Roundworms: sizes and what do roundworms look like? Features of human roundworm

Ascariasis affects most of the world's population. The causative agent of this type of helminthiasis is the human roundworm. Helminth belongs to the class of nematodes, which are roundworms. What is the external and internal structure We will look at roundworms later in the article.

Many people are susceptible to ascariasis

Building outside

Under the antienzyme cover, the helminth has longitudinal ribbons of one layer that perform the functions of muscles; together with the epithelium, they form the walls of the body. Thanks to this structural feature of the roundworm, it is able to move through the intestines.

Ascaris - structure of the helminth

At one end of the worm's body there is an oral cavity, similar to a pump, which swallows food, after which it enters the intestines.

Building from the inside

The roundworm has the following internal body structure features:

The female is capable of reproducing several hundred thousand eggs per day

Ascaris eggs enter the environment along with feces. A person secretes up to two hundred thousand eggs per day, which become invasive only when exposed to favorable conditions. They can for a long time carry low temperatures, but are very sensitive to ultraviolet radiation, under the influence of which they often die.

Eggs become invasive only after exposure to favorable conditions

Only once in a moist and warm environment do the eggs mature and become invasive a week after entering the soil.

The main target of the larvae is the respiratory organs or the liver, from where they again enter the intestines, where their development is completed.

Once in the lungs, the larvae do not stay there for a long period, having passed specific cycle development. After this, they cause a cough syndrome in a person, after which they enter the oral cavity. When a person swallows saliva, the larvae safely enter the gastric tract, and then to the intestinal, where they turn into sexually mature individuals and become reproductive.

Signs of roundworm infection

The vital activity of helminths affects general health infected person. Feeding at the expense of the main host and affecting the walls of the intestinal mucosa, roundworms cause the following symptoms in humans:

• bad feeling;
• increased irritability;
• frequent abdominal pain;
• nausea;
• increased appetite;
• irregular or frequent loose stools;
• sleep disturbance.

Roundworms destroy human immunity

Often roundworms become the culprits of frequent colds, as they contribute to a decrease in the body’s protective functions.

The danger of helminthic infestation

Roundworms not only lead to a decrease in immunity, but also threaten the emergence of serious illnesses. Poisoning the body from the inside, they cause intoxication in humans. First of all, the digestive system suffers, which malfunctions. A person may experience dyspepsia, as well as irritable bowel syndrome.

The consequences of ascariasis can be very serious

Larvae that enter the brain cause terrible headaches in humans and can also provoke encephalopathy. If not diagnosed in a timely manner, this condition can lead to death.

When larvae settle in the myocardium, a person develops ischemic disease leading to myocardial infarction.

How to prevent infection?

The main preventive rule in preventing helminth infestation is washing and processing of agricultural food products plant origin. Hand hygiene also plays an important role. Before each use of food, they should be washed thoroughly with soap.

Doctors advise taking anthelmintic tablets as a preventive measure.

Question 1. Describe the structural features of roundworm. What is cuticle? What is its significance?

The digestive system begins with the mouth opening, surrounded by 3 lips (ridges). Semi-digested food by the host first enters the short pharynx, then into the midgut, where it is finally digested and absorbed. The midgut passes into the hindgut, ending in the anus.

Cuticle (from Latin cuticula - skin), in invertebrates - a derivative of cells of a single-layer integumentary epithelium. Performs mainly protective and support functions.

Question 2. What is the role of the body cavity in the roundworm?

The body cavity is the space between the internal organs and the skin-muscular sac, which is filled with cavity fluid. The cavity provides free placement of internal organs. The cavity fluid, under pressure above atmospheric pressure, gives elasticity to the body of the roundworm and performs the function of a hydroskeleton, and also transfers nutrients and waste products (transport function).

Question 3. How does it work? nervous system nematodes?

The nervous system is formed by the peripharyngeal nerve ring surrounding the anterior part of the esophagus. Several short branches extend forward from the ring; Six trunks are directed back, and two of them, passing along the median dorsal and abdominal lines, are more powerful than the others. Both main nerve trunks are connected to each other by numerous jumpers, which look like thin half-rings encircling the body.

Question 4. What departments make up digestive system roundworms? What do you think is the biological significance emergence hindgut and anus?

