Video lesson “Type flatworms. Type Flatworms

"Features of the structure of the planaria" - The internal structure of the white planaria. White planaria or dairy. White planaria. General signs 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. Different kinds planarian. 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. Composition of the group. Flatworms. The structure of the planaria. Structure. Capturing food by white planaria. Location of muscles. Nervous system and sense organs. Musculature. Throat and intestine. Nutrition and movement. Complication of the body cavity. Turbellaria class. Ringed worms. The nervous system of the white planaria.

All worms can be divided into three types (flat, ringed, round), each of which has its own characteristics. characteristic features. This type refers to invertebrates lacking a body cavity and possessing bilateral symmetry.

The main signs of the type of flatworms

• digestive;
• nervous;
• sexual;
• excretory.

This type has the presence of several systems and even the rudiments of organs

Circulatory system

Not available, but the function of the blood is performed by the parenchyma, consisting of connective cells. It is she who transports nutrients in the body.

Digestive system

Rather simplified, it consists of a pharynx and intestines.

The pharynx is powerful, can:

• suck;
• twist and wrap around your prey.

The intestine consists of two sections - anterior and middle, most often branched. It has a closed structure, so that all undigested waste exits through the mouth. The mouth opening is located closer to the middle of the body of the worm.

Free worms are mostly predators and they even have a kind of adaptation for capturing prey. This system is not observed in all classes; more primitive worms do not have it. For example, tapeworms feed on the entire surface.

excretory system

The excretory system is quite large and consists of many tubules that combine and lead to the excretory pores.

The parenchyma contains special cells that drive harmful substances into the tubules. For humans, these excretory products are very dangerous and toxic along with poison.

Muscular system

Presented, which form muscle fibers covered with epithelium. By contracting these fibers, the worms can move about.

Nervous system

In the upper part of the worm there are two head nodes, two nerve trunks descend from them. Longitudinal nerve trunks penetrate the body of the worm completely and are interconnected by transverse nerves, similar to a short flight of stairs.

With the help of dermal cilia, some worms can:

• feel the temperature
• other external stimuli.

And among free worms there are representatives who have developed organs of vision (pigments that react to light) and balance.

species diversity

There are three classes of this type:

1. Flukes.
2. Tape.
3. Eyelash worms.

Flukes: class representatives and characteristics

Class members:

General characteristics of the class flukes:

Tapeworms: representatives of the class and characteristics

General characteristics of the tapeworm class:

Class members:

• is in stagnant water - ponds, ditches, very active. Covered with cilia, uses them to move on the water surface and attach to the bottom. The length is about 35 cm. The digestive system is developed, it feeds mainly on crustaceans and small invertebrates. Reproduction is sexual and asexual (divided in half, and then each half is completed). Wide range of habitat, found almost everywhere.
• Ehrenberg mesostoma- a flat leaf-shaped body, slightly convex, transparent and colorless, in old worms it is brown. Unlike planarians, the intestines are straight, not branched. Live attached to aquatic plants. The mesostoma is predatory, preying on crustaceans, worms, insects and even freshwater hydras. It is able to tolerate the drying up of reservoirs, live in flooded meadows, puddles, and after their drying out, the eggs of the mesostom remain capable of development.
• Ground worm rhynchodemus- soil worm, lives in damp places, most often under stones. Habitat Europe and North America. It can reach 12 mm, the color is brown with red longitudinal spots. Cilia are preserved on the ventral side of the body, moves by muscle contraction. Predator that eats insects.

General characteristics of ciliary worms:

a brief description of

Typical representatives of ciliary worms are planaria(Fig. 1).

Rice. 1.Morphology of flatworms on the example of dairy planaria. A - the appearance of the planaria; B, C - internal organs(scheme); D - part of the transverse section through the body of the dairy planaria; D - terminal cell of the protonephridial excretory system: 1 - oral opening; 2 - throat; 3 - intestines; 4 - protonephridia; 5 - left lateral nerve trunk; 6 - head ganglion; 7 - peephole; 8 - ciliary epithelium; 9 - circular muscles; 10 - oblique muscles; 11 - longitudinal muscles; 12 - dorsoventral muscles; 13 - parenchyma cells; 14 - cells forming rhabdites; 15 - rabdits; 16 - unicellular gland; 17 - a bunch of cilia (flickering flame); 18 - cell nucleus

general characteristics

Appearance and covers . The body of ciliary worms is elongated, foliate. Sizes vary from a few millimeters to several centimeters. The body is colorless or white. Most often, ciliary worms are painted in various colors with grains. pigment embedded in the skin.

body covered single layer ciliated epithelium. The covers have skin glands scattered throughout the body or collected in complexes. Of interest is the variety of skin glands - rhabdit cells, which contain light-refracting rods rabdites. They lie perpendicular to the surface of the body. When the animal is irritated, the rhabdites are thrown out and swell greatly. As a result, mucus is formed on the surface of the worm, possibly playing a protective role.

Skin-muscular sac . Under the epithelium is basement membrane, which serves to give the body a certain shape and to attach muscles. The combination of muscles and epithelium forms a single complex - skin-muscle sac. The muscular system is made up of several layers smooth muscle fibers. The most superficial circular muscles, somewhat deeper longitudinal and the deepest diagonal muscle fibers. In addition to the listed types of muscle fibers, ciliary worms are characterized by dorso-abdominal, or dorsoventral, muscles. These are bundles of fibers running from the dorsal side of the body to the ventral side.

