pyramids - the apexes - form one or more renal papillae. The urine-conducting tubules open into the renal calyces (in ruminants, pigs) or the renal pelvis (in horses, sheep).

The following types of kidneys are distinguished: multiple, grooved multipapillary, smooth multipapillary, smooth unipapillary (Fig. 6.2).

Rice. 6.2. Scheme of the structure of different types of nights: A- multiple kidney; 6 - grooved multipapillary bud; V- smooth multipapillary bud; G- smooth single-papillary bud;

I - kidney; 2 - stalks of the ureter; 3 - ureter;

• 4 - renal papilla; 5 - renal calyx; 6 - renal grooves;
• 7 - pelvis; 8 - common papilla; 9 - cut arcuate vessels;

I- urine separating layer; II- boundary layer;

III- urine diversion layer

[Pismenskaya V.N., Boev V.I. Workshop on the anatomy and histology of farm animals. M.: KolosS, 2010. P. 202]

Multiple kidney consists of many individual small buds. A hollow stalk extends from each bud. The stalks unite into large branches that flow into a common ureter. In the area of ​​its exit there is a renal fossa. The buds of cattle fruits have this structure.

IN grooved multipapillary buds individual buds grow together in their middle sections. On the outside, the kidney is divided by grooves into separate lobules, and a section shows numerous papillae. The renal pelvis is absent, and therefore the stalks in the kidneys open in two main passages, and the latter form a common ureter. The kidneys of cattle have this structure.

IN smooth multipapillary buds the surfaces are smooth, since the cortical zone has completely merged, and the section shows the renal pyramids with the papilla. The renal calyces open into the renal pelvis, from which the ureter emerges. Pigs have such kidneys.

Smooth single-papillary buds characterized by the fusion of the cortical and medullary zones with one common papilla projecting into the renal pelvis. Such kidneys are found in horses, small ruminants, deer, and rabbits. Kidneys are classified as category I by-products.

Excretory organs.During the metabolic process, breakdown products are formed. Some of these products are used by the body. Other metabolic products that are not used by the body are removed from it.

Depending on the way of life, the nature of nutrition and the characteristics of metabolism, excretory organs of different structures and functions were formed in different animals. In insects, this function is performed by tubular outgrowths of the intestines, through which liquid with decay products is removed from the body cavity. In the intestines, most of the water is absorbed back. Some breakdown products can accumulate in special organs, for example, uric acid in the fatty body of a cockroach. A significant part of the products of protein metabolism is excreted through the gills. In mammals, metabolic products are excreted through the kidneys, lungs, intestines and sweat glands.

Carbon dioxide, water and some volatile substances are removed from the body through the lungs. The intestines secrete some salts in the stool. Sweat glands secrete water, salts, and some organic substances. However, the main role in excretory processes belongs to the kidneys.

Kidney function. The kidneys remove water, salts, ammonia, urea, and uric acid from the body. Through the kidneys, many foreign and toxic substances formed in the body or taken in the form of drugs are removed from the body.

The kidneys help maintain homeostasis (constancy of the composition of the internal environment of the body). Excess water or salts in the blood can cause a change in osmotic pressure, which is dangerous for the functioning of body cells. The kidneys remove excess water and mineral salts from the body, restoring the constancy of the osmotic properties of the blood.

The kidneys maintain a certain constant blood reaction. When acidic or, on the contrary, alkaline metabolic products accumulate in the blood, the secretion of either acidic or alkaline salts increases through the kidneys.

When eating meat, the body produces a lot of acidic metabolic products, and accordingly the urine becomes more acidic. When eating alkaline plant foods, the urine reaction shifts to the alkaline side.

In maintaining a constant blood reaction, the ability of the kidneys to synthesize ammonia plays a very important role, which binds acidic products, replacing sodium and potassium in them. In this case, ammonium salts are formed, which are excreted in the urine, and sodium and potassium are stored for the needs of the body.

Kidney structure. The kidneys produce urine from substances carried in the blood. The structure of the kidney is complex. It distinguishes between the outer, darker, cortical layer and the inner; light, medullary layer. The structural and functional unit of the kidney is the nephron. All processes that result in the formation of urine occur in the nephron.

Each nephron begins in. in the renal cortex, a small capsule shaped like a double-walled bowl, inside which there is a glomerulus of blood capillaries. There is a slit cavity between the walls of the capsule, from which the urinary tubule begins, which meanders and then passes into the medulla. This is a convoluted lot of the first order. In the medulla of the kidney, the tubule straightens, forms a loop and returns to the cortex. Here the urinary tubule twists again, forming a convoluted tubule of the second order. The convoluted tubule of the second order flows into the excretory duct - the collecting duct. The collecting ducts fuse together to form common excretory ducts. These excretory ducts pass through the medulla of the kidney to the tips of the papillae, which project into the cavity of the renal pelvis. Urine from the renal pelvis enters the ureters, which are connected to the bladder.

Blood supply to the kidneys. The kidneys are abundantly supplied with blood. The arteries of the kidneys branch into smaller blood vessels to form arterioles. The arteriole, suitable for the nephron capsule - the afferent vessel - in the capsule breaks up into many capillary loops, forming a capillary glomerulus. The capillaries of the glomerulus reassemble into an arteriole - now it is called the efferent vessel, a vessel through which blood flows from the glomerulus. It is characteristic that the lumen of the efferent vessel is narrower than the lumen of the afferent vessel and the pressure here increases, which creates favorable conditions for the formation of urine through filtration.

The efferent vessel, emerging from the glomerulus of capillaries, again branches into capillaries and densely entwines convoluted tubules of the first and second order with a capillary network. Thus, in the kidney we encounter such a feature of blood circulation when the blood passes through a double network of capillaries: first through the capillaries of the glomerulus, then through the capillaries that fly off the convoluted tubules. Only after this the capillaries form small veins, which, enlarge, form the renal vein, which flows into the lower hollow branch.

Urine formation. It is believed that urine formation occurs in two phases. The first phase is filtration. At this stage, substances carried by the blood into the capillaries of the glomerulus are filtered into the cavity of the nephron capsule. Due to the fact that the lumen of the afferent vessel is wider than that of the efferent vessel, the pressure in the glomerulus of capillaries reaches high values ​​(up to 70 mm Hg). High pressure in the capillaries of the glomerulus is ensured by food and the fact that the renal arteries arise directly from the abdominal aorta and blood enters the kidneys under greater pressure.

So, in the capillaries of the glomerulus the blood pressure reaches 70 mmHg. Art., and the pressure in the capsule cavity is viscous (about 30 mm Hg). Due to the pressure difference, substances in the blood are filtered into the cavity of the nephron capsule.

Water and all substances dissolved in the plasma, with the exception of especially large molecules, such as protein, are filtered into the cavity of the capsule from the blood plasma flowing through the capillaries of the glomerulus. The liquid filtered into the lumen of the capsules is called primary urine. In composition, it is blood plasma without proteins.

In the second phase of urine formation, water and some components of primary urine are absorbed back into the blood. From the primary urine flowing through the convoluted tubules, water, many salts, glucose, amino acids and some other substances are absorbed into the blood. Urea and uric acid are not reabsorbed, so their concentration in the urine increases along the tubules.
In addition to reverse absorption, an active process of secretion also occurs in the tubules, i.e., the release of certain substances into the lumen of the tubules. Thanks to the secretory function of the tubules, substances are removed from the body that for some reason cannot be filtered from the glomerulus of capillaries into the cavity of the nephron capsule.

As a result of reverse absorption and active secretion, secondary (final) urine is formed in the urinary tubules. Each type of animal is characterized by a certain composition and amount of urine.

Regulation of kidney activity. Kidney activity is regulated by nervous and humoral mechanisms. The kidneys are abundantly supplied with fibers of the sympathetic nervous system and the vagus nerve. When the sympathetic nerve approaching the kidneys is irritated, the blood vessels of the kidneys narrow, the amount of blood flowing in decreases, the pressure in the glomeruli drops, and as a result, urine output decreases.

Urination sharply decreases during painful stimulation. This occurs due to a reflex narrowing of the blood vessels of the kidney during pain. If a dog is surgically brought out the ends of the ureters, sutured them to the skin of the abdomen and begins to introduce water into the stomach, combining this with the sound of a trumpet, then after several such combinations the sound of a trumpet alone (without introducing water into the stomach) causes copious discharge of urine. This is a conditioned reflex.

By conditioned reflex, urine retention can also be caused. If a dog's paw is irritated with a strong electric current, the pain will reduce urine production. After repeated application of painful stimulation, the mere presence of the dog in the room where the painful stimulation was applied causes a decrease in urine formation.

However, when all the nerves leading to the animal's kidney are cut, it continues to work. Even the kidney transplanted to the neck continued to produce urine. The amount of urine released depends on the body's need for water.

If there is not enough water in the body and the animal is thirsty, then the osmotic pressure of the blood increases due to lack of water. This leads to irritation of receptors located in blood vessels. Impulses from them are sent to the central nervous system. From there they reach the endocrine gland - the pituitary gland, which increases the production of antidiuretic hormone (AD1). This hormone, entering the blood, is brought to the convoluted tubules of the kidneys and causes increased reabsorption of water in the convoluted tubules, the volume of final urine decreases, water is retained in the body, and the osmotic pressure of the blood is equalized.

The thyroid hormone increases urine formation, and the adrenal hormone adrenaline causes a decrease in urine formation.

Literature: Khripkova A.G. et al. Physiology of animals: Textbook. manual for electives. course for students of grades IX-X / A. G. Khripkova, A: B. Kogan, A. P. Kostin; Ed. A. G. Khripkova. - 2nd ed., revised - M.: Education, 1980.-192 pp., ill.; 2 l. ill.

Pyelonephritis(Pyelonephritis) - inflammation of the renal pelvis and kidneys. The disease is more common in cattle and pigs.

Etiology. Pyelonephritis often occurs as a result of hematogenous spread of the infectious agent from a purulent focus located outside the organs of the urinary apparatus; both the lymphogenous route of its entry from the intestine and the ascending route with purulent foci in the urinary tract and genitals are possible.

In cows, pyelonephritis is observed in the last months of pregnancy and especially after calving, accompanied by postpartum complications: retained placenta, endometritis, myometritis and vaginitis.

Among the microflora most often involved in the development of the disease are Corinebacterium suis, Colibacterium pseudotuberculosus ovis, Bacterium renalis ov'is, pyelonephritis bovum, streptococci, Escherichia coli, staphylococci, but there may also be mixed microflora. Increased pressure in the pelvis and urinary tract, as well as poor circulation in the kidneys, contribute to the development of the disease.

Pathogenesis.

In the development of pyelonephritis, one infectious agent is not enough; for its occurrence, a decrease in the body’s reactivity, a violation of the nervous regulation of the urinary organs and the presence of difficulties in the outflow of urine are necessary. The latter causes stretching of the renal pelvis and creates favorable conditions for the penetration of the infectious agent into the renal tissue.

The developing inflammatory process first affects the intertubular interstitial tissue with the involvement of blood vessels in the process. In this regard, the function of the tubular apparatus is affected (their epithelium flattens and atrophies), then the process covers the glomeruli. All this first causes a decrease in reabsorption in the tubules and the development of polyuria with hyposthenuria and pyuria, and later the concentrating ability of the kidneys is impaired and renal failure occurs. If acute pyelonephritis becomes chronic, then the latter ends in non-phrosclerosis and death of the animal.

Pathological changes.

The kidneys are increased in volume, the capsule firmly fuses with the cortex. The perirenal fatty tissue is edematous; serous exudate is found under the fibrous capsule. On a section in the medullary layer, numerous ribbon-shaped pustules, purulent (softened) or curdled foci are found. The renal pelvis is dilated and contains a yellowish-brown or dirty-gray viscous mass consisting of particles of dead tissue, blood clots and pus. The mucous membrane of the pelvis is often thickened, hyperemic, ulcerated in places and has a grayish-yellow overlay. The renal papillae are hyperemic and covered with purulent deposits. Sometimes, instead of a papilla, cysts filled with pus are formed. With a long course of the disease, necrotic areas are delimited from healthy tissue by granulation elements. If the inflammatory process develops only in the medulla, then the surface of the kidneys can remain completely smooth. Sometimes instead of kidneys they find a cyst filled with pus.

