Gill type of breathing. Gill breathing

Reproduction. Amphibians are dioecious. The genitals are paired, consisting of slightly yellowish testes in the male and pigmented ovaries in the female. Efferent ducts extend from the testes and penetrate into the anterior part of the kidney. Here they connect to the urinary tubules and open into the ureter, which simultaneously performs the function of the vas deferens and opens into the cloaca. The eggs fall from the ovaries into the body cavity, from where they are released through the oviducts, which open into the cloaca.

Frogs have well-defined sexual dimorphism. Thus, the male has tubercles on the inner toe of the front legs ("nuptial callus"), which serve to hold the female during fertilization, and vocal sacs (resonators), which enhance the sound when croaking. It should be emphasized that voice first appears in amphibians. Obviously, this is related to life on land.

Frogs reproduce in the spring during their third year of life. Females spawn eggs into the water, and males irrigate them with seminal fluid. Fertilized eggs develop within 7-15 days. Tadpoles - the larvae of frogs - are very different in structure from adult animals (Table 19). After two to three months, the tadpole turns into a frog.

Class Amphibians = Amphibians.

The first terrestrial vertebrates that still retained contact with the aquatic environment. The class has 3,900 species and includes 3 orders: tailed (salamanders, newts), legless (tropical caecilians) and tailless (toads, tree frogs, frogs, etc.).

Secondary aquatic animals. Since the egg does not have an amniotic cavity (together with cyclostomes and fish, amphibians are anamnians), they reproduce in water, where they undergo the initial stages of their development.

At different stages of their life cycle, amphibians lead a terrestrial or semi-aquatic lifestyle and are distributed almost everywhere, mainly in areas with high humidity along the banks of fresh water bodies and on damp soils. Among amphibians there are no forms that could live in salty sea water. Various modes of movement are characteristic: species are known that make fairly long jumps, move at a walk or “crawl”, lacking limbs (caecilians).

Basic characteristics of amphibians.

Amphibians retained many of the features of their purely aquatic ancestors, but at the same time they acquired a number of features characteristic of true terrestrial vertebrates.

Tailed and tailless animals are characterized by larval development with gill breathing in fresh water (frog tadpoles) and their metamorphosis into an adult breathing with lungs. In legless animals, upon hatching the larva takes the form of an adult animal.

The circulatory system is characterized by two circles of blood circulation. The heart is three-chambered.

It has one ventricle and two atria.

The cervical and sacral sections of the spine are separated, each having one vertebra.

Adult amphibians are characterized by paired limbs with articulated joints. The limbs are five-fingered.

The skull articulates movably with the cervical vertebra by two occipital condyles.

The pelvic girdle is tightly attached to the transverse processes of the sacral vertebra.

The eyes have movable eyelids and nictitating membranes to protect the eyes from clogging and drying out. Accommodation improves due to the convex cornea and flattened lens.

The forebrain enlarges and divides into two hemispheres. The midbrain and cerebellum are slightly developed. 10 pairs of cranial nerves depart from the brain.

To capture sound waves from the air, the eardrum appears, followed by the middle ear (tympanic cavity), in which the auditory ossicle is located - the stapes, which conducts vibrations to the inner ear. The Eustachian tube communicates with the middle ear cavity and the oral cavity. Choanae appear - internal nostrils, and the nasal passages become through.

Body temperature is not constant (poikilothermia) depends on the ambient temperature and only slightly exceeds the latter.

Aromorphoses:

Lungs and pulmonary breathing appeared.

The circulatory system has become more complex, the pulmonary circulation has developed, i.e. Amphibians have two circles of blood circulation - large and small.

The heart is three-chambered.

Paired five-fingered limbs were formed, representing a system of levers with articulated joints and intended for movement on land.

A cervical region has formed in the spine, which provides movement of the head, and a sacral region - the place of attachment of the pelvic girdle.

The middle ear, eyelids, and choanae appeared.

Muscle differentiation.

Progressive development of the nervous system.

Phylogeny.

Amphibians evolved from ancient lobe-finned fish in the Devonian period of the Paleozoic era approximately 350 million years ago. The first amphibians, Ichthyostegas, resembled modern tailed amphibians in appearance. Their structure had features characteristic of fish, including rudiments of the gill cover and lateral line organs. Cover.

