home Drugs Rectum. Topography of the rectum. Walls, relation to the peritoneum of the rectum. What is the structure of the human rectum? Where is the rectum located?

Rectum. Topography of the rectum. Walls, relation to the peritoneum of the rectum. What is the structure of the human rectum? Where is the rectum located?

Rectum(Latin - rectum, Greek - proktos) - terminal section, which serves for the formation, accumulation and further removal of feces. The average length of the rectum is 13-16 cm. Its diameter varies throughout, and in the widest part it reaches 16 mm.

The rectum is a natural continuation and originates at the level of the upper edge of the second sacral vertebra. Most of it is located in the pelvis and only a small part (anal canal) belongs to the perineum.

In front, the rectum borders on the bladder, seminal vesicles, prostate in men, and on the posterior wall of the cervix and vagina in women. The sacrum and coccyx are located at the back; the space between the intestinal wall and the periosteum is filled with a fatty layer. On the sides there are the ischiorectal fossae, in which the iliac vessels and ureters pass.

In the sagittal plane, the rectum has an S-shape, and seems to follow the course of the sacrum and coccyx. The upper bend is facing backward and corresponds to the concavity of the sacrum; subsequently, the direction of the intestine changes to the opposite, and a second bend is formed at the coccyx, convexly facing forward. Next, the intestine goes back and down, continuing into the anal canal, and ends with the anus.

Structure

Sections of the rectum

The rectum has 3 sections:

Rectosigmoid (supraampullary);
Ampulla - upper ampullary, middle ampullary, lower ampullary sections;
Anal canal.

Rectosigmoid region- This is a small area that represents the transition zone between the sigmoid colon and the ampulla of the rectum. Its length is 2-3 cm, and its diameter is about 4 cm. At this level, the peritoneum covers the intestine on all sides, forming a short triangular one, which then quickly disappears. Muscle fibers, unlike the overlying sections, are distributed evenly around the circumference, and are not collected in ribbons. The direction of the blood vessels also changes from transverse to longitudinal.

Ampoule- the longest and widest part of the rectum. Its length is 8-10 cm, and its diameter in a healthy person is about 8-16 cm; with a decrease in tone it can reach 40 cm.

In the upper ampullary section, the peritoneum covers the intestine on three sides - in front and on the sides, downwards the peritoneal cover gradually disappears, passing to the uterus (in women) or the bladder (in men), as well as on the side walls of the pelvis. Thus, the lower parts of the rectum are located extraperitoneally, covered by the peritoneum only a small section of the anterior wall of the intestine.

Anal canal- the transition zone between the intestine itself and the anus. The canal is about 2-3 cm long and is surrounded by muscle sphincters. In the normal state, due to the tonic contraction of the internal sphincter, the anal canal is tightly closed.

The structure of the rectal wall

Mucous membrane.

The internal lining in the upper sections is represented by single-layer transitional epithelium, in the lower sections – multilayered squamous epithelium. The mucous membrane forms 3-7 transverse folds that have a helical motion, as well as numerous unstable longitudinal folds that smooth out easily. In the anal canal there are 8-10 permanent longitudinal folds - the columns of Morgagni, between which depressions are formed - the anal sinuses.

Submucosal layer.

The submucosa in the rectum is highly developed, which ensures the mobility of the mucosa and promotes the formation of folds. Vessels and nerves pass through the submucosal layer.

Muscular membrane.

The muscular layer has 2 layers: circular (inside) and longitudinal (outside).

In the upper part of the anal canal, the circular layer thickens sharply and forms the internal sphincter. Outside of it and somewhat distally is the external sphincter, formed by striated muscle fibers.

The longitudinal muscles are distributed evenly in the walls of the intestine and below are intertwined with the external sphincter and the levator ani muscle.

Functions

The rectum performs the following functions:

Reservoir and evacuation. The rectum serves as a reservoir for the accumulation of feces. Stretching of the rectal ampulla with feces and gases causes irritation of the interoreceptors located in its wall. From the receptors, impulses travel through sensory nerve fibers to the brain, and then through motor pathways are transmitted to the muscles of the pelvic floor, abdominal muscles and smooth muscles of the rectum, causing their contraction. The sphincters, on the contrary, relax, due to which the intestines are released from the contents.
Hold function. In the passive state, the internal sphincter is contracted and the anal canal is closed, so that the contents are retained inside the intestine. After the urge to defecate occurs, the smooth muscles of the intestine contract and the internal sphincter relaxes involuntarily. The external sphincter is voluntary, that is, its contraction is subject to volitional effort. Thus, a person can independently regulate.
. In the rectum, water, alcohol and some other substances, including medicinal ones, are absorbed. The absorption function is important in medicine, allowing the use of rectal forms of drugs.

