Subcutaneous worm rishta

There are worms that live in human blood. These include schistosomes. Their main habitat is blood vessels. However, they are able to penetrate into various organs, causing symptoms of damage to the genitourinary system, liver, and kidneys.

In the blood may be the larvae of some helminths. For example, in tapeworms, this is how they spread through the organism of the intermediate host. With the blood flow, the larvae migrate to various organs, where they are fixed and form cysts containing the heads of adult worms. The latter, when they enter the digestive tract of the final host, attach to the intestinal wall, giving rise to a sexually mature individual.

Flatworms: general characteristics

The body of flatworms is capable of performing complex and varied movements.

All flatworms have common structural features:

• The outer cover is represented by the cuticle. In free-living individuals, it is covered with cilia, the surface of the body of worms is usually smooth.
• Under the outer cover there are several layers of muscle fibers.
• There is no body cavity.
• The digestive system has only one opening - the mouth. The intestine ends blindly. Some worms are completely devoid of digestive organs. So, tapeworms, which absorb nutrients with the whole body from the intestinal lumen of the host, do not need them.
• There is no circulatory system and blood, as well as respiratory organs.
• The excretory system is represented by a network of tubes that permeate the entire body.
• The nervous system is primitive. Near the pharynx there are several ganglia, from which nerve trunks connected by jumpers depart. The sense organs are formed only in free-living individuals and some worms at the larval stages of development.

The system that is really well developed is the sexual system. Flatworms are hermaphrodites. Reproduction is possible with the participation of 2 individuals or by self-fertilization.

flukes

The development cycle of trematodes is one of the most complex. Miracidia emerge from eggs released into the environment. In water, the latter feel comfortable and exist for some time as free-living organisms. The next stage is the introduction of miracidia into the first intermediate host. The larva does this with the help of a special cutting apparatus on the head. The host is usually a mollusk.

Their life cycle can take place in several hosts and is accompanied by a regular alternation

Here miracidia turns into a sporocyst, which gives rise to the next stage of the development cycle - redia. Those, in turn, are the precursors of cercariae, which leave the intermediate host and re-enter the aquatic environment. Further, the development cycle follows one of two options. Cercariae are transformed into cysts directly in the external environment (attached to algae) or in the body of the second intermediate host (mollusk, fish, amphibian).

These are the longest worms with a transparent shell

Infection of the final host occurs when it eats the infected organs of the intermediate host. The cycle of development ends with the attachment of the head from the cyst to the intestinal wall and the development of an adult worm. The latter can reach considerable sizes (for example, a wide tapeworm grows up to 10 m long).

For flukes, a person is the final host, but for tapeworms it can also be an intermediate host.

What symptoms occur when a person is infected with a helminth? The clinic of the disease is due, first of all, to which organ was affected. Sexually mature worms usually live in the intestines, therefore, in the general picture of the disease, symptoms characteristic of digestive disorders prevail: nausea, gas formation, stool disorders, and abdominal pain.

Helminths secrete waste products that, getting into the bloodstream, cause poisoning and symptoms of intoxication (fever, fatigue, and others). In addition, they are perceived by the immune system as an allergen. Therefore, helminthiases are often accompanied by symptoms of an allergic reaction (skin rash, itching).

Structural features Bilaterally symmetrical - a single cavity of symmetry divides the body into left and right halves. Development occurs from three germ layers: ectoderm, endoderm and mesoderm. The third germ layer appears for the first time in the course of evolution and gives rise to the development of parenchymal cells that fill the gaps between the organs and the muscular system. Left half Right half

Structural features Body sizes from 2-3 mm to 20 m. The body is elongated and flattened in the dorsal-abdominal direction; has a ribbon-like or leaf-like shape. The presence of developed organ systems is characteristic: muscular, digestive (absent in ribbon), excretory nervous and sexual.

Integuments of the body and the muscular system The cells of the epithelium and muscles are separate formations. The skin-muscle sac consists of a single-layer epithelium (in aquatic forms, the epithelium has cilia) and three layers of smooth muscles: annular, longitudinal, and oblique). Some representatives also have dorso-abdominal muscles. Movement is provided by muscle contraction (flukes and tapeworms) or by cilia of the integumentary epithelium and muscle contraction (ciliary worms).

The digestive system has two sections - anterior (mouth, pharynx) and middle (intestinal branches). The intestine is closed blindly, the posterior intestine and anus are absent. Undigested food remains are removed through the mouth. Tapeworms have no digestive system (represented by separate digestive cells).

Excretory system Formed by a system of tubules, one end of which begins in the parenchyma with a stellate cell with a bundle of cilia, and the other flows into the excretory duct. The duct unites into one or two common channels, ending in excretory pores.

Nervous system. Sense organs. It consists of supraglottic ganglions (ganglia) and longitudinal nerve trunks that run along the body and are connected by transverse nerve bridges. Sense organs - touch and chemical sense. Free-living people have organs of touch and balance.

Hepatic fluke Hepatic flukes, usually up to 3 cm long, 1.3 cm wide. Hepatic flukes of the order Opisthorchis cause opisthorchiasis, early symptoms - liver enlargement, allergic reactions and gastrointestinal disturbances; late stage symptoms - pain radiating to the back, biliary colic, headaches and dizziness, insomnia. Treatment is with anthelmintic, choleretic and enzyme preparations. High frequency electromagnetic radiation is also used.

Development cycle The life cycles of different genera are different. In species of the genus Fasciola, development occurs with one intermediate host (freshwater snail), and infection of the final host occurs when swallowed with water or eaten with coastal plants of the resting stage - adolescaria. In species of the genera Opisthorchis and Clonorchis, the second intermediate host is freshwater fish, and infection of the final host occurs by eating raw fish with invasive stages. In species of the genus Dicrocoelium, terrestrial lung snails and ants serve as intermediate hosts, and infection of the final host (usually a herbivore) occurs when an infected ant is eaten with grass.

Bull tapeworm (tapeworm) It affects cattle and humans, causing teniarinhoz. Tapeworm infestation is particularly prevalent in equatorial Africa, Latin America, the Philippines, and parts of Eastern Europe. An adult bull tapeworm consists of more than 1000 segments and reaches 4-40 meters in length. The laying of the reproductive apparatus begins at about the 200th segment. Length of mature proglottids mm, width 5-7 mm. The scolex (head section) is equipped with 4 suckers without hooks (therefore unarmed). The life span of bovine tapeworm in the human intestine, if no deworming measures are taken, is years. A tapeworm produces ~ 600 million eggs per year, ~ 11 billion in a lifetime.

Development cycle Segments containing eggs are excreted from the human intestine (the main host). Together with the grass, they enter the stomach of the cow (intermediate host). Six hooked larvae emerge from the eggs, which penetrate into the blood vessels of the intestine and then into the muscles. In the muscles, the larva turns into Finns (a vial with a tapeworm head inside). When a person eats poorly processed finny meat, the tapeworm head attaches to the intestinal wall and begins to produce segments.

Structural features Bilaterally symmetrical. Sizes from a few micrometers (soil) to several meters (sperm whale nematode). They have a non-segmented body with a dense cuticle. The ciliary cover is partially or completely reduced. Body filiform, fusiform, non-segmented, round in cross section.

The digestive system is formed by the anterior, middle and hindgut. The foregut is differentiated into sections: mouth with cuticular lips, pharynx and esophagus. The middle and hindgut are not divided into sections. The digestive tract ends at the anus.

The excretory system is represented by 1-2 skin glands (modified protonephridia). These are large cells, from which two channels depart on the sides of the cell. At the posterior end of the body, the channels end blindly, and in front they open into the external environment with an excretory pore.

Nervous system. Sense organs Ladder-type nervous system. It is represented by the head nerve nodes (ganglia), the peripharyngeal nerve ring and several nerve trunks (dorsal and abdominal), median transverse bridges. The sense organs are represented by the organs of touch and chemical sense. Marine forms have light-sensitive receptors. Scheme of the roundworm nervous system: 1 - oral papillae with tactile endings and the nerves innervating them, 2 - peripharyngeal nerve ring, 3 - lateral head ganglia, 4 - abdominal nerve trunk, 5 - lateral nerve trunks, 6 - ring nerves, 7 - posterior ganglion , 8 - sensitive papillae with corresponding nerves, 9 - anus, 10 - dorsal nerve trunk

Ascaris human Ascarids are large roundworms, their length can reach 40 centimeters. Most often affect the organs of the gastrointestinal tract, causing ascariasis. The favorite habitat of adults is the small intestine. Roundworms are bisexual worms. Ascaris females can produce more than 200 thousand eggs per day. Fertilized eggs from the human intestine enter the soil. They develop larvae. Infection occurs when drinking water from open reservoirs, eating poorly washed vegetables, fruits that have eggs with larvae. In the human body, the larva migrates: once in the intestine, it perforates its walls and enters the blood stream.