Complete blockage of the ureter or renal pelvis leads to hydronephrosis: the renal parenchyma atrophies, and the retention sac formed as a result of stretching of the renal capsule is filled with a liquid similar in composition to normal urine. The walls of the ureter are thickened and ulcerated. There is mucus and hemorrhage in the bladder.

Symptoms.

Pyelonephritis often develops against the background of metritis, vaginitis, urocystitis, etc. Its signs are varied and depend on whether the lesion is unilateral or bilateral.

In the acute course of the disease, fever, increased heart rate, breathing, loss of appetite, exhaustion and death are noted. In a chronic course, the course is sluggish, exacerbations periodically appear with a slight increase in body temperature, decreased appetite, hypotension of the forestomach and increased fatigue. Pigs experience increased sensitivity to palpation in the kidney area and pain when urinating. Urine contains grayish-yellowish, mucopurulent clots and blood. In the final phase of the disease, the pigs do not rise, there is no appetite or thirst, and death occurs within 1-2 days. Sometimes the disease progresses at lightning speed: depression, deep depression, collapse, and death occurs within 12 hours. In cows, when palpating the iliac region, severe pain is noted. Rectal examination sometimes reveals thickening of the ureters, enlarged kidneys, and fluctuation of the renal pelvis.

Animals lose fat; Some experience painful and frequent urination. A thick purulent mass is discharged from the vagina. Urine is cloudy, sometimes bloody, viscous, alkaline, contains up to 2% protein and a large amount of free ammonia. In the urine sediment there is renal epithelium, purulent bodies, during an exacerbation - red blood cells and casts. Neutrophilic leukocytosis in the blood. If the concentrating ability of the kidneys is impaired, the density of urine decreases. In a unilateral process, the healthy kidney compensates for the work of the diseased kidney for a long time. Animals die due to symptoms of uremia.

Flow.

In the acute course, the disease lasts 1-2 days in pigs, 2-3 weeks in cows and ends in death or becomes chronic, which lasts for months and nephrosclerosis often develops.

The diagnosis is made based on a clinical examination of the animal and the results of a urine test. Characteristics of pyelonephritis are the presence of protein in the urine, an increase in the number of leukocytes, the presence of renal epithelial cells, casts, and bacteriuria.

Differential diagnosis.

It is necessary to exclude chronic nephritis, urocystitis, etc. With pyelitis and pyelonephritis, the urine remains cloudy for a longer time, and with urocystitis it quickly separates into two layers. In addition, with pyelitis, cells of the glands of the renal pelvis are found in the urine. In chronic nephritis, the number of red blood cells is increased, there are cylinders, and individual cells of the renal epithelium. The prognosis is unfavorable, especially in chronic cases.

The human body is a reasonable and fairly balanced mechanism.

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The structure of the kidneys of mammals

KIDNEYS | Encyclopedia Around the World

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• HUMAN ANATOMY
• METABOLIC DISORDERS
• UROLOGY

KIDNEYS, the main excretory (removing end products of metabolism) organ of vertebrates. Invertebrates, such as the snail, also have organs that perform a similar excretory function and are sometimes called kidneys, but they differ from the kidneys of vertebrates in structure and evolutionary origin.

Function.

The main function of the kidneys is to remove water and metabolic end products from the body. In mammals, the most important of these products is urea, the main final nitrogen-containing product of protein breakdown (protein metabolism). In birds and reptiles, the main end product of protein metabolism is uric acid, an insoluble substance that appears as a white mass in excrement. In humans, uric acid is also formed and excreted by the kidneys (its salts are called urates).

The human kidneys excrete about 1–1.5 liters of urine per day, although this amount can vary greatly. The kidneys respond to increased water intake by increasing the production of more dilute urine, thereby maintaining normal body water levels. If water intake is limited, the kidneys help conserve water in the body by using as little water as possible to make urine. The volume of urine may decrease to 300 ml per day, and the concentration of excreted products will be correspondingly higher. Urine volume is regulated by antidiuretic hormone (ADH), also called vasopressin. This hormone is secreted by the posterior pituitary gland (a gland located at the base of the brain). If the body needs to conserve water, ADH secretion increases and urine volume decreases. On the contrary, when there is excess water in the body, ADH is not released and the daily volume of urine can reach 20 liters. Urine output, however, does not exceed 1 liter per hour.

Structure.

Mammals have two kidneys located in the abdomen on either side of the spine. The total weight of two kidneys in a person is about 300 g, or 0.5–1% of body weight. Despite their small size, the kidneys have an abundant blood supply. Within 1 minute, about 1 liter of blood passes through the renal artery and exits back through the renal vein. Thus, in 5 minutes, a volume of blood equal to the total amount of blood in the body (about 5 liters) passes through the kidneys to remove metabolic products.

The kidney is covered with a connective tissue capsule and a serous membrane. A longitudinal section of the kidney shows that it is divided into two parts, called the cortex and medulla. Most of the substance of the kidney consists of a huge number of very thin convoluted tubes called nephrons. Each kidney contains more than 1 million nephrons. Their total length in both kidneys is approximately 120 km. The kidneys are responsible for producing the fluid that eventually becomes urine. The structure of the nephron is the key to understanding its function. At one end of each nephron there is an extension - a round formation called the Malpighian body. It consists of a two-layer, so-called. Bowman's capsule, which encloses the network of capillaries that form the glomerulus. The rest of the nephron is divided into three parts. The coiled part closest to the glomerulus is the proximal convoluted tubule. Next is a thin-walled straight section, which, turning sharply, forms a loop, the so-called. loop of Henle; it distinguishes (sequentially): descending section, bend, ascending section. The coiled third part is the distal convoluted tubule, which flows together with other distal tubules into the collecting duct. From the collecting ducts, urine enters the renal pelvis (actually the expanded end of the ureter) and then along the ureter into the bladder. Urine is discharged from the bladder through the urethra at regular intervals. The cortex contains all the glomeruli and all the convoluted parts of the proximal and distal tubules. The medulla contains the loops of Henle and the collecting ducts located between them.

Urine formation.

In the glomerulus, water and substances dissolved in it leave the blood through the walls of the capillaries under the influence of blood pressure. The pores of the capillaries are so small that they trap blood cells and proteins. Consequently, the glomerulus acts as a filter that allows fluid to pass through without proteins, but with all the substances dissolved in it. This fluid is called ultrafiltrate, glomerular filtrate, or primary urine; it is processed as it passes through the rest of the nephron.

In the human kidney, the volume of ultrafiltrate is about 130 ml per minute or 8 liters per hour. Since a person's total blood volume is approximately 5 liters, it is obvious that most of the ultrafiltrate must be absorbed back into the blood. Assuming that the body produces 1 ml of urine per minute, then the remaining 129 ml (more than 99%) of water from the ultrafiltrate must be returned to the bloodstream before it becomes urine and is excreted from the body.

Ultrafiltrate contains many valuable substances (salts, glucose, amino acids, vitamins, etc.) that the body cannot lose in significant quantities. Most are reabsorbed as the filtrate passes through the proximal tubule of the nephron. Glucose, for example, is reabsorbed until it completely disappears from the filtrate, i.e. until its concentration approaches zero. Since the transport of glucose back into the blood, where its concentration is higher, goes against the concentration gradient, the process requires additional energy and is called active transport.

As a result of the reabsorption of glucose and salts from the ultrafiltrate, the concentration of substances dissolved in it decreases. The blood turns out to be a more concentrated solution than the filtrate, and “attracts” water from the tubules, i.e. water passively follows actively transported salts (see OSMOSIS). This is called passive transport. With the help of active and passive transport, 7/8 of the water and substances dissolved in it are absorbed back from the contents of the proximal tubules, and the rate of decrease in the volume of the filtrate reaches 1 liter per hour. Now the intracanalicular fluid contains mainly “waste”, such as urea, but the process of urine formation is not yet complete.

The next segment, the loop of Henle, is responsible for creating very high concentrations of salts and urea in the filtrate. In the ascending limb of the loop, active transport of dissolved substances, primarily salts, occurs into the surrounding tissue fluid of the medulla, where as a result a high concentration of salts is created; due to this, from the descending bend of the loop (permeable to water), part of the water is sucked out and immediately enters the capillaries, while the salts gradually diffuse into it, reaching their highest concentration in the bend of the loop. This mechanism is called countercurrent concentrating mechanism. The filtrate then enters the distal tubules, where other substances can pass into it due to active transport.

Finally, the filtrate enters the collecting ducts. Here it is determined how much liquid will be additionally removed from the filtrate, and therefore what the final volume of urine will be, i.e. volume of final, or secondary, urine. This stage is regulated by the presence or absence of ADH in the blood. The collecting ducts are located between the numerous loops of Henle and run parallel to them. Under the influence of ADH, their walls become permeable to water. Because the concentration of salts in the loop of Henle is so high and water tends to follow the salts, it is actually drawn out of the collecting ducts, leaving a solution with a high concentration of salts, urea, and other solutes. This solution is the final urine. If there is no ADH in the blood, then the collecting ducts remain poorly permeable to water, water does not come out of them, the volume of urine remains large and it turns out to be diluted.

Animal kidneys.

The ability to concentrate urine is especially important for animals that have difficult access to drinking water. The kangaroo rat, for example, living in the desert of the southwestern United States, produces urine 4 times more concentrated than that of a human. This means that the kangaroo rat is capable of removing toxins in very high concentrations using a minimal amount of water.

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KIDNEYS

Kidney - gene (nephros) - a paired organ of dense consistency of red-brown color. The kidneys are built like branched glands and are located in the lumbar region.

The kidneys are quite large organs, approximately the same on the right and left, but not the same in animals of different species (Table 10). Young animals have relatively large kidneys.

The kidneys are characterized by a bean-shaped, somewhat flattened shape. There are dorsal and ventral surfaces, convex lateral and concave medial edges, cranial and caudal ends. Near the middle of the medial edge, vessels and nerves enter the kidney and the ureter emerges. This place is called the renal hilum.

10. Kidney mass in animals

Rice. 269. Urinary organs of cattle (from the ventral surface)

The outside of the kidney is covered with a fibrous capsule that connects to the kidney parenchyma. The fibrous capsule is surrounded externally by a fatty capsule, and on the ventral surface it is also covered with a serous membrane. The kidney is located between the lumbar muscles and the parietal layer of the peritoneum, i.e. retroperitoneal.

The kidneys are supplied with blood through the large renal arteries, which receive up to 15-30% of the blood pushed into the aorta by the left ventricle of the heart. Innervated by the vagus and sympathetic nerves.

In cattle (Fig. 269), the right kidney is located in the area from the 12th rib to the 2nd lumbar vertebra, with its cranial end touching the liver. Its caudal end is wider and thicker than the cranial one. The left kidney hangs on a short mesentery behind the right one at the level of the 2-5th lumbar vertebrae; when the scar is filled, it moves slightly to the right.

On the surface, the kidneys of cattle are divided by grooves into lobules, of which there are up to 20 or more (Fig. 270, a, b). The grooved structure of the kidneys is the result of incomplete fusion of their lobules during embryogenesis. On the section of each lobule, the cortical, medullary and intermediate zones are distinguished.

The cortical, or urinary, zone (Fig. 271, 7) is dark red in color and located superficially. It consists of microscopic renal corpuscles arranged radially and separated by stripes of the medullary rays.

The medullary or urinary drainage zone of the lobule is lighter, radially striated, located in the center of the kidney, and is shaped like a pyramid. The base of the pyramid faces outwards; From here the brain rays exit into the cortical zone. The apex of the pyramid forms the renal papilla. The medullary zone of adjacent lobules is not divided by grooves.

Between the cortical and medullary zones, an intermediate zone is located in the form of a dark strip. In it, arcuate arteries are visible, from which radial interlobular arteries are separated into the cortical zone. Along the latter there are renal corpuscles. Each body consists of a glomerulus - a glomerulus and a capsule.