Methods for examining the rectum

Digital examination is a mandatory method of examining the rectum, which is carried out before any other instrumental method. Before starting a digital examination, the abdomen is palpated, women undergo a gynecological examination, and the condition of the perianal area is assessed.

To conduct the examination, the patient takes a knee-elbow position, the doctor treats a gloved finger with Vaseline and inserts it into the anus. Depending on the purpose of the study and the expected pathology, the patient's position may change.

This examination allows you to assess the tone of the sphincter, the condition of the mucous membrane of the rectum, perirectal tissue and the lymph nodes located in it. In men, digital examination can be used to assess the condition of the prostate gland.

Sigmoidoscopy allows you to visually assess the condition of the rectal and partially sigmoid mucosa, its color, the severity of the vascular pattern, the presence of various defects and neoplasms, determine the width of the intestinal lumen at its different levels, folding, mobility of the mucous layer, and identify the source of bleeding. The examination is carried out using a special device - a sigmoidoscope.

This method resembles sigmoidoscopy, but is more specialized and is used for targeted examination of the anal canal. Anoscopy is not very informative in diagnosing diseases of the rectal and sigmoid intestines.

A high-tech method using a device based on flexible optical fiber, which allows you to examine the entire large intestine.

Thanks to the high resolution of the equipment, colonoscopy allows you to detect diseases at the earliest stages, perform multiple colonoscopy, and remove polyps.

X-ray examination method. To carry it out, a contrast agent is injected into the rectum using an enema, and then X-rays are taken. Indications for this method are neoplasms of the large intestine.

The study is carried out with a special rectal sensor and allows you to assess the condition of the intestinal wall, its thickness, and clarify the size of pathological foci.

and profilometry

These methods are intended to assess the closing ability of the anal sphincter.

Allows you to visualize rectal tumors that are not visible with other research methods.

Table of contents of the topic "Anatomy of the large intestine":

Rectum. Topography of the rectum. Walls, relation to the peritoneum of the rectum.

Rectum, rectum, serves for the accumulation of feces. Starting at the level of the promontory, it descends into the small pelvis in front of the sacrum, forming two bends in the anteroposterior direction: one, upper, convexly facing backward, corresponding to the concavity of the sacrum - flexura sacralis; second, lower, facing in the area of the coccyx with the convexity forward, - perineal - flexura perinealis.

Upper rectum corresponding flexura sacralis, is placed in the pelvic cavity and is called pars pelvina; towards flexura perinealis it expands to form ampoule - ampulla recti, with a diameter of 8 - 16 cm, but can increase with overflow or atony up to 30 - 40 cm.

The final part of the recti, going backwards and downwards, continues in anal canal, canalis analis, which, having passed through the pelvic floor, ends with the anus, anus (ring - Greek proktos; hence the name of inflammation - proctitis).
The circumference of this section is more stable, 5 - 9 cm. The length of the intestine is 13 - 16 cm, of which 10-13 cm is in the pelvic section, and 2.5 - 3 cm in the anal section. In relation to the peritoneum, three parts are distinguished in the rectum: the upper one, where it is covered with peritoneum intraperitoneally, with a short mesentery - mesorectum, middle, located mesoperitoneally, and lower - extraperitoneal.

With the development of rectal surgery, it is now more convenient to divide it into five sections: supramullary (or rectosigmoid), superior ampullary, mid-ampullary, inferior ampullary and perineal (or canalis analis).

The wall of the rectum consists of mucous and muscular membranes and located between them muscular plate of the mucous membrane, lamina muscularis mucosae, And submucosa, tela submucosa.

mucous membrane, tunica mucosa, thanks to the developed layer of the submucosa, it gathers into numerous longitudinal folds, which are easily smoothed out when the intestinal walls are stretched. IN canalis analis longitudinal folds in the amount of 8 - 10 remain constant in the form of so-called columnae anales. The grooves between them are called anal sinuses, sinus anales, which are especially pronounced in children. Mucus accumulating in the anal sinuses facilitates the passage of feces through the narrow canalis analis.

The anal sinuses, or anal crypts as clinicians call them, are the most common portal of entry for pathogenic microorganisms.