Structural features Bilateral symmetry of the body. Sizes from 0.5 mm to 3 m. The body is divided into the head lobe, trunk and anus. The polychaetes have a separate head with eyes, tentacles and antennae. The body is segmented (external and internal segmentation). The trunk contains from 5 to 800 identical ring-shaped segments. The segments have the same external and internal structure (metamerism) and perform similar functions. The metameric structure determines the high degree of regeneration.

Integuments of the body and muscular system The body wall is formed by a skin-muscular sac, consisting of a single-layer epithelium covered with a thin cuticle, two layers of smooth muscles (outer annular and inner longitudinal) and a single-layer epithelium of the secondary body cavity. With the contraction of the circular muscles, the body of the worm becomes long and thin, with the contraction of the longitudinal muscles, it shortens and thickens.

Body cavity Secondary - whole (has an epithelial vystilka). In most, the body cavity is divided by transverse partitions corresponding to body segments. The cavity fluid is a hydroskeleton and an internal environment; it is involved in the transport of metabolic products, nutrients and reproductive products.

The digestive system consists of three sections: anterior (mouth, muscular pharynx, esophagus, goiter), middle (tubular stomach, midgut) and posterior (hindgut, anus). The glands of the esophagus and midgut secrete enzymes to digest food. Absorption occurs in the midgut.

The circulatory system is closed. There are two vessels: dorsal and abdominal, connected in each segment by annular vessels. Through the dorsal vessel, blood moves from the posterior end of the body to the anterior, along the abdominal vessel from front to back. The movement of blood is carried out due to the rhythmic contractions of the walls of the spinal vessel and the annular vessels ("heart") in the pharynx. Many people have red blood.

The excretory system is of the Metanephidial type. Metanephridia look like tubes with funnels, two in each segment. The funnel, surrounded by cilia, and convoluted tubules are in one segment, and a short tubule that opens outwards with an opening - an excretory pore - is in the next segment.

Nervous system. Sense organs. It is represented by supraesophageal and subpharyngeal nerve nodes (ganglia), which are connected to the peripharyngeal nerve ring and the abdominal nerve chain, consisting of paired nerve nodes in each segment, connected by longitudinal and transverse nerve trunks. Polychaetes have organs of balance and vision (2-4 eyes). Most have only olfactory, tactile, and light-sensitive cells.

Reproduction and development Soil and freshwater forms are mainly hermaphodites. Sex glands develop only in certain segments. Insemination is internal. The type of development is direct. Asexual reproduction is carried out by budding and fragmentation (due to regeneration). Marine representatives are dioecious. Development with metamorphosis, trochophore larva.

summary of other presentations

"Features of the structure of the planaria" - The internal structure of the white planaria. White planaria or dairy. White planaria. General characteristics of the type. The structure of the white planaria. General signs. The excretory system of a planaria. Eyelash worms. Coelenterates. Variety of flatworms. Planarian body regeneration. White planaria. Various types of planarians. Bilateral and radial symmetry of the body. Body layers of planaria and hydra. The internal structure of a planaria.

"The structure of flatworms" - Movement. Digestive system of flukes. Nervous system. Sense organs. Eyelash worms. Turbellaria. excretory system. Sexual system. Life cycles of tapeworms. The reproductive system of flukes. Flukes are extremely prolific. Flukes class. Gas exchange and transport of substances. Digestive system of ciliaries. Type Flatworms. Tape worms. Development of flukes. The reproductive system is tape.

"The structure of planaria" - Type Flatworms. excretory system. The appearance in the process of development of the third germ layer. Eggs are covered with dense shells. Dairy planaria. Space between organs. Planarian movements. Sexual system. Digestive system. Signs of flatworms. Planarian body. Type Ciliary worms. Flatworms. The internal structure of a planaria. Ring muscles. Single layer epithelium. Nervous system.

