Who is the main host of roundworms? Type Roundworms

• feeling of heaviness in the lower abdomen;
• nausea and vomiting;
• general malaise;
• frequent diarrhea.

• the helminth has a pale pink tint;

• female body length – 20-40 mm, male – 15-20 mm;
• Dioecious individuals reproduce sexually.

For gastrointestinal infection and ascaris penetration into the liver clinical symptoms is expressed in the following manifestations:

1. Abdominal pain, accompanied by bouts of vomiting and constant nausea.
2. Diarrhea occurs with bloody discharge in feces.
3. Pressure on the liver and bile ducts promotes the formation of obstructive jaundice.
4. Lack of appetite and uncontrolled weight loss.

The symptoms of pulmonary ascariasis are more problematic to recognize, since Clinical signs perceived as other diseases of the respiratory system, such as bronchitis, pneumonia, etc. The presence of helminths in the lungs is accompanied by the following symptoms:

• dry paroxysmal cough and chest wheezing;
• dyspnea;
• low-grade body temperature.

Undiagnosed ascariasis in the lungs leads to the development of bronchial asthma.

When roundworm penetrates the brain, a person experiences severe headaches, epileptiform seizures and convulsions occur, and there is pronounced neurosis and depression.

Important! All clinical manifestations require careful diagnostic examination and related medical effects.

• Piperazine;
• Albendazole;
• Vermox, etc.

The characteristic features of this type of organization are as follows:

1. The body is thin, cylindrical, elongated and pointed at the ends. In cross section it is round (which gives the type its name).
2. The skin-muscle bag consists of an outer multilayer cellular structure cuticles, located underneath single layer epithelium and layer longitudinal muscle fibers, thanks to the contractions of which the body can bend like a snake.
3. Body cavity —primary, filled with liquid under greater than atmospheric pressure. Cavity fluid gives the body elasticity and, thanks to this, plays the role of hydroskeleton. She also provides transportation nutrients and waste products.
4. For the first time in the animal world digestive system It is represented through a digestive tube, divided into three sections - the foregut, middle and hindgut. Anterior section begins with the oral opening leading to oral cavity and a pharynx capable of working as a pump. The pharynx is separated from the midgut by a valve. IN midgut food is digested and absorbed. The midgut is followed by the ectodermal hindgut, opening on the ventral side of the body , anus.
5. The excretory system is represented by a pair of lateral longitudinal canals, merging under the pharynx into one duct and opening on the ventral side of the body with an excretory opening. The final waste products accumulate in the cavity fluid, and from it enter the excretory canals.
6. Nervous system presented circumpharyngeal ring ganglion and extending from it by several longitudinal nerve trunks, interconnected by semicircular nerve bridges. There are organs of taste and touch, and free-living roundworms have light-sensitive eyes.
7. Roundworms —dioecious animals that reproduce only sexually. In roundworms, males and females are externally distinguishable (sexual dimorphism). Reproductive system It has tubular structure: in the female there are paired ovaries, oviducts, uterus and unpaired vagina, in the male there is an unpaired testis, vas deferens, ejaculatory duct, copulatory apparatus. Fertilization is internal, development usually occurs with incomplete transformation (with the larval stage).

Figure 11.6. Appearance(a) and internal structure(b) roundworms: 1 - oral opening; 2 — pharynx; 3 — intestines; 4 - vagina; 5 — uterus; 6 —oviduct; 7—ovary; 8 - ejaculatory duct; 9 — testis; 10 — vas deferens.

The development cycle is complex, associated with the release of eggs into the external environment and migration of larvae in the human body. Fertilized eggs, covered with dense protective shells, enter the soil from the human intestine. In the presence of oxygen and sufficient high temperature The larva develops in them within about a month. The egg becomes contagious (invasive). With contaminated water and food products eggs fall into thin section human intestines. Here the larvae are freed from the shell, pierce the intestinal mucosa with their elastic body and penetrate into blood vessels. With the blood flow through the portal and inferior vena cava, they enter the right atrium, right ventricle and lungs (by pulmonary arteries). From lung tissue penetrate the bronchi, from them into the trachea, and then into the pharynx. During migration, the larvae develop in the presence of oxygen. From the pharynx they enter the intestines, where they complete their development cycle. Life expectancy is about a year.

Roundworms are ubiquitous and have a high number of individuals, which indicates the biological progress of this group of animals. Their ancestors are considered to be ancient eyelash worms.