In the thickness of the tissue between the sinuses and the anus there is a venous plexus; its painful, heavily bleeding expansion is called hemorrhoids.

In addition to longitudinal folds, in the upper parts of the rectum there are transverse folds of the mucous membrane, plicae transversdles recti, similar to the semilunar folds of the sigmoid colon. However, they differ from the latter in their small number (3 - 7) and their helical motion, which promotes the forward movement of feces. Submucosa, tela submucosa, highly developed, which predisposes to prolapse of the mucous membrane out through the anus.

Muscular membrane, tunica muscularis, consists of two layers: internal - circular and external - longitudinal. The internal one thickens in the upper part of the perineal section to 5 - 6 mm and forms here the internal sphincter, i.e. sphincter ani internus, 2 - 3 cm high, ending at the junction of the anal canal with the skin. (Immediately under the skin lies a ring of striated voluntary muscle fibers - m. sphincter ani externus, part of the muscles of the perineum).
The longitudinal muscle layer is not grouped in teniae, as in colon, but is distributed evenly on the anterior and posterior walls of the intestine. Below, the longitudinal fibers intertwine with the fibers of the levator ani muscle, m. levator ani (perineal muscle), and partly with the external sphincter.

From the above description it is clear that the final segment of the intestine - the rectum - acquires the features of the conductive section of the digestive tube, just like its initial part - the esophagus. In both of these sections of the digestive canal, the mucous membrane has longitudinal folds, the muscles are located in two continuous layers (inner - circular, narrowing and outer - longitudinal, expanding), and towards the hole opening outward, the myocytes are supplemented with striated arbitrary fibers.
There are also similarities in development: at both ends of the primary intestine, during embryogenesis, a breakthrough occurs at the blind ends of the tube - the pharyngeal membrane during the formation of the esophagus and the cloacal membrane during the formation of the rectum. Thus, the similarity of development and function (carrying out the contents) of the esophagus and rectum also determines the known similarity of their structure.

By these similarities with the esophagus, the final part of the rectum differs from the rest of it, which develops from the endoderm and contains smooth muscle.

Topography of the rectum

Posterior to the rectum are the sacrum and coccyx, and in front of men, it adjoins its section, devoid of peritoneum, to the seminal vesicles and vas deferens, as well as to the area of the bladder lying between them that is not covered by it, and even lower to the prostate gland.
In women, the rectum borders the front of the uterus and the posterior wall of the vagina along its entire length, separated from it by a layer of connective tissue, septum rectovaginale. There are no strong fascial bridges between the fascia of the rectum and the anterior surface of the sacrum and coccyx, which makes it easier during operations to separate and remove the intestine along with its fascia, covering the blood and lymphatic vessels.

Educational video on rectal anatomy

Anatomy of the rectum on a cadaveric specimen from Associate Professor T.P. Khairullina understands

The rectum is the final part of the human digestive tract.

The anatomy and physiology of the rectum differs from that of the large intestine. The rectum has an average length of 13-15 cm, the diameter of the intestine ranges from 2.5 to 7.5 cm. The rectum is conventionally divided into two parts: the ampulla of the intestine and the anal canal (anus). The first part of the intestine is located in the pelvic cavity. Behind the ampulla is the sacrum and coccyx. The perineal part of the intestine has the form of a slit located longitudinally, which passes through the thickness of the perineum. In men, in front of the rectum there is a prostate gland, seminal vesicles, bladder and ampulla of the vas deferens. In women, the vagina and uterus. In the clinic, it is convenient to use the conditional division of the rectum into the following parts:

supramullary or rectosigmoid;
superior ampullary;
mid-ampullary;
inferior ampullary part;
crotch part.

Clinical anatomy of the organ

The rectum has bends: frontal (not always present, changeable), sagittal (constant). One of the sagittal bends (proximal) corresponds to the concave shape of the sacrum, which is called the sacral bend of the intestine. The second sagittal curve is called perineal and is projected at the level of the coccyx, in the thickness of the perineum (see photo). The rectum on the proximal side is completely covered by the peritoneum, i.e. located intraperitoneally. The middle part of the intestine is located mesoperitoneally, i.e. covered with peritoneum on three sides. The terminal or distal part of the intestine is not covered by the peritoneum (located extraperitoneally).