"The structure of the white planaria" - Integuments of the body. Platehelminthes. Nephridia and accumulation kidneys. Variety of flatworms. Group members. Flatworms. The structure of the planaria. Structure. Capturing food by white planaria. Location of muscles. Nervous system and sense organs. Musculature. Throat and intestine. Food and movement. Complication of the body cavity. Turbellaria class. Ringed worms. The nervous system of the white planaria.

Flatworms, which are included in the group of bilaterally symmetrical, are studied by the science of biology. Flatworms (Platyhelminthes) are not the only representatives of this group; more than 90% of animals belong to it, including annelids and roundworms, arthropods, mollusks, etc.

Types of flatworms are diverse and distributed throughout the world. There are about 25 thousand of them.

Scientific classification of flatworms

Flatworms belong to the kingdom Bilateral (symmetrical on both sides). In connection with some disputes that arose when trying to divide flatworms into different groups, scientists attribute them to a paraphyletic group. It includes representatives of a small part of the descendants of the same ancestors.

The structure of the internal organs of a flatworm

The body of flatworms is elongated and flattened, without a cavity inside. That is, its entire space is filled with cells. Inside are layers of muscles, which, together with the shell of the worm, form a musculocutaneous sac.

There are systems of internal organs:

• The digestive system is represented by a mouth and a blind (having no exit) intestine. Nutrients enter through the mouth, and can be absorbed through the entire surface of the body.
• The nervous system consists of brain ganglia and nerve columns. Some classes of flatworms have primitive organs of balance and vision.
• The excretory system consists of special tubules, but most often the excretion occurs over the entire surface of the body.
• The reproductive system is represented by both female (ovaries) and male (testes) reproductive organs. Flatworms are hermaphrodites.

Differences between flat and roundworms

Roundworms differ from flatworms in that their body has a round shape in cross section. Roundworms are also called nematodes. Possessing a bilaterally symmetrical body structure, they have developed muscles. But the main difference from flatworms is that round ones have an internal body cavity, while flat ones do not.

Variety of classes of flatworms

The table "Flatworms" clearly shows the division of the species into classes, of which modern science has seven.

class name	Habitat		Life cycle
Monogeneans (flukes)	With the help of an attachment disc at the posterior end of the worm, Monogenea is attached to the gills of fish and the skin of amphibians and turtles.	Very small, on average no more than 1 mm	For the whole life, the worm has one host, to which it enters in the form of a free-swimming larva
cestoid		Length ranges from 2.5 to 38 cm	The larvae develop in the body of crustaceans when the egg is swallowed. After eating a crustacean by aquatic vertebrates, an already adult individual easily moves from the intestines of a new host to the body cavity, where it lives and reproduces.
aspidogaster	They live in the bodies of molluscs, freshwater and marine fish	An adult rarely reaches a size of more than 15 mm	Changes of hosts occur several times during the life cycle of worms
Trematodes (flukes)			They have multiple owners throughout their lives. The larva lives first in which it subsequently dies. Ingested by ingestion of cercariae (ready to colonize the organs of the definitive larval host)
Gyrocotylides		2 to 20 cm	Hypothetically, the larvae first develop in the body of the intermediate host, and only then move into the fish. But due to the fact that chimeric fish are deep-sea, the hypothesis has not been experimentally confirmed.
Tape	The habitat of flatworms is the intestines of a mammal and a person, to the wall of which they firmly stick with the help of a head.	They can reach sizes up to 10 m.
Eyelash	Mostly free-living worms, live in fresh and salt water bodies, sometimes in moist soil	Body length ranges from microscopic to 40 cm	A larva that looks like an adult worm emerges from the egg, living among plankton until it grows up.

Eyelash worms

They are predators that eat small invertebrates, arthropods and even large mollusks. They swallow small prey whole or tear off pieces from it with strong sucking movements.

The body of worms is able to regenerate itself. A prominent representative is the planarian, in which even a small part of the body grows anew into a full-fledged individual.

Flatworms in home aquariums

Helminths can be a big problem for aquarium hobbyists.

The habitat of flatworms is mostly aquatic. Being flukes, flatworms can attach by means of an attachment disc to the surface of the gills and skin of aquarium fish.

Adult worms lay eggs, which hatch into larvae that live on the skin of the fish. Gradually, they crawl onto the gills, where they grow, reaching puberty.