The digestive system is represented by a straight tube starting from the mouth and ending at the anus. It consists of three sections: anterior, middle and posterior.

Appearance posterior section intestines and anus ensures the movement of food in one direction and its better absorption

Question 5. Describe the development of roundworm. Which physical factors environment determine the development of the larvae in the environment?

Male and female roundworms live in the human intestines for about a year. After fertilization, the female begins to lay approximately 250 thousand eggs every day. Together with feces they enter the external environment(most often into the soil). If there is oxygen in the environment, a larva develops in the egg within 3-4 weeks, and the egg becomes infectious to humans. Eggs can enter a person's mouth with unwashed vegetables and fruits, through dirty hands. A larva emerges from the egg in the intestine. For further development, it needs an oxygen environment. Therefore, the larva breaks through the intestinal villi and penetrates into blood vessels. Then it passes through the bloodstream into the liver, heart, lungs, and from them it rises through the trachea into the pharynx, from which it is swallowed and again enters the intestines. Such complex and lengthy (about two weeks) movements in the human body are necessary for the larva to grow and develop. Once again in the intestine, the grown larva turns into an adult.

Question 6. How can you become infected with roundworms? What is the geography of distribution of ascariasis?

Ascariasis is one of the most common diseases caused by helminths. This is explained by the fact that roundworm eggs, leaving the human intestines with feces, develop in the soil of the garden, vegetable garden, yard, i.e., in places visited by humans. Eggs retain the ability to develop further for up to 5 years or more. Therefore, in the absence of sewerage and hygiene skills, a person can easily become infected with ascariasis.

Question 7. What hygiene measures must be observed to prevent ascariasis? Why?

It is necessary to observe the rules of personal hygiene: clean hands, pure water, cleanly washed and well-cooked products. Do not eat unwashed fruits and vegetables. After playing with pets, be sure to wash your hands.

According to statistics, every fourth inhabitant of our planet suffers from ascariasis. The disease occurs in both children and adults. It can be difficult to detect roundworms due to their movement up the intestines. Ovohelminthoscopy is used as a diagnosis to detect worm eggs in the feces.

What is human roundworm?

Taking a magnifying glass in your hands, it is possible to examine the mouth opening of the worm.

All nematode worms have a mouth surrounded by three lips. In the female, the tubes of the reproductive system can be seen through the thin skin. The live worm is very active.

The body of the worm is narrowed at the anterior and posterior ends. A cross section shows that the body is round. The skin consists of three layers. The first layer is the cuticle. The second is a layer of epithelial cells. The third layer consists of muscles. All these three layers form the walls of the body or, in other words, a skin-muscle sac. This skin-muscular structure of the body allows the roundworm to move actively.

Internal structure of roundworm

Roundworm organ systems

Let's look at the main organ systems of the worm, which have their own characteristics. The digestive and reproductive systems are located inside the body.

Reproduction and development of human roundworm

Ascaris is a representative of geohelminths. In order for a larva to become a worm, it needs to get into the soil and then into the host. Roundworms are dioecious worms. The female's reproductive system is extremely productive. It produces 200 thousand eggs per day. She has two ovaries and two uteruses. The male individual has a long filamentous testis. After mating, he dies.

Helminth eggs enter the soil along with feces. When a fertilized egg enters the ground, it goes through several stages of development. It is surrounded by several layers of protection. The egg matures in the soil. The temperature range suitable for this is 15-30 C. Most often, eggs are found on unwashed vegetables and plants. Optimal humidity is not lower than 8%.

Unlike an adult worm, the larva breathes oxygen. Thus, with dirty hands, unprocessed vegetables and plants, as well as through unboiled water, the larva enters the human intestine. Gastric juice or hydrochloric acid destroy the protective shell of the larva, it begins to develop and migrate through organ systems. At this stage, the larva needs oxygen from the lungs in order to become a mature worm. And she finds him.

With its sharp end it “drills” into the walls intestinal epithelium and enters the blood vessels.

This is how the roundworm’s migration path begins through the human body to the lungs. With the bloodstream, it enters the chambers of the heart and reaches the human respiratory system. Already a roundworm larva in the human lungs. “Traveling” through the capillaries, the larvae reach the alveoli and stop there for two weeks. From there they enter the pharynx and move with saliva to the stomach. Finally, the larva enters the small intestine and lives there for about a year if left untreated. The process of emergence of an adult worm takes 2-3 weeks.

