3. The digestive system The dog's body is built from complex organic substances - proteins, carbohydrates, fats. The most important of these is protein. In addition to these organic substances, the body also contains inorganic substances - salts and a large amount of water (from 65 to

5. System of organs of blood and lymph circulation The cells of the body require a constant supply of nutrients and the removal of unnecessary and harmful substances - the products of their vital activity. These functions in the body are performed by the system of blood and lymph circulation organs. The system

6. System of organs of urinary excretion In the process of constantly occurring metabolism in the body, waste products of cell nutrition and mainly protein breakdown products that are harmful to the body are formed. In addition, the body accumulates substances that are not harmful, but

7. System of organs of reproduction Reproduction is one of the most important functions of the body and ensures the continuation of the genus. To perform the functions associated with reproduction, in dogs the reproductive apparatus is used. The genital apparatus of the male. The male genital apparatus consists of

8. The system of organs of internal secretion The organs of internal secretion are glands that produce and secrete special substances directly into the blood - hormones. A characteristic feature of hormones is their ability in negligible amounts to exert

Respiratory diseases V. A. Lipin

Examination of the respiratory organs To determine the disease of the respiratory organs during the examination of the dog, the following methods are used: examination, palpation, percussion and auscultation. Of the additional methods, X-ray examination is used. By examination

Chapter IX The Respiratory System, Nose, and Sinuses The Air We Breath Clean fresh air nourishes the lungs and purifies the soul, just as good nutrition provides vital energy to the body (it is no coincidence that the words "soul" and "breath" come from the same root in all languages) .

Topic 8. AGE FEATURES OF THE RESPIRATORY ORGANS 8.1. The structure of the respiratory organs and the vocal apparatus. The nasal cavity. When breathing with a closed mouth, air enters the nasal cavity, and with an open one - into the oral cavity. Bones and cartilages are involved in the formation of the nasal cavity, of which

8.1. The structure of the respiratory organs and the vocal apparatus. The nasal cavity. When breathing with a closed mouth, air enters the nasal cavity, and with an open one - into the oral cavity. Bones and cartilage are involved in the formation of the nasal cavity, which also make up the skeleton of the nose. Most of

nasal cavity. The anterior part of the nose in dogs is easily mobile; its posterior border runs approximately at the level of the canine, and the free end protrudes somewhat forward, beyond the body of the incisor bones. The movable area has a cartilaginous skeleton, slightly expanding towards the free end (Fig. 336). The cartilaginous nasal septum thickens towards the oral margin and forms small paired (dorsal and ventral) lateral cartilages of the nose (2, 3).
The dorsal lateral cartilage curves and hangs from the dorsal margin of the nasal septum. It is thin, long and the convex side is directed outward. Towards the oral (free) end, it becomes shorter and is the frame of the upper wing of the nose. The ventral lateral cartilage originates from the lower edge of the septum. It is smaller, but much thicker than the dorsal one, and also convex to the outside. It does not reach the most anterior end of the nasal septum, since there is an additional cartilage in the form of a triangular plate (4); it serves as the skeleton of the medial wing of the nose.
The area of ​​the nose (Fig. 362) puts on the usual hairy skin with its inherent sebaceous and sweat glands. Only in the anterior part - the nasal mirror - does it change greatly, as it loses hair and any glands; the epidermis here is of considerable thickness and is divided from the surface by many grooves into small fields of a mirror. The nasal mirror covers the top of the nose from all sides, without falling, however, on the upper lip; on its front surface, along the midsagittal line, there is a groove, or filter, in different breeds of unequal depth. The nasal mirror in healthy animals is moistened and, due to the constant evaporation of the liquid, is always somewhat cooled.

The dog is a typical representative of the wolf family (Canidae), a predatory animal; Under natural conditions, it is active at dusk. The structure of the body is adapted to an active lifestyle. The skeleton is distinguished by great strength with relative lightness. When walking, the dog leans on its toes. Nails are blunt and strong, not retractable.

The respiratory system of a dog has a structure typical of mammals. Air enters the nasal cavity through the nostrils, where it is heated and cleaned of the main mass of dust. The anterior part of the nose in dogs is easily mobile. The cartilaginous nasal septum thickens towards the oral margin and forms small (dorsal and ventral) lateral cartilages.

The area of ​​the nose is covered with the usual hairy skin, but in the anterior area (nasal speculum) it is devoid of hair, so the epidermis is of considerable thickness here and is divided from the surface by many grooves into small areas of the speculum. In the nasal cavity are the dorsal and ventral shells, and in its posterior-upper section there are curls of the labyrinth of the ethmoid bone.

The lining of the nasal cavity contains a mass of cells associated with odor recognition. The nasal cavity is followed by the nasopharynx and larynx, which is a complex cartilaginous formation. The larynx is relatively wide and almost square in shape.

Elastic fibers of the vocal cords are stretched between the cartilages of the larynx, their vibrations create sounds. Dogs can make a wide variety of sounds: barking, howling, growling, screeching, snorting, whining. The tone of sounds changes significantly. Different sound signals carry information about the intentions of the dog, its emotional state, that is, they have some language functions. Dogs widely use sound signals in communication, perfectly understanding each other. If desired, an observant owner can also learn to understand his pet perfectly.

The lower part of the dog's larynx passes into the trachea, which splits into two bronchi passing into the lungs. The trachea consists of 42 - 46 rounded rings. The lungs themselves are a paired hollow organ, divided into lobes. Each lobe, in turn, is divided into smaller lobules consisting of vesicles (alveoli).

The left lung has three lobes - apical, cardiac and diaphragmatic. The right lung has four lobes - apical, accessory, cardiac and diaphragmatic. In the alveoli of the lungs, air oxygen passes into the blood, enters into combination with the hemoglobin of erythrocytes and is transported to organs and tissues, venous blood is released from carbon dioxide, which is excreted from the body with exhaled air.

The cardiac notch, which lies between the 3rd and 7th ribs, leaves the ventral portion of the heart exposed.

The entire inner surface of the lungs is lined with a layer of mucus-covered cells. Mucus precipitates dust particles and gradually brings them out. However, the self-cleaning capabilities of the lungs are not unlimited - in heavily dusty and smoky air, solid particles, being deposited, gradually clog individual alveoli and thereby weaken the respiratory function.

4. Respiratory system

Respiration is the process by which the body takes in oxygen and releases carbon dioxide. This vital process consists in the exchange of gases between the body and the atmospheric air surrounding it. When breathing, the body receives the oxygen it needs from the air and removes the carbon dioxide accumulated in the body to the outside. The exchange of gases in the body must occur continuously. The cessation of breathing for at least a few minutes entails the death of the animal. Breathing is externally manifested by a series of alternating expansions and contractions of the chest. The process of respiration is composed of: from air exchange between the lungs and atmospheric air, from gas exchange between the lungs and blood - external, or pulmonary, respiration, and from gas exchange between blood and tissues - internal, or tissue, respiration. Respiration is carried out by the organ system, or breathing apparatus. It consists of airways - the nasal cavity, larynx, trachea and lungs. The chest also participates in the act of breathing.

nasal cavity. The nasal cavity is the first section of the airways. The bones of the nasal cavity are the facial bones, the ethmoid bone, and the anterior edge of the sphenoid and frontal bones. Inside, the nasal cavity is divided into two halves by the nasal septum. Its anterior part is cartilaginous, and the posterior part is bony. The nasal cavity begins with two, somewhat split at the bottom, openings called nostrils. The walls of the nostrils are formed by lateral cartilages extending from the front of the nasal septum. These cartilages prevent the walls of the nostrils from collapsing during inhalation. Between the nostrils is an area of ​​skin with a rough, slightly bumpy surface (usually black), devoid of hair, called the nasal planum. The movable part of a dog's nose is called the lobe. In a healthy dog, the nasal planum is always somewhat moist and cool.

In each half of the nasal cavity there are thin, spirally curved bone plates - nasal conchas. They divide the nasal cavity into three passages - lower, middle and upper. The lower nasal passage is initially narrow, but becomes wider posteriorly and merges with the middle passage. The upper passage is narrow and shallow. The lower and middle nasal passages are used for the passage of air during quiet breathing. When you take a deep breath, does the air flow reach the upper nasal passage? where the organ of smell is located (Fig. 48).

The initial part of the nasal cavity is covered with a flat, stratified epithelium, turning in deeper parts into a cylindrical, ciliated epithelium. The latter is characterized by the fact that at the free end of the cell there are bundles of thin mobile filaments called cilia or ciliated hairs, from which the name of the epithelium comes.