Anatomy of the rectal sphincters

On the border between the sigmoid colon and the rectum there is the sigmorectal sphincter, or according to the author O'Berne-Pirogov-Muthier. The basis of the sphincter is made up of smooth muscle fibers, located circularly, and the auxiliary element is a fold of the mucous membrane, occupying the entire circumference of the intestine, located circularly. Along the intestine there are three more muscle sphincter.

The third sphincter or proximal (according to the author Nelaton), has approximately the same structure as the first sphincter: it is based on circular smooth muscle fibers, and an additional element is a circular fold of the mucosa, which occupies the entire circumference of the intestine.
Internal sphincter of the rectum, or involuntary. It is located in the area of the perineal flexure of the intestine, ending at the border where the superficial layer of the external anal sphincter connects with its subcutaneous layer. The base of the sphincter consists of thickened smooth muscle bundles that run in three directions (circularly, longitudinally and transversely). The length of the sphincter is from 1.5 to 3.5 cm. The longitudinal fibers of the muscle layer are woven into the distal sphincter and into the external sphincter of the anus, connecting with the skin of the latter. The thickness of this sphincter is greater in men; it gradually increases with age or with certain diseases (accompanied by constipation).
Voluntary external sphincter. The basis of the sphincter is the striated muscle, which is a continuation of the puborectalis muscle. The sphincter itself is located in the pelvic floor. Its length ranges from 2.5 to 5 cm. The muscular part of the sphincter is represented by three layers of fibers: the subcutaneous part of the circular muscle fibers, a cluster of superficial muscle fibers (united and attached to the bones of the coccyx at the back), a layer of deep muscle fibers associated with the fibers of the puborectalis muscle . The external voluntary sphincter has auxiliary structures: cavernous tissue, arteriolo-venular formations, connective tissue layer.

All rectal sphincters provide the physiological process of defecation.

Wall structure

The walls of the rectum consist of three layers: serous, muscular and mucous (see photo). The upper part of the intestine is covered with a serous membrane in front and on the sides. In the uppermost part of the intestine, the serosa covers the posterior part of the intestine and passes into the mesorectum. The mucous membrane of the human rectum forms multiple longitudinal folds that are easily straightened. From 8 to 10 longitudinal mucous folds of the anal canal are permanent. They have the shape of columns, and between them there are depressions called the anal sinuses and ending with semilunar valves. The valves, in turn, form a slightly protruding zigzag line (it is called anorectal, dentate or comb), which is the conventional boundary between the squamous epithelium of the rectal anal canal and the glandular epithelium of the ampullary part of the intestine. Between the anus and the anal sinuses there is a ring-shaped zone called hemorrhoidal. The submucosa provides easy movement and stretching of the mucous membrane, due to its loose connective tissue structure. The muscle layer is formed by two types of muscle fibers: the outer layer has a longitudinal direction, the inner layer has a circular direction. The circular fibers thicken to 6 mm in the upper half of the perineal part of the intestine, thereby forming the internal sphincter. Muscle fibers in the longitudinal direction are partially woven into the external sphincter. They also connect to the levator ani muscle. The external sphincter, up to 2 cm high and up to 8 mm thick, contains voluntary muscles, covers the perineal section, and also ends with the intestine. The mucous layer of the rectal wall is covered with epithelium: the anal columns are lined with flat non-keratinizing epithelium, the sinuses are lined with stratified epithelium. The epithelium contains intestinal crypts, extending only to the intestinal columns. There are no villi in the rectum. A small number of lymphatic follicles are found in the submucosa. Below the intestinal sinuses there is a boundary between the skin and the mucous membrane of the anus, which is called the anal-cutaneous line. The skin of the anus has a flat, non-keratinizing stratified pigmented epithelium, papillae are pronounced in it, and the anal glands are located in its thickness.

Blood supply

Arterial blood approaches the rectum through the unpaired superior rectal and rectal arteries (middle and lower). The superior rectal artery is the last and largest branch of the inferior mesenteric artery. The superior rectal artery provides the main blood supply to the rectum to its anal region. The middle rectal arteries depart from the branches of the internal iliac artery. Sometimes they are absent or not equally developed. Branches of the inferior rectal arteries arise from the internal pudendal arteries. They provide nutrition to the external sphincter and the skin of the anal area. In the layers of the rectal wall there are venous plexuses, called subfascial, subcutaneous and submucosal. The submucosal, or internal, plexus is connected to the others and is located in the form of a ring in the submucosa. It consists of dilated venous trunks and cavities. Venous blood flows through the superior rectal vein into the portal vein system, and through the middle and lower rectal veins into the inferior vena cava system. Between these vessels there is a large network of anastomoses. The superior rectal vein lacks valves, so the veins in the distal rectum often dilate and develop symptoms of venous stasis.