The vascular glomerulus is formed by the capillaries of the afferent artery, and the two-layer capsule surrounding it is formed by special excretory tissue. The efferent artery emerges from the choroid glomerulus. It forms a capillary network on a convoluted tubule, which starts from the glomerular capsule. The renal corpuscles with convoluted tubules make up the cortical zone. In the region of the medullary rays, the convoluted tubule becomes the straight tubule. The set of straight tubules forms the basis of the medulla. Merging with each other, they form papillary ducts, which open at the apex of the papilla and form a ethmoidal field. The renal corpuscle, together with the convoluted tubule and its vessels, constitute the structural and functional unit of the kidney - the nephron. In the renal corpuscle of the nephron, liquid - primary urine - is filtered from the blood of the vascular glomerulus into the cavity of its capsule. During the passage of primary urine through the convoluted tubule of the nephron, most (up to 99%) water and some substances that cannot be removed from the body, such as sugar, are absorbed back into the blood. This explains the large number and length of nephrons. Thus, a person has up to 2 million nephrons in one kidney.

Buds that have superficial grooves and many papillae are classified as grooved multipapillary. Each papilla is surrounded by a renal calyx (see Fig. 270). Secondary urine secreted into the calyces passes through short stalks into two urinary ducts, which connect to form the ureter.

Rice. 270. Kidneys

Rice. 271. Structure of the renal lobule

Rice. 272. Topography of the kidneys (from the ventral surface)

In a pig, the kidneys are bean-shaped, long, flattened dorsoventrally, and belong to the smooth multipapillary type (see Fig. 270, c, d). They are characterized by complete fusion of the cortical zone, with a smooth surface. However, the section shows 10-16 renal pyramids. They are separated by cords of cortical substance - renal columns. Each of the 10-12 renal papillae (some papillae merge with each other) is surrounded by a renal calyx, which opens into a well-developed renal cavity - the pelvis. The wall of the pelvis is formed by mucous, muscular and adventitial membranes. The ureter begins from the pelvis. The right and left kidneys lie under the 1-3 lumbar vertebrae (Fig. 272), the right kidney does not come into contact with the liver. Smooth multipapillary buds are also characteristic of humans.

The horse's right kidney is heart-shaped, and the left kidney is bean-shaped, smooth on the surface. The section shows complete fusion of the cortex and medulla, including the papillae. The cranial and caudal parts of the renal pelvis are narrowed and are called the renal ducts. There are 10-12 renal pyramids. Such buds belong to the smooth single-papillary type. The right kidney extends cranially to the 16th rib and enters the renal depression of the liver, and caudally to the first lumbar vertebra. The left kidney lies in the area from the 18th thoracic to the 3rd lumbar vertebra.

The dog's kidneys are also smooth, single-papillary (see Fig. 270, e, f), of a typical bean-shaped shape, located under the first three lumbar vertebrae. In addition to horses and dogs, smooth single-papillary buds are characteristic of small ruminants, deer, cats, and rabbits.

In addition to the three types of kidneys described, some mammals (polar bear, dolphin) have multiple kidneys of a grape-shaped structure. Their embryonic lobules remain completely separated throughout the animal's life and are called buds. Each kidney is built according to the general plan of a regular kidney; in section, it has three zones, a papilla and a calyx. The kidneys are connected to each other by excretory tubes that open into the ureter.

After the birth of an animal, the growth and development of the kidneys continues, which can be seen, in particular, in the example of the kidneys of calves. During the first year of extrauterine life, the mass of both kidneys increases almost 5 times. The kidneys grow especially intensively during the milk period after birth. At the same time, the microscopic structures of the kidneys also change. For example, the total volume of the renal corpuscles increases by 5 times during the year, and by 15 times by the age of six, the convoluted tubules lengthen, etc. At the same time, the relative mass of the kidneys decreases by half: from 0.51% in newborn calves to 0. 25% in yearlings (according to V.K. Birikh and G.M. Udovin, 1972). The number of renal lobules remains virtually constant after birth.

Details Section: Anatomy of Pets

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Internal structure of mammals Mammalian organ systems

Compared to other amniotes, the mammalian digestive system is characterized by significant complexity. This is manifested in an increase in the total length of the intestine, its clear differentiation into sections and increased function of the digestive glands.

The structural features of the system in different species are largely determined by the type of nutrition, among which herbivory and mixed type of nutrition predominate. Eating exclusively animal food is less common and is characteristic mainly of predators. Plant foods are used by terrestrial, aquatic and underground mammals. The type of nutrition of mammals determines not only the specific structure of animals, but also in many ways their way of existence and their system of behavior.

Terrestrial inhabitants use various types of plants and their parts - stems, leaves, branches, underground organs (roots, rhizomes). Typical “vegetarians” include ungulates, proboscis, lagomorphs, rodents and many other animals.

Among herbivorous animals, specialization in food consumption is often observed. Many ungulates (giraffes, deer, antelopes), proboscideans (elephants) and a number of others feed mainly on the leaves or twigs of trees. The juicy fruits of tropical plants form the basis of nutrition for many tree inhabitants.

The wood is used by beavers. The food supply for mice, squirrels, and chipmunks consists of a variety of seeds and fruits of plants, from which reserves are made for the wintering period. There are many species that feed mainly on grasses (ungulates, marmots, gophers). The roots and rhizomes of plants are consumed by underground species - jerboas, zokor, mole rats and mole rats. The diet of manatees and dugongs consists of aquatic grasses. There are animals that feed on nectar (certain species of bats, marsupials).

Carnivores have a wide range of species that make up their food supply. Invertebrates (worms, insects, their larvae, mollusks, etc.) occupy a significant place in the diet of many animals. Insectivorous mammals include hedgehogs, moles, shrews, bats, anteaters, pangolins and many others. Insects are often eaten by herbivorous species (mice, gophers, squirrels) and even quite large predators (bears).

Among aquatic and semi-aquatic animals there are piscivores (dolphins, seals) and zooplankton feeders (baleen whales). A special group of carnivorous species consists of predators (wolves, bears, felines, etc.) that hunt large animals, either alone or in a pack. There are species that specialize in feeding on the blood of mammals (vampire bats). Carnivores often consume plant foods - seeds, berries, nuts. These animals include bears, martens, and canines.

The digestive system of mammals begins with the vestibule of the mouth, which is located between the fleshy lips, cheeks and jaws. In some animals it is expanded and is used to temporarily reserve food (hamsters, gophers, chipmunks). The oral cavity contains a fleshy tongue and heterodont teeth sitting in the alveoli. The tongue serves as an organ of taste, participates in the capture of food (anteaters, ungulates) and in chewing it.

Most animals are characterized by a complex dental system, which includes incisors, canines, premolars and molars. The number and ratio of teeth varies among species with different types of nutrition. Thus, the total number of teeth in a mouse is 16, a hare - 28, a cat - 30, a wolf - 42, a wild boar - 44, and a marsupial opossum - 50.

To describe the dental system of different types, a dental formula is used, the numerator of which reflects the number of teeth in half of the upper jaw, and the denominator - the lower jaw. For ease of recording, the letter designations of different teeth are accepted: incisors - i (incisive), canines - c (canini), premolars - pm (praemolares), molars - m (molares). Predatory animals have well-developed canines and molars with cutting edges, while herbivores (ungulates, rodents) have predominantly strong incisors, which is reflected in the corresponding formulas. For example, the dental formula of a fox looks like this: (42). The dental system of a hare is represented by the formula: (28), and of a boar: . (44)

The dental system of a number of species is not differentiated (pinnipeds and toothed whales) or is weakly expressed (in many insectivorous species). Some animals have a diastema - a space on the jaws devoid of teeth. It arose evolutionarily as a result of a partial reduction of the dental system. The diastema of most herbivores (ruminants, lagomorphs) was formed due to the reduction of the canines, part of the premolar teeth, and sometimes the incisors.

The formation of a diastema in predatory animals is associated with an enlargement of the fangs. The teeth of most mammals are replaced once during ontogenesis (diphyodont dental system). In many herbivorous species, teeth are capable of constant growth and self-sharpening as they wear (rodents, rabbits).

The ducts of the salivary glands open into the oral cavity, the secretion of which is involved in wetting food, contains enzymes for breaking down starch and has an antibacterial effect.

Through the pharynx and esophagus, food passes into a well-demarcated stomach, which has a different volume and structure. The walls of the stomach have numerous glands that secrete hydrochloric acid and enzymes (pepsin, lipase, etc.). In most mammals, the stomach has a retort-shaped stomach and two sections - cardiac and pyloric. In the cardial (initial) part of the stomach, the environment is more acidic than in the pyloric part.

The stomach of monotremes (echidna, platypus) is characterized by the absence of digestive glands. In ruminants, the stomach has a more complex structure - it consists of four sections (rumen, mesh, book and abomasum). The first three sections make up the “forestomach,” the walls of which are lined with stratified epithelium without digestive glands. It is intended only for fermentation processes to which the absorbed herbal mass is exposed under the influence of symbiont microbes. This process takes place in an alkaline environment of three sections. The partially fermented mass is regurgitated portionwise into the mouth. Chewing it thoroughly (chewing gum) helps to enhance the fermentation process when food re-enters the stomach. Gastric digestion is completed in the rennet, which has an acidic environment.

The intestine is long and clearly divided into three sections - thin, thick and straight. The total length of the intestine varies significantly depending on the feeding pattern of the animal. For example, its length exceeds the body size in bats by 1.5–4 times, in rodents by 5–12 times, and in sheep by 26 times. At the border of the small and large intestines there is a cecum, intended for the fermentation process, so it is especially well developed in herbivorous animals.

The ducts of the liver and pancreas flow into the first loop of the small intestine, the duodenum. The digestive glands not only secrete enzymes, but also actively participate in metabolism, excretory functions and hormonal regulation of processes.

The digestive glands also have the walls of the small intestine, so the process of digesting food continues there and the absorption of nutrients into the bloodstream occurs. In the thick section, thanks to fermentation processes, difficult-to-digest food is processed. The rectum serves to form excrement and reabsorb water.

Respiratory organs and gas exchange.

The main gas exchange in mammals is determined by pulmonary respiration. To a lesser extent, it occurs through the skin (approximately 1% of total gas exchange) and the mucous membrane of the respiratory tract. Lungs of alveolar type. The mechanism of thoracic breathing is due to the contraction of the intercostal muscles and the movement of the diaphragm - a special muscle layer separating the thoracic and abdominal cavities.

Through the external nostrils, air enters the vestibule of the nasal cavity, where it is warmed and partially cleared of dust, thanks to the mucous membrane with ciliated epithelium. The nasal cavity includes the respiratory and olfactory sections. In the respiratory section, further purification of the air from dust and disinfection occurs due to bactericidal substances secreted by the mucous membrane of its walls. This section has a well-developed capillary network, ensuring a partial supply of oxygen to the blood. The olfactory region contains outgrowths of the walls, due to which a labyrinth of cavities is formed, increasing the surface for capturing odors.

Through the choanae and pharynx, air passes into the larynx, supported by a system of cartilage. In front are unpaired cartilages - the thyroid (characteristic only for mammals) with the epiglottis and cricoid. The epiglottis covers the entrance to the respiratory tract when swallowing food. At the back of the larynx lie the arytenoid cartilages. Between them and the thyroid cartilage are the vocal cords and vocal muscles, which determine the production of sounds. Cartilaginous rings also support the trachea, which follows the larynx.

Two bronchi originate from the trachea, which enter the spongy tissue of the lungs with the formation of numerous small branches (bronchioles), ending in alveolar vesicles. Their walls are densely permeated with blood capillaries that ensure gas exchange. The total area of ​​the alveolar vesicles significantly (50–100 times) exceeds the body surface, especially in animals with a high degree of mobility and level of gas exchange. An increase in the respiratory surface is also observed in mountain species that are constantly experiencing oxygen deficiency.

