Does roundworm have a digestive system? Structural features of human roundworm. Treatment and prevention of invasion of human roundworm

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

Ascariasis affects many people

building outside

Under the anti-enzymatic 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. Due to this structural feature of the roundworm, it is able to move through the intestines.

Ascaris - the structure of the helminth

At one end of the body, the worm has a mouth cavity, similar to a pump, which swallows food, after which it enters the intestines.

Building from the inside

In roundworm, the structural features of the body from the inside are as follows:

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

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

Eggs only become invasive when exposed to favorable conditions

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

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

Once in the lungs, the larvae do not stay there for a long period, having passed a certain development cycle. After that, they cause a cough syndrome in a person, after which they enter the oral cavity along with sputum. When saliva is swallowed by a person, the larvae safely enter the gastrointestinal tract, and then into the intestinal tract, where they turn into sexually mature individuals and become reproductive.

Signs of Ascaris Infection

The vital activity of helminths is reflected in the general well-being of an infected person. Eating 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.

Ascaris destroy human immunity

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

Danger of worm infestation

Roundworms lead not only to a decrease in immunity, but also threaten the occurrence of serious diseases. Poisoning the body from the inside, they cause intoxication in a person. First of all, the digestive system suffers, which fails. 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. In the absence of timely diagnosis, this condition threatens a person with a fatal outcome.

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

How to prevent infection?

The main preventive rule in the prevention of helminth infestation is the washing and processing of agricultural food of plant origin. Hand hygiene is also important. They should be thoroughly washed with soap and water before each meal.

Doctors advise taking anthelmintic pills as a preventive measure

According to statistics, every fourth inhabitant of our planet suffers from ascariasis. The disease occurs in both children and adults. Detecting roundworm is not so easy, because of its movement up the intestines. As a diagnosis, ovohelminthoscopy is used to detect worm eggs in the feces.

What is the human roundworm

Picking up a magnifying glass, 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.

From the anterior and posterior ends, the body of the worm is narrowed. When cross-sectioned, it is seen that the body is round. The skin is made up of three layers. The first layer is the cuticle. The second is a layer of epithelial cells. The third layer is made up of muscles. All these three layers form the walls of the body or, in other words, the skin-muscular sac. Such a skin-muscular structure of the body allows the roundworm to actively move.

The internal structure of roundworm

Ascaris organ systems

Consider the main organ systems of the worm, which have their own characteristics. Inside the body are the digestive and reproductive systems.

Reproduction and development of human roundworm

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

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

Unlike the adult worm, the larva breathes oxygen. So 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 the organ systems. At this stage, the larva needs oxygen from the lungs in order to become a sexually mature worm. And she finds him.

With its sharp end, it “perforates” the walls of the intestinal epithelium and enters the blood vessels.

Thus begins the migration path of roundworm through the human body to the lungs. With the bloodstream, it enters the chambers of the heart and reaches the human respiratory organs. Already a roundworm larva in the lungs of a person. "Traveling" through the capillaries, the larvae reach the alveoli and stay 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 not treated. The process of appearance of an adult worm takes 2-3 weeks.

What harm does ascaris cause to the host's organs

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

Invasion (infection) with ascaris leads to the disease - ascariasis, which is the second most common after enterobiasis (helminthiasis caused by pinworms).

The head end of the human roundworm is provided with three lips surrounding the mouth opening. In addition, the digestive system includes a long esophagus and a digestive tube with an anus at the end of the body. On the sides of the worm, longitudinal lines are clearly visible - the locations of the tubular excretory system. The nervous system of the nematode is represented by the pharyngeal ganglion, from which nerve trunks extend in all directions.

Roundworms are dioecious biological species, the structure of which has both internal and external distinctive features in female and male individuals.

Human roundworm females are larger than males - their length reaches 40 cm, and their diameter is 6 mm. The body of a sexually mature female is elongated and ends in a conical point. In the anterior third of the body, there is a vulva that opens outwards and looks like an annular constriction. The anal opening is localized on the ventral part of the body closer to the terminal end.

The reproductive system in females is represented by paired tubes, consisting of two large uteruses, thin oviducts and filiform ovaries (right and left). Both uterus communicate with the vagina, which opens outward in the form of a genital opening on the abdominal surface. The maturation and development of human roundworm eggs occurs in the ovaries, the structural feature of which is a special core - rachis (rachis). Around the rachis germinal cells of ascaris ripen - oogonia, which, after fertilization by the spermatozoa of the male, reach the uterus and turn into eggs there.

The structure of the body of male roundworms

Male roundworms are smaller in size - up to 25 cm long and up to 4 mm in diameter. The end part of the body of males in the natural state is spirally bent to the ventral side. Closer to the tail, on the ventral side of the body, there is an anus and tactile organs - preanal and postanal papillae.