Double layer. The epidermis is multilayered, the corium is thin, but abundantly supplied with capillaries. Amphibians have retained the ability to produce mucus, but not with individual cells, as in most fish, but with formed mucous glands of the alveolar type. In addition, amphibians often have granular glands with a poisonous secretion of varying degrees of toxicity. The skin color of amphibians depends on special cells - chromatophores. These include melanophores, lipophores and iridocytes.

Under the skin of frogs there are extensive lymphatic lacunae - reservoirs filled with tissue fluid and allowing, under unfavorable conditions, to accumulate a supply of water. divided into axial and accessory, as in all vertebrates. The vertebral column is more differentiated into sections than in fish and consists of four sections: cervical, trunk, sacral and caudal. The cervical and sacral sections each have one vertebra. Anurans usually have seven trunk vertebrae, and all caudal vertebrae (about 12) merge into a single bone - the urostyle. Caudates have 13 - 62 trunk and 22 - 36 caudal vertebrae; in legless animals the total number of vertebrae reaches 200–300. The presence of a cervical vertebra is important because Unlike fish, amphibians cannot turn their body so quickly, and the cervical vertebra makes the head mobile, but with a small amplitude. Amphibians cannot turn their heads, but they can tilt their heads.

The type of vertebrae in different amphibians may vary. In legless and lower caudate vertebrae are amphicoelous, with a preserved notochord, like in fish. In higher caudates, the vertebrae are opisthocoelous, i.e. The bodies are curved in front and concave in the back. In tailless animals, on the contrary, the anterior surface of the vertebral bodies is concave and the posterior surface is curved. Such vertebrae are called procoelous. The presence of articular surfaces and articular processes not only ensures a strong connection of the vertebrae, but also makes the axial skeleton mobile, which is important for the movement of tailed amphibians in water without the participation of limbs, due to the lateral bending of the body. In addition, vertical movements are possible.

The amphibian skull is a modified skull of a bony fish, adapted to terrestrial existence. The brain skull remains predominantly cartilaginous for life. The occipital region of the skull contains only two lateral occipital bones, which are carried along the articular condyle, with the help of which the skull is attached to the vertebrae. The visceral skull of amphibians undergoes the greatest transformations: secondary upper jaws appear; formed by the premaxillary and maxillary bones. The reduction of gill breathing led to a radical change in the hyoid arch. The hyoid arch is transformed into an element of the hearing aid and the sublingual plate. Unlike fish, the visceral skull of amphibians is directly attached by the palatoquadrate cartilage to the bottom of the brain skull. This type of direct connection of the components of the skull without the participation of elements of the hyoid arch is called autostyly. Amphibians lack elements of the operculum.

The accessory skeleton includes the bones of the girdles and free limbs. Like fish, the bones of the shoulder girdle of amphibians are located in the thickness of the muscles that connect them to the axial skeleton, but the girdle itself is not directly connected to the axial skeleton. The belt provides support for the free limb.

All land animals constantly have to overcome gravity, which fish do not have to do. The free limb serves as a support, allows you to lift the body above the surface and provides movement. The free limbs consist of three sections: proximal (one bone), intermediate (two bones) and distal (relatively large number of bones). Representatives of different classes of terrestrial vertebrates have structural features of one or another free limb, but all of them are of a secondary nature.

In all amphibians, the proximal part of the free forelimb is represented by the humerus, the intermediate part by the ulna and radius in caudates, and a single bone of the forearm (it is formed as a result of the fusion of the ulna and radius) in anurans. The distal section is formed by the wrist, metacarpus and phalanges of the fingers.

The girdle of the hind limbs articulates directly with the axial skeleton, with its sacral section. A reliable and rigid connection of the pelvic girdle with the spinal column ensures the functioning of the hind limbs, which are more important for moving amphibians.

