The structure of a chicken must be presented to every novice poultry farmer and experienced farmer in order to promptly notice various ailments of the livestock and apply this knowledge when slaughtering and processing meat. In addition, understanding the anatomy of chickens is useful for those who want to improