Let's study the internal structure of a rabbit together. Rabbit skeleton: structure and features Respiratory system and its role in the life of a rabbit

A rabbit (live) blood is distributed approximately as follows: in the muscles about 1/4 of the total blood, in the liver - about 1/4, in the heart and large vessels - about 1/4 and 1/4 in all other organs.

The total amount of blood in rabbits is 32 - 67 ml (from 4.5 to 6.7% of their weight). Blood pH 7.25 - 7.43. Specific gravity 1.0425. There are 4.5 million red blood cells in 1 ml of blood in newborn rabbits, on average about 5 million in adults (from 2.76 to 6.32 million), in males they are 7 - 8% more than in females. There are an average of 8800 leukocytes in 1 ml of blood (from 6000 to 10000), platelets 300 - 800 thousand.

100 ml of rabbit blood contains 8.4 - 12.4 g of hemoglobin, males have 2 - 3% more.

Features of the rabbit's vessels are: a sharply curved and low-lying aortic arch, a loose type of origin of the main trunks from the aortic arch, the presence of the left anterior vena cava, etc. There are sharp features in the location of arterial and venous vessels, for example, the subcutaneous location of the veins etc.

The lymphatic system of rabbits also has characteristic differences, relating, first of all, to the lymph nodes, which in a rabbit are large, but not numerous.

The heart, like the lungs, is poorly developed in a rabbit. The number of heart contractions in rabbits is 120-160 per minute.

Structure of the heart

The main distinctive features in the structure of the rabbit’s heart are: the comparative isolation of the sinus region from the right atrium with the preservation of remnants of the sinus valves at their border, the penetration of individual myocardial fibers in the walls of the pulmonary veins far into the lungs, poor differentiation of the atrial valves. ventricular valves, the presence in the embryonic period of distant prototypes of the Eustachian and Tebesian valves of humans, etc.

Location of the heart

The rabbit's heart is slightly shifted to the left and obliquely elongated along the inner surface of the sternum. It extends from the posterior edge of the 2nd rib to the posterior edge of the 4th rib (sometimes the anterior edge of the 5th). Material from the site

The location of a rabbit's heart has its own characteristics. Due to the sharply narrowed anterior part of the chest cavity and a slight displacement of the heart forward compared to other animals, it lies in the middle mediastinum, at the very beginning of the chest, in a very cramped position. Because of this, it is located directly under the trachea, which is strongly pressed into its base. The rabbit's heart fills almost the entire front part of the chest cavity. Therefore, the aortic arch is very low, sharply curved and pulled forward, and the aorta itself is shifted sharply to the left, located to the left of the trachea and jutting into the upper edge of the left lung.

All this is reflected in the topographic relationship of the heart with the apices of the lungs. Thus, the end of the right apex of collapsed lungs lies at the level of the anterior contour of the heart, and the left - usually in the middle of its base. However, in the natural, straightened state of the lungs, the heart is almost completely covered from the sides by their lobes, especially on the right, which is explained by the rounded shape of the chest in a rabbit. Only below, in the region of the anterior third, the heart, adjacent to the sternum, is free from the lungs enclosing it. This is clearly visible when the viscera are removed as a whole from the chest cavity, if the lungs are previously fixed in an extended position.

The external and internal structure of the rabbit is fundamentally similar to the organisms of other mammals. Although it has certain differences associated with belonging to the hare family. They have thick fur and large ears, the length of which can reach one third of the size of the entire body. Depending on which breed they belong to, the appearance of the animals may vary slightly, but the structure of the internal organs corresponds to the general characteristics of the rabbit genus.

Features of the anatomical structure and constitution

Many years of selection work aimed at breeding meat, fur and ornamental breeds made it possible to create animals that differ from each other in some features of their anatomical structure. In modern rabbit breeding, there are 4 main types of rabbit constitution:

• animals of rough body constitution with a disproportionately large head, massive skeleton and well-developed muscles;
• standard rabbits with a strong body constitution, a wide chest, a well-developed muscular system and a small, elongated or rounded head;
• delicate animals of decorative breeds with poorly developed muscles and fragile bones;
• rabbits with a raw constitution are large in size, but have loose muscles, their hair is not thick, and a large amount of fat accumulates under the skin.