Muscular system different from the muscular system of fish. The trunk muscles retain their metameric structure only in the legless. In caudates, the metamerism of segments is disrupted, and in tailless amphibians, sections of muscle segments begin to separate, differentiating into ribbon-shaped muscles. The muscle mass of the limbs increases sharply. In fish, the movements of the fins are ensured mainly by muscles located on the body, while the five-fingered limb moves due to muscles located in itself. A complex system of muscles - antagonists - flexor and extensor muscles appears. Segmented muscles are present only in the region of the spinal column.

The muscles of the oral cavity become more complex and specialized (masticatory, tongue, floor of the mouth), not only involved in the capture and swallowing of food, but also providing ventilation of the oral cavity and lungs.– in general. In amphibians, due to the disappearance of gills, the relative position of the pericardial cavity has changed. She was pushed to the bottom of the chest into the area covered by the sternum (or coracoid). Above it, in a pair of coelomic canals, lie the lungs. Cavities containing the heart and lungs. Separates the pleurocardial membrane. The cavity in which the lungs are located communicates with the main coelom.

Nervous system. The brain is of the ichthyopsid type, i.e. the main integrating center is the midbrain, but the amphibian brain has a number of progressive changes. The amphibian brain has five sections and differs from the fish brain mainly in the greater development of the forebrain and the complete separation of its hemispheres. In addition, the nerve substance already lines, in addition to the bottom of the lateral ventricles, also the sides and roof, forming the medullary vault - the archipallium. The development of the archipallium, accompanied by strengthening connections with the diencephalon and especially the midbrain, leads to the fact that associative activity regulating behavior in amphibians is carried out not only by the medulla oblongata and midbrain, but also by the forebrain hemispheres. The elongated hemispheres in front have a common olfactory lobe, from which two olfactory nerves originate. Behind the forebrain is the diencephalon. The epiphysis is located on its roof. On the underside of the brain there is an optic chiasm (chiasma). The infundibulum and the pituitary gland (lower medullary gland) extend from the bottom of the diencephalon.

The midbrain is represented as two round optic lobes. Behind the optic lobes lies the underdeveloped cerebellum. Immediately behind it is the medulla oblongata with the rhomboid fossa (fourth ventricle). The medulla oblongata gradually passes into the spinal cord.

In amphibians, 10 pairs of head nerves arise from the brain. The eleventh pair is not developed, and the twelfth pair extends outside the skull.

The frog has 10 pairs of true spinal nerves. The three anterior ones take part in the formation of the brachial plexus, which innervates the forelimbs, and the four posterior pairs take part in the formation of the lumbosacral plexus, which innervates the hind limbs.

Sense organs provide orientation for amphibians in water and on land.

All larvae and adults with an aquatic lifestyle have lateral line organs. They are represented by a cluster of sensitive cells with nerves corresponding to them, which are scattered throughout the body. Sensitive cells perceive temperature, pain, tactile sensations, as well as changes in humidity and chemical composition of the environment.

Olfactory organs.

Amphibians have a small external nostril on each side of the head, which leads into an elongated sac that ends in the internal nostril (choana). The choanae open at the front of the roof of the oral cavity. In front of the choanae on the left and right there is a sac that opens into the nasal cavity.

This is the so-called vomeronasal organ. It contains a large number of sensory cells.

Its function is to receive olfactory information about food.

The organs of vision have a structure characteristic of a terrestrial vertebrate. This is expressed in the convex shape of the cornea, the lens in the form of a biconvex lens, and movable eyelids that protect the eyes from drying out. begins with the oral fissure leading into the oropharyngeal cavity. It houses a muscular tongue. The ducts of the salivary glands open into it. The tongue and salivary glands first appear in amphibians. The glands serve only to wet the bolus of food and do not participate in the chemical processing of food. On the premaxillary, maxillary bones, and vomer there are simple conical teeth, which are attached to the bone with their base. The digestive tube is differentiated into the oropharyngeal cavity, a short esophagus that carries food into the stomach, and a voluminous stomach. Its pyloric part passes into the duodenum - the beginning of the small intestine. The pancreas lies in the loop between the stomach and duodenum. The small intestine smoothly passes into the large intestine, which ends in a pronounced rectum that opens into the cloaca.

The digestive glands are the liver with the gallbladder and the pancreas. The liver ducts, together with the gallbladder duct, open into the duodenum. The pancreatic ducts empty into the gallbladder duct, i.e. This gland does not have independent communication with the intestines.

That. The digestive system of amphibians differs from the similar system of fish in the greater length of the digestive tract; the final section of the large intestine opens into the cloaca.

Circulatory system closed. Two circles of blood circulation. The heart is three-chambered. In addition, the heart has a venous sinus that communicates with the right atrium, and the conus arteriosus extends from the right side of the ventricle. Three pairs of vessels depart from it, homologous to the gill arteries of fish. Each vessel begins with an independent opening. All three vessels of the left and right sides first go through a common arterial trunk, surrounded by a common membrane, and then branch.

The vessels of the first pair (counting from the head), homologous to the vessels of the first pair of gill arteries of fish, are called carotid arteries, which carry blood to the head. Through the vessels of the second pair (homologous to the second pair of gill arteries of fish) - the aortic arches - blood is directed to the back of the body.

The subclavian arteries depart from the aortic arches, carrying blood to the forelimbs.

Venous blood from the anterior end of the body is collected through two pairs of jugular veins. The latter, merging with the cutaneous veins, which have already absorbed the subclavian veins, forms two anterior vena cava. They carry mixed blood into the venous sinus, since arterial blood moves through the skin veins.

Amphibian larvae have one circulation; their circulatory system is similar to the circulatory system of fish.

Amphibians develop a new circulatory organ - the red bone marrow of the long bones. Red blood cells are large, nuclear, white blood cells are not the same in appearance. There are lymphocytes.

Lymphatic system. In addition to the lymphatic sacs located under the skin, there are lymphatic vessels and hearts. One pair of lymphatic hearts is placed near the third vertebra, the other - near the cloacal opening. The spleen, which looks like a small round red body, is located on the peritoneum near the beginning of the rectum.

Respiratory system. Fundamentally different from the respiratory system of fish. In adults, the respiratory organs are the lungs and skin. The airways are short due to the absence of the cervical spine. Represented by the nasal and oropharyngeal cavities, as well as the larynx. The larynx opens directly into the lungs with two openings. Due to the reduction of the ribs, the lungs are filled by swallowing air - according to the principle of a pressure pump.

Anatomically, the respiratory system of amphibians includes the oropharyngeal cavity (upper airways) and the laryngeal-tracheal cavity (lower airways), which directly passes into the sac-like lungs. During embryonic development, the lung is formed as a blind outgrowth of the anterior (pharyngeal) section of the digestive tube, and therefore remains connected to the pharynx in adulthood.

That. The respiratory system in terrestrial vertebrates is anatomically and functionally divided into two sections - the airway system and the respiratory section. The airways carry out two-way transport of air, but do not participate in gas exchange itself; the respiratory department carries out gas exchange between the internal environment of the body (blood) and atmospheric air. Gas exchange occurs through the surface liquid and occurs passively in accordance with the concentration gradient.

The system of gill covers becomes unnecessary, therefore the gill apparatus in all terrestrial animals is partially modified, its skeletal structures are partially included in the skeleton (cartilages) of the larynx. Ventilation of the lungs is carried out due to forced movements of special somatic muscles during the respiratory act.

excretory system, as in fish, it is represented by primary, or trunk buds. These are compact bodies of a reddish-brown color, lying on the sides of the spine, and not ribbon-shaped, like those of fish. From each kidney a thin Wolffian canal stretches to the cloaca. In female frogs it serves only as a ureter, and in males it serves as both a ureter and a vas deferens. In the cloaca, the Wolffian canals open with independent openings. It also opens separately into the cloaca and bladder. The final product of nitrogen metabolism in amphibians is urea. In aquatic amphibian larvae, the main product of nitrogen metabolism is ammonia, which is excreted in solution through the gills and skin.

Amphibians are hyperosmotic animals in relation to fresh water. As a result, water constantly enters the body through the skin, which does not have mechanisms to prevent this, like other terrestrial vertebrates. Sea water is hyperosmotic in relation to the osmotic pressure in the tissues of amphibians; when they are placed in such an environment, water will leave the body through the skin. This is why amphibians cannot live in sea water and die in it from dehydration.