What harm does roundworm cause to the host's organs?

Follow the rules of personal hygiene, do not be lazy in handling food and boiling water; such rules will help avoid infection with helminths, in particular ascariasis.

Figure: Human roundworm (male below)

Skin-muscle sac of human roundworm

The body of the roundworm is covered on the outside with a dense multilayer shell, under which there is a layer of muscles fused with it. These muscles are only longitudinal, so the roundworm can bend its body, but is not able to extend or shorten it.

Body cavity of a human roundworm

Figure: dissected human roundworm

Under the skin-muscle sac there is a body cavity. It does not have its own walls, that is, it is simply a space filled with liquid in which the digestive and reproductive organs are located. The liquid in the body cavity is under pressure, so the body of the roundworm is dense, constantly maintaining its shape. In addition, this liquid serves as an intermediary in the distribution of nutrients and in the removal of unnecessary processed substances.

Digestive organs of the human roundworm.

At the front end of the roundworm's body there is a mouth surrounded by three lips. From the mouth, through a muscular pharynx, which sucks food, food passes into the intestines - a thin straight tube. Undigested food remains are removed through anal, or anus , located at the posterior end of the roundworm's body.

Reproduction and development of the human roundworm

Roundworms are dioecious. The female has two ovaries, the males have one testis in the form of long thin convoluted tubes. The roundworm is extremely prolific: the female lays hundreds of thousands (up to 200,000) eggs every day, covered with a very dense shell. Eggs from the human intestine fall into the soil, where sufficient moisture and air access contribute to their development. After 2-3 weeks, larvae develop inside the eggs.
Eggs with larvae, together with poorly washed vegetables or with insufficiently clean hands, can get into a person’s mouth, and from there into the intestines. Here the larvae emerge from the eggs and burrow into the intestinal walls, and from there they enter the blood vessels. Together with the blood flow, they are carried into the lungs. Here the larvae penetrate through the walls of the alveoli (pulmonary vesicles) into the bronchi, trachea and oral cavity. Then, with phlegm or saliva, they return to the intestines, where they grow into adult worms. This journey of larvae through the human body lasts 1-2 weeks.

Harm of human roundworm

Although roundworms do not feed on human blood or intestinal cells, they poison the body with toxic secretions, causing intestinal disorders and headaches. When larvae drill through the walls of the lung, they can cause pulmonary diseases. The main control measures are prevention and compliance with hygiene rules. If you become ill, you should consult a doctor.

What do roundworms look like? For human roundworms, their characteristics appearance is this: it is a worm of a dirty, grayish-white color. Females are different from males. The length of the female roundworm is up to 45 cm, males are usually shorter, up to 25 cm, with a slightly curved end of the body, which is inserted into the female’s vagina during fertilization. This is how they reproduce. Fertilized eggs finally mature in the vagina; they are small in size and not visible to the naked eye.

At the same time, the life cycle human roundworm passes into small intestine, without exiting, unlike pinworms. Absorbing useful material, it also actively releases products of its own vital activity, poisoning the human body with toxins.

Development in the human body

With the bloodstream, immature individuals can enter both the liver and the heart, but do not stay there, heading to the lungs. Roundworm worms develop in the lungs, causing symptoms consistent with bronchitis in a person.

Individual on adult stage remains to live in the small intestine, causing symptoms of gastrointestinal disease. Thus, when asking where roundworms live, one cannot exclude the main human organs and systems.

Migration stage of larval development

In the first stage, roundworm larvae emerge from the swallowed egg in a very short time. a short time. Swallowed egg unpacks under the influence gastric juice and intestinal digestive enzymes. All protective membranes dissolve and enter the intestine at the migration stage. For further development, they need to get into the lungs. To begin with, they penetrate the intestinal walls, and only then enter the bloodstream of the veins.

Migration of larvae through various organs

The next stage is the delivery of immature individuals to the lungs, where the roundworm develops until maturity. Life cycle roundworm suggests that this process takes from a week to two, but first some of the roundworms in the blood enter the liver and even the heart. The structural features of the larvae are such that the most favorable conditions for their further development are the human lungs, there is enough oxygen, optimal humidity and temperature.

