Roundworms And Their Structure: Types And Characteristics

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Roundworms And Their Structure: Types And Characteristics
Roundworms And Their Structure: Types And Characteristics

Video: Roundworms And Their Structure: Types And Characteristics

Отличия серверных жестких дисков от десктопных
Video: Roundworms 2023, February
Anonim
  • 1 Features of the structure
  • 2 Ascaris
  • 3 Pinworms
  • 4 Vlasoglav
  • 5 Trichinella
  • 6 Hookworm

Science knows more than 500 thousand varieties of roundworms. They live in soil, fresh and sea water. Some of them lead a parasitic existence. This type of worm is dioecious. These parasites have a limited number of cells in the body, so their capabilities in terms of regeneration and growth are rather limited. These parasites reproduce only sexually. All these worms can be divided into biohelminths, which require an intermediate host, and geohelminths, whose larvae and eggs develop in the soil. In our article, the type will be described in detail - roundworms.

Structural features

type roundworms
type roundworms

All parasites of the human body are divided into classes. The roundworm type is a class of nematode. Free-living and parasitic nematodes are known to science. The roundworm has the following structural features:

  • there is a primary cavity in the body;
  • the worm has an anus and a back of the intestine;
  • type annelids are dioecious individuals.

The main signs of roundworms:

  1. They have an unsegmented body, rounded in cross section. Its surface is three-layered and consists of meso-, endo- and ectoderm. The worm has a skin-muscle sac.
  2. All types of annelids have a pseudo-goal - this is the primary cavity of the body, filled with liquid. It gives the body additional elasticity and acts as a hydroskeleton. This liquid is also responsible for metabolic processes. It is here that all the internal organs are located that form the digestive, nervous, excretory, muscular and reproductive systems.
  3. The structure of roundworms is such that they have no respiratory and circulatory systems.
  4. The peculiarities of roundworms are also in the fact that their digestive system is represented by a through tube starting with the mouth opening. The mouth is surrounded by cuticular lips. At the end of the digestive tube is the anus. The entire tube is divided into three sections. Pinworms have a special enlargement of the esophagus called the bulbus.
  5. As for the nervous system, it consists of the periopharyngeal ring, cerebral ganglia and nerve trunks (abdominal, dorsal, and two lateral trunks). The most developed abdominal and dorsal rods. They are connected with special jumpers.
  6. No matter how many species of round worms, all have poorly developed sense organs. As a rule, they are composed of tactile bumps and special organs of chemical sensation.
  7. The excretory system of the roundworm consists of a small number of excretory phagocytic cells. They accumulate metabolic products and foreign substances that enter the body cavity.
  8. Nematodes are roundworms that have a tubular structure of the genitals. The number of female genital organs, as a rule, is paired. The male, on the other hand, has unpaired genitals. His reproductive apparatus consists of a testis and a vas deferens, which passes into the ejaculatory canal and opens into the back of the intestine. The body structure of the female is somewhat different. Her reproductive apparatus consists of paired ovaries, from which there are two tubular oviducts and a paired uterus. It unites into a common vagina.

We have listed the common signs that are typical for representatives of the roundworm type. However, the external structure of individual individuals may differ slightly. So, if we describe the group of roundworms, the representatives of this class are as follows:

  • roundworm;
  • whipworm;
  • pinworms;
  • hookworm;
  • trichinella;
  • guinea worm.

If we consider the type of roundworms, the general characteristic was described above by us. Now it's time to list the features and lifestyle of the most common parasites belonging to this class.

Ascaris

rather large helminth
rather large helminth

This is a rather large helminth, the female of which can grow up to 40 cm, the males - about 20 centimeters. Ascaris has a cylindrical body narrowed towards the ends. The body of the male from the posterior end is twisted in a spiral towards the abdomen.

The eggs of the parasite reach 60 microns in size. They are oval in shape, yellowish-brown in color, with a bumpy surface. The eggs are protected from external influences by a multilayered thick shell.

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These roundworms are human parasites from the class of geohelminths, that is, they need to get into the soil to ripen the eggs. There they can be with human feces. The egg ripens within a couple of weeks at high humidity, temperatures in the range of 24-25 degrees and the presence of oxygen. They are resistant to negative environmental factors and retain their invasiveness for six or more years.