Reproductive system. In males, the reproductive organs are represented by a pair of round, whitish testes adjacent to the ventral surface of the kidneys. Thin seminiferous tubules stretch from the testes to the kidneys. Sexual products from the testis are sent through these tubules to the bodies of the kidneys, then to the Wolffian canals and through them to the cloaca. Before flowing into the cloaca, the Wolffian canals form a small expansion - seminal vesicles, which serve for the temporary storage of sperm.

The reproductive organs of females are represented by paired ovaries of a granular structure. Above them are the fat bodies. They accumulate nutrients that ensure the formation of reproductive products during hibernation. In the lateral parts of the body cavity there are highly convoluted light oviducts, or Müllerian canals. Each oviduct into the body cavity in the region of the heart opens with a funnel; the lower uterine part of the oviducts is sharply expanded and opens into the cloaca.

Ripe eggs fall out into the body cavity through a rupture in the ovarian walls, then are captured by the funnels of the oviducts and move along them to the cloaca.

Wolffian canals in females perform only the functions of the ureters.

In tailless amphibians, fertilization is external. The eggs are immediately irrigated with seminal fluid.

External sexual characteristics of males:

Males have a genital wart on the inner toe of the forelimbs, which reaches a special development at the time of reproduction and helps males hold females during fertilization of eggs.

Males are usually smaller than females. amphibians are accompanied by metamorphosis. The eggs contain relatively little yolk (mesolecithal eggs), so radial crushing occurs. A larva emerges from the egg - a tadpole, which in its organization is much closer to fish than to adult amphibians. It has a characteristic fish-like shape - a long tail surrounded by a well-developed swimming membrane, on the sides of the head it has two to three pairs of external feathery gills, there are no paired limbs; There are lateral line organs; the functioning kidney is the pronephros (pre-kidney). Soon the external gills disappear, and in their place three pairs of gill slits with their gill filaments develop. At this time, the similarity of the tadpole with a fish is also a two-chambered heart, one circle of blood circulation. Then, by protrusion from the abdominal wall of the esophagus, paired lungs develop. At this stage of development, the arterial system of the tadpole is extremely similar to the arterial system of lobe-finned and lungfishes, and the only difference is that due to the absence of the fourth gill, the fourth afferent gill artery passes into the pulmonary artery without interruption. Even later, the gills are reduced. In front of the gill slits, a fold of skin is formed on each side, which, gradually growing back, tightens these slits. The tadpole switches entirely to pulmonary breathing and swallows air through its mouth. Subsequently, the tadpole develops paired limbs - first the front ones, then the hind ones. However, the anterior ones remain hidden under the skin longer. The tail and intestines begin to shorten, mesonephros appears, the larva gradually moves from plant food to animal food and turns into a young frog.

During the development of the larva, its internal systems are reconstructed: respiratory, circulatory, excretory, digestive. Metamorphosis ends with the formation of a miniature copy of the adult individual.

Ambystomas are characterized by neoteny, i.e. They reproduce with larvae, which for a long time were mistaken for an independent species, which is why they have their own name - axolotl. This larva is larger than the adult. Another interesting group are proteas that live permanently in water and retain external gills throughout their lives, i.e. signs of a larva.

The metamorphosis of a tadpole into a frog is of great theoretical interest, because not only proves that amphibians descended from fish-like creatures, but makes it possible to reconstruct in detail the evolution of individual organ systems, in particular the circulatory and respiratory systems, during the transition of aquatic animals to terrestrial ones.

Meaning amphibians is that they eat many harmful invertebrates and themselves serve as food for other organisms in the food chain.

The exchange of gases, or respiration, is expressed in the body’s absorption of oxygen from the environment (water or atmosphere) and the release of carbon dioxide into the latter as the final product of the oxidative process occurring in the tissues, due to which the energy necessary for life is released. Oxygen is perceived by the body in various ways; they can mainly be characterized as: 1) diffuse breathing and 2) local breathing, i.e., by special organs.