The respiratory rate is largely determined by the size of the animal, the intensity of metabolic processes and physical activity. The smaller the mammal, the relatively higher the heat loss from the body surface and the more intense the level of metabolism and oxygen demand. The most energy-intensive animals are small species, due to which they feed almost constantly (shrews, shrews). During the day they consume 5–10 times more feed than their own biomass.

Ambient temperature has a significant influence on breathing rate. An increase in summer temperature by 10° leads to an increase in the respiratory rate of predatory species (fox, polar bear, black bear) by 1.5–2 times.

The respiratory system plays a significant role in maintaining temperature homeostasis. Along with exhaled air, a certain amount of water (“polypnoe”) and thermal energy are removed from the body. The higher the summer temperature, the more often the animals breathe and the higher the “polypnoe” indicators. Thanks to this, animals manage to avoid overheating of the body.

The circulatory system of mammals is basically similar to that of birds: the heart is four-chambered, lies in the pericardial sac (pericardium); two circles of blood circulation; complete separation of arterial and venous blood.

The systemic circulation begins with the left aortic arch, emerging from the left ventricle, and ends with the vena cava, returning venous blood to the right atrium.

The unpaired innominate artery (Fig. 73) originates from the left aortic arch, from which the right subclavian and paired carotid arteries depart. Each carotid artery, in turn, is divided into two arteries - the external and internal carotid arteries. The left subclavian artery arises directly from the aortic arch. Having circled the heart, the aortic arch stretches along the spine in the form of the dorsal aorta. Large arteries depart from it, supplying blood to internal systems and organs, muscles and limbs - splanchnic, renal, iliac, femoral and caudal.

Venous blood from the body organs is collected through a number of vessels (Fig. 74), from which the blood drains into the common vena cava, carrying blood to the right atrium. From the front of the body it runs through the anterior vena cava, which takes blood from the jugular veins of the head and the subclavian veins, which extend from the forelimbs. On each side of the neck there are two jugular vessels - the external and internal veins, which merge with the corresponding subclavian vein, forming the vena cava.

Many mammals exhibit asymmetrical development of the anterior vena cava. The innominate vein flows into the right anterior vena cava, formed by the confluence of the veins on the left side of the neck - the left subclavian and jugular. It is also typical for mammals to preserve rudiments of the posterior cardinal veins, which are called azygos (vertebral) veins. An asymmetry can also be traced in their development: the left azygos vein connects with the right azygos vein, which flows into the right anterior vena cava.

From the back of the body, venous blood returns through the posterior vena cava. It is formed by the fusion of vessels extending from the organs and hind limbs. The largest of the venous vessels forming the posterior vena cava are the azygos caudal, paired femoral, iliac, renal, genital and a number of others. The posterior vena cava passes, without branching, through the liver, penetrates the diaphragm and carries venous blood into the right atrium.

The portal system of the liver is formed by one vessel - the portal vein of the liver, which arises as a result of the confluence of veins coming from the internal organs.

These include: the splenogastric vein, anterior and posterior mesenteric veins. The portal vein forms a complex system of capillaries that penetrate the liver tissue, which at the exit unite again and form short hepatic veins that flow into the posterior vena cava. The renal portal system in mammals is completely reduced.

The pulmonary circulation originates from the right ventricle, where venous blood from the right atrium enters, and ends at the left atrium. From the right ventricle, venous blood exits through the pulmonary artery, which splits into two vessels leading to the lungs. Blood oxidized in the lungs enters the left atrium through paired pulmonary veins.

The size of the heart varies among different species of mammals. Small and active animals have a relatively larger heart. The same pattern can be observed in relation to the heart rate. Thus, the pulse rate of a mouse is 600 per minute, that of a dog is 140, and that of an elephant is 24.

Hematopoiesis occurs in various organs of mammals. Red blood cells (erythrocytes), granulocytes (neutrophils, eosinophils and basophils) and platelets are produced by the bone marrow. Red blood cells are anucleate, which increases their transfer of oxygen to organs and tissues, without wasting it on their own respiration processes. Lymphocytes are formed in the spleen, thymus and lymph nodes. The reticuloendothelial system produces cells of the monocytic series.

Excretory system.

Input-salt metabolism in mammals is mainly carried out by the kidneys, the work of which is coordinated by pituitary hormones. A certain proportion of water-salt metabolism is carried out by the skin, equipped with sweat glands, and the intestines.

The kidneys of mammals, like all amniotes, are of the metanephridial type (pelvic). The main excretion product is urea. The kidneys are bean-shaped, suspended from the dorsal side on the mesentery. The ureters depart from them, flowing into the bladder, the ducts of which open in males on the copulatory organ, and in females - in the vestibule of the vagina.

Mammalian kidneys have a complex structure and are characterized by a high filtering function.

The outer (cortical) layer is a system of glomeruli, consisting of Bowman's capsules with glomeruli of blood vessels (Malpighian corpuscles). Filtration of metabolic products occurs from the blood vessels of the Malpighian corpuscles into Bowman's capsules. The primary filtrate in its content is blood plasma, devoid of proteins, but containing many substances useful to the body.

An efferent tubule (nephron) arises from each Bowman's capsule. It has four sections - the proximal convoluted, loop of Henle, distal convoluted and collecting duct. The nephron system forms lobules (pyramids) in the medulla of the kidneys, clearly visible on a macro section of the organ.

In the upper (proximal) section, the nephron makes several bends that are intertwined with blood capillaries. It reabsorbs (reabsorbs) water and other beneficial substances into the blood - sugars, amino acids and salts.

In the following sections (loop of Henle, distal convoluted) further absorption of water and salts occurs. As a result of the complex filtering work of the kidney, the final metabolic product is formed - secondary urine, which flows through the collecting ducts into the renal pelvis, and from it into the ureter. The reabsorption activity of the kidneys is enormous: up to 180 liters of water per day pass through the human renal tubules, while only about 1–2 liters of secondary urine are formed.

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Kidney physiology

The kidneys play an exceptional role in the normal functioning of the body. By removing decay products, excess water, salts, harmful substances and some medications, the kidneys thereby perform an excretory function.

In addition to the excretory function, the kidneys also have other, no less important functions. By removing excess water and salts from the body, mainly sodium chloride, the kidneys thereby maintain the osmotic pressure of the internal environment of the body. Thus, the kidneys take part in water-salt metabolism and osmoregulation.

The kidneys, along with other mechanisms, ensure the constancy of the reaction (pH) of the blood by changing the intensity of the release of acidic or alkaline salts of phosphoric acid when the blood pH shifts to the acidic or alkaline side.

The kidneys are involved in the formation (synthesis) of certain substances, which they subsequently remove. The kidneys also perform a secretory function. They have the ability to secrete organic acids and bases, K+ and H+ ions. This ability of the kidneys to secrete various substances plays a significant role in the implementation of their excretory function. And finally, the role of the kidneys has been established not only in mineral, but also in lipid, protein and carbohydrate metabolism.

Thus, the kidneys, regulating osmotic pressure in the body, the constancy of the blood reaction, carrying out synthetic, secretory and excretory functions, take an active part in maintaining the constancy of the composition of the internal environment of the body (homeostasis).

The structure of the kidneys. In order to more clearly understand the work of the kidneys, it is necessary to become familiar with their structure, since the functional activity of the organ is closely related to its structural features. The kidneys are located on both sides of the lumbar spine. On their inner side there is a depression in which there are vessels and nerves surrounded by connective tissue. The kidneys are covered with a connective tissue capsule. The size of an adult human kidney is about 11 × 10-2 × 5 × 10-2 m (11 × 5 cm), weight on average 0.2-0.25 kg (200-250 g).

On a longitudinal section of the kidney, two layers are visible: the cortical layer is dark red and the medulla layer is lighter (Fig. 39).

Rice. 39. Structure of the kidney. A - general structure; B - a section of renal tissue enlarged several times; 1 - Shumlyansky capsule; 2 - convoluted tubule of the first order; 3 - loop of Henle; 4 - convoluted tubule of the second order

A microscopic examination of the structure of mammalian kidneys shows that they consist of a large number of complex formations - the so-called nephrons. The nephron is the functional unit of the kidney. The number of nephrons varies depending on the type of animal. In humans, the total number of nephrons in the kidney reaches an average of 1 million.

The nephron is a long tubule, the initial section of which, in the form of a double-walled bowl, surrounds the arterial capillary glomerulus, and the final section flows into the collecting duct.

The following sections are distinguished in the nephron: 1) the Malpighian corpuscle consists of the Shumlyansky vascular glomerulus and the surrounding Bowman’s capsule (Fig. 40); 2) the proximal segment includes the proximal convoluted and straight tubules; 3) the thin segment consists of thin ascending and descending limbs of the loop of Henle; 4) the distal segment is composed of the thick ascending limb of the loop of Henle, the distal convoluted and communicating tubules. The excretory duct of the latter flows into the collecting duct.

Rice. 40. Scheme of the Malpighian glomerulus. 1 - bringing vessel; 2 - efferent vessel; 3 - capillaries of the glomerulus; 4 - capsule cavity; 5 - convoluted tubule; 6 - capsule

Different segments of the nephron are located in specific areas of the kidney. The cortical layer contains vascular glomeruli, elements of the proximal and distal segments of the urinary tubules. The medulla contains elements of the thin segment of the tubules, thick ascending limbs of the loops of Henle and collecting ducts (Fig. 41).

Rice. 41. Scheme of the structure of the nephron (according to Smith). 1 - glomerulus; 2 - proximal convoluted tubule; 3 - descending part of the loop of Henle; 4 - ascending part of the loop of Henle; 5 - distal convoluted tubule; 6 - collecting tube. In circles - the structure of the epithelium in various parts of the nephron

The collecting ducts, merging, form common excretory ducts, which pass through the medulla of the kidney to the tips of the papillae, protruding into the cavity of the renal pelvis. The renal pelvis opens into the ureters, which in turn empty into the bladder.

Blood supply to the kidneys. The kidneys receive blood from the renal artery, which is one of the large branches of the aorta. The artery in the kidney is divided into a large number of small vessels - arterioles, bringing blood to the glomerulus (afferent arteriole a), which then break up into capillaries (the first network of capillaries). The capillaries of the vascular glomerulus, merging, form an efferent arteriole, the diameter of which is 2 times less than the diameter of the afferent arteriole. The efferent arteriole again breaks up into a network of capillaries intertwining the tubules (the second network of capillaries).

Thus, the kidneys are characterized by the presence of two networks of capillaries: 1) capillaries of the vascular glomerulus; 2) capillaries intertwining the renal tubules.

Arterial capillaries turn into venous capillaries, which later, merging into veins, give blood to the inferior vena cava.

The blood pressure in the capillaries of the glomerulus is higher than in all capillaries of the body. It is equal to 9.332-11.299 kPa (70-90 mm Hg), which is 60-70% of the pressure in the aorta. In the capillaries entwining the kidney tubules, the pressure is low - 2.67-5.33 kPa (20-40 mm Hg).

All blood (5-6 l) passes through the kidneys in 5 minutes. During the day, about 1000-1500 liters of blood flows through the kidneys. Such abundant blood flow allows you to completely remove all substances that are unnecessary and even harmful to the body.

The lymphatic vessels of the kidneys accompany the blood vessels, forming a plexus at the porta renal, surrounding the renal artery and vein.

Innervation of the kidneys. In terms of the wealth of innervation, the kidneys occupy second place after the adrenal glands. Efferent innervation is carried out mainly by sympathetic nerves.

Parasympathetic innervation of the kidneys is slightly expressed. A receptor apparatus is found in the kidneys, from which afferent (sensitive) fibers depart, running mainly as part of the splanchnic nerves.

A large number of receptors and nerve fibers are found in the capsule surrounding the kidneys. Excitation of these receptors can cause pain.

Recently, the study of the innervation of the kidneys has attracted special attention in connection with the problem of their transplantation.

Juxtaglomerular apparatus. The juxtaglomerular, or periglomerular, apparatus (JGA) consists of two main elements: myoepithelial cells, located mainly in the form of a cuff around the afferent arteriole of the glomerulus, and cells of the so-called macula densa of the distal convoluted tubule.

JGA is involved in the regulation of water-salt homeostasis and maintaining constant blood pressure. JGA cells secrete a biologically active substance - renin. The secretion of renin is inversely related to the amount of blood flowing through the afferent arteriole and to the amount of sodium in the primary urine. With a decrease in the amount of blood flowing to the kidneys and a decrease in the amount of sodium salts in it, the release of renin and its activity increase.

In the blood, renin interacts with the plasma protein hypertensinogen. Under the influence of renin, this protein transforms into its active form - hypertensin (angiotonin). Angiotonin has a vasoconstrictor effect, due to which it is a regulator of renal and general blood circulation. In addition, angiotonin stimulates the secretion of the hormone of the adrenal cortex - aldosterone, which is involved in the regulation of water-salt metabolism.

In a healthy body, only small amounts of hypertensin are produced. It is destroyed by a special enzyme (hypertensinase). In some kidney diseases, the secretion of renin increases, which can lead to a persistent increase in blood pressure and disruption of water-salt metabolism in the body.

Mechanisms of urine formation

Urine is formed from blood plasma flowing through the kidneys and is a complex product of the activity of nephrons.

Currently, urine formation is considered as a complex process consisting of two stages: filtration (ultrafiltration) and reabsorption (reabsorption).

Glomerular ultrafiltration. In the capillaries of the Malpighian glomeruli, water is filtered from the blood plasma with all the inorganic and organic substances of low molecular weight dissolved in it. This fluid enters the glomerular capsule (Bowman's capsule), and from there into the renal tubules. Its chemical composition is similar to blood plasma, but contains almost no proteins. The resulting glomerular filtrate is called primary urine.

In 1924, the American scientist Richards obtained direct evidence of glomerular filtration in animal experiments. He used microphysiological research methods in his work. In frogs, guinea pigs and rats, Richards exposed the kidney and inserted a thin micropipette into one of Bowman's capsules with a microscope, with the help of which he collected the resulting filtrate. An analysis of the composition of this liquid showed that the content of inorganic and organic substances (with the exception of protein) in the blood plasma and primary urine is exactly the same.

The filtration process is facilitated by high blood pressure (hydrostatic) in the capillaries of the glomeruli - 9.33-12.0 kPa (70-90 mm Hg).

The higher hydrostatic pressure in the capillaries of the glomeruli compared with the pressure in the capillaries of other areas of the body is due to the fact that the renal artery arises from the aorta, and the afferent arteriole of the glomerulus is wider than the efferent arteriole. However, the plasma in the glomerular capillaries is not filtered under all this pressure. Blood proteins retain water and thereby prevent urine from filtering. The pressure created by plasma proteins (oncotic pressure) is 3.33-4.00 kPa (25-30 mmHg). In addition, the filtration force is also reduced by the pressure of the liquid located in the cavity of Bowman's capsule, which is 1.33-2.00 kPa (10-15 mm Hg).

Thus, the pressure under the influence of which the filtration of primary urine is carried out is equal to the difference between the blood pressure in the capillaries of the glomeruli, on the one hand, and the sum of the pressure of blood plasma proteins and the pressure of the fluid located in the cavity of Bowman’s capsule, on the other. Therefore, the filtration pressure value is 9.33-(3.33+2.00)=4.0 kPa. Urine filtration stops if blood pressure is below 4.0 kPa (30 mmHg) (critical value).

A change in the lumen of the afferent and efferent vessels causes either an increase in filtration (narrowing of the efferent vessel) or its decrease (narrowing of the afferent vessel). The amount of filtration is also affected by changes in the permeability of the membrane through which filtration occurs. The membrane includes the endothelium of the glomerular capillaries, the main (basal) membrane and the cells of the inner layer of Bowman's capsule.

Tubular reabsorption. In the renal tubules, reabsorption (reabsorption) of water, glucose/part of the salts and a small amount of urea from primary urine into the blood occurs. As a result of this process, final, or secondary, urine is formed, which in its composition differs sharply from the primary. It does not contain glucose, amino acids, or some salts and the concentration of urea is sharply increased (Table 11).

Table 11. Contents of certain substances in blood plasma and urine

During the day, 150-180 liters of primary urine are formed in the kidneys. Due to the reabsorption of water and many dissolved substances in the tubules, the kidneys excrete only 1-1.5 liters of final urine per day.

Reabsorption can occur actively or passively. Active reabsorption is carried out due to the activity of the epithelium of the renal tubules with the participation of special enzyme systems with energy consumption. Glucose, amino acids, phosphates, and sodium salts are actively reabsorbed. These substances are completely absorbed in the tubules and are absent in the final urine. Due to active reabsorption, reabsorption of substances from urine into the blood is possible even when their concentration in the blood is equal to the concentration in the tubular fluid or higher.

Passive reabsorption occurs without energy consumption due to diffusion and osmosis. A major role in this process belongs to the difference in oncotic and hydrostatic pressure in the capillaries of the tubules. Due to passive reabsorption, water, chlorides, and urea are reabsorbed. The removed substances pass through the wall of the tubules only when their concentration in the lumen reaches a certain threshold value. Substances that are to be eliminated from the body undergo passive reabsorption. They are always found in urine. The most important substance in this group is the final product of nitrogen metabolism - urea, which is reabsorbed in small quantities.

The reabsorption of substances from urine into the blood varies in different parts of the nephron. Thus, in the proximal part of the tubule, glucose, partially sodium and potassium ions are absorbed, in the distal part - sodium chloride, potassium and other substances. Throughout the entire tubule, water is absorbed, and in its distal part it is 2 times more than in the proximal part. The loop of Henle occupies a special place in the mechanism of reabsorption of water and sodium ions due to the so-called rotary-countercurrent system. Let's consider its essence. The loop of Henle has two branches: descending and ascending. The epithelium of the descending limb allows water to pass through, and the epithelium of the ascending limb is not permeable to water, but is capable of actively absorbing sodium ions and transferring them into the tissue fluid, and through it back into the blood (Fig. 42).

Rice. 42. Scheme of operation of the rotary-counterflow system (according to Best and Taylor). The darkened background shows the concentration of urine and tissue fluid. White arrows - release of water, black arrows - sodium ions; 1 - convoluted tubule, passing into the proximal part of the loop; 2 - convoluted tubule emerging from the distal part of the loop; 3 - collecting tube

Passing through the descending loop of Henle, urine releases water, thickens, and becomes more concentrated. The release of water occurs passively due to the fact that at the same time active reabsorption of sodium ions occurs in the ascending section. Entering the tissue fluid, sodium ions increase the osmotic pressure in it and thereby contribute to the attraction of water from the descending limb into the tissue fluid. In turn, an increase in urine concentration in the loop of Henle due to the reabsorption of water facilitates the transition of sodium ions from urine into tissue fluid. Thus, in the loop of Henle, large amounts of water and sodium ions are reabsorbed.

In the distal convoluted tubules, further absorption of sodium, potassium, water and other substances occurs. Unlike the proximal convoluted tubules and the loop of Henle, where the reabsorption of sodium and potassium ions does not depend on their concentration (obligatory reabsorption), the amount of reabsorption of these ions in the distal tubules is variable and depends on their level in the blood (facultative reabsorption). Consequently, the distal sections of the convoluted tubules regulate and maintain the constant concentration of sodium and potassium ions in the body.

In addition to reabsorption, the process of secretion occurs in the tubules. With the participation of special enzyme systems, active transport of certain substances from the blood into the lumen of the tubules occurs. Of the products of protein metabolism, creatinine and para-aminohippuric acid undergo active secretion. This process manifests itself in full force when substances foreign to it are introduced into the body.

Thus, active transport systems function in the renal tubules, especially in their proximal segments. Depending on the state of the body, these systems can change the direction of active transfer of substances, i.e., they provide either their secretion (excretion) or reverse absorption.

In addition to carrying out filtration, reabsorption and secretion, renal tubular cells are capable of synthesizing certain substances from various organic and inorganic products. Thus, hippuric acid (from benzoic acid and glycocol) and ammonia (by deamination of some amino acids) are synthesized in the cells of the renal tubules. The synthetic activity of the tubules is also carried out with the participation of enzyme systems.

Function of collecting ducts. Further absorption of water occurs in the collecting tubes. This is facilitated by the fact that the collecting ducts pass through the medulla of the kidney, in which the tissue fluid has a high osmotic pressure and therefore attracts water.

Thus, urine formation is a complex process in which, along with the phenomena of filtration and reabsorption, the processes of active secretion and synthesis play an important role. If the filtration process occurs mainly due to the energy of blood pressure, i.e., ultimately due to the functioning of the cardiovascular system, then the processes of reabsorption, secretion and synthesis are the result of the active activity of tubular cells and require energy expenditure. This is associated with the kidneys' greater need for oxygen. They use 6-7 times more oxygen than muscles (per unit mass).

Regulation of kidney activity

Regulation of kidney activity is carried out by neurohumoral mechanisms.

Nervous regulation. It has now been established that the autonomic nervous system regulates not only the processes of glomerular filtration (by changing the lumen of blood vessels), but also tubular reabsorption.

The sympathetic nerves innervating the kidneys are mainly vasoconstrictor. When they are irritated, the excretion of water decreases and the excretion of sodium in the urine increases. This is due to the fact that the amount of blood flowing to the kidneys decreases, the pressure in the glomeruli drops, and, consequently, the filtration of primary urine decreases. Transection of the celiac nerve leads to increased urine output from the denervated kidney.

Parasympathetic (vagus) nerves act on the kidneys in two ways: 1) indirectly, by changing the activity of the heart, they cause a decrease in the strength and frequency of heart contractions, as a result of which blood pressure decreases and the intensity of diuresis changes; 2) regulating the lumen of the kidney vessels.

With painful stimulation, diuresis reflexively decreases until it stops completely (painful anuria). This is due to the fact that a narrowing of the renal vessels occurs due to stimulation of the sympathetic nervous system and an increase in the secretion of the pituitary hormone - vasopressin.

The nervous system has a trophic effect on the kidneys. Unilateral denervation of the kidney is not accompanied by significant difficulties in its functioning. Bilateral transection of nerves causes disruption of metabolic processes in the kidneys and a sharp decrease in their functional activity. A denervated kidney cannot quickly and subtly rearrange its activity and adapt to changes in the level of water-salt load. After introducing 1 liter of water into the animal's stomach, an increase in diuresis in the denervated kidney occurs later than in a healthy one.

In the laboratory of K. M. Bykov, through the development of conditioned reflexes, a pronounced influence of the higher parts of the central nervous system on the functioning of the kidneys was shown. It has been established that the cerebral cortex causes changes in the functioning of the kidneys either directly through the autonomic nerves or through the pituitary gland, changing the release of vasopressin into the bloodstream.

Humoral regulation is carried out mainly by the hormones vasopressin (antidiuretic hormone) and aldosterone.

The posterior pituitary hormone vasopressin increases the permeability of the wall of the distal convoluted tubules and collecting ducts for water and thereby promotes its reabsorption, which leads to a decrease in urine output and an increase in the osmotic concentration of urine. With an excess of vasopressin, a complete cessation of urine formation (anuria) may occur. A lack of this hormone in the blood leads to the development of a serious disease - diabetes insipidus. With this disease, a large amount of light-colored urine with a low relative density, which lacks sugar, is released.

Aldosterone (hormone of the adrenal cortex) promotes the reabsorption of sodium ions and the excretion of potassium ions in the distal portions of the tubules and inhibits the reabsorption of calcium and magnesium in their proximal portions.

Quantity, composition and properties of urine

A person excretes on average about 1.5 liters of urine per day, but this amount is not constant. For example, diuresis increases after drinking heavily and consuming protein, the breakdown products of which stimulate urine formation. On the contrary, urine formation decreases with the consumption of small amounts of water, protein, and with increased sweating, when a significant amount of liquid is excreted through sweat.

The intensity of urine formation fluctuates throughout the day. More urine is produced during the day than at night. A decrease in urine formation at night is associated with a decrease in the body’s activity during sleep, with a slight drop in blood pressure. Night urine is darker and more concentrated.

Physical activity has a pronounced effect on urine formation. With prolonged work, there is a decrease in urine excretion from the body. This is explained by the fact that with increased physical activity, blood flows in greater quantities to the working muscles, as a result of which the blood supply to the kidneys decreases and urine filtration decreases. At the same time, physical activity is usually accompanied by increased sweating, which also helps to reduce diuresis.

Urine color. Urine is a clear, light yellow liquid. When it settles in the urine, a sediment forms, which consists of salts and mucus.

Urine reaction. The urine reaction of a healthy person is predominantly slightly acidic, its pH ranges from 4.5 to 8.0. The reaction of urine may vary depending on nutrition. When consuming mixed food (animal and plant origin), human urine has a slightly acidic reaction. When eating primarily meat and other protein-rich foods, the urine reaction becomes acidic; plant foods contribute to the transition of the urine reaction to neutral or even alkaline.

Relative density of urine. The density of urine is on average 1.015-1.020 and depends on the amount of fluid taken.

Composition of urine. The kidneys are the main organ for removing nitrogenous products of protein breakdown from the body - urea, uric acid, ammonia, purine bases, creatinine, indican.

Urea is the main product of protein breakdown. Up to 90% of all urine nitrogen comes from urea. In normal urine, protein is absent or only traces of it are detected (no more than 0.03% o). The appearance of protein in the urine (proteinuria) usually indicates kidney disease. However, in some cases, namely during intense muscular work (long-distance running), protein may appear in the urine of a healthy person due to a temporary increase in the permeability of the membrane of the choroidal glomerulus of the kidneys.

Among the organic compounds of non-protein origin in the urine there are: salts of oxalic acid, which enter the body with food, especially plant foods; lactic acid released after muscle activity; ketone bodies formed when the body converts fats into sugar.

Glucose appears in the urine only in cases when its content in the blood is sharply increased (hyperglycemia). The excretion of sugar in the urine is called glucosuria.

The appearance of red blood cells in the urine (hematuria) is observed in diseases of the kidneys and urinary organs.

The urine of a healthy person and animals contains pigments (urobilin, urochrome), which determine its yellow color. These pigments are formed from bilirubin in bile in the intestines and kidneys and are secreted by them.

A large amount of inorganic salts is excreted in the urine - about 15·10-3-25·10-3 kg (15-25 g) per day. Sodium chloride, potassium chloride, sulfates and phosphates are excreted from the body. The acidic reaction of urine also depends on them (Table 12).

Table 12. Amount of substances included in urine (excreted in 24 hours)

Excretion of urine. The final urine flows from the tubules into the pelvis and from it into the ureter. The movement of urine through the ureters into the bladder is carried out under the influence of gravity, as well as due to the peristaltic movements of the ureters. The ureters, entering the bladder obliquely, form a kind of valve at its base that prevents the reverse flow of urine from the bladder.

Urine accumulates in the bladder and is periodically removed from the body through the act of urination.

The bladder contains so-called sphincters, or sphincters (ring-shaped muscle bundles). They tightly close the outlet of the bladder. The first of the sphincters - the sphincter of the bladder - is located at its exit. The second sphincter - the urethral sphincter - is located slightly lower than the first and closes the urethra.

The bladder is innervated by parasympathetic (pelvic) and sympathetic nerve fibers. Excitation of sympathetic nerve fibers leads to increased peristalsis of the ureters, relaxation of the muscular wall of the bladder (detrusor) and increased tone of its sphincters. Thus, stimulation of the sympathetic nerves promotes the accumulation of urine in the bladder. When parasympathetic fibers are stimulated, the wall of the bladder contracts, the sphincters relax and urine is expelled from the bladder.

Urine continuously flows into the bladder, which leads to increased pressure in it. An increase in pressure in the bladder to 1.177-1.471 Pa (12-15 cm water column) causes the need to urinate. After urination, the pressure in the bladder decreases to almost 0.

Urination is a complex reflex act consisting of simultaneous contraction of the bladder wall and relaxation of its sphincters. As a result, urine is expelled from the bladder.

An increase in pressure in the bladder leads to the emergence of nerve impulses in the mechanoreceptors of this organ. Afferent impulses enter the spinal cord to the center of urination (II-IV segments of the sacral region). From the center, along the efferent parasympathetic (pelvic) nerves, impulses go to the detrusor and sphincter of the bladder. A reflex contraction of its muscle wall and relaxation of the sphincter occurs. At the same time, from the center of urination, excitation is transmitted to the cerebral cortex, where a feeling of the urge to urinate occurs. Impulses from the cerebral cortex travel through the spinal cord to the urethral sphincter. The act of urination begins. Cortical control manifests itself in delaying, intensifying, or even voluntarily inducing urination. In young children, cortical control of urinary retention is absent. It is produced gradually with age.

Kidney diseases. Clinic, diagnosis and treatment of small domestic animals.

Anatomical and physiological features of the structure of the kidneys in dogs and cats

The kidneys are paired organs located in the lumbar region under the vertebral bodies. The dog has single-papillary kidneys with a smooth surface. They make up 0.5-0.71% of body weight. In cats, the kidneys are short, thick and round, with one conical nipple. The mass of the kidneys is 0.34 body weight. On their surface there are grooves from veins.

The outside of the kidney is covered with a connective tissue membrane - the kidney capsule. In cats, the capsule is fibrous and very dense. On the medial edge of the kidney there is a depression called the renal hilum. The main blood vessels, nerves, lymphatic vessels and the ureter pass through them. From the gate, the passage leads into an expanded cavity - the renal pelvis, the surface of which is lined with a mucous membrane with stratified transitional epithelium.

A longitudinal section of the kidney shows two layers with a narrow strip between them. The outer part of the kidney is a smooth, reddish-brown cortical, or urine-secreting layer. It is distinct from the whitish-gray medulla that extends from the inner cortex to the hilum of the kidney.

Histological studies have established that each kidney consists of approximately 1 million nephrons, which are the structural and functional units of the kidneys. A special feature of the structure of the kidneys of dogs and cats are very long nephron loops, which explains the production of concentrated urine in these animals.

Mechanism of urine formation

All circulating blood passes through the kidneys in a few minutes. In a pig weighing 90-100 kg, up to 1.5 thousand liters of blood flows through the kidneys during the day. Such abundant blood flow ensures an intensive process of urine formation. Urine formation is considered a complex process consisting of two stages: filtration and reabsorption.

Glomerular filtration. In the capillaries of the glomeruli of the renal corpuscle, water with all inorganic substances of low molecular weight dissolved in it is filtered from the blood plasma. This fluid enters the capsule of the renal glomerulus, and from there into the renal tubules. Its chemical composition is similar to blood plasma, but contains almost no proteins. The resulting glomerular filtrate is called primary urine. The filtration process is facilitated by high hydrostatic blood pressure in the capillaries of the glomeruli - 70-90 mm Hg. The higher hydrostatic pressure in the capillaries of the glomeruli compared with the pressure in the capillaries of other areas of the body is due to the fact that the renal artery arises from the aorta, and the afferent arteriole of the glomeruli is wider than the efferent arteriole. However, from the indicated value 70-90 mm Hg. Art. it is necessary to subtract the oncotic pressure of plasma proteins, which prevents filtration, and the pressure of the fluid located in the glomerular cavity. Together both values ​​are 35-40 mmHg. Art. Consequently, the filtration pressure is actually 30-40 mmHg. Art. Urine filtration stops if blood pressure is below a critical value - 30 mm Hg. Art.

Tubular reabsorption. In the renal tubules, reverse absorption (reabsorption) from primary urine into the blood of water, glucose, some salts and a small amount of urea occurs. The final, secondary urine is formed, which in its composition differs sharply from the primary. It does not contain glucose, amino acids, some salts and the concentration of urea is sharply increased. During the day, the kidneys produce 2-2.5 liters of primary urine per 1 kg of live weight. Due to the reabsorption of water and many substances dissolved in it into the canal, the kidneys excrete about 1% of the volume of primary urine per day.

Reabsorption can occur actively or passively. Active reabsorption is carried out due to the activity of the epithelium of the renal tubules with the participation of special enzymes. Glucose, amino acids, phosphates, and sodium salts are actively reabsorbed. These substances are completely absorbed in the tubules and are absent in the final urine. Due to the act of reabsorption, it is possible for substances to flow back from urine into the blood when their concentration in the blood is equal to the concentration in the tubular fluid or higher.

Passive reabsorption occurs without energy consumption due to diffusion and osmosis. A major role in this process belongs to the difference in oncotic and hydrostatic pressure in the capillaries of the tubules. Due to passive reabsorption, water, chlorides, and urea are reabsorbed. The removed substances pass through the wall of the tubules only when their concentration in the lumen reaches a certain threshold value. Substances that are excreted from the body and are always found in the urine undergo passive reabsorption. Among them, the most important is the final product of nitrogen metabolism - urea, which is reabsorbed in small quantities.

Diseases of the urinary organs, depending on the location of the lesion (kidneys, urinary tract or kidneys and urinary tract), may have symptoms that require the use of various methods of investigation and treatment. Through a sequential study of the case, answers to the following questions should be found:

1. Are we talking about primary or secondary (symptomatic) diseases of the urinary organs?
2. Is the cause of the disease in the kidneys or in the urinary tract?
3. In kidney disease, is it possible to more accurately anatomically determine the location: in the glomeruli, tubules, renal pelvis, or in the intermediate space?
4. Is the disease acute or chronic?
5. Is it easy and reversible or is it an irreversible lesion?
6. What is the etiology of the lesions?

Due to the large reserve capacity of the kidneys, the disease occurs for a long time without clinical manifestations. Only after 66-75% of the functional elements of the kidneys are affected are symptoms of renal failure detected. Therefore, chronic kidney diseases are much more common than acute ones.

The kidneys are often the target of secondary damage from systemic diseases such as infections, shock, immune diseases, or organ diseases. Since kidney diseases affect most body functions, laboratory tests are of great importance for diagnosis.

Leading symptoms of kidney disease: uremic syndrome, anuria, oliguria, polydipsia, polyuria, proteinuria, cylindruria, kidney reduction, uneven contours of the kidney, pain on palpation, enlarged kidneys, anemia.

Associated symptoms of diseases of the urinary organs: anorexia, vomiting, diarrhea, bad breath, weakness, decreased physical activity, exhaustion, increased thirst and urination, dehydration, pain in the paralumbar region, tenesmus, licking of the vulva or penis, fever, anemia , calcification of tissues, weakened immunity, epileptic seizures, hypertension, edema, accumulation of fluid in serous cavities. Pathological changes in urination

Quantity. Determining the daily amount of urine (diuresis) is a valuable indicator of renal excretory function and water metabolism. A dog's normal diuresis is 24-41 ml/kg per day. Polyuria - the separation of an increased amount (60-100 ml/kg body weight per day) of urine often causes polydipsia (pathologically increased thirst) and is associated with low specific gravity of urine. Polyuria is observed when taking large amounts of liquid, resorption of transudates and exudates, edema, with diabetes mellitus and diabetes insipidus, chronic heart disease, and with nervous excitement.

Pathogenesis of polyuria: tubular lesions and nephron destruction increase the rate of flow of the primary filtrate and thus reduce the reabsorption of water and electrolytes. Damage to the collecting ducts reduces the effect of antidiuretic hormone. The osmotically active substances remaining in the lumens of the tubules have a secondary diuretic effect. Polyuria can, regardless of the level of urea in the blood serum, often act as an early symptom of renal failure.

Oliguria- excretion of a small amount of urine (< 6 мл/кг массы тела в сутки) может быть связана с недостаточной гидратацией организма, повышенным потоотделением, при лихорадке, рвоте, поносе, гипотензии, токсикозах, недостаточности кровообращения, почечной недостаточности, заболевании почек, некоторых инфекционных заболеваниях (лептоспироз и др.).

Anuria- complete cessation of urine flow into the bladder.