The reproductive system of male roundworms, unlike females, is represented by an unpaired tube, consisting of a filiform testis, a vas deferens larger in diameter, and an ejaculatory canal that opens into the cloaca (hindgut). Spicules - paired organs for fertilization of females - reach a size of 2 mm.

Features of the structure and development of human roundworm eggs

Due to high fecundity, up to 25 million eggs can be present in the body of the female at the same time, which she lays in batches of 200-250 thousand per day.

Together with the host's excrement, fertilized and unfertilized helminth eggs are excreted. To achieve an invasive (mature) state, they must enter the soil, and stay there at a certain temperature and humidity from one and a half to two weeks.

Fertilized eggs measuring 50 - 65 x 45 - 50 microns have an ovoid or spherical shape and are covered on top with several layers of the shell: tuberous outer, and smooth inner. This protective coating provides resistance to external influences and preservation of the viability of the embryo for a long period (up to 5 years or more!). Inside each of the helminth eggs contains a spherical fine-grained blastomere.

The outer protein shell of the Ascaris egg, when it leaves the body of the female in the human intestine, is stained with faeces in brown, making the eggs opaque. The inner shell contains several lipid layers and is designed to protect the developing roundworm embryo from destruction by chemical factors. Fat-dissolving substances are fatal to them - gasoline, hot sunlight, alcohols or ethers.

The role of larvae in the roundworm development cycle

The larvae are formed inside the eggs within 10 - 40 days in the presence of oxygen and in a humid environment. Outwardly, they resemble adults, but are significantly inferior to them in size. Their growth and development is accompanied by repeated molts with a change in the cuticle. When maturing, the larva becomes mobile and acquires an invasive ability (the ability to further develop in the host body).

Ingestion of ascaris eggs by a person occurs when food or water contaminated with soil is consumed, however, the development of helminthic invasion is possible only if mature eggs enter the body of the host. In the intestine, roundworm eggs release larvae that can penetrate the intestinal wall into the surrounding blood capillaries.

Further, with the blood flow, the larvae freely migrate throughout the body, settling in the liver, lungs, brain and feeding on serum and blood cells. In typical cases, the larvae that have entered the lungs actively penetrate from the vessels into the alveoli, and then move with the help of the ciliated epithelium to the oropharynx, where they are reflexively swallowed along with sputum.

This type of animal combines spindle-shaped worms: their body is round in cross section, pointed at both ends and not divided into segments. Their length is usually a few millimeters, rarely reaches a meter. They all look alike. This is one of the most successful types in the animal kingdom!

Roundworms are a group of worms that have an elongated, non-segmented, round body in cross section, a primary cavity filled with liquid (in which internal organs are located) and not connected with the external environment. In the body they have a through intestinal tube, which ends with an anus.

External structure

The body of roundworms is gradually narrowed towards the anterior and posterior ends, almost round in cross section, non-segmented. Outside, the body is covered with a cuticle, under it lies a layer of epithelial cells. Below are the muscles - four longitudinal single-layer tapes. This structure allows roundworms to crawl, bending the body. The cuticle, epithelial cells, and muscles form the skin-muscle sac (body walls). Between it and the intestine is the primary body cavity. It is filled with liquid, which, due to pressure, maintains a constant shape of the body, promotes the distribution of nutrients throughout the body of the animal, and the movement of decay products to the excretory organs.

These animals were the first to learn to burrow into the ground or other food-rich substrate, such as plant tissue. So they have found not only a new habitat with its food reserves, but also shelter from predators - large ciliary worms.

With such a life, the mouth of roundworms is located strictly at the front end of the body. The pressure inside the hydroskeleton makes it difficult to swallow food. Therefore, their muscular pharynx acts like a pump with valves: it sucks in food, and then pushes it into the intestine by force.

The external similarity of roundworms is due to the fact that, despite their wide distribution, they all live in a similar environment - in a nutrient substrate. In the bottom silt and soil, this "soup" is made up of the remains of organisms, along with bacteria and protozoa, and in plants and animals - the nutrients of their bodies. The main difficulty in these conditions is caustic chemicals. But the cuticle reliably protects from them. Some species are able to survive even in vinegar.

The internal structure of the body of a roundworm

Digestive system

The mouth opening is located at the anterior end of the body and is surrounded by lips. The anterior part of the intestine, the pharynx, has dense muscular walls. Free-living nematodes feed on bacteria, algae, organic debris - detritus. Some have cuticle outgrowths in the pharynx - peculiar teeth. With the help of their nematodes pierce the integuments of animals and plants.

body cavity

Previously, nutrients were distributed throughout the body by a branched intestine. Now that the gut has turned into a straight tube, this function has been taken over by the body cavity - the fluid-filled space between the skin-muscle sac and the gut.

