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Ascaris — Life cycle and the structure of the human roundworm

Among a wide variety of helminths, an important social importance of the human Ascaris, or Ascaris lumbricoides.

Askarida — ZHiznennyj cikl i stroenie chelovecheskoj askaridy

The internal structure of the Ascaris gives her the opportunity to implement active life simultaneously in different systems — digestive, respiratory, Central nervous, circulatory.

This is a fairly common large worms, the penetration of which into the human body occurs ascariasis. This bot on the planet suffers every 4 people. Often occurs in children, rarely in adults. The main habitat is the human digestive system.

The parasite belongs to the species of round worms, which is ideally suited to living in the internal environment of a person because of the uniqueness of their morphology, adaptation, physiology.

Unlike other representatives, such as beef tapeworm, they have no organs of attachment, so they have to move themselves towards the food. This feature and leads them to living mainly in the small intestine.

External sign

Female worm in Mature age reach a length of about 40 cm, the male is much smaller, varying from 15 to 25 cm of the Male representatives have morphological differences from the female members of the presence of the folded back end to the abdominal wall.

Body shape fusiform nematodes are elongated. Colouring — pale lager, light pink, translucent, sometimes with a grey tint. Both Mature individuals have three lips around the mouth opening. Through the thin wall of the female are visible branched sex tube.

Askarida — ZHiznennyj cikl i stroenie chelovecheskoj askaridy

The adult worm is movable, the behavior is active. The movement is only in the opposite direction from the Central axis of the movement directions, zigzag. This is due to lack of musculature in the transverse direction. The fibers of the muscles along the torso.

With the reduction of one of the longitudinal muscles, the worm wriggles in the appropriate direction.

Morphology and physiology

The structure of the worm roundworm has a number of features characteristic for nematodes and round worms:

  1. razdelyaet organisms,
  2. the presence of smooth striated muscle,
  3. multi-layered cuticle,
  4. the absence of a secondary cavity and by the presence of primary,
  5. formed by the nervous system in the form of nerve trunks extending from the pharyngeal ring,
  6. atrophied organs of respiration and circulation.

The cavity of the body

On both ends of the worm front, rear narrows. On the side of the body has a round profile, its cavity is represented by the gap between the internal organs and the wall. The cavity is filled with a colorless liquid.

Askarida — ZHiznennyj cikl i stroenie chelovecheskoj askaridy

The inner epithelial layer of the primary cavity is absent, which is a characteristic contrast to the secondary. The digestive and sexual organs located in the inner enclosed space.

Functions cover

  • the reference, being the external skeleton that wraps the internal organs and fluids,
  • the transport of nutrients from the digestive system in epithelial, muscle, reproductive,
  • the transfer of metabolic products to the excretory organs.

Performing the function of the water skeleton, the body of the worm protects it from external influences, poisonous substances, digestion by digestive enzymes of the gastrointestinal tract of the host and carries on metabolism, and replaces the hematopoietic system, the presence of more developed organisms.

Muscles and epithelial covering

The epithelium of the nematode forms an outside layer of flexible cuticle, also called the hypodermis consisting of 10 layers. Layered hypodermis produces a composition which does not digest the intestinal helminth enzymes. The cut of the cuticle of the roundworm is thin-walled shell that completely covers the parasite.

Hypodermis is simultaneously both flexible and durable properties, without disturbing, the most active move. Four roller cuticle located in the lateral, dorsal and ventral parts. In the rollers is excretory organs in the form of longitudinal channels. The channels represented by the grooves between the muscular frame and hypodermis.

Muscular layerformed of longitudinal fibers. The shell cavity is a layer of epithelial cells and muscular fibres, thus forming a skin — muscle bag or the wall of the body.

This feature gives you the opportunity to travel extensively in the intestine, but because of the structure of the muscular frame gives him a straight line to move like others in the roundworms.

Digestion

Structures of the digestive system represented by an empty tube forming the intestines with the basic medium, as well as the front and rear sections. The first two Department of ectodermal origin, the rear is formed from the endoderm.

The gut is represented by a closed and very winding cavity located in the Central part, passing through all of the parasite. The absorption of nutritional substances is carried out in the middle section of the intestine.

Askarida — ZHiznennyj cikl i stroenie chelovecheskoj askaridy
Ascaris injure the mucous membrane of the intestine of man, poisoning his body with toxic substances (products of metabolism)

The relatively primitive structure of digestion is due to the constant presence of the worm in the surrounding environment of the food mass, which is processed for absorption with enzymes of the intestine of the host.

Parasitic species suck them into your intestine through the mouth with three lips with a thick muscular pharynx.

Nervous system

Has a fairly simple structure. Ganglion formed by one node, in the form of a peripharyngeal ring, placed in the front part of the parasite. From pharyngeal ring along the waste six nerve dorsal and ventral bundles. They are responsible for the sensitivity and carry out the organization of muscle control from the nervous plexus in the movement.

Askarida — ZHiznennyj cikl i stroenie chelovecheskoj askaridy

Receptors as they do not exist, there are tactile bumps in the papillomas are primarily located around the mouth.

Living in the digestive environment of the intestine that lacks any physical stimuli, and natural enemies, other sensitive education atrophied.

Respiratory system

The habitat of the worm is anaerobic, not requiring the presence of oxygen, therefore there is no need for the respiratory system — the lungs, available to the more developed facilities. This natural adaptation of the human roundworm is associated with the absence of air in the human intestine.

The metabolism is provided by cellular respiration. It is carried out by glycolysis of glycogen in the cytoplasm of cells. This anaerobic type occurring without participation of oxygen, characteristic of anaerobic organisms.

Excretory system

Liquid products are removed through the excretory opening in the anterior end of the parasite. The removal of the digestive tract is via a private located in the back of the anal passage.

Reproductive system

Nematodes are dioecious individual. Reproductive organs are in the form of hollow convoluted tubules. Males present a testis is going on in the VAS deferens, exiting at the rear intestine. After mating occurs the death of the male.

Askarida — ZHiznennyj cikl i stroenie chelovecheskoj askaridy
Roundworms reproduce only sexually

The female representatives have two ovaries, extending the tubes and passing into the uterus. Next they form an unpaired vagina, which opens a hole in the ventral side. The female produces eggs released into the environment.

Human Ascaris is a dangerous representative of its class, which is well adapted to existence in the inner human environment.

Morphological, physiological features of the structure allow to interfere with his digestion by enzymes of the intestine of the host, actively use nutrients from the environment, to carry out anaerobic metabolism through glycolysis, independent