In contrast to acute urinary retention with anuria, the bladder is empty; urine is not excreted by the kidneys or does not enter the bladder due to an obstruction along the upper urinary tract. Depending on the cause, prerenal, renal and postrenal anuria are distinguished. Prerenal anuria occurs due to cessation or insufficient blood flow to the kidney, for example, in shock, severe heart failure, peripheral edema, and fluid retention in the tissues. Renal anuria is caused by kidney disease or injury with significant damage to the renal parenchyma. Postrenal anuria is a consequence of impaired urine outflow due to obstruction or compression of the lower urinary tract.

Pollakiuria- frequent urination, which is based on: increased sensitivity of the mucous membrane of the walls of the bladder and the back of the urethra as a result of the inflammatory process. This is a symptom of various pathological conditions (prostatitis, cystitis, urethritis, vaginitis), and is also observed during hypothermia and severe anxiety.

Dysuria- painful, difficult and frequent urination can occur with acute cystitis, tumors, bladder stones, acute prostatitis, hyperplasia and prostate cancer. The most common manifestation of dysuria is stranguria - urination in small portions due to sudden difficulty, which is accompanied by pain and false urges.

Ishuria- urinary retention due to the inability to empty the bladder, despite the presence of urine in it. Often the cause of ischuria is mechanical obstructions (hyperplasia, tumor or abscess of the prostate gland, stones and tumor of the bladder, narrowing of the urethra as a result of an inflammatory process or injury, etc.).

Urine examination

Urine- biological fluid produced by the kidneys and released through the urinary tract. End products of metabolism, drugs and other foreign substances are removed from the body with urine. Urine examination allows us to identify kidney diseases and disorders of their function, as well as some metabolic changes that are not associated with damage to other organs. Therefore, it is mandatory when examining a patient.

Physical properties of urine

The color of urine normally ranges from straw yellow to rich yellow and depends on the presence of pigments urochrome, urobilin, urozein, etc. A change in the color of urine is observed in liver pathology, hemolytic processes with the release of more concentrated urine (diarrhea, vomiting toxicosis, fever). Lightly colored urine is observed with severe insufficiency of the concentrating ability of the kidneys (relative density less than 1010), with polyuria. The color of urine with bilirubinuria is from bright yellow to brown (yellow foam appears when shaken), with urobilinuria - amber, reddish-yellow, with hematuria - red or brown. Some medications and foods change the color of urine: it becomes red after including beets in the diet and taking amidopyrine, bright yellow after taking riboflavin, tetracycline.

Normal urine is almost completely clear. Its turbidity may be due to the abundance of formed elements, microbes, precipitation of salts, and mucus.

Urine reaction (pH). In dogs that eat meat, the urine reaction is acidic, while in dogs that eat meat-free food, it is alkaline. In cats, the urine reaction is slightly alkaline (pH 7.5). Acid urine is produced in diabetes mellitus, severe kidney failure, and urolithiasis (oxalaturia).

The relative density (specific gravity) of dog urine ranges from 1.016-1.060 (on average 1.025), in cats - on average 1.055 and depends on metabolism, the content of protein and salts in food, the amount of fluid drunk, and sweating. Kidney diseases in which their ability to concentrate urine is impaired (chronic nephritis, nephrosclerosis) lead to a decrease in its density, extrarenal fluid loss leads to an increase. The highest density of urine is observed with glycosuria in patients with diabetes mellitus.

Chemical composition of urine

Protein. Normally, in dogs and cats, the amount of protein in the urine is in the range of 0-0.03 g/l. Proteinuria is the most sensitive indicator of nephropathy. It is necessary to distinguish between renal or actual proteinuria (protein comes from the nephron) and false or postrenal proteinuria, in which proteins come as a result of bleeding in the urinary tract or the formation of immunoglobulin. False proteinuria occurs with inflammation of the urinary tract, prostate or uterus. True proteinuria can be distinguished from false proteinuria by centrifugation and examination of the urinary sediment. A mild form of proteinuria and a large sediment indicate false proteinuria as a urinary tract disease, a large amount of protein and a small sediment indicate the presence of kidney disease. The presence of hyaline casts confirms the renal origin of proteinuria. Temporary mild proteinuria can be caused by physiological or extrarenal causes (heavy loads, heart failure, hyperthermia, anemia, hypothermia, allergies, use of penicillin, sulfonamides, burns, dehydration). Severe proteinuria is observed in glomerulonephritis (acute and chronic), amyloidosis, nephrotic syndrome, pyelonephritis, tumors, hydronephrosis, and immune diseases. Proteinuria should be assessed taking into account clinical symptoms (fluid accumulation, swelling) and other laboratory parameters.

Glucose in normal urine is not determined by testing methods accepted in clinical laboratories. Glycosuria can be physiological and pathological. Physiological glycosuria is observed when large amounts of carbohydrates are administered with food. Pathological glycosuria can be renal or extrarenal. Renal glycosuria is caused by impaired reabsorption of glucose in the nephron tubules, and the level of glucose in the blood is normal or slightly reduced. It is observed in chronic nephritis, acute kidney failure. Pathological extrarenal glycosuria is most often caused by metabolic disorders and occurs with diabetes mellitus, thyrotoxicosis, cortisone overdose, and trauma to the central nervous system. In case of diabetes mellitus, the amount of glucose in the daily volume of urine should be determined.

Bilirubin is normally absent in urine, appears with jaundice (parenchymal, mechanical, hemolytic)

Microscopic examination of urine sediment.

Leukocytes can normally be found up to 10 in the field of view of the microscope. The appearance of them in large numbers (more than 20 in the field of view) indicates an inflammatory process in the urinary organs (pyuria), but does not indicate the location of inflammation. Pyuria is caused by inflammation in the kidneys, bladder, urethra, and less commonly in the renal pelvis. Infected discharge from the prostate, vagina or uterus can also cause pyuria. The localization of the inflammatory process is determined by the presence of other formed elements, taking into account clinical manifestations.

Red blood cells. Normally, there may be single, unchanged red blood cells in the field of view of the microscope. Excretion of blood in the urine - hematuria. If the presence of blood in the urine is determined by the naked eye, they speak of gross hematuria; if red blood cells are detected only when examined under a microscope - microhematuria. There are renal and extrarenal hematuria. Renal hematuria is observed with tumors and tuberculosis of the kidney, glomerulonephritis, pyelonephritis, nephrolithiasis. With renal hematuria, red blood cells will be slightly changed and leached. Extrarenal hematuria occurs during inflammatory processes in the urinary tract and when they are injured. In this case, unchanged red blood cells are detected. In addition, hematuria can be the result of a blood clotting disorder due to diseases of the liver, blood, or an overdose of anticoagulants; congestive hematuria - with decompensation of cardiac activity, which disappears with improvement of its function.

Cylinders- these are protein secretions of the distal part of the cylindrical urinary tubules, the number of which increases with damage to the tubules and proteinuria. Urinary casts are not found in alkaline urine. Neither the number nor the type of urinary casts indicate the severity of the disease and are not specific for any type of kidney damage. If urinary casts are not observed, this may not mean the absence of kidney disease. Casts are more easily identified in the first morning urine.

Hyaline casts- protein casts of nephron tubules are observed in the urine in all kidney diseases, with dehydration and proteinuria, but their number does not depend on the severity of the pathological process. In normal urine, single hyaline casts are found in the specimen.

Granular casts are formed from granular-degenerated epithelial cells of the kidneys. Occurs with tubular necrosis and all acute and chronic kidney diseases.

Epithelial casts are formed from the epithelium of nephron tubules. Appear in urine in various kidney diseases.

Brown-pigmented casts are granular or epithelial casts pigmented with hemosiderin. Occurs with glomerulonephritis

Red blood cell casts are composed of red blood cells and are found in glomerulonephritis.

Leukocyte casts consist of leukocytes and are formed during a purulent process in the kidneys - pyelonephritis.

Fatty-granular casts are found in the urine in the nephrotic form of chronic glomerulonephritis, lipoid nephrosis.

Waxy casts indicate severe kidney damage and appear to be the result of a qualitative change in protein.

Hyaline-droplet cylinders consist of hyaline droplets and are a consequence of its irreversible changes. Observed in advanced pathological processes in the kidneys (chronic glomerulonephritis, nephrotic syndrome).

Epithelium. Normally, single cells of the bladder epithelium are found in urine sediment. In various diseases of the urinary system, epithelial cells of the urethra, bladder, renal pelvis and ureter, nephron tubules, and prostate gland may appear in significant numbers and with varying degrees of degeneration.

Bacteria. The presence of bacteria is normal in urine collected through spontaneous voiding or through a catheter. The decisive factor is the number of bacteria, which again depends on the method of collecting urine and the sex of the animal. By quantifying a culture of bacteria cultured from urine, the concentration of bacteria can be determined. A deviation from the norm is 100,000 bact./ml in urine taken during spontaneous urination; suspicion is caused by 1000-10,000 bact./ml in urine taken during spontaneous urination or using a catheter. In bitches, bacterial counts of 10,000 to 100,000 bact./ml may be normal. In the native preparation, 1 bacterium in the oil immersion field of view corresponds to 10,000 bact./ml. When centrifuging at speeds below 3000 rpm, bacteria hardly settle out. The presence of a urinary tract infection can be signaled by bacteriuria, hematuria and pyuria occurring simultaneously.

Unorganized urine sediment consists of various salts. The elements of acidic urine sediment include uric acid and amorphous urates, alkaline - amorphous phosphates, tripelphosphates. Ammonium urate, oxalates, neutral phosphates and calcium carbonate can be found in both acidic and alkaline urine

Kidney diseases

Glomerulonephritis- inflammation of the renal glomeruli, and to a lesser extent the tubules, accompanied by circulatory disorders in the kidneys with retention of water and salt in the body, often the development of arterial hypertension. There are acute and chronic glomerulonephritis. The disease can develop independently (primary glomerulonephritis) or in connection with another systemic disease (secondary glomerulonephritis).

Glomerulonephritis is acute th - acute diffuse immune inflammation of the renal glomeruli.

Etiology and pathogenesis. Along with streptococcal infection (nephritogenic beta-hemolytic streptococcus), other infectious and invasive diseases (plague, parvovirus enteritis, infectious hepatitis, leptospirosis, babesiosis) also play a significant role in the etiology of acute glomerulonephritis. Acute glomeluronephritis is often associated with sensitization to drugs (sulfonamides, antibiotics, non-steroidal anti-inflammatory drugs), foods, and pollen. The disease can be caused by vaccination or contact with organic solvents. Cooling is an important triggering factor for acute glomeluronephritis, often having independent significance.

Morphologically, a picture of diffuse immunocomplex inflammation of the glomeruli with proliferation of mesangial and endothelial cells, exudation into the cavity of the capsule of the glomeruli of leukocytes, erythrocytes, and fibrin is revealed.

The pathogenesis of glomerulonephritis is currently associated with immune disorders. In response to an infection entering the body, antibodies appear to streptococcal antigens, which, combining with the streptococcal antigen, form immune complexes that activate complement. These complexes first circulate in the vascular bed and are then deposited on the outer surface of the basement membrane of the glomerular capillaries, as well as in the glomerular mesangium.

In addition to antigens of bacterial origin, other exogenous antigens (drugs, foreign proteins, etc.) can also take part in the formation of immune complexes. Immune complexes are fixed on the basement membrane in the form of separate clumps.

The factor that directly causes glomerular damage is complement: its breakdown products cause local changes in the capillary wall and increase its permeability. Neutrophils rush to the sites of deposition of immune complexes and complement, the lysosomal enzymes of which increase damage to the endothelium and basement membrane, separating them from each other. Proliferation of mesangial and endothelial cells is observed, which contributes to the elimination of immune complexes from the body. If this process is effective enough, then recovery occurs. If there are a lot of immune complexes and the basement membrane is significantly damaged, then a pronounced mesangial reaction will lead to chronicity of the process and the development of an unfavorable variant of the disease.

The pathogenesis of symptoms of acute glomeluronephritis is associated with sodium and water retention due to the developing decrease in glomerular filtration and with an increase in capillary permeability: edema, hematuria, proteinuria, volume-, sodium-dependent hypertension. Sometimes extrarenal manifestations of immune activity are observed: vasculitis, serous myocarditis.