Passing through the nasal cavity, the air warms up (up to 30-32 °) and is cleared of foreign mineral and organic particles suspended in it. This is facilitated by a large surface of the folded mucous membrane, covered with ciliated epithelium, the purpose of which is to trap small particles of air dust with the movement of its cilia, which are then released from the nose with mucus. Irritation of the cilia causes sneezing.

In the olfactory region of the mucous membrane there are cells of special sensitivity, the so-called olfactory. Their irritation with particles of odorous substances causes a sensation of smell. This part of the nasal cavity serves as an organ of smell.

Larynx. Inhaled air, heading from the nasal cavity to the trachea, passes through the larynx. The larynx lies below the entrance to the esophagus, communicating with the nasal cavity through the nasopharynx. The larynx is made up of five cartilages connected by muscles and ligaments. One of these cartilages, encircling the entrance to the trachea, is called the annular or cricoid, the other is the thyroid, and the two located on top are the arytenoids. The anterior cartilage protruding into the pharynx is called the epiglottis.

The cavity of the larynx is lined with a mucous membrane covered with ciliated epithelium. Irritation of the mucous membrane of the larynx causes coughing. G the inner side of the larynx, the mucous membrane forms folds, which are based on the vocal cords and muscles. The vocal cords, directed with their free ends towards each other, limit the glottis. When the muscles contract, the vocal cords tighten and the glottis narrows. With a strong exhalation of air, the tense vocal cords are vibrated, as a result of which a sound (voice) is created.

Trachea, or windpipe. The trachea is a tube consisting of annular cartilaginous plates (a type of corrugated gas mask tube). In a dog, the trachea is nearly cylindrical. The ends of the cartilaginous plates do not reach each other. They are connected by a flat stretched transverse ligament, which protects them from damage when pressed, for example, with a collar. From the side of this ligament, the trachea is adjacent to the esophagus located above it. The mucous membrane lining the trachea is covered with ciliated epithelium, between the cells of which individual mucous glands are scattered. The cilia of the ciliated epithelium fluctuate towards the larynx, due to which the secreted mucus, and with it small dust particles, are easily removed from the trachea (Fig. 49).

With a significant accumulation, they are thrown out by coughing shocks.

Lungs. A dog has two lungs, a right and a left. The lungs lie in the chest cavity, almost completely occupy it and are supported in their position by the bronchi, blood vessels and fold of the pleura. Each lung is divided into three lobes - apical, cardiac and diaphragmatic. In the right lung, the dog has an additional lobe (Figures 50 and 51).

The structure of the lungs is as follows. The trachea, entering the chest cavity, divides into two large bronchi, which enter the lungs. In the lungs, the bronchi branch into smaller branches and approach, in the form of terminal bronchi, the so-called respiratory lobules. Entering the lobules of the lung, each bronchus divides into branches, the walls of which protrude in the form of a large number of small sacs called pulmonary alveoli. In these alveoli, gas exchange takes place between air and blood.

The pulmonary artery approaches the lungs from the heart. Entering the lungs, it branches parallel to the bronchi and gradually decreases in size. In the lobules of the lung, the pulmonary artery forms a dense network of tiny capillaries that surround the surface of the alveoli. Rice. 51. A cast of two lobules of the bronchi. After passing through the alveoli, the capillaries, merging into larger vessels, form the pulmonary veins, which run from the lungs to the heart.

Thoracic cavity. The chest cavity is cone shaped. Its side walls are the skeleton of the chest with intercostal muscles, the diaphragm is located behind, and the cervical muscles, blood vessels and nerves are located in front.

The chest cavity is lined with a serous membrane called the parietal pleura. The lungs are also lined with a serous membrane called the pulmonary pleura. Between the parietal and pulmonary pleura remains a narrow gap filled with a small amount of serous fluid. There is a negative pressure in this narrow gap, as a result of which the lungs are always in a somewhat stretched state and are always pressed close to the chest wall and follow all its movements.

In addition to the lungs, the heart is located in the chest cavity and the esophagus, blood vessels and nerves pass through.