Lymphatic system

Lymphatic vessels and nodes play a large role in the spread of infections and tumor metastases. In the thickness of the mucous membrane of the rectum lies a network of lymphatic capillaries, consisting of one layer. In the submucosal layer there are plexuses of lymphatic vessels of three orders. In the circular and longitudinal layers of the rectum there are networks of lymphatic capillaries. The serous membrane is also rich in lymphatic formations: it has a superficial finely looped and deep broadly looped network of lymphatic capillaries and vessels. The lymphatic vessels of the organ are divided into three types: extramural upper, middle and lower. From the walls of the rectum, lymph is collected by the upper lymphatic vessels, they run parallel to the branches of the superior rectal artery and empty into the lymph nodes of Gerota. Lymph from the side walls of the organ is collected in the middle lymphatic vessels of the rectum. They are directed under the fascia of the levator ani muscle. From them, lymph flows into the lymph nodes located on the walls of the pelvis. From the lower rectal lymphatic vessels, lymph goes to the inguinal lymph nodes. The vessels begin from the skin of the anus. Lymphatic vessels from the intestinal ampulla and from the mucous membrane of the anal canal are connected to them.

Innervation

Different parts of the intestine have separate branches of innervation. The rectosigmoid and ampullary parts of the rectum are innervated mainly by the parasympathetic and sympathetic nervous systems. The perineal section of the intestine is due to the branches of the spinal nerves. This may explain the low pain sensitivity of the ampullary part of the rectum and the low pain threshold of the anal canal. Sympathetic fibers provide innervation to the internal sphincter, a branch of the pudendal nerves - the external sphincter. Branches arise from the 3rd and 4th sacral nerves, providing innervation to the levator ani muscle.

Functions

The main function of this section of the intestine is to evacuate feces. This function is largely controlled by the consciousness and will of a person. New research has established that there is a neuroreflex connection between the rectum and the internal organs and systems of the body, carried out through the cerebral cortex and the lower levels of the nervous system. Food begins to be evacuated from the stomach just a few minutes after eating. On average, the stomach is empty of its contents after 2 hours. By this time, the first portions of chyme reach the bauhinium valve. Up to 4 liters of liquid pass through it per day. The human colon absorbs about 3.7 liters of the liquid part of chyme per day. Up to 250-300 grams are evacuated from the body in the form of feces. The human rectal mucosa ensures the absorption of the following substances: sodium chloride, water, glucose, dextrose, alcohol, and many medications. About 40% of the total mass of feces consists of undigested food debris, microorganisms, and waste products of the digestive tract. The ampullary part of the intestine acts as a reservoir. Feces and gases accumulate in it, stretch it, and irritate the interoceptive apparatus of the intestine. The impulse from the higher parts of the central nervous system reaches the striated muscles of the pelvic floor, the smooth muscles of the intestine and the striated fibers of the abdominal muscles. The rectum contracts, the anus rises, the muscles of the anterior abdominal wall, the pelvic floor diaphragm contract, and the sphincters relax. These are physiological mechanisms that ensure the act of defecation.

Measuring rectal temperature

The rectum is a closed cavity, so the temperature in it is relatively constant and stable. Therefore, the results of thermometry in the rectum are the most reliable. The temperature of the rectum is almost equal to the temperature of human organs. This method of thermometry is used in a certain category of patients:

patients with severe exhaustion and weakness;
children under 4-5 years of age;
patients with thermoneuroses.

Contraindications include diseases of the rectum (hemorrhoids, proctitis), stool retention when the ampullary part of the intestine is filled with feces, and diarrhea. Before you start measuring temperature, you need to lubricate the end of the thermometer with petroleum jelly. An adult patient can lie on his side; it is more convenient to place children on their stomach. The thermometer is inserted no more than 2-3 cm. An adult patient can do this himself. During the measurement, the patient continues to lie down, the thermometer is held with the fingers of the hand, which lies on the buttocks. Avoid abrupt insertion of the thermometer, its rigid fixation, or movement of the patient during measurement. The measurement time will be 1-2 minutes if you use a mercury thermometer.

Normal temperature in the rectum is 37.3 - 37.7 degrees.

After measuring, place the thermometer in a disinfectant solution and store it in a separate place. The following symptoms may indicate diseases of the rectum.