Depending on the type of body structure, animals are classified as meat, meat and fur, or decorative breeds. The latter can have a body length from 20-25 cm to 1 m, and the color of their fur is distinguished by a wide variety of colors and shades.

Small animals with long ears

Rabbits of different breeds differ from each other in appearance. The same signs can be both positive and negative for different representatives of the hare family.

Males have a larger head than females, but it should always be in proportion to the rest of the body. The color of the shiny eyes varies from black to red and pink (in albinos).

Most rabbits have long and erect ears that can reach one third of the entire body length. But there are also fold-eared breeds.

The neck can be standard or shortened, but its muscles should easily support the massive head of even giant individuals. The structure of rabbits can be cylindrical (chinchillas), traditionally stocky (Viennese blues) or rectangular (silvers). Animals of downy breeds resemble a ball in appearance.

A characteristic sign of a properly developing rabbit is a straight back and lower back. Humpbacking is considered a defect, and such animals should not be allowed to reproduce.

Females of large breeds may have massive dewlaps. This is not a defect, but a sign of the normal condition of the animal.

Muscular body and soft fur

The structure of the croup and rump can be round or wide (females crawl easier), and a chopped or drooping croup is a serious defect and the first sign that a rabbit needs to be culled.

The paws must be strong and support the body weight. Any curvature and clubfoot are considered defects and may indicate the development of rickets.

The belly of healthy rabbits is large and elastic. The presence of any hardening in it indicates health problems and requires immediate treatment. The female rabbit must have at least four pairs of well-developed mammary glands. The skin of a healthy animal is elastic. In males it is somewhat rougher than in females.

Rabbit fur is soft and silky. It has different thickness and length, but is sure to shine in healthy animals. Eared animals have a uniform one-color (white giant, New Zealand rabbits) or multi-colored fur color (Russian ermines). Representatives of some breeds (chinchillas) may have a zonal coat color.

Females that bear offspring are somewhat larger than males, although the external structure of their body is more delicate. Animals quickly reach sexual maturity and can produce from 24 to 60 cubs per year.

Musculoskeletal system of the rabbit

The basis of the skeletal system of rabbits is a long spinal column, to which the skull, sternum with ribs, as well as the front and hind limbs are attached with the help of cartilage and connective tissue.

There are a total of 212 bones in the rabbit's body. In babies, the weight of bones can reach 15% of the total mass of the animal, and in an adult this figure decreases to 10%.

Experts divide the axial skeleton, consisting of the spine and cranium, as well as the peripheral skeleton, which includes the chest, pelvic bones and limbs.

The structure of a rabbit's skull differs little from the skull of any other mammal. The spine is divided into cervical, thoracic, lumbar, sacral and caudal sections.

Neck mobility is achieved through 7 cervical vertebrae. Muscles are attached to the pectoral, lumbar and sacral bones, providing high mobility and jumping ability of these animals.

The anatomy of meat breed rabbits is rougher, and the powerful bones of the limbs allow them to hold a weight reaching 12-15 kg. The muscles are represented by striated muscles, and the walls of blood vessels are smooth muscle tissue, which ensures the passage of blood and nutrients.

The internal organs of a rabbit are covered with a fatty layer that protects them from mechanical damage.

Structure of the cardiovascular system

The cardiac striated muscle pushes blood, directing it to all organs and tissues of the animal. The rabbit's heart is a small muscular sac consisting of two atria and two ventricles. With an average weight of 6-6.5 g, it contracts from 110 to 160 times per minute.

Through the systemic circulation, arterial blood enters the organs and tissues of the animal. Poor blood returns through the veins to the heart. Through the pulmonary circulation it is redirected to the lungs, where it is again enriched with oxygen necessary for the normal functioning of the body.

The body of an average-sized rabbit contains about 280 ml of blood, which includes red blood cells, white blood cells, and platelets.

The constant movement of blood ensures the maintenance of temperature in the animal’s body. In winter, the standard figure is about 37 degrees Celsius, and in hot weather it can rise to 40-41.

The bone marrow is responsible for the formation of blood, and the spleen destroys damaged or excess blood cells.

Features of the gastrointestinal tract

The digestive system of rabbits is represented by the jaw apparatus, esophagus, stomach and intestines, in which food is processed and broken down, as well as nutrients are absorbed.