The life cycle of ascaris in the human body is as follows:

  1. After the egg is in the intestine, its shell is dissolved by digestive juices, and the larva emerges from it.
  2. It enters the bloodstream through the intestinal walls. Then it migrates through the liver to the right atrium, ventricle and lungs.
  3. From there, through the pulmonary capillaries, the larva enters the bronchi and trachea, provoking a cough.
  4. During a cough, it is swallowed again and again ends up in the intestines. Here she reaches the state of a sexually mature individual, lives and reproduces up to a year.

Pinworms

rather small whitish worm
rather small whitish worm

These parasites (roundworms) become the culprit of enterobiasis. It is a rather small, whitish worm that can grow up to a centimeter in length. He has a straight slender body, pointed at the ends. The posterior end of the males is spirally twisted.

As for the eggs of the parasite, they are translucent and colorless. Their shape is asymmetrical oval. They are slightly thickened on one side. They reach 50 microns in length. As a rule, in the human body, adults live in the small intestine and feed on its contents. At night, females crawl out of the anal passage and lay eggs in the perianal folds, which causes severe itching in this place. After that, the female dies.

Since the life expectancy of a sexually mature pinworm reaches 58 days, self-healing of the patient may occur, if no re-infection has occurred. As for males, they die immediately after mating with females and leave the body naturally (with feces).

Vlasoglav

the parasite is the causative agent of trichocephalosis
the parasite is the causative agent of trichocephalosis

This parasite is the causative agent of trichocephalosis. The above characteristic of the roundworm type quite clearly describes the structure of the whipworm. The parasite lives in the cecum, as well as in the large intestine (its upper section). An adult grows up to 5 cm in length.

The anterior threadlike elongated part of the worm's body is thinner than the posterior part. The esophagus is located in it. The posterior end of the male is thickened and spirally twisted. Here is the intestines and the reproductive system. The eggs of this worm look very much like a barrel with cork-shaped lids at the ends. They are light transparent and reach 50 microns in length.

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This type of geohelminth parasitizes without migration. For the eggs to mature and become invasive, they must enter the soil with the faeces. People become infected by eating eggs with fruits, herbs and water.

Trichinella

the parasite causes trichinosis
the parasite causes trichinosis

This parasite causes trichinosis. The larvae of this helminth live in muscle tissues, and adults in the human intestine. This is a fairly small parasite. So, females grow up to 0.35 cm, as for males, they are no more than 0.16 cm long.

This worm is a biohelminth. Its life cycle is as follows:

  1. Infection occurs when eating infected meat (heat treatment does not kill helminth larvae). The parasite can inhabit both the human body and the body of animals.
  2. After swallowing, the larvae quickly reach the mature stage.
  3. Males die immediately after fertilization of females, which lay up to two thousand larvae and also die.
  4. The larvae penetrate through the intestinal walls into the lymphatic system and spread through the bloodstream through the body, settling in the muscles. The migration period lasts 14-48 days.
  5. The larvae are encapsulated in muscle fibers. In such a dense shell, they can survive for several decades.

Hookworm

the worm lives in the small intestine
the worm lives in the small intestine

Krivogolovka usually lives in warm and humid climates. It is a reddish worm-like parasite up to 10-18 mm long. It got this name because its front end is wrapped towards the back. The oral cavity has 4 chitinous teeth. Eggs are transparent, oval, slightly flattened.

The worm lives in the small intestine, where it can live for up to five years. It is referred to as geohelminths. Ankylostoma migrates in the human body like roundworms. Eggs with feces enter the external environment, where in a day larvae emerge from them, feeding on feces. After they reach the filarial stage, the larvae become infectious.

Sometimes infection occurs by the oral route, but more often the filariae penetrate the skin. From the intestine, the larvae migrate to the blood vessels and lungs. Then they rise through the bronchi into the trachea, from where, during a cough reflex, they are thrown into the mouth and swallowed. After that, they settle in the duodenum.

Krivogolovka damages the mucous membrane and feeds on human blood. The parasite secretes anticoagulants that prevent clotting. Because of this, the patient may have intestinal bleeding.

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