Breathing mechanism. To inhale, the chest cavity must expand. The intercostal muscles, contracting, raise the ribs. At the same time, the middle of the ribs rises upwards and somewhat departs from the midline, and the sternum, which is motionlessly connected to the ends of the ribs, follows the movement of the ribs. This increases the volume of the chest cavity. The expansion of the chest cavity is also facilitated by the movement of the diaphragm. In a calm state, the diaphragm is a dome, the convex part of which is directed towards the chest cavity. When inhaling, this dome becomes flatter, the edges of the diaphragm adjacent to the chest wall move away from it, and the chest cavity increases. The lungs, with each expansion of the chest, passively follow its walls and expand by the pressure of the air in the alveoli. The pressure of this air, due to the increase in the volume of the alveoli, becomes less than atmospheric pressure, as a result of which the outside air rushes into the alveoli and inhalation occurs.

After inhalation comes exhalation. During exhalation, the muscles of the chest and diaphragm relax. The costal ligaments and cartilages, by virtue of their elasticity, tend to take their former position. The abdominal organs (liver, stomach), pushed aside by the diaphragm during inspiration, return to their normal position. All this causes a decrease in the chest cavity, the walls of which begin to put pressure on the lungs, and they collapse. In addition, the lungs collapse due to their elasticity, and at the same time the air pressure in them becomes greater than atmospheric pressure, which creates conditions conducive to pushing the air out of the lungs - exhalation occurs. With increased exhalation, the abdominal muscles are also actively involved. They move the abdominal organs towards the chest, which increases pressure on the diaphragm.

When exhaling, the lungs are not completely freed from the air contained in them, which is called residual.

There are three types of breathing: abdominal, thoracic and costo-abdominal. In a calm dog, the type of breathing is abdominal. With deep breathing, it becomes costabdominal. Thoracic type of breathing occurs only with shortness of breath.

The respiratory rate, that is, the number of inhalations and exhalations per minute, in a dog in a calm state ranges from 14 to 24. Depending on various conditions (pregnancy, age, internal and external temperature), the respiratory rate may change. Young dogs breathe more frequently. The dog's respiratory rate increases greatly during heat and during muscular work.

Respiratory movements are regulated by the respiratory center located in the medulla oblongata. The excitation of the respiratory center occurs mainly automatically. In the blood washing it, an excess of carbon dioxide appears, which excites the cells of the respiratory center. This creates a kind of self-regulation system of breathing. On the one hand, the accumulation of carbon dioxide causes increased ventilation of the lungs and promotes the removal of carbon dioxide from the blood. On the other hand, when increased ventilation of the lungs leads to saturation of the blood with oxygen and a decrease in the content of carbon dioxide in it, the excitability of the respiratory center decreases and breathing is delayed for a while. The sensitivity of the respiratory center is very high. Breathing changes dramatically during muscular work, when the products of muscle metabolism (lactic acid) do not have time to oxidize and enter the blood in a significant amount, stimulating the respiratory center. The excitation of the respiratory center can also occur in a reflex way, that is, as a result of excitation of the peripheral nerves leading to the medulla oblongata. So, for example, pain sensations can cause a short cessation of breathing, followed by a long breath, sometimes accompanied by a groan or bark. A short cessation of breathing also occurs when cold is applied to the end, for example, when immersed in cold water.

Gas exchange in the lungs and tissues. The exchange of gases in the lungs and tissues occurs due to diffusion. The essence of this physical phenomenon is as follows: the air entering the alveoli of the lungs contains more oxygen and less carbon dioxide than the blood flowing to the lungs. Due to the difference in gas pressure, oxygen will pass through the walls of the alveoli and capillaries into the blood, and carbon dioxide will pass in the opposite direction. Therefore, the composition of exhaled and inhaled air will be different. Inhaled air contains 20.9% oxygen and 0.03% carbon dioxide, and exhaled air contains 16.4% oxygen and 3.8% carbon dioxide.

Oxygen from the alveoli of the lungs is transported to the blood throughout the body. The cells of the body are in dire need of oxygen and suffer from an excess of carbon dioxide. Oxygen in the cells is consumed for oxidative processes, so it is less in the cells than in the blood. Carbon dioxide, on the contrary, is constantly formed and there is more of it in the cells than in the blood. Due to this difference between blood and tissues, gas exchange or the so-called tissue respiration occurs.

The relationship of the respiratory organs with the functions of other organs. The respiratory organs are closely related to the circulatory system. The heart lies next to the lungs and is partially covered by them. Constant ventilation of the lungs during breathing cools the heart muscle and protects it from overheating.