The general laws of the migration cycle may be violated: sometimes the larvae settle in the liver, heart muscle, and brain. Roundworm worms in the liver cause destruction of hepatocytes and obstructive jaundice, with damage to the brain - disorders similar to signs of brain tumors, in the heart - signs of ischemia and other pathologies.

Re-ingestion of larvae when coughing

During the period of maturation in the lungs, the larvae cause symptoms of pulmonary diseases, which are accompanied by a cough with sputum, sometimes streaked with blood, elevated temperature, general intoxication of the body. On radiographic images at this moment, small pinpoint petrification and compactions can be detected.

In the digestive system, the larvae grow into adult, sexually mature individuals, which begin to intensively feed and reproduce, releasing toxins into the host’s body. All future life roundworms in the intestines - release of toxins and numerous eggs.

What do roundworms eat?

In the small intestine, ideal conditions are created for the life of roundworms: food is already fermented, decomposed to the desired state, no effort is required to chew and digest it. A semi-liquid, mushy mass is the ideal menu. They absorb nutrients, positioned with the head end towards the incoming food masses, and bring them to the desired state in their own digestive system.

Morphological characteristics

The roundworm is a long worm with pointed ends, grayish-white in color. At one end there is a mouth, which leads into a fairly developed digestive system, next to it there are excretory pores or openings. Human roundworms have a three-layered shell, or cuticle, that replaces the exoskeleton and protects internal organs from damage and compression.

For the eggs released by the female to fully mature, the roundworm development cycle is required under certain conditions. Since the habitat of adults is the intestines, eggs are released in the feces of a sick person. Once in the ground, after a while a full-fledged larva develops in the egg, which can cause infection in the human body. The optimal temperature for the development of larvae from an egg is from +20 to +30 degrees.

Ascaris eggs isolated from an infected organism do not lose their viability for a long time. They survive in temperatures down to -25 degrees and can survive for up to 12 years. The only way to destroy an roundworm egg is by heating, direct sun rays, ether, kerosene, gasoline.

Exclusively with unwashed hands, with dirty vegetables or fruits. A cat or dog can also bring a “gift” on its paws or fur. Dust, insects, unboiled water are all potential risk factors.

The life cycle of an roundworm that has entered the body continues with unpacking. Shedding the membrane, it penetrates the intestinal wall, and migrates further through the bloodstream until it reaches the lungs.

Laying eggs

Massive release of eggs begins from the moment the individuals enter the intestines. The female releases fertilized eggs, which are then released into the external environment with the contents of the intestine. They are perfectly protected from adverse conditions environment: the larva located inside the egg is enclosed in several dense shells. It can only be destroyed with fat-soluble agents or ultraviolet irradiation.

Egg development

In order to develop further, to the invasive stage, in which they can already be transmitted, the egg must mature. Favorable conditions considered warm, moist soil with constant temperature environment. At temperatures from + 20 degrees to + 25 degrees, the maturation of the invasive stage of the larva occurs in 2-3 weeks.

Ripening at subzero temperatures takes much longer, up to 3 months. Frost down to -25 degrees delays development, but does not kill the larva.

Larval stages in soil

A ripe egg of a human roundworm will wait in the wings to get into human body. A larva ready for invasion cannot unpack on its own; it requires exposure to enzymes from the gastric juice and rectum. Therefore, the larvae do not emerge into the soil, but remain contagious. long time inside the white shell of the egg. The canonical description of the egg at this moment: a larva, ready to contact the host. After full maturation, the larva waits for its host sometimes for 10-12 years.

The structure of roundworm

Digestive system

• front;
• average;
• lower sections.

Body cavity

Gas exchange and metabolism

How does the roundworm breathe? Adults do not need to breathe: they do not have a respiratory system in the sense to which we are accustomed. Instead, anaerobic gas exchange throughout the body is established. Breathing for roundworm is an atavism.

Excretory system

The system for removing toxins and unnecessary substances functions thanks to two tubes, the exits of which are located next to the mouth. Excretory system Roundworm performs the function of kidneys in the human body.

Nervous system

The roundworm has a developed nervous system: two trunks extend from the peripharyngeal nerve ring. One is located along the belly, the other along the back.

Sense organs