The movement is carried out due to the beating of the cilia (in small forms) or the contraction of the skin-muscular sac (in large representatives).

clearly defined body cavity ciliary worms do not. All gaps between organs are filled parenchyma- loose connective tissue. The small spaces between the parenchyma cells are filled with an aqueous liquid, due to which the transfer of products from the intestine to the internal organs and the transfer of metabolic products to the excretory system can be carried out. In addition, the parenchyma can be considered as a supporting tissue.

Digestive system ciliary worms blindly closed. Mouth also serves for swallowing food, and for throwing out undigested food. The mouth is usually located on the ventral side of the body and leads to throat. In some large ciliary worms, such as freshwater planaria, the mouth opening opens into pharyngeal pocket, in which is muscular throat, able to stretch and protrude out through the mouth. midgut in small forms of ciliary worms is channels branching in all directions, and in large forms, the intestines are represented three branches: one front, going to the front end of the body, and two rear running along the sides to the posterior end of the body.

Main Feature nervous system ciliary worms compared to coelenterates is concentration of nerve elements at the anterior end of the body with the formation of a double node - the brain ganglion, which becomes the coordinating center of the whole body. depart from the ganglion longitudinal nerve trunks connected by transverse ring jumpers.

sense organs ciliary worms are relatively well developed. organ of touch whole skin serves. In some species, the function of touch is performed by small paired tentacles at the anterior end of the body. Sense organs of balance represented by closed sacs - statocysts, with hearing stones inside. organs of vision are almost always available. The eye may be one pair or more.

excretory system first appears as separate system. It is represented two or multiple channels, each of which one end opens outwards, A the other is strongly branched, forming a network of channels of various diameters. The thinnest tubules or capillaries at their ends are closed by special cells - stellate(see fig. 1, D). From these cells in the lumen of the tubules depart bunches of cilia. Due to their constant work, there is no stagnation of fluid in the body of the worm, it enters the tubules and is subsequently excreted. The excretory system in the form of branched canals, closed at the ends by stellate cells, is called protonephridia.

reproductive system quite varied in structure. It can be noted that in comparison with coelenterates in ciliary worms special excretory ducts appear For

expelling germ cells. Eyelash worms hermaphrodites. Fertilization - internal.

Reproduction. In most cases in a sexual way. For most worms direct development, but in some marine species development occurs with metamorphosis. However, some ciliary worms can reproduce and asexually through transverse fission. At the same time, in each half of the body, regeneration missing organs.

With a little frown, let's start the description worms. What to do if there are such trump cards in the thick "deck" of the natural diversity of life forms.

I write "trump cards" not only because " worms". The evolution of multicellularity from two-layer has led to much more perfect forms of organisms with a three-layer body structure. And then nature had to tinker for a long time, creating not one, but whole.

Somehow it even becomes a shame for all mammals, which represent only a separate class of organisms in the type of chordates. And here, "some kind of worms" - and whole three types: flatworms, roundworms and annelids.

Well, let's start everything in order, so:

……………… Type Flatworms (three layers)

…………………………………. K l . A. With. With. s

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.. Ciliary worms……………………….. Flukes……………………….. Tapeworms

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White planaria…. Liver fluke …… …………… Bull tapeworm ________________________________________________________________________________________________

……………………………………………….. More than 15 thousand species

Habitat : marine and fresh water bodies, moist soil, human and animal organisms.

……..
Structure: bilaterally symmetrical . For the first time in embryos, a third germ layer – mesodermfrom which parenchymal cells and the muscular system develop. Body flattened.

………..
Integuments of the body and muscular system: skin-muscular sac - from a single-layer epithelium (may be with eyelashes) and three layers smooth muscles (circular, longitudinal and oblique).

Movement: muscle contraction (flukes, tapeworms) or movement of cilia andmuscles (ciliary worms).

body cavity: absent , the internal organs are located inparenchyma.

Digestive system:has two sections - anterior (mouth, pharynx) and middle (branches intestines). The bowel is closed anal opening is missing and leftover food is removed. through the mouth. At the tapeworms digestive systemabsent- absorption of food by all cells of the body. As you remember, this is one of the forms of biological progress -.

excretory system: appears for the first time formed by a system of tubules. one end starts in the parenchyma stellate cell with a bunch of cilia, and the other flows into excretory duct. ducts combined into one or two common channels ending excretory pores. Elementary unit of the system areprotonephridia.

Nervous system:from supraesophageal ganglions(ganglia) and longitudinal nerves trunks, related cross jumpers(ladder type).

Sense organs: touch And chemosensitive cells. Free-living people have organsvision And balance.…………..

reproductive system: To usually hermaphrodites.Men'sreproductive system: testes, vas deferens, ejaculatory duct and copulatory organ. Women'sreproductive system: ovary, oviduct, uterus, yolk glands.

1. The appearance of the third germ layer -mesoderm.
2. The appearance of the excretory system - protonephridia.
3. Emergence of the nervous system ladder type.

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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 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).