Diffuse breathing consists in the absorption of oxygen and the release of carbon dioxide by the entire surface of the outer integument - skin and epithelial membrane of the digestive tube - intestinal respiration, i.e. without organs specially adapted for this purpose. This method of gas exchange is characteristic of some types of primitive multicellular animals, such as sponges, coelenterates and flatworms, and is due to their lack of a circulatory system.

It goes without saying that diffuse respiration is inherent only in organisms in which the body volume is small and its surface is relatively large, since it is known that the volume of the body increases in proportion to the cube of the radius, and the corresponding surface - only to the square of the radius. Consequently, with a large body volume, this method of breathing turns out to be insufficient.

However, even with more or less appropriate volume-to-surface ratios, diffuse respiration still cannot always satisfy organisms, since the more energetically life activity is manifested, the more intense oxidative processes in the body must occur.

With intense manifestations of life, despite the small volume of the body, it is necessary to increase its area of ​​​​contact with the environment containing oxygen, and special devices to accelerate ventilation of the respiratory tract. An increase in the area of ​​gas exchange is achieved by the development of special respiratory organs.

Special respiratory organs vary significantly in the details of their construction and location in the body. For aquatic animals such organs are gills, for terrestrial animals they are trachea and in invertebrates, and for vertebrates they are lungs.

Gill breathing. Gills are external and internal. Primitive external gills are simple protrusions of villous shoots of the skin, abundantly supplied with capillary vessels. In some cases, such gills in their function differ little from diffuse respiration, being only its higher stage (Fig. 332- A, 2). They are usually concentrated in the anterior areas of the body.

The internal gills are formed from the folds of the mucous membrane of the initial section of the digestive tube between the gill slits (Fig. 246-2-5; 332- 7). The skin adjacent to them forms abundant branches in the form of petals with a large number of capillary blood vessels. The internal gills are often covered with a special fold of skin (the operculum), the oscillatory movements of which improve exchange conditions, increasing the flow of water and removing used portions.

Internal gills are characteristic of aquatic vertebrates, and the act of gas exchange in them is complicated by the passage of portions of water to the gill slits through the oral cavity and movements of the gill operculum. In addition, their gills are included in the blood circulation. Each gill arch has its own vessels, and thus, at the same time, a higher differentiation of the circulatory system is achieved.

Of course, with gill methods of gas exchange, cutaneous respiration can also remain, but so weak that it is relegated to the background.

When describing the oropharynx of the digestive tract, it was already said that the gill apparatus is also characteristic of some invertebrates, such as hemichordates and chordates.

Pulmonary breathing-a very advanced method of gas exchange that easily serves the organisms of massive animals. It is characteristic of terrestrial vertebrates: amphibians (not in the larval state), reptiles, birds and mammals. The act of gas exchange concentrated in the lungs is joined by a number of organs with other functions, as a result of which the pulmonary method of breathing requires the development of a very complex set of organs.

When comparing aquatic and terrestrial types of respiration of vertebrates, one important anatomical difference should be kept in mind. During gill respiration, portions of water one after another enter the primitive mouth and are released through the gill slits, where oxygen is extracted from it by the vessels of the gill folds. Thus, the gill breathing apparatus of vertebrates is characterized by an entrance and a number of exit openings. During pulmonary breathing, the same openings are used to introduce and remove air. This feature is naturally associated with the need to take in and push out portions of air for faster ventilation of the gas exchange area, i.e., with the need to expand and contract the lungs.

It can be assumed that the distant, more primitive ancestors of vertebrates had independent muscular tissue in the walls of the swim bladder that transformed into a lung; Its periodic contractions pushed the air out of the bubble, and as a result of its straightening, due to the elasticity of the bubble walls, fresh portions of air were collected. Elastic tissue, along with cartilaginous tissue, still dominates as a support in the respiratory organs.

Subsequently, with the increase in the vital activity of organisms, this mechanism of respiratory movements became imperfect. In the history of development, it was replaced by a force concentrated either in the oral cavity and the anterior section of the trachea (amphibians), or in the walls of the chest and abdominal cavities (reptiles, mammals) in the form of a specially differentiated part of the trunk muscles (respiratory muscles) and, finally, diaphragm. The lung obeys the movements of these muscles, expanding and contracting passively, and retains the elasticity necessary for this, as well as a small muscular apparatus as an auxiliary device.