Type Roundworms

Response Plan:

• General characteristics of Roundworms
• Body structure of human roundworm
• Reproduction and development of human roundworm
• Classification of Roundworms, variety of species
• The significance of Roundworms in nature and human life

General characteristics of Roundworms

Veils. On the outside, the skin-muscle sac is covered with a protective shell - the cuticle. During the growth of worms, it is periodically reset and then resumed. Below the cuticle is the hypodermis, which is the result of the fusion of skin cells. Under the hypodermis there are 4 ribbons of longitudinal muscles. During contraction, the dorsal and ventral bands act in opposite ways, and the body of the worm can bend in the dorsal-abdominal direction. The cuticle, hypodermis and muscles form a skin-muscular sac.

Digestive system. At the level of Roundworms, a grandiose event occurs in the evolution of the digestive system, which made all subsequent types of animals happy. It is in Roundworms that the hindgut and anus first appear. Now their digestive system consists of three sections: anterior, middle and posterior sections intestines. The anterior section is usually divided into the mouth, muscular pharynx and esophagus. Digestion occurs in the midgut. With the appearance of the anus, food begins to move in one direction, which makes it possible various departments specialize and perform their digestive function more efficiently.

Excretory organs– in some protonephridia, there is an excretory opening in the front of the body on the ventral side. Some representatives have modified skin glands, they are called "cervical glands". Some have no excretory organs.

Nervous system and sensory organs. Nervous system of the scalene type (orthogonal). It consists of a peripharyngeal nerve ring surrounding the pharynx, and 6 nerve trunks extending forward and backward, of which the dorsal and abdominal ones are the most developed. The trunks are connected by jumpers (commissures). There are organs of touch and organs of chemical sense (smell). Free-living animals have primitive eyes.

Reproduction. Most Roundworms are dioecious organisms, which ensures genetic diversity in their offspring. There is sexual dimorphism (females differ in appearance from males) Development is indirect, that is, with a larval stage, without a change of host.
Genital organs in the form of tubes. The male testes open through the vas deferens into the final section of the intestine - the cloaca. The male has copulatory organs - cuticular needles, with the help of which he introduces sperm into the female's genital tract. Fertilization is internal. In the female, the paired ovaries continue into the oviducts, which pass into two uteri, which open with the genital opening on the ventral side of the body.

Representatives: The phylum is divided into several classes, the most numerous among them being the class Nematodes: Roundworms, pinworms.

Body structure of human roundworm

New concepts and terms: cuticle, helminth, invasion, copulatory organs, sexual dimorphism, hydroskeleton, anus, detritivore.

Questions for consolidation.

Literature:

1. Bilich G.L., Kryzhanovsky V.A. Biology. Full course. In 3 volumes - M.: LLC Publishing House "Onyx 21st century", 2002
2. Pimenov A.V., Pimenova I.N. Zoology of invertebrates. Theory. Tasks. Answers: Saratov, OJSC publishing house "Lyceum", 2005.
3. Chebyshev N.V., Kuznetsov S.V., Zaichikova S.G. Biology: a guide for applicants to universities. T.2. – M.: Novaya Volna Publishing House LLC, 1998.
4. www.collegemicrob.narod.ru
5. www.deta-elis.prom.ua

The shape of a spindle, and in cross section it is round. Hence the type. The body of roundworms is not divided into segments.

Evolutionary neoplasm - primary cavity body, or pseudo-goal. The pseudocoel is filled with intercellular fluid and contains internal organs. The fluid serves as a hydroskeleton, gives the body elasticity and facilitates the exchange of substances between organs.

The body of roundworms is made of three layers. Upper layer cuticle, it acts as an exoskeleton. The cuticle also protects the body from damage.

The second layer consists of epithelial cells (hypodermis), where metabolic processes. From the inside, a layer merges with the hypodermis - muscle cells.

The muscles of roundworms are smooth. In total there are four longitudinal single-layer muscles. They allow roundworms to crawl by bending their bodies.

Thanks to the availability smooth muscle, roundworms can move very quickly and vigorously. For example, large nematodes can fit into fairly narrow openings.

Differentiated organ systems of roundworms

Roundworms have a total of five organ systems. Only the circulatory and respiratory system. During evolution, these systems appeared in annelids.

The digestive system is represented by a through tube. At the anterior end of the body there is a mouth opening surrounded by lips. The digestive tube ends with the anus, which is also an evolutionary neoplasm.

The excretory system of roundworms includes skin glands with an excretory duct.

Roundworms have special organs - phagocytic. They retain insoluble metabolic products and foreign bodies that enter the body.

As for the reproductive system, roundworms are dioecious. The female genital organs are paired: ovaries, oviducts, uterus and genital opening. The male has unpaired genitalia, including the testis and vas deferens.

The nervous system of roundworms consists of a peripharyngeal nerve ring and six nerve trunks. The nerve trunks are connected by jumpers. As sensory organs, roundworms have tactile tubercles and chemical sense organs.

Where do roundworms live?

Roundworms live in the most diverse environments. The life of some species takes place in the wild. They live in soil and water (regardless of its salt content).

Diagram of the body structure of a (hermaphroditic) nematode: 1 - anterior end of the body, bearing a mouth; 2 - intestine; 3 - cloaca; 4 - excretory system; 5 - testis; 6 - nerve ring; 7 - dorsal nerve; 8 - ventral nerve trunk; 9 - excretory opening.

Roundworms have a developed skin-muscle sac. The body is covered with a smooth or ringed cuticle, under which the hypodermis is located, and under it are strands of longitudinal muscles. Along the circumference of the body, the hypodermis forms 4 ridges (“chords”) protruding into the body cavity - dorsal (dorsal), ventral (abdominal) and two lateral. Inside the dorsal and abdominal cavity there are nerve trunks, and in the lateral ones there are sensory nerves and excretory canals.

Between the skin-muscle sac and internal organs bodies more or less large forms the primary body cavity is located - a pseudocoelom, which differs from the secondary (coelom) by the absence of an epithelial lining. In small marine nematodes, there is virtually no body cavity, and the slit-like space between the body wall and the organs is filled with an extracellular matrix.

With the exception of some sensory organs, nematodes lack flagellar cells. The circulatory and respiratory systems are absent.

Digestive system of roundworms

Excretory system of roundworms

It is assumed that the main bodies excretory system nematodes are a unicellular (or less often two- or multicellular) cervical gland, or lateral intracellular canals (renettes), and large pseudocoelomocyte cells. Renetta has a voluminous body and has excretory duct, opening outward with an adjustable pore. Pseudocoelomocytes do not have ducts - they isolate and utilize metabolic products. In addition, ammonia can be released from the body of nematodes by diffusion through the body wall.

Nervous system of roundworms

The nervous system consists of a peripharyngeal nerve ring and several longitudinal nerves. The nerve ring is located at the level of the middle of the pharynx and is inclined with its dorsal edge forward (in some groups the forward slope is reversed). In its structure, the nerve ring is a single circular ganglion and, apparently, serves as the main association body. The ventral nerve trunk and dorsal nerve originate from it; the remaining longitudinal nerves are not directly connected to it. The ventral nerve trunk contains the bodies of neurons; other longitudinal nerves do not have bodies and are bundles of processes of neurons of the ventral trunk. All longitudinal trunks pass intraepithelially - in the ridges of the hypodermis. The sense organs are represented by numerous sensilla: tactile setae, labial papillae (papillae), complementary organs of males, olfactory amphids and sensory glandular organs - phasmids. At the posterior end of the body of free-living nematodes there are terminal tail glands, the secretion of which serves to attach to the substrate. These sensory organs are mechano-, chemo-, or less often photoreceptors or have mixed sensitivity and are always associated with glandular cells. The main organs of long-range chemical reception are amphids - complexly arranged paired organs at the anterior end of the body, having a variety of shapes. Other sensory organs of the head include the cephalic sensilla, subordinate in their arrangement to radial symmetry and located in three or two rows. Some free-living nematodes, in addition, have internal mechanoreceptors - metanemes.

Sexual dimorphism of roundworms

The vast majority of nematodes have distinct external genitalia. dimorphism and dioecious, but hermaphrodites are also known. Nematodes lay eggs and, less often, are viviparous. Fertilized eggs hatch into larvae. This happens in external environment or also in the female genital tract (ovoviviparity). In males, the posterior end of the body is bent to ventral side and there is a complex copulatory apparatus. The role of holding the female during copulation is played by various complementary organs and (in rhabditid nematodes) bursae. Sperm are introduced using spicules that extend from the cloacal opening. The internal genital organs are initially paired and have a tubular structure. Females have a single or double set of ovary, oviduct and uterus; the vagina is always the only one. Males have one or two testes with vas deferens and an unpaired ejaculatory duct. Nematode sperm are extremely varied structure, lack flagella and have amoeboid (but not actin) motility.

Development cycle of roundworms

Development occurs without metamorphosis. In the most general case V life cycle There are 4 juvenile stages and one adult stage. The transition between stages occurs during the molting process. Since some molting may occur in the egg membranes, the number of free stages can be reduced. In rhabditid nematodes, the so-called The dauer stage is a modified third juvenile stage that plays a dispersal role and survives unfavorable environmental conditions.