At birth, rabbits have 16 teeth, which are replaced by 28 adult teeth by the end of the third week.

Teeth grow throughout their lives, so animals must constantly sharpen them by eating hard food. Read more in the article “How many teeth do rabbits have.”

Rabbits are herbivores; their stomach is quite large and can hold up to 2000 cubic meters. see plant-based eating.

Fiber is not broken down in the stomach and enters the intestines in crushed form.

The remains of undigested food and waste products are eliminated from the body 9 hours after consumption.

The respiratory system and its role in the life of a rabbit

The respiratory organs are represented by the nose, pharynx, trachea and lungs. The complex structure of the nasal cavity allows animals to cool the hot summer air and warm it in the winter, thus protecting the lungs from burns and frostbite.

The respiratory rate of rabbits is very high. On average, he is able to take up to 282 breaths per minute, passing about 5,000 cubic meters through the paired lungs. cm air. In the alveoli, oxygen is absorbed by hemoglobin, which is part of red blood cells, and is distributed throughout the body along with the blood.

Rabbits are very sensitive and can suffocate from ammonia fumes that accumulate in rarely cleaned cages. Animals grow very quickly in the fresh air. They have an excellent appetite, get sick little and quickly gain industrial weight. At the same time, their skin acquires excellent production characteristics.

Other internal organ systems

The excretory and genitourinary systems of a rabbit are represented by the kidneys, ureters and urethra, as well as sweat and sebaceous glands, which protect the body from hypothermia and excessive heating.

The kidneys filter venous blood, clearing it of harmful substances. Disruption of their work leads to a sharp deterioration in the pet’s health and death.

The fluid that accumulates in the bladder, called urine, is discharged through the urethra into the external environment. It is saturated with urea and ammonia and must be promptly removed from the cells.

The genital organs of males are represented by paired testes, which begin to produce sperm within 3.5-4 months after birth. During one mating, the male can secrete up to 3.5 ml.

A female rabbit has a uterus, a pair of ovaries, an oviduct, a vagina and a genital slit through which the processes of fertilization and giving birth are carried out.

Nervous system and endocrine glands

Like other mammals, rabbits have a well-developed brain and spinal cord, as well as a peripheral nervous system. The brain has several convolutions, and a large amount of gray matter makes these animals intelligent. Eared cats quickly get accustomed to the feeder and tray, recognize their owners and love to spend time in their arms.

Nerve endings penetrate all organs of the body. This makes rabbits sensitive to pain and allows them to react faster to danger. The endocrine glands, which produce hormones and other biologically active substances, play a huge role in the life processes of animals.

The thyroid gland, which produces the hormone thyroxine, is responsible for the normal growth and development of young animals, as well as the passage of metabolic reactions in the body of rabbits. The pancreas controls the process of digesting food, and the adrenal glands ensure water and fat metabolism.

Without testes and ovaries, reproduction of these animals is impossible, and the pituitary gland produces more than 10 different hormones that have a positive effect on the nervous system and other vital processes.

Sense organs

Since rabbits in nature are the main food of predatory animals, their sense organs are of particular importance, allowing them to respond to threats in a timely manner and hide in burrows.

The vision of these animals is complex. It is represented by a pair of eyes that can detect colors. Rabbits are farsighted, but do not see very well at close range.

Rabbits see perfectly in the dark and have a 300-340 degree all-round vision.

Thanks to their resonating large ears, rabbits have very sensitive hearing. They are able to turn their ears in different directions, picking up high-frequency sounds with which they communicate with each other.

Fold-eared rabbit breeds have lost the ability to hear well and will not be able to survive on their own in natural conditions.

Rabbits have a good sense of smell and can distinguish thousands of odors. Special hairs located in the nasal cavity help them with this.

The anatomical structure of rabbits is very similar to the body structure of other mammals, but still has its own characteristics.

Today we will look at the structure of the skeleton, internal organs and main body systems of these animals.

Skeleton

The rabbit skeleton has 112 bones and is necessary to protect internal organs and carry out movements. The weight of the skeleton in adults is about 10% of the total body weight, in young animals - 15%. The bones that make up the skeleton are connected by cartilage, tendons and muscles. The rabbit skeleton consists of a peripheral and axial skeleton.