Skin respiration becomes so insignificant that its role is reduced to almost zero.

Gas exchange in the lungs of terrestrial vertebrates, as well as in aquatic ones, is closely connected with the circulatory system through the organization of a separate, respiratory, or pulmonary circulation.

It is quite clear that the main structural changes in the body during pulmonary breathing come down to: 1) an increase in the contact of the working area of ​​the lungs with air and 2) a very close and no less extensive connection of this area with the thin-walled capillaries of the blood circulation.

The function of the breathing apparatus - to pass air into its numerous channels for gas exchange - speaks for the nature of its construction in the form of an open, gaping system of tubes. Their walls, compared to the soft intestinal tube, are composed of harder supporting material; in some places in the form of bone tissue (nasal cavity), and mainly in the form of cartilage tissue and easily pliable, but elastic tissue that quickly returns to normal.

The mucous membrane of the respiratory tract is lined with special ciliated epithelium. Only in a few areas does it change into a different form in accordance with other functions of these areas, such as in the olfactory region and in the places of gas exchange itself.

Along the pulmonary respiratory tract, three distinctive areas attract attention. Of these, the initial cavity, the nasal cavity, serves to receive air, which is examined here for smell. The second section, the larynx, is a device for isolating the respiratory tract from the digestive tract when a food coma passes through the pharynx, for making sounds and, finally, for producing cough impulses that expel mucus from the respiratory tract. The last section - l e g k and e - represents the organ of direct exchange of gases.

Between the nasal cavity and the larynx there is a cavity common with the digestive apparatus of the pharynx, and between the larynx and the lungs there is a breathing passage.

body throat, or trachea. Thus, the passing air is used by the described expanding sections in three different directions: a) perceived odors, b) devices for making sounds and, finally, V) gas exchange, of which the last is the main one.

Animal breathing – set of processes that providehit into the body from the environmentoxygen , hiscell use for the oxidation of organic substances andexcretion carbon dioxide from the body.This kind of breathing is calledaerobic , and organisms –aerobes .

OK. No. 28. Biology.

Green algae chlorella

Ciliate slipper

The breathing process in animals is conventionally divided into three stages :

External respiration = gas exchange. Thanks to this process, the animal receives oxygen and gets rid of carbon dioxide, which is the end product of metabolism.

Transport of gases in the body– this process is provided either by special tracheal tubes or internal body fluids (blood containing hemoglobin- a pigment that can attach oxygen and transport it into cells, as well as carry carbon dioxide out of cells).

Internal breathing- occurs in cells. Simple nutrients (amino acids, fatty acids, simple carbohydrates) with the help of cell enzymes are oxidized and broken down, during which the ENERGY necessary for the life of the body is released.

The main importance of respiration is the release of energy from nutrients with the help of oxygen, which takes part in oxidation reactions.

Some protozoa - anaerobic organisms, i.e. organisms, not requiring oxygen. Anaerobes There are facultative and obligate. Facultatively anaerobic organisms are organisms that can live both in the absence of oxygen and in its presence. Obligate anaerobic organisms are organisms for which oxygen is toxic. They can only live in the absence of oxygen. Anaerobic organisms do not need oxygen to oxidize nutrients.

Brachionella is an anaerobic ciliate

Intestinal Giardia

Human roundworm

By way of breathing and the structure of the respiratory apparatus in animals there are 4 types of respiration:

Skin respiration - This is the exchange of oxygen and carbon dioxide through the integument of the body. This process is based on the most important physical process - diffusion . Gases enter only in a dissolved state through the covers shallowly and at low speed. Such respiration occurs in organisms that are small in size, have moist integuments, and lead an aquatic lifestyle. This - sponges, coelenterates, worms, amphibians.

Tracheal breathing –

carried out using

connected systems

tubes – trachea , which

permeate the entire body, without

participation of liquids. WITH

their environment

connect special

holes – spiracles.

Organisms with a tracheal

breathing is also small in size (no more than 2 cm, otherwise the body will not have enough oxygen). This - insects, millipedes, arachnids.