Constipation. To determine the cause of constipation, you should consult a specialist and undergo the necessary research. Constipation can be a sign of serious diseases: intestinal obstruction, tumor diseases, intestinal diverticulosis.
Symptoms indicating the presence of a chronic anal fissure: bloody discharge after defecation, pain before and after defecation. A proctologist will detect this disease during a routine visual examination.
Sharp, intense pain in the rectal area, poor general health and increased temperature with signs of intoxication are indications for calling emergency services. The listed symptoms may indicate an inflammatory process of subcutaneous fatty tissue - paraproctitis.
The reason for contacting a specialist is nonspecific symptoms characteristic of many diseases of the rectum (cancer, polyps, hemorrhoids): sudden weight loss, there is an admixture of blood and mucus in the stool, the patient is bothered by severe pain before and after defecation.

Rectum, located in the pelvic cavity, at its posterior wall, formed by the sacrum, coccyx and the posterior section of the pelvic floor muscles. It starts from the end of the pelvic part of the sigmoid colon at the level of the third sacral vertebra and ends in the perineal area with the anus. Its length is 14-18 cm. The diameter of the rectum varies from 4 cm (starting from the sigmoid colon) to 7.5 cm in the middle part (ampulla) and again decreases to a slit at the level of the anus.

Consists of two parts: pelvic and perineal. The first is located above the pelvic diaphragm, in the pelvic cavity, and in turn is divided into a narrower supramullary section and a wide ampulla of the rectum, ampulla recti. The second part of the rectum lies under the pelvic diaphragm, in the perineum, and represents the anal canal, canalis analis.

The pelvic part of the rectum forms a bend in the sagittal plane, open anteriorly, corresponding to the concavity of the sacrum - the sacral bend, flexura sacralis; The upper part of the intestinal bend follows from front to back and down, the lower part - from back to front and down.

In the frontal plane, the pelvic part forms inconsistent bends; the upper part of the bend goes from left to top to bottom and to the right, the lower part goes in the opposite direction. The second bend in the sagittal plane, but already concave back, is located at the transition of the pelvic part to the perineal part; Having passed the pelvic diaphragm, the rectum sharply turns (almost at a right angle) back, forming a perineal bend, flexura perinealis. At this level, the rectum seems to go around the top of the coccyx. The length of the pelvic part ranges from 10 to 14 cm, the perineal part is about 4 cm.

At the level of the lower edge of the third sacral vertebra, the rectum begins to lose its serous cover: first from the posterior surface, then from the lateral and, finally, from the anterior. Thus, the upper, supramullary, section of the pelvic part of the rectum is located intraperitoneally, the upper part of the ampulla is surrounded by a serous membrane on three sides, and the lowest section of the ampulla lies retroperitoneal, since the peritoneum covers only a small area of the anterior wall here.

The line along which the peritoneum leaves the intestinal wall follows obliquely from above, from behind downward and forward. As the wall of the pelvic rectum loses its peritoneal covering, it is replaced by the visceral fascia of the pelvis, which forms the sheath of the rectum.

The perineal part of the rectum has the form of a longitudinal slit and opens in the recess of the intergluteal groove with the anus, anus, almost halfway between the coccyx and the root of the scrotum in men or the posterior commissure of the labia majora in women, at the level of the transverse line connecting both ischial tuberosities.

The structure of the rectal wall.

The serous membrane (peritoneum), tunica serosa, is part of the wall of the rectum only for a small extent. The extraperitoneal part of the pelvic rectum is surrounded by the visceral fascia of the pelvis; the fascia is not directly adjacent to the muscular layer of the intestinal wall. Between the visceral fascia and the muscle layer lies a layer of fatty tissue, there are nerves that supply the intestine with blood vessels and lymph nodes. The anterior section of the fascia of the rectum is a plate that separates the intestine from the organs lying in front: the bladder, prostate gland, etc. This plate is a derivative of the fused serous layers of the deepest part of the peritoneal recess of the small pelvis; it goes from the bottom of the rectouterine recess (or rectovesical recess in men) to the tendon center of the perineal muscles and is called the peritoneal-perineal fascia, fascia peritoneoperinealis, or rectovesical septum, septum rectovesicale. Dorsally, the rectal fascia ends in the midline of the posterior wall of the rectum.