Did you know? In the wild, rabbits live very short lives - only 1 year, while domestic rabbits sometimes live up to 12 years.

Peripheral

This part of the skeleton includes the bones of the limbs:

1. Pectorals, consisting of the humerus, shoulder blades, hands, and forearm. The hand has a certain number of bones: metacarpals - 5, carpals - 9 fingers.
2. Pelvic, having the pelvis, ilium, ischium and pubis, legs, thighs, feet, 4 fingers and 3 phalanges.

Axial

This part of the skeleton consists of the main bones - the skull and ridge.

1. The skull, consisting of the brain and facial sections. The skull is characterized by the presence of movable bones that are connected to each other by certain sutures. The brain section contains 7 bones, represented by the parietal, occipital, temporal and others. The facial section has the maxillary, nasal, lacrimal, zygomatic, and palatine bones. The shape of the skull is elongated, and there is an external resemblance to the skull of other mammals. The main part of the skull is occupied by organs that perform breathing and eating.
2. A body characterized by the presence of a spinal column, sternum, and ribs. The ridge is divided into 5 sections or divisions. The rabbit's spine is quite flexible due to the presence of menisci connecting the vertebrae.

The main parts of the spine are represented by:

• cervical, consisting of 7 vertebrae;
• thoracic, consisting of 13 vertebrae, which are connected by ribs and form the chest, containing the heart and lungs;
• lumbar with 7 vertebrae;
• sacral with 4 vertebrae;
• caudal with 15 vertebrae.

Important! Meat breeds of rabbits have wider vertebrae than normal ones, which often helps breeders in choosing the right animal when purchasing.

The extent to which the muscles of rabbits are developed allows one to prematurely form an understanding of the peculiarities of the appearance and taste of meat.

The muscular system of rabbits is represented by:

• the muscles of the body, which, in turn, consists of striated muscles, covering absolutely all the muscles of the body;
• the muscles of the internal organs, which covers the smooth muscles covering the respiratory organs, organs of the digestive system, and vascular walls.

Small rabbits have an underdeveloped muscular system, which takes up less than 20% of the animal’s total weight, and as they grow older, the muscles increase and reach 40%.

Nervous system

The nervous system of rabbits consists of:

• central, represented by the brain and spinal cord;
• peripheral, represented by skeletal muscle nerves, blood vessels and skin.

The hemispheres of the brain of this animal are separated by a small groove; the brain has three sections, represented by the middle, posterior, and medulla oblongata, each of which is necessary to perform separate functions. For example, thanks to the oblong section, the respiratory organs and circulatory processes work.

The spinal canal allows the spinal cord to be located, the beginning of which is in the brain and the end in the seventh cervical vertebra. The weight of the spinal cord is 3.5 g. The peripheral section consists of spinal and cranial nerves and nerve endings.

This system covers all processes in the rabbit’s body that deal with blood, that is, the hematopoietic organs, lymphatic system, veins, arteries and capillaries. Each element is necessary to perform certain functions.

The rabbit's body contains on average 250–300 ml of blood. In winter, the animal is characterized by a low body temperature, which is +37 °C, in summer it is increased - +41 °C.

The rabbit's heart has 4 chambers, consisting of two ventricles and two atria. Its weight is 7 g, its position is in the pericardial serous cavity. The normal pulse for an animal is within 140 beats per minute.

Important! If a rabbit’s body temperature increases by 3 degrees in summer and reaches +44 °C, it will die.

Digestive system

This system in the body allows the processing of food consumed by the rabbit. The full cycle - from entry to processing of food in the gastrointestinal tract - is three days.

Teeth

At birth, the baby rabbit already has 16 teeth; during the growth process, at 3 weeks, the milk teeth are replaced by molars. Adults have 28 teeth, and their growth occurs steadily throughout life.

The jaws consist of large incisors, designed for chewing hard food, and molars, which are necessary for grinding other food. Food that has been crushed by the teeth is transported into the pharynx, the next stage is transportation to the esophagus and stomach.

Stomach

In a rabbit, it is a hollow organ with a volume of about 200 cubic meters. cm, which is capable of producing gastric juice. Gastric enzymes in rabbits are highly active when compared to other animals. The fiber that the eared animals consume is not digested by the stomach; it is sent to the intestines.