Breathing movements of the chest promote blood circulation.

The respiratory organs are closely connected with digestion. When breathing, the diaphragm presses on the abdominal organs and, above all, on the liver, which contributes to a better secretion of bile. The diaphragm helps the act of defecation. Breathing is closely related to the muscles. Even slight muscle tension causes increased breathing.

The respiratory organs are an important factor in thermoregulation.

The respiratory organs of the dog are represented by the upper respiratory tract and lungs. The upper respiratory tract includes the nostrils, nasal passages and cavities, nasopharynx, larynx, trachea, and large bronchi. The inhaled air, passing through them, is subjected to thermoregulation, purification from mechanical particles (dust). The mucous membrane lining the upper respiratory tract has bactericidal properties. Therefore, microbes die in the upper respiratory tract, and sterile air enters the lungs.

For dogs, the function of chemical analysis of the inhaled air is of particular importance. The olfactory receptors are located in the nasal passages. The dog, before taking a deep breath, makes frequent shallow breaths, during which the air is in continuous contact with the receptor apparatus, and the animal receives rich information about the external environment. This behavior is especially noticeable in dogs in unfamiliar surroundings. Obviously, the dog trusts the sense of smell more than the human. During the walk, the dog bypasses "its" territory, evaluates it with the help of the olfactory organs, not forgetting to leave odorous marks.

The mechanism of inhalation and exhalation occurs due to the contraction of the respiratory muscles - the diaphragm and the muscles of the chest. When inhaling, the external intercostal muscles and the diaphragm contract.

The volume of the chest increases, due to the vacuum in the pleural cavity, the lungs are stretched, and the air passively fills them. When the respiratory muscles relax, the chest decreases in volume, and the air is squeezed out of them. There is an exhalation.

The frequency of respiratory movements is regulated by the central nervous system, the functional activity of which depends on the concentration of carbon dioxide, oxygen and the pH of the blood. At rest, medium and large dogs make 10-30 movements, small animals breathe more often.

Actually, gas exchange occurs in the lungs as a result of the difference in the partial pressure of oxygen and carbon dioxide. The partial pressure of oxygen is higher in the alveolar air, so it passes into the blood. In the case of carbon dioxide, the picture is opposite: in the venous blood, the partial pressure of CO 2 is higher than in the alveolar air, and carbon dioxide actively passes from the blood into the alveoli of the lung tissue.

Oxygen transport in the blood occurs with the help of erythrocyte hemoglobin, and carbon dioxide transport occurs due to carbonates and bicarbonates of blood plasma.

NON-RESPIRATORY FUNCTIONS OF THE RESPIRATORY ORGANS

Together with the inhaled air, foreign or even harmful substances and particles can enter the respiratory system in the form of aerosols or gases. However, after contact with the mucous membrane of the upper respiratory tract, most of them are removed from the body. The penetration depth of foreign air components depends on the size of these particles. Large particles (dust), whose dimensions exceed 5 microns, are deposited on the mucosa due to inertial forces in places where the bronchi are bent. Heavy particles cannot go around the bend of the bronchi and, by inertia, hit the wall of the bronchus. According to the same scheme, air is released from particles ranging in size from 0.5 to 5.0 microns. However, this process already occurs in the bronchioles of the lungs. Particles smaller than 0.5 μm penetrate into the alveoli of the lungs and penetrate into the mucous membrane of the respiratory epithelium.

The nature of breathing has a great influence on the retention of foreign particles in the upper respiratory tract of a dog: with slow and deep microparticles penetrate into the lungs, frequent and superficial helps to purify the air in the upper respiratory tract.

Thus, particles adsorbed on the mucous membrane of the upper respiratory tract are expelled towards the nasopharynx or nasal passages due to oscillatory movements of the ciliated epithelium. Then they are either swallowed or thrown into the external environment due to a sharp exhalation (sneezing). In the lung alveoli, foreign particles are phagocytized by macrophages. Bacterial cells are exposed to bactericidal substances in the mucus of the lung epithelium (complement system, opsonins, lysozyme). As a result, all corpuscular particles are destroyed or transported by macrophages outside the respiratory organs.