The clinical picture consists of a combination of renal symptoms with symptoms of damage to the cardiovascular, pulmonary and central nervous systems. Acute glomeluronephritis develops 2-3 weeks after an infectious disease, vaccination, tonsillitis, or pharyngitis. Clinically, such animals exhibit elevated temperature and violent vomiting. A sudden increase in blood pressure is combined with gross hematuria (urine in the form of “meat slop”), edema, and oliguria. Hypertension is usually accompanied by bradycardia and sinus arrhythmia. Often there is pain in the back muscles when pressing with fingers, transient paresis of the pelvic limbs, a desire to lie in a cold place, and arching of the back. Oliguria can be severe up to anuria with the development of transient acute renal failure. Acutely developing hypervolemic hypertension, often associated with serous myocarditis? often complicated by eclampsia and heart failure. Early signs of the latter include the appearance of tachycardia, gallop rhythm, and expansion of the cavities of the heart. Circulatory disorders often develop in the pulmonary circulation (cardiac asthma, interstitial pulmonary edema). Acute glomerulonephritis lasts no more than two weeks and often ends in death.

With glomerulonephritis, hypoalbuminemia develops due to persistent proteinuria. When the albumin level drops below 15 g/l, the development of ascites, hydrothorax and subcutaneous edema begins. These symptoms also depend on the degree of hypertension. Because of it and the reduced osmotic pressure, fluid is removed from the blood, which reduces the total blood volume and stimulates the renin-angiotensin-aldosterone mechanism, which, on the contrary, increases sodium and water retention.

The diagnosis of acute glomerulonephritis should be suspected with the sudden development of oliguria, edema and arterial hypertension in young animals shortly after an infectious disease, tonsillitis, pharyngitis, vaccination. Laboratory testing of blood and urine is crucial. Most patients have moderate normochromic anemia, a significant increase in ESR, neutrophilia with a shift to the left, a significant increase in urea and creatinine in the blood serum. When examining urine, an increased content of red blood cells (mostly leached), pyuria and bacteriuria, and the presence of all types of urinary casts are noted. Proteinuria is usually low, but with cyclic and prolonged acute glomerulonephritis it can reach 10 g/l.

Differential diagnosis. The symptoms of acute glomerulonephritis are not specific, and therefore, when making a diagnosis, it is necessary to differentiate acute glomerulonephritis from a number of similar diseases. Acute glomerulonephritis must be distinguished from chronic glomerulonephritis. This is not difficult with a clear acute onset of acute glomerulonephritis and the subsequent complete reversal of symptoms. Most often, diagnosis is complicated in the absence of an acute onset, as well as in the long-term persistence of certain signs of the disease (primarily urinary syndrome). It is difficult to differentiate acute glomerulonephritis from pyelonephritis due to the presence of leukocyturia in both diseases. However, AGN is accompanied by more massive proteinuria and, in some cases, edema. AGN must be differentiated from chronic diffuse connective tissue diseases, in which glomerulonephritis appears as one of the manifestations of the disease. This situation usually occurs when urinary, hypertensive and edematous syndromes are severe and other symptoms of the disease are insufficiently clear, more often with systemic lupus erythematosus. If leptospirosis is suspected, blood serum is examined serologically, but not earlier than 7-12 days of illness.

Treatment. The animal is given complete rest. A salt-restricted diet is prescribed, which helps reduce water accumulation and hypertension, and in the case of kidney failure, protein. Limit fluid intake. The total amount of fluid consumed per day should be equal to the volume of urine excreted over the previous day plus 7-10 ml/kg/day. A course of antibacterial therapy should be carried out only if the connection between AGN and infection has been reliably established and no more than 3 weeks have passed since the onset of the disease. Semi-synthetic penicillins are usually prescribed in standard dosages. Diuretics are prescribed only for fluid retention, increased blood pressure and the appearance of heart failure. Furosemide is the most effective. To stimulate diuresis, use veroshpiron, aminophylline 2-4% solution 5-10 ml in 10-20 ml of 20-40% glucose solution intravenously 1-2 times a day. To avoid hypokalemia, potassium supplements are used. The administration of glucocorticosteroids (prednisolone) for 1-1.5 months as monotherapy or in combination with heparin is indicated. Heparin has a wide spectrum of action: it improves microcirculation in the kidneys, has an anti-inflammatory and moderate immunosuppressive effect. In cases of severe oliguria, mannitol and rheopolyglucin are administered intravenously. For renal colic, antispasmodics and analgesics (baralgin, no-shpa, analgin) are used. For attacks of eclampsia, the use of magnesium sulfate 25% solution, Relanium, papaverine 2% solution, aminophylline 2.4% solution intravenously is indicated.

The prognosis for acute glomerulonephritis is favorable provided that treatment is started in a timely manner. Most symptoms disappear with treatment after 1-2 months, and recovery gradually occurs. In exceptional cases, death may occur due to cerebral hemorrhage or acute heart failure. It must be remembered that the most appropriate treatment for each individual case is carried out directly veterinarian.

Chronic glomerulonephritis (CGN)- chronic diffuse immunoinflammatory damage to the glomeruli, progressing and spreading to the entire renal parenchyma, resulting in the development of nephrosclerosis and renal failure. CGN can be an independent disease or one of the manifestations of another (for example, infective endocarditis, systemic lupus erythematosus). In the latter case, a situation difficult for correct diagnosis may arise when kidney damage comes to the fore in the picture of the disease in the absence or minimal severity of other signs of a systemic disease. At the same time, the addition of renal pathology can smooth out the previously vivid picture of the underlying disease. These situations can be referred to as “nephritic masks” of various diseases. CGN in 10-20% of cases develops as an outcome of AGN with a progressive course of the disease.

Pathogenesis . There are two possible mechanisms of kidney damage: immunocomplex and antibody. The immune complex mechanism for CGN is similar to that described for AGN. CGN develops in cases where hyperplasia of the endothelium and mesangial cells is insufficient and immune complexes are not removed from the kidney, which leads to a chronic course of the inflammatory process. The development of CGN is also determined by the antibody mechanism: in response to the introduction of various antigens into the body, the immunocompetent system produces antibodies that are tropic to the basement membrane of the capillaries, which are fixed on its surface. The membrane is damaged, and its antigens become foreign to the body, resulting in the production of autoantibodies, which are also fixed on the basement membrane. Complement settles on the membrane in the area where the autoantigen-autoantibody complex is localized. Next, neutrophils migrate to the basement membrane. When neutrophils are destroyed, lysosomal enzymes are released that increase membrane damage. At the same time, the coagulation system is activated, which enhances coagulating activity and fibrin deposition in the area where the antigen and antibody are located. The release of vasoactive substances by platelets fixed at the site of membrane damage enhances inflammatory processes. The chronic course of the process is determined by the constant production of autoantibodies to antigens of the basement membrane of the capillaries. In addition to immune mechanisms, non-immune mechanisms also take part in the progression of CGN, among which mention should be made of the damaging effect of proteinuria on the glomeruli, a decrease in the synthesis of prostaglandins (worsening renal hemodynamics), arterial hypertension (accelerating the development of renal failure), and the nephrotoxic effect of hyperlipidemia. A long-term inflammatory process, flowing in waves (with periods of remissions and exacerbations), ultimately leads to sclerosis, hyalinosis, desolation of the glomeruli and the development of chronic renal failure. The development of renal glomerular and tubular failure leads to loss of the concentrating ability of the kidneys. With the loss of the kidneys' ability to excrete urine of a constant specific gravity, polyuria appears, which ultimately leads to dehydration of the body. Damaged glomeruli excrete nitrogen waste less, and altered tubules reabsorb sodium less. Due to the large loss of sodium, thirst and acidosis appear. In dogs weighing 30-40 kg, daily sodium loss can be 1-3 g (corresponding to 2.5-7.5 g table salt).

Symptoms the diseases are less pronounced than with AGN. Polydipsia, polyuria and severe dehydration are noted. The kidneys are reduced in size, compacted and lumpy (wrinkled kidney - nephrosclerosis). With the progression of renal glomerular sclerosis, the excretion of nitrogenous wastes from the body becomes even more difficult, the reabsorption of calcium is impaired and its level in the plasma decreases. To maintain calcium balance, it is washed out of the skeletal bones. The accumulation of urea and its decomposition product, ammonia, in the blood causes chronic poisoning of the body with primary damage to the nervous system - uremia. The animal has a fetid ammonia odor from the mouth, apathy, anemia, decreased skin elasticity, vomiting and persistent diarrhea (gastroenteritis), osteodystrophy (the first sign is a rubbery consistency of the lower jaw). Cylindruria is unstable. In the final stage, vomiting of blood, profuse diarrhea, muscle twitching and tonic-clonic convulsions are observed. CGN occurs over a long period of time, with periods of exacerbations alternating with temporary relief of symptoms.

Diagnosis. Chronic glomerulonephritis is diagnosed in a certain sequence:

• First of all, it is necessary to make sure that the clinical picture of the disease is caused precisely by glomerulonephritis, and not by other kidney damage (pyelonephritis, amyloidosis, kidney tumor, urolithiasis, etc.), since urinary syndrome can also be observed in other kidney diseases.
• Determine whether chronic or acute glomerulonephritis.
• Having diagnosed CGN, it should be established that CGN is an independent disease or that kidney disease has developed against the background of some other disease.

The supporting signs for diagnosing CGN are: consistently observed urinary syndrome; duration of the disease - several months; absence of reasons that could cause the appearance of urinary syndrome; in the presence of arterial hypertension and edematous syndrome, exclude other causes that cause them.

It is most difficult to distinguish between acute and chronic glomerulonephritis. The diagnosis of AGN makes possible an acute onset of the disease with the appearance of urinary syndrome, arterial hypertension and edema. However, such clinical symptoms can also occur during exacerbation of CGN, and then CGN can be mistaken for the onset of AGN. The question of diagnosis can only be resolved through dynamic monitoring of the patient; complete disappearance of symptoms is in favor of AGN, persistence of symptoms is in favor of CGN.

Treatment. Frequent feeding and a low-protein diet with a high content of table salt are recommended. Eliminate foci of chronic infection (sore teeth, pyometra, etc.). There are pathogenetic and symptomatic therapy. Pathogenetic therapy includes the use of immunosuppressive drugs. Monotherapy with glucocorticosteroids (prednisolone) at a dose of 1 mg/kg for 2 months. Followed by a slow reduction to a maintenance dose is recommended in the first year of the disease or in case of recurrent nephrotic syndrome without hypervolemia. Other immunosuppressive drugs are cytostatics, which are prescribed for the following indications: ineffectiveness of corticosteroids; presence of complications of corticosteroid therapy; nephritis in systemic diseases, when corticosteroids are not effective enough, etc. Azathioprine, cyclophosphamide, chlorbutin are used. The drug is taken for 6 months. and more. You can additionally prescribe prednisolone in small doses.

The processes of hemocoagulation and aggregation are affected by heparin and antiplatelet agents. Heparin is prescribed for CGN of the nephrotic type with a tendency to thrombosis, and for exacerbation of CGN with the presence of severe edema for 1.5-2 months. 20,000-40,000 units/day. Along with heparin, antiplatelet agents are prescribed - chimes (300-600 mg/day). When CGN activity is high, the so-called four-component regimen is used, including a cytostatic agent, prednisolone, heparin and chimes. The course of treatment can last for weeks or even months. When the effect is achieved, the dosage of the drugs is reduced.

Symptomatic therapy includes the prescription of diuretics and antibiotics for infectious complications. Diuretics are prescribed for CGN of the nephrotic type with severe edema as a means that only improves the patient’s condition (but does not have an effect on the pathological process in the kidneys)

For dehydration and acidosis, intravenous drip administration of solutions of sodium chloride and sodium bicarbonate is practiced. For uremia, B vitamins and ascorbic acid are additionally prescribed.

Forecast. The life expectancy of patients with CGN depends on the state of nitrogen excretion function of the kidneys. A urea content in the blood of more than 35 mmol/l should be considered unfavorable, more than 50 mmol/l - as evidence of the inevitable death of the animal within a year.

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