Intestines

Residues of food that the stomach cannot cope with enter the intestines, which carry out the final processes of digestion.

The organ is represented by:

1. The small intestine, which breaks down substances, including amino acids, which go directly into the blood.
2. The large intestine, which deals with fermentation processes. Food that has not been broken down and digested comes out as feces, its amount is 0.2 g per day. In the daytime, feces are characterized by a hard form, at night - soft. Feces that are excreted at night are eaten by animals, due to which they receive the necessary proteins, vitamins K and B.

Respiratory system

The respiratory organs of a rabbit are represented by the nose, pharynx, trachea and lungs, which provide the body with oxygen. Inhaling air, the nose warms it, moistens it, and cleanses it of impurities. Then it begins to move into the pharynx, trachea and lungs.

Rabbits breathe faster than other mammals. The norm is 280 breaths per minute. Ushastiki have accelerated gas exchange processes: consuming about 480 cubic meters. cm of oxygen, they release 450 cubic meters. cm carbon dioxide.

Sense organs

Individuals have the following sense organs:

1. Smell, which is possible thanks to prescription cells located deep in the nose. The cells have 11 hairs that respond to a variety of aromas. Thanks to their sense of smell, individuals choose a mate for mating, and the female can distinguish her cubs from strangers by smell.
2. Taste, which is captured by special papillae covering the tongue.
3. By touch, the functioning of which occurs with the participation of sensitive skin located on the eyelids, lips, back and forehead. Thanks to this sense, pets can orient themselves in space, perceive temperature changes and avoid overheating, and respond to painful stimuli. Thanks to their antennae, animals can move at night when the cage is completely dark. Hairs located above the eyelids allow rabbits to navigate and sense obstacles.
4. By sight, which is provided by the eyes, consisting of a ball-shaped eyeball connected to the brain. Rabbits can distinguish colors, and their vision feature is farsightedness and the ability to navigate in the dark.
5. By hearing, due to the large ears that allow rabbits to detect and recognize sounds well.

Genitourinary system

This system in the body of rabbits consists of the genital and urinary organs. The urinary organs are necessary for removing waste products from the body. The amount of urine excreted directly depends on the age and nutrition of the animals. One individual can excrete no more than 400 ml of urine per day. The urinary canal is located very close to the genital apparatus.

Did you know? Animals communicate with each other thanks to high-frequency sounds. To catch some of them, individuals can turn their ears in different directions.

Mammals have two oval kidneys, which lie in the lumbar region and are necessary for the processes of breakdown of proteins, mineral salts and other substances.

The basis of the rabbit's skeletal system is the skeleton , which consists of 212 bones movably and immovably connected into a single whole with the help of joints, ligaments, cartilage and muscle tissue, not counting the teeth and auditory bones. The skeletal weight of a newborn rabbit is 15% of its body weight, and that of an adult is about 10%. The skeleton of a meat rabbit has less weight. It performs supporting and protective functions: it protects internal organs (brain, stomach, heart, lungs, liver, etc.) from damage.

In terms of bone structure, rabbits are no different from other farm animals. Bone, as an organ, consists of a compact and spongy substance. On the outside it is covered with periosteum and healine cartilage. Inside the bone is red bone marrow. Bone is constantly undergoing processes of destruction and restoration.

The skeleton is divided into axial and peripheral (Fig. 1).

The axial skeleton includes the bones of the head, trunk and tail. In the peripheral – the bones of the thoracic and pelvic limbs.

Rice. 1. Rabbit skeleton:

1 – skull bones; 2 – cervical vertebrae; 3 – thoracic region; 4 – lumbar region; 5 – sacral section; 6 – tail section; 7 – shoulder blade; 8 – ribs; 9 – bones of the thoracic limb; 10– bones of the pelvic limb

The head skeleton can be divided into the cerebral and facial sections. The bones of the head are movably connected to each other using sutures. The cerebral part of the skull serves as a container for the brain; it is formed by four unpaired (sphenoid, ethmoid, occipital, interparietal) and three paired (parietal, temporal and frontal) bones. When fixedly connected, they form the cranial bone. The facial part of the skull consists of seven paired lamellar bones (maxillary, nasal, incisive, lacrimal, zygomatic, palatine, pterygoid), nasal concha and unpaired bones - vomer and hyoid. The facial section is highly developed and makes up 3/4 of the entire skull. It serves as the basis of the oral and nasal cavities, in which the individual organs of the digestive and respiratory systems are located. The mandibular and hyoid bones are moving parts.