Lung macrophages are adapted to the conditions of the alveoli, i.e., they are active in an oxygen-rich environment. Therefore, hypoxia inhibits phagocytosis in the lungs. Animal stress is also accompanied by a decrease in the protective properties of the respiratory organs, since corticosteroids suppress the activity of macrophages. A viral infection also leads to a similar result. Alveolar macrophages constitute the dog's front line of defense. In the case when a large amount of corpuscular particles is inhaled, other phagocytes come to the aid of macrophages - primarily blood neutrophils.

However, with excessive activity of phagocytes, the reactive oxygen radicals and proteolytic enzymes released by them can damage the epithelium itself, lining the pulmonary alveoli. In order to restrain the excessive activity of phagocytes, protease inhibitors (α-antitrypsin) and antioxidants (glutathione peroxidase) enter the mucus of the lung epithelium. These substances protect the lungs from the damaging effects of their own protective system of the respiratory system.

The penetration of harmful gases in the respiratory air into the body of a dog depends on their concentration and solubility. Gases with high solubility (for example, SO 2) in small concentrations are retained in the nasal cavities due to adsorption on the mucous membrane, but in high concentrations they penetrate into the lungs.

Gases with low solubility reach the pulmonary alveoli in an unchanged state. However, toxic gases stimulate protective mechanisms such as bronchospasm, mucus hypersecretion, coughing and sneezing, which block their diffusion or provide mechanical removal from the respiratory system.

With a huge capillary area (a reactive surface with fixed enzymes), a high oxygen supply and a developed cellular antitoxic system, the lungs are an ideal place for thorough blood purification from biologically active and, therefore, potentially dangerous metabolites for the body. Thus, the endothelial cells of the pulmonary capillaries absorb the entire volume of serotonin produced in the dog's body. A number of prostaglandins, bradykinin and angiotensin are also metabolized here. Neutrophils found in the lungs ensure the destruction of leukotrienes.

Macrophages of the respiratory organs are related to the regulation of fat metabolism. The fact is that blood with a high level of lipids enters the lungs. A high lysing activity of macrophages in relation to lipoproteins entering the body with lymph from the gastrointestinal tract was noted. As a result of the absorption of lipoproteins by macrophages, the latter increase in size (mast cells), and the blood is cleared of excess fatty substances. With active blood flow and hyperventilation of the lungs (physical activity), excess fat is oxidized and removed from the body in the form of thermal energy with exhaled air.

Peculiar breathing of dogs in conditions of high temperatures - shortness of breath is a normal physiological phenomenon. The respiratory rate under these conditions can exceed 100 for 1 min. The physiological meaning of shortness of breath is hyperventilation of the upper respiratory tract and lungs in order to increase evaporation from the mucous membrane. Evaporation of moisture is accompanied by cooling of the surface of the upper respiratory tract and lungs and the blood flowing to them. Consequently, in dogs, the respiratory organs also perform the function of thermoregulation in conditions of elevated temperatures.

Thus, the physiological role of the respiratory organs in the dog is not limited to gas exchange. The respiratory system of the dog is involved in the reactions of immunity, metabolism, thermoregulation of the body.

FEATURES OF THE DIGESTIVE SYSTEM

The digestive system is one of the most plastic physiological systems, which provides a relatively quick adaptation of animals to a variety of sources of proteins, fats and carbohydrates. The dog is an omnivore, although its ancestors were mostly predators. The dog's digestive system has been studied in great detail. She has a rather short gastrointestinal tract, well adapted to the use of mixed diets, including both animal and vegetable foods.

The dog grabs food with the help of incisors. Mechanical processing of food oral cavity rather superficial: the animal cuts the meat into large pieces, crushes them with molars and swallows, i.e., there is no thorough grinding of food in the dog's mouth.

If the dog is very hungry, then it can swallow very large pieces, practically without chewing them. True, often after such a meal, the dog burps the contents of the stomach and re-chews the food.

It is believed that the dog captures food with the help of incisors, premolars and molars (especially the 4th upper and 5th lower) provide crushing. Fangs are a murder weapon for hunters and a fighting weapon in fights for other dogs.

The teeth determine the age of dogs. The first milk teeth appear in puppies at the age of two weeks. A full set of milk teeth is formed (depending on the breed) at the age of 1-2 months. For example, in German Shepherd puppies at the age of 5-6 weeks, all milk teeth are miscalculated. And in standard schnauzer puppies, a complete set of teeth is formed later - at 7-9 weeks of age.

Normally, by 6 months of age, all milk teeth are replaced by permanent ones. Starting from the age of 12-18 months, a noticeable abrasion of teeth begins, and this phenomenon proceeds at the same rate in most dogs, that is, it is a general biological phenomenon. There is a prejudice that the degree of abrasion of the teeth determines the nature of nutrition. In particular, bones accelerate this process. Our personal experience with keeping dogs is rather the opposite: the bones strengthen the jaws and improve the blood supply to the gums.

The basis for determining the dog's age is the wear rate, primarily of the upper edge of the incisors. So, by the 2nd year of life, the teeth of the hooks wear out; to the 3rd - this process captures the middle incisors; to the 4th - the teeth disappear on the edges; by the 5th year of life, teeth are distinguishable only on the upper margins; by the age of 10, the incisors have an obverse oval edge; by 12 some incisors begin to fall out; by 14 canines, premolars and molars begin to fall out. The above scheme is rather approximate, and individual individuals do not fit into it. So, the 15-year-old mittelynna-utser known to us can be given no more than 2 years according to the picture of abrasion of teeth.

In addition to mechanical processing, food in the oral cavity is affected by saliva. Three large paired salivary glands open into the oral cavity - parotid, submandibular and sublingual. In addition, on the tongue, cheeks and lips of the dog there are multiple small salivary glands that secrete mucus.

Salivation in a dog occurs at the sight, smell of food, and also during its reception. Especially strong salivation is observed in dogs when they gnaw something, for example, a bone. The total amount of saliva per day reaches 1 liter in a medium-sized dog. However, the level of salivation is highly dependent on the moisture content of the feed. More saliva is separated on dry food like "Chapi" than on liquid soup.

Under the action of saliva, dry food is moistened, the food lump is mucilaginous. Moisturizing the feed is provided mainly by the saliva of the parotid glands - it is quite liquid. The saliva of the submandibular and sublingual glands is mixed, that is, it wets and licks food. Small mucous glands secrete saliva containing a mucus-like substance called mucin.

After such processing, the food lump is easily swallowed by the animal. Saliva contains glycolytic enzymes, i.e., enzymes that act on the carbohydrate part of the feed. Therefore, carbohydrate food is partially broken down in the dog's mouth already. But taking into account the short residence time of food in the dog's mouth, it is unlikely that a deep transformation of carbohydrates in the dog's mouth is possible.

Dog saliva is highly bactericidal due to the presence of lysozyme in it, a substance that can destroy the bacterial cell wall. Consequently, in the oral cavity, food is partially disinfected by the action of saliva. The same reason underlies the high effectiveness of dog licking wounds. Licking a wound on the body, the dog cleans it of dirt, produces a bactericidal treatment of the wound and, in addition, due to saliva kinins, increases the rate of blood clotting in damaged vessels.

The stomach of dogs is a simple one-chamber, only partial digestion of food occurs in it, and only proteins and emulsified fats undergo deep transformation.

Digestion in the dog's stomach occurs under the influence of gastric juice, which includes hydrochloric acid, enzymes, minerals and mucus. The secretion of gastric juice is carried out according to certain laws, which were studied in detail by our outstanding compatriot, Nobel Prize winner in physiology IP Pavlov.

In accordance with modern concepts, the secretion of gastric juice is carried out in three phases.

First phase- nervous. The sight and smell of food leads to the release of the so-called ignition gastric juice. Nervous excitation associated with the expectation of food leads to the fact that nerve impulses from the CNS excite the intramural nervous system of the stomach, which, in turn, stimulates the secretion of gastrin and hydrochloric acid by the cells of the gastric wall. Gastrin excites the nerve endings of the intramural nervous system of the stomach, which leads to the release of acetylcholine. Acetylcholine paired with gastrin excite the parietal cells of the digestive glands of the stomach, which causes an even greater secretion of HCL.

Second phase- neuro-humoral - is provided by ongoing nervous excitation, irritation of the receptor apparatus of the stomach and absorption of extractive substances of the feed into the blood. A complex of enzymes in the composition of gastric juice is secreted into the lumen of the stomach.

Third phase gastric juice secretion - purely humoral. It develops as a result of absorption into the blood of the products of hydrolysis of proteins and fats.

While gastrin is being secreted, the pH value of the gastric chyme is constantly decreasing. When the pH reaches 2.0, inhibition of gastrin secretion begins. At pH 1.0, gastrin secretion stops. At such a low pH value, the pyloric sphincter opens and the gastric chyme is evacuated in small portions into the intestine.

The gastric juice of a dog contains many proteolytic enzymes: several forms of pepsin, cathepsin, gelatinase, chymosin elastase (the latter is found in large quantities in the gastric juice of suckling puppies). All these enzymes break the internal bonds of long protein chains in food. The final fragmentation of protein molecules occurs in the small intestine.

The role of the stomach in fat digestion is limited to emulsified fats. A fat emulsion is a mixture of tiny fat particles and water molecules. The prevalence of fat emulsions in dog foods is very limited. An example of the emulsification of fats can only be whole milk. Therefore, gastric lipase is most active in puppies during the lactation period. In adult dogs, there is virtually no digestion of fats in the stomach. Moreover, fatty foods also inhibit the digestion of proteins in the stomach.

IN thin department intestines all nutrients of the feed - proteins, fats, carbohydrates - are subjected to deep splitting. Pancreatic enzymes, intestinal juice and bile are involved in this process.

Here, in the small intestine, the absorption of hydrolysis products also occurs. Proteins are broken down and absorbed in the form of amino acids, carbohydrates - in the form of monosaccharides (glucose), fats - in the form of fatty acids, mono-glycerides and glycerol.

At the dog large intestineka comparatively short. Nevertheless, it has its own irreplaceable functions. In particular, the absorption of water and mineral salts dissolved in it occurs in the large intestine. In the large intestine, although limited, but in conditions of poor nutrition, a vital synthesis of B vitamins and essential amino acids occurs.

It should be said that biologically active substances synthesized in the thick section by symbiotic microbes can no longer be absorbed practically in this part of the intestine. Consequently, this synthesis has a biological meaning only in case of autocaprophagy, i.e., the eating of one's own excrement during forced starvation of dogs.

The large intestine in its wall has a huge number of lymphoid formations that are related to the immune defense of the body, for example, the formation of | 3-lymphocytes.

Motor function of the intestine very pronounced in the dog. It is represented by three types of contractions - worm-like, pendulum-shaped, segmenting peristalsis and anti-peristalsis. Worm-like peristalsis ensures the movement of food gruel through the digestive tube. Pendulum-shaped and segmenting - mixing chyme with digestive juices. Antiperistalsis for a dog is an absolutely normal phenomenon:

when the stomach is full, the dog is freed from excess food;

when cartilage, bones are consumed, secondary more thorough processing is often required, which the dog does after burping.

In many lactating bitches with a strong maternal instinct, the following behavior can be observed: the dog eats clearly more than its capacity, and then regurgitates the food to the puppies.

A medium-sized lactating bitch was eating a nearly pail of food waste in the backyard of a canteen. Then she moved with great difficulty towards her kennel (at the same time, her stomach literally dragged along the ground). Finally, reaching the kennel, she regurgitated the contents of the stomach on the puppies. Thus, using her own stomach for transportation, she created a large supply of food for the puppies. Moreover, the regurgitated food mass looked more preferable for the adult members of the dog pack as compared to the unprocessed food.

The gastronomic preferences of dogs often shock their owners. Even among urban dogs provided with good nutrition, the phenomenon of coprophagia, i.e., eating the feces of other animal species (horses, cattle and humans), is common.

When slaughtering sheep and cattle, several dogs (domestic and neglected) were given the right to choose. After slaughter and opening of the abdominal cavity, all dogs preferred the gastrointestinal tract, i.e., gastric and intestinal chyme turned out to be more attractive than meat. This phenomenon is quite normal and understandable. Chyme contains semi-digested nutrients and, in addition, is rich in vitamins of microbiological origin, minerals of endogenous origin.

Chyme eating and coprophagia is a way to meet the dog's needs for biologically active substances and nutrients that are easily available for assimilation. Such behavior of dogs should not be regarded as abnormal. Objections on the part of a person in this matter have an exclusively aesthetic background.

The frequency of bowel movements and the amount of excreted feces in dogs varies depending on the breed (live weight), the volume of the daily ration and the frequency of feeding.