Features of the structure of human roundworm
Ascaris is a round parasitic worm that causes a disease in humans called ascariasis and parasitizes in the small intestine.
An adult 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 flow of food masses. The body of the worm is not divided into segments, it has a rounded shape.
The main aromorphoses of the roundworm type, which include roundworms, are as follows:
- The presence of the rear intestine, the presence of the anus
- The primary body cavity is a pseudo-goal.
- Male and female parasites.
The upper epithelial layer of the roundworm is formed by a dense, inextensible cuticle, which has a flexible structure. Under it is the hypodermis, which serves as a kind of skeleton of the worm, and also helps to protect it from mechanical injury, from human digestive enzymes and from toxic effects. It is in the hypodermis that metabolic processes take place. The muscle sac is located under the hypodermis. The body of the worm is filled with fluid, which gives it elasticity.
Content:
- Roundworm appearance
- Digestive system of roundworm
- Ascaris reproductive system
- Ascaris nervous system
Roundworm appearance
Adults may be whitish yellow or whitish pink. The shape of their body is fusiform, pointed on both sides.
Females can reach 40 cm in length, males are almost two times smaller, their maximum body length is 25 cm. The body of the female is straight, and in the male, the posterior end has a characteristic bend towards the abdomen.
Digestive system of roundworm
Around the mouth of the worm, there are sensitive bumps, which are called papillomas. There are three of these tubercles. Such a structure of the mouth apparatus allows worms to swallow large volumes of semi-liquid food, since they feed on the contents of the human intestine.
The digestive system of ascaris is represented by the esophagus and the tubular intestine. It is not completely reduced in these worms; therefore, food is finally digested in their ectodermal hind gut. The worms expel processed food through the anus.
Ascaris reproductive system
Roundworms reproduce sexually. Their genitals are represented by convoluted filiform tubes. Ascaris individuals are dioecious.
The female reproductive system 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 excreted. 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 genitals and phagocytic cells. They are located at the posterior end of the oblong 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 worms is formed by a ring-shaped ganglion. Nerve endings branch off from this ring and penetrate the body of the roundworm. The sensory cells of 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.
The respiratory system in ascaris is not developed. Oxygen is poison for these anaerobic creatures.
Article author: Mochalov Pavel Alexandrovich | d. m. n. therapist
Education: Moscow Medical Institute. IM Sechenov, specialty - "General Medicine" in 1991, in 1993 "Occupational Diseases", in 1996 "Therapy".