The liquid is not cells, it would leak out if it were not packed in an impermeable elastic cover. This cover is formed by a layer of ectoderm cells and is covered with a cuticle - a strong film. The cuticle not only protects against mechanical damage and toxic substances, but also restrains the pressure of the cavity fluid.

As a result, the body cavity, surrounded by the cuticle and filled with fluid, acquires the elasticity of an inflated ball and forms a hydroskeleton. It is the hydroskeleton that gives the roundworms their characteristic shape and serves as a support for the muscles. Their muscles are only longitudinal. They are located inside the cavity, along the walls of the body. Contracting alternately either the dorsal or abdominal muscles, the worm bends and moves forward, lying on one side.

Gas exchange and metabolism

excretory system

The excretory system consists of two lateral blindly closed canals. They open outward through an excretory opening on the ventral side of the anterior part of the body. The walls of the channels are formed by one or several very long cells (their length can reach 40 cm). harmful substances formed in the body enter the cavity fluid, then into the channels of the excretory system and are excreted.

Nervous system

The nervous system of nematodes is represented by longitudinal nerve trunks connected by ring bridges. Nerves branch off from them to the muscles and sense organs.

sense organs

reproduction

Nematodes are dioecious animals. The genital organs are tube-shaped: in females they are paired, in males they are unpaired. Females have paired ovaries and oviducts, one uterus and a genital opening that opens on the ventral side of the body.

The male has one filiform testis, gradually turning into a larger spermatic duct. It flows into the hindgut just before the anus. The male has retractable cuticular needles, with the help of which he injects spermatozoa into the female's genital opening.

Every day, one female of human roundworm is capable of producing 200,000 eggs. The eggs are covered with a dense shell that protects them from the effects of adverse factors (drying, etc.). Cleavage of the egg and development of the larva lasts about a month and can only occur in a humid environment with sufficient oxygen.

Development cycle of human roundworm

Human infection occurs when eggs with larvae are ingested with contaminated water or food. Eggs can be found on poorly washed berries (especially strawberries) or vegetables from areas where human excrement is used to fertilize.

In the human intestine, the egg shell is destroyed, the emerging larvae pierce the intestinal wall, enter the bloodstream and reach the heart, and then through the pulmonary artery to the lungs. In the lungs, the larvae molt twice, penetrate into the alveoli, pass through the trachea into the pharynx, and from here, together with sputum and saliva, enter the intestine for the second time. Only after such migration do the larvae reach their sexually mature form in the small intestines. The entire development cycle occurs in one host.

An adult individual does not have organs of attachment to the human intestine and is kept in it due to constant movement, which has a direction towards the intake of food masses. The body of the worm is not divided into segments, it has a rounded shape.

The main aromorphoses of the type of roundworms, which include roundworms, are as follows:

The presence of the posterior intestine, the presence of the anus.

The primary body cavity is a pseudo-goal.

The upper epithelial layer of roundworm is formed by a dense, inextensible cuticle, which has a flexible structure. Below it is the hypodermis, which performs the function of a kind of skeleton of the worm, and also contributes to its protection from mechanical injuries, from human digestive enzymes and from toxic effects. It is in the hypodermis that metabolic processes take place. Under the hypodermis are the muscular sac. The body of the worm is filled with fluid, which gives it elasticity.

Appearance of roundworm

Adults may be whitish yellow or whitish pink. The shape of their body is spindle-shaped, pointed on both sides.

Females can reach 40 cm in length, males are almost half as long, their maximum body length is 25 cm. The body of the female is straight, while the rear end of the male has a characteristic bend towards the abdomen.

Digestive system of roundworm

Around the mouth of the worm are sensitive tubercles, which are called papillomas. There are three of these tubercles. This structure of the oral apparatus allows the worms to swallow large volumes of semi-liquid food, as they feed on the contents of the human intestine.

The digestive system of roundworms is represented by the esophagus and tubular intestine. It is not completely reduced in these worms, so food is finally digested in their ectodermal hindgut. Processed food worms are removed through the anus.

Roundworms reproduce sexually. Their genitals are represented by convoluted filamentous tubes. Roundworm individuals are dioecious.

The reproductive system of the female is represented by two ovaries with oviducts, 2 uterus and 1 vagina. Every day, females can lay 200-240 thousand eggs, which, together with feces, are brought out. The eggs themselves are covered with a dense protective shell, consisting of five layers. It protects them from damage and provides food for the larvae.

Males have reproductive organs and phagocytic cells. They are located at the posterior end of the elongated body. It is in phagocytic cells that the accumulation of insoluble metabolic products occurs. The male has one testis, which passes into the vas deferens and into the hindgut.

Ascaris nervous system

The nervous system of the worms is formed by a ganglion, which has an annular shape. Nerve endings branch off from this ring and penetrate the body of the roundworm. The tactile cells of the worms are located in the pits and tubercles. They provide chemosensitivity of parasites and make it possible to find the most favorable places for them in the intestine.