In different breeds, individual parts of the skull are developed differently. In terms of head size, black-brown rabbits are superior to white and gray giants, Soviet chinchilla animals, and especially silver rabbits.

The bones of the body include the bones of the spinal column, sternum and ribs. The spinal column is divided into five sections (cervical, thoracic, lumbar, sacral and caudal). Each section of the spinal column consists of an unequal number of segments: there are 7 in the cervical, 12–13 in the thoracic, 6–7 in the lumbar, 4 in the sacral, and 14–16 in the caudal. Each vertebra has an opening through which the spinal cord passes. The vertebrae are connected to each other by cartilaginous plates (discs), thereby ensuring the flexibility of the spine.

15.7% of a rabbit's body length is the cervical spine. Due to the uniqueness of the first two vertebrae on the neck, the rabbit can make various movements with its head.

The thoracic vertebrae are not reduced. A vertebra is divided into a body, a neural arch and processes. Each thoracic vertebra is articulated through joints by a pair of arcuate bones - ribs, of which there are 12-13 pairs in the thoracic region. Connecting below with the sternum, seven pairs of ribs (true ribs) form the rib cage, which contains the vital organs - the heart and lungs.

The longest section of the spinal column (32% of body length) is the lumbar section. The bodies of the lumbar vertebrae are elongated, with large lower ridges.

By the width of the lumbar vertebrae one can judge the meatiness of rabbits, and also select them according to this indicator.

The relatively short sacrum consists of four vertebrae that merge into one sacral bone.

The caudal region occupies 13% of the total length of the spinal column.

The peripheral skeleton consists of the skeletons of the thoracic and pelvic limbs, represented by the skeleton of the girdles (scapula, pelvis) and the skeleton of the free limbs.

The skeleton of the thoracic limb consists of a scapula (girdle), humerus, forearm, hand, which includes 9 short carpal and 5 metacarpal bones and 5 fingers. The finger consists of phalanges: the first is of two, the rest are of three.

The skeleton of the pelvic girdle and free limbs are represented by the skeleton of the pelvic limbs. The pelvic girdle consists of the innominate pelvic bones, which are fixedly connected to each other. The free limb consists of the femur, tibia, paw of six tarsals, four metatarsals and four toes. All toes of the hind paws are represented by three phalanges.

The peripheral skeleton of the rabbit, unlike other farm animals, includes the clavicle, which is a thin and rounded bone that connects the manubrium of the sternum and the scapula.

There are no significant differences in the connection of bones in rabbits from other farm animals.

Rabbit muscular system - This is an active part of the system of organs of derivative movement. The appearance and quality of meat largely depend on muscle development. The muscles of rabbits are divided into the muscles of the body and internal organs. The first consists of striated muscle tissue and occupies the bulk of all muscles. The muscles of the internal organs, represented mainly by smooth muscle tissue, make up a small part of the total muscles. It is located in thin layers in the walls of the digestive, respiratory, bladder, genital organs, in the walls of blood vessels, and in the skin at the roots of the hair.

Circulatory system

The circulatory system includes the heart - the central organ that promotes the movement of blood through the vessels - and blood vessels - arteries (distribute blood from the heart to the organs), veins (return blood to the heart) and capillaries (carry out the exchange of substances between blood and tissues). Vessels of all three types communicate with each other along the way through anastomoses that exist between vessels of the same type and between different types of vessels. There are arterial, venous or arteriovenous anastomoses. Due to them, networks are formed (especially between capillaries), collectors, collaterals - lateral vessels accompanying the course of the main vessel.

Heart- the central organ of the cardiovascular system, propelling blood through the vessels, like a motor. This is a powerful hollow muscular organ located obliquely vertically in the mediastinum of the thoracic cavity, in the area from the 3rd to 6th ribs, in front of the diaphragm, in its own serous cavity.