The muscular layer, tunica muscularis, of the rectum consists of two layers: the outer longitudinal, stratum longitudinale, less thick, and the inner circular, stratum circulare, thicker. The longitudinal layer is a continuation of the muscle bands of the sigmoid colon, which here expand and cover the intestine in a continuous layer. On the anterior and posterior walls, the longitudinal muscle bundles are more developed. The longitudinal muscle layer of the lower part of the ampulla is woven into bundles coming from the anterior sacrococcygeal ligament - the rectococcygeal muscle, m. rectococcygeus. Part of the muscle fibers of the longitudinal layer is woven into the levator ani muscle, m. levator ani, and part reaches the skin of the anus.

In men, on the anterior surface of the lower part of the rectum, part of the longitudinal muscle bundles forms a small rectourethral muscle, m. rectouretralis. This muscle is attached to the tendon center of the perineum where the membranous part of the urethra passes through it. In addition, slightly higher in men there is a rectovesical muscle, which is a muscle bundle that connects the longitudinal muscle bundles of the bladder with the same bundles of the rectum.

The circular muscular layer of the rectum extends all the way to the anus; here it thickens, forming the internal sphincter of the anus, m. sphincter ani internus. Anterior to the anus, bundles of its muscles are woven into the sphincter of the membranous part of the urethra (in men) and into the muscles of the vagina (in women). Around the anus in the subcutaneous tissue is the external anal sphincter, m. sphincter ani externus. This muscle belongs to the group of striated muscles of the perineum. Its outer, more superficial part covers the medial section of the levator ani muscle; the deeper section is adjacent to the circular layer of the rectum, which forms the internal sphincter here. The levator ani muscle enters the space between the external and internal sphincters of the rectum. The anterior part of this muscle is the pubococcygeus muscle, m. pubococcygeus, covers the perineal part of the rectum in the form of a loop from behind.

The muscles of the circular layer of the rectum form thickenings at the location of the transverse folds of the mucous membrane (see below). The most pronounced thickening is located 6-7 cm above the anus. Here the transverse folds of the rectum, plicae transversales recti, are clearly distinguished; the middle of them is the most pronounced; a large number of circular muscle fibers lie in its thickness.

The mucous membrane, tunica mucosa, of the rectum is covered with epithelium, contains intestinal glands (crypts), glandulae intestinales (criptae), but is devoid of villi; in the submucosa, tela submucosa, there are single lymphatic follicles. Throughout the pelvic section of the rectum, the mucous membrane forms three, sometimes more, transverse folds, plicae transversales recti, covering half the circumference of the intestine. Of these three folds, the upper one is located at a level of up to 10 cm from the anus. In addition to transverse folds, the mucous membrane has a large number of unstable folds running in different directions. The mucous membrane of the lower part of the rectum (anal, anal, canal) forms up to 10 longitudinal folds - anal (anal) columns, columnae anales, the width and height of which increase downwards. The upper ends of the anal columns correspond to the rectal-anal line, linea anorectalis. Distal to the anal columns is a slightly swollen annular area with a smooth surface of the mucous membrane - the intermediate zone. The protruding intermediate zone, as it were, closes the depressions between the pillars from below, turning them into pockets - the anal (anal) sinuses, sinus anales. The anal glands lie at the bottom of these sinuses. The transverse folds of the intermediate zone, closing the sinuses from below, as if connecting the anal columns, are called anal valves, valvulae anales. The combination of the anal valves forms a ridge of the mucous membrane - the anal (anal) ridge, pecten analis. The submucosa of the anal column zone and the intermediate zone is loose tissue in which the rectal venous plexus lies. In the intermediate zone, this plexus forms a continuous ring; In the submucosa of the area of the anal columns, in addition to the venous plexuses, there are bundles of longitudinal muscle points.

The rectum is the final section of the large intestine and the entire digestive tract as a whole. Its length in an adult is 14-18 cm, and its diameter ranges from 4-7.5 cm.

The rectum has three main parts:
supramullary part - located immediately after the end of the sigmoid colon;
ampoule or ampullary part; The ampullary part of the rectum received its name for its characteristic shape in the form of an expansion;
anal canal – the lower, narrower part of the rectum; passes through the perineum and ends at the anus ( anus).
Since the first two parts are located in the pelvic cavity, they form the pelvic rectum. The anal canal is otherwise called the perineal section of the rectum.

Structure and function of the rectum

The rectum is located in the pelvic cavity. Its main function is the accumulation and final formation of feces. Thanks to two anal sphincters - external and internal - the lumen of the rectum closes, holding feces.