Gill breathing – with the help of specialized formations with a dense network of blood vessels. These outgrowths are called gills . In aquatic animals - polychaetes, crustaceans, mollusks, fish, certain species of amphibians. In invertebrate animals, gills are usually external, while in chordates they are internal. Gill-breathing animals have additional forms of respiration through the skin, intestines, surface of the mouth, and swim bladder.

Polychaete with gills

Crustacean gills

Nudibranch

Pulmonary respiration – this is breathing with the help of internal specialized organs – lungs.

Lungs– These are hollow thin-walled bags, braided with a dense network of tiny blood vessels - capillaries. Diffusion of oxygen from the air into the capillaries occurs on the inner surface of the lungs. Accordingly, the larger the internal surface, the more active the diffusion.

Almost all terrestrial vertebrates breathe through their lungs. reptiles, birds, some terrestrial invertebrates - spiders, scorpions, pulmonary mollusks, and some aquatic animals - lungfish. Air enters the lungs through Airways.

Lungs of a mammal

Reptile lung

Respiratory system of birds

Breathing in animals is determined by their way of life and is carried out using the integument, trachea, gills and lungs.

Respiratory system – a set of organs for conducting air or water that contain oxygen and exchanging gases between the body and the environment.

The respiratory organs develop as outgrowths of the outer integument or walls of the intestinal tract. The respiratory system includes the airways and gas exchange organs. In vertebrates Airways – nasal cavity, larynx, trachea, bronchi ; A respiratory system -lungs .

Comparative characteristics of the respiratory organs.

Functions of the respiratory system:

Delivery of oxygen to body cells and removal of carbon dioxide from body cells and gas exchange(main function).

Body temperature regulation(because water can evaporate through the surface of the lungs and respiratory tract)

Purification and disinfection of incoming air(nasal mucus)

Questions for self-control.

Comparative characteristics of the respiratory organs of animals.

Evolution of the respiratory system

Stages of the breathing process

Breath– a set of processes that ensure the supply of oxygen to the body from the environment, necessary for the oxidation of organic substances in the mitochondria of the cell, and the release of carbon dioxide

Breathing types:

Breathing type:

Cellular.
Organisms: single-celled animals (amoeba, green euglena, slipper ciliates); coelenterates (jellyfish, coral polyps); some worms.

Single-celled organisms absorb oxygen dissolved in water over the entire surface of the body by diffusion.

Oxygen is involved in the breakdown of complex organic substances, resulting in the release of energy that is necessary for the life of the animal.
The carbon dioxide produced as a result of respiration is also released through the entire surface of the body.

Tracheal breathing is breathing using a system of united tracheal tubes that permeate the entire body.

Organisms: class Insects (beetles, butterflies, grasshoppers, flies)

The insect's abdomen is divided into 5–11 parts (segments). Each of them has a pair of small holes - spiracle. Branching tubes extend inward from each spiracle - trachea, which permeate the entire body of the insect. Watching the cockchafer, you can notice how its abdomen either decreases in volume or increases in size. These are breathing movements. When you inhale, air containing oxygen enters the body through the spiracles, and when you exhale, air saturated with carbon dioxide comes out.

In spiders (class Arachnids), the respiratory organs are represented not only by tracheas, but also by pulmonary sacs, which communicate with the external environment through the respiratory openings.

Gill respiration is breathing using specialized structures with a dense network of blood vessels.

Organisms: many aquatic inhabitants (fish, crayfish, mollusks)

Fish breathe oxygen dissolved in water with the help of special branched skin outgrowths called gills. Fish constantly swallow water. From the oral cavity, water passes through the gill slits, washes the gills and comes out from under the gill covers. Gills consist of gill arches And gill filaments, which are penetrated by many blood vessels. From the water that washes the gills, oxygen enters the blood, and carbon dioxide is removed from the blood into the water. The gills located inside the body are called internal gills.
Some animals, such as amphibians, have dense tufts of gills on the surface of their bodies. Such gills are called - external. This is the structure of Proteus, a blind cave animal from the western regions of Yugoslavia, and axolotls (which are similar in general appearance to newts) - their homeland is Mexico.