The heart of mammals is four-chambered, completely divided from the inside by the interatrial and interventricular septa into two halves - right and left, each of which consists of two chambers - the atrium and the ventricle. The right half of the heart, by the nature of the circulating blood, is venous, oxygen-poor, and the left half is arterial, oxygen-rich. The atria and ventricles communicate with each other through the atrioventricular orifices. The embryo (fetus) has an opening through which the atria communicate, and there is also an arterial (botal) duct through which blood from the pulmonary trunk and aorta mixes. By the time of birth, these holes are closed. If this does not happen in a timely manner, the blood mixes, which leads to serious disturbances in the functioning of the cardiovascular system.

The main function of the heart is to ensure continuous blood flow in the vessels. In this case, blood in the heart moves in only one direction - from the atria to the ventricles, and from them to the large arterial vessels. This is ensured by special valves and rhythmic contractions of the heart muscles - first the atria, and then the ventricles, and then there is a pause and everything repeats all over again.

The heart wall consists of three membranes (layers): endocardium, myocardium and epicardium. The endocardium is the inner lining of the heart, the myocardium is the cardiac muscle (it differs from skeletal muscle tissue by the presence of insertion bars between the individual fibers), the epicardium is the outer serous lining of the heart. The heart is enclosed in a pericardial sac (pericardium), which isolates it from the pleural cavities, fixes the organ in a certain position and creates optimal conditions for its functioning. The walls of the left ventricle are 2–3 times thicker than the right.

The heart rate largely depends on the condition of the animal, as well as on its age, physiological state and ambient temperature. Under the influence of heart contractions (due to blood flow), sequential contraction of blood vessels and their relaxation occur. This process is called blood pulsation, or pulse. The pulse is determined by the femoral artery or brachial artery for 0.5–1 min (four fingers are placed on the inner surface in the area of ​​the femoral canal or shoulder, and the thumb is placed on the outer surface of the thigh or shoulder). In newborn rabbits, the pulse rate is 280–300 beats/min, in an adult it is 125–175 beats/min.

According to its functions and structure blood vessels are divided into conducting and feeding. Conducting vessels are arteries (they conduct blood from the heart, the blood in them is scarlet, bright, as it is saturated with oxygen, they are located deeper in the animal’s body, under the veins); veins (supply blood to the heart, the blood in them is dark, because it is saturated with metabolic products from the organs, they are located closer to the surface of the body); nourishing, or trophic, capillaries (microscopic vessels located in the tissues of organs). The main function of the vascular bed is twofold - conducting blood (through arteries and veins), as well as ensuring metabolism between blood and tissues (links of the microcircular bed) and redistribution of blood. Having entered the organ, the arteries repeatedly branch into arterioles, precapillaries, which turn into capillaries, then into postcapillaries and venules. Venules, which are the last link of the microcircular bed, merge with each other and enlarge to form veins that carry blood out of the organ. Blood circulation occurs in a closed system consisting of a large and small circle.

Blood - it is a liquid tissue that circulates in the circulatory system. This is a type of connective tissue that, together with lymph and tissue fluid, makes up the internal environment of the body. It transports oxygen from the pulmonary alveoli to the tissues (due to the respiratory pigment hemoglobin contained in red blood cells) and carbon dioxide from the tissues to the respiratory organs (this is done by salts dissolved in plasma), as well as nutrients (glucose, amino acids, fatty acids, salts, etc.) to tissues, and final metabolic products (urea, uric acid, ammonia, creatine) from tissues to excretory organs, and also transports biologically active substances (hormones, mediators, electrolytes, metabolic products - metabolites). The blood does not come into contact with the cells of the body; nutrients pass from it to the cells through the tissue fluid that fills the intercellular space. This liquid tissue is involved in the regulation of water-salt metabolism and acid-base balance in the body, in maintaining a constant body temperature, and also protects the body from the effects of bacteria, viruses, toxins and foreign proteins. The volume of circulating blood in a rabbit’s body is 5–6.7% of the total live weight and depends on the age, type and breed of the animal.

Blood consists of two important components - formed elements and plasma. Formed elements account for approximately 30–40% of the volume of all blood, plasma – 70%. The formed elements include erythrocytes, leukocytes and platelets (Table 5).