The rectal wall consists of four layers:
mucous membrane;
submucosal layer;
the muscular membrane responsible for the forward movement of feces;
connective tissue membrane.

The rectal mucosa forms many small vertical folds in which feces can be retained and create the preconditions for inflammation.

The subcutaneous fat surrounding the anus contains a venous plexus, which becomes the anatomical basis for the formation of nodes in hemorrhoids.

The rectum contains numerous nerve endings, which is associated with the importance of the evacuation function and the complexity of the act of defecation, which is largely controlled by consciousness.

Embryonic development

Initially, the human embryo develops a cloaca - a single channel for removing all waste products ( both urine and feces). At the seventh week of embryonic development, the urinary-rectal septum divides the cloaca into two sections and gives rise to the subsequent formation of the rectum.

Violation of the mechanisms of formation of the rectum leads to various congenital defects in children - this can be anal atresia, rectal atresia and congenital fistulas connecting the rectum and the genitourinary system ( bladder or urethra).

Diseases of the rectum

1.Haemorrhoids
Hemorrhoids are the expansion and inflammation of hemorrhoidal venous nodes located in the fatty tissue of the anus. In fact, hemorrhoids are a vascular disease that has the same origin and mechanism as the well-known varicose veins.

The causes of hemorrhoids are hereditary predisposition, chronic constipation, sedentary lifestyle, and heavy lifting. In women, hemorrhoids often first appear during pregnancy or childbirth.

Symptoms of hemorrhoids are:
formation of protrusion in the anus;
bowel disorder ( usually constipation);
pain at rest and during bowel movements;
bleeding from damaged nodes.

Regular blood loss can lead to the development of anemia - anemia. Hemorrhoids can be complicated by necrosis and thrombosis of hemorrhoids - conditions that are life-threatening for the patient.

To treat hemorrhoids, suppositories, ointments, gels, and sclerotherapy are used. For moderately severe hemorrhoids, folk remedies can be successfully used - suppositories made from potatoes, propolis, garlic, honey, etc. In severe cases, surgical treatment is resorted to.
2. Proctitis
Proctitis is an inflammation of the rectum, or more precisely, its mucous membrane. The disease is manifested by pain, bleeding, a feeling of incomplete bowel movements, and fever. Long-term inflammation of the rectum can lead to the formation of ulcers and fistulas.
Proctitis is treated with anti-inflammatory drugs, antibiotics, and diet therapy.
3. Rectal prolapse
Rectal prolapse ( otherwise rectal prolapse) is a consequence of weakness of the pelvic floor muscles. In children, rectal prolapse is usually treated conservatively; in elderly patients, as a rule, it is necessary to resort to surgery.
4. Anal fissure
A crack is formed due to mechanical trauma ( for example, hard stool for constipation) or inflammatory process. In children, an anal fissure can form as a result of scratching during itching from helminthiasis.
A rectal fissure is manifested by pain, bleeding and spasm during bowel movements. In the treatment of rectal fissures, local emollients, healing and anti-inflammatory agents are used. To avoid injury to the fissure during defecation, a milk diet and cleansing enemas are prescribed.
5. Rectal polyps
Polyps are growths on the intestinal wall. People with polyps usually have no pain - the disease is asymptomatic. However, it should be remembered that this pathology can cause inflammation and cancer formation.
6. Rectal cancer
Malignant tumor of the rectum is a serious disease with a poor prognosis. Rectal cancer quickly spreads to neighboring organs and metastasizes.

Signs of adenocarcinoma and other types of rectal malignancies:
pain radiating to the lumbar region, perineum, tailbone;
bleeding;
an admixture of mucus and blood in the stool;
weakness, weight loss;
sensation of a foreign body in the anus;
painful bowel movement.
In the later stages, the pain becomes almost constant, feces may appear in the urine or vaginal discharge.

Early diagnosis of rectal cancer is difficult due to the lack of specific complaints. Patients may regard the presence of blood in the stool as a manifestation of hemorrhoids or fissures. Regular examination by a specialist for these diseases and the use of various examination methods ( Ultrasound, examination using a colonoscope, laboratory analysis of blood, urine and feces, taking a smear from the rectal mucosa) will help make the correct diagnosis and begin timely treatment.

To treat rectal cancer in modern oncology, surgical treatment is used, as well as chemotherapy and radiotherapy. Surgical treatment consists of resection ( partial removal) or complete removal of the rectum.