Some types of flatworms get into the home aquarium with soil, live food. Their larvae can be on the surface of algae, on the skin of new fish inhabiting the aquarium.

• Pseudophyllidea (wide tapeworm). Infection with them can occur if raw, poorly salted fish is present in the diet. In the human small intestine, the tapeworm can live for decades, reaching a length of up to 20 m.
• Aeniarhynchus saginatus ( bull tapeworm). The habitat of flatworms is the intestines of humans and cattle. Sticking to its walls, the helminth grows up to 10 m. The larvae can be in other internal organs, in hard-to-reach places (brain, muscles, liver), so it is often impossible to completely get rid of them. The patient may be fatal. Infection occurs when helminth eggs enter the stomach with insufficiently thermally processed food, from dirty hands.
• Echinococcus (Echinococcus) is often found in dogs and cats, from them passing into the body to humans. Despite their small size - only 5 mm - the ability of its larvae to form Finns that paralyze internal organs is deadly. The larvae are able to penetrate into the respiratory, bone, urinary systems. Echinococcus flatworms are often found in the brain, liver and other internal organs. A person can easily become infected with larvae excreted in the feces of a dog, which spread to the coat, and from there to all household items and food.
• The liver fluke is the culprit of cholecystitis, hepatic colic, disruption of the stomach and intestines, and allergies. The habitat of flatworms is mainly the liver of humans and warm-blooded animals, the biliary tract. The body length of the fluke does not exceed 3 cm. The peculiarity is that not only mature individuals, but also their larvae, are capable of reproduction.

Prevention of helminth infection

Preventive measures for the entry of eggs and larvae of helminths into the human body are as follows:

• It is necessary to wash hands thoroughly with soap and water before each meal, after visiting public places, toilets, streets, communicating with pets.
• Wash raw vegetables and fruits with warm soapy water.
• Do not eat raw meat and fish.
• Long-term heat treatment of food, especially meat, fish.
• Pay attention to the timely prevention of helminthic invasions of domestic animals.
• Regularly, at least once a year, take a stool test for worm eggs.

7. Type flatworms

1. Fill in the summary table in your notebooks throughout the study of representatives of all types of worms

	1	2	3
Type of worms	flat	Round	ringed
Habitat	freshwater and marine waters, terrestrial wet environments, some inside animals and plants	Soil, fresh water, seas, animals and plants (parasites)	Fresh and marine water bodies, soil, there are parasites
Food	The mouth opening is the pharynx-gut. The remains are removed through the mouth opening.	mouth opening, digestive system through in the form of a tube, anus	Mouth, pharynx, esophagus, midgut, hindgut, anus
Breath		Breathe with the entire surface of the body, there is no respiratory system	through the wet surface of the body or with the help of gills
Circulation	missing	missing	closed or partially closed circulatory system, contracting vessel walls
Selection	Branched tubules ending in parenchyma with stellate cells	modified skin glands, phagocytic cells	altered segmental glands found in every segment of the body
reproduction	Hermaphrodites. Sex glands: testes and ovaries.	dioecious	hermaphrodites and dioecious

2. Is the statement true: "Adult parasitic worms have cilia"?

3. Find in the text of the paragraph a description of the skin-muscle sac. Explain why it is called that.

Under the integumentary tissue is the skin muscles - this is a musculocutaneous sac, inside which the internal organs are located.

4. Remember the internal structure of the coelenterates. Compare the internal structure of coelenterates and flatworms. Note any complications.

Flatworms do not have an internal cavity, and the internal organs, combined into systems, are located inside the skin-muscle sac.

5. Write down the definitions of the concepts:

Bilateral symmetry - an imaginary axis of symmetry can be drawn through the animal's body and the right side is, as it were, a mirror image of the left

Intermediate host - an organism in which larvae of worms develop and stay for some time

suckers, hooks, proboscis

Worms produce many eggs in order to survive. Many eggs die either without finding an intermediate host, or when they enter the body of an unusual animal.

8. Specify the characteristics corresponding to each class of flatworms

A - class Ciliary worms
B - class Flukes
B - class Tapeworms

Answer:
A - 1, 7, 9, 6
B - 2, 3, 8, 11
B - 2, 4, 5, 8, 10