Table 5

Blood composition of a healthy rabbit

Hematocrit – 34–44%

Red blood cells – 5-7 million/mm 3

Hemoglobin – 10–15 g/100 ml

Leukocytes – 6-13 thousand/mm 3

Lymphocytes – 60%

Platelets – 125–250 thousand/µl

Blood amount – 55–63 ml/kg live weight

Erythrocytes, or red blood cells, carry oxygen from the lungs to organs and tissues; the immunological characteristics of the blood, determined by the combination of erythrocyte antigens, that is, the blood group, depend on them. Leukocytes, or white blood cells, are divided into granular (eosinophils, basophils and neutrophils) and non-granular (monocytes and lymphocytes). The percentage of individual forms of leukocytes constitutes the leukocyte form of blood. All types of leukocytes participate in the body's defense reactions. Platelets, or blood platelets, take part in the blood clotting process.

Blood plasma is its liquid part, consisting of water (91–92%) and organic and mineral substances dissolved in it. The ratio of the volumes of formed elements and blood plasma as a percentage is called the hematocrit number.

Circulatory system The circulatory system includes the heart - the central organ that promotes the movement of blood through the vessels - and blood vessels - arteries (distribute blood from the heart to the organs), veins (return blood to the heart) and capillaries (carry out exchange

Lymphatic System The lymphatic system is a specialized part of the cardiovascular system. It consists of lymph, lymphatic vessels and lymph nodes. It performs two main functions: drainage and protective. Lymph is transparent yellowish

Digestive system The dog's digestive system consists of the oral cavity, pharynx, esophagus, stomach, small and large intestines, liver and pancreas. The oral cavity is formed by the upper and lower lips, cheeks, gums, teeth, soft and hard palate,

Respiratory system The respiratory system performs the function of gas exchange: it ensures the entry of oxygen into the animal’s body and the removal of carbon dioxide from it. The breathing process occurs due to the contraction of the diaphragm. The respiratory system includes

Urinary system The urinary system performs the functions of cleansing the body of processed waste products and removing excess water. It is formed by the kidneys, ureters, bladder and urethra. The kidneys are

Reproductive system Like many other mammals, a dog has external and internal genitalia. The genitalia of the female (bitch) are represented by the vulva, vagina, uterus, 2 oviducts and ovaries (paired gland). External genitalia - vulva and vagina -

Circulatory system The circulatory system includes: the heart - the central organ that promotes the movement of blood through the vessels, blood vessels - arteries that distribute blood from the heart to the organs, veins that return blood to the heart, and blood capillaries through

Circulatory system The circulatory system consists of the heart, blood vessels, blood and hematopoietic organs. The dog's heart is located in the chest cavity. Like all mammals, it is four-chambered, consisting of two atria and two ventricles and

Nervous system The Caucasian Shepherd should have a strong nervous system. Only in this case will she be able to complete any work assigned to her. A strong nervous system determines the performance of the Caucasian Shepherd, its activity and endurance. As a rule,

Circulatory system The circulatory system includes the heart - the central organ that promotes the movement of blood through the vessels and blood vessels - arteries that distribute blood from the heart to the organs, veins that return blood to the heart, and blood capillaries through

Lymphatic System The lymphatic system is a specialized part of the cardiovascular system. It consists of lymph, lymphatic vessels and lymph nodes. It performs two main functions - drainage and protective. Lymph is transparent yellowish

Circulatory system The circulatory system includes the heart - the central organ that promotes the movement of blood through the vessels, and blood vessels - arteries that distribute blood from the heart to the organs, veins that return blood to the heart, and blood capillaries through

Circulatory system The circulatory system includes: the heart - the central organ that promotes the movement of blood through the vessels, and blood vessels - arteries that carry blood from the heart to the organs, veins that return blood to the heart and blood capillaries through the walls

Respiratory organs and circulatory system The respiratory system of canaries is very complex. From the neck to the intestines there are air sacs connected to the lungs, as well as to the cavities of hollow and spongy bones. The lungs are designed so that air passes through them 2 times - the first

Circulatory system The circulatory system consists of the heart, blood vessels and hematopoietic organs. The dog's heart is located in the chest cavity. Like all mammals, it is 4-chambered, consists of 2 atria and 2 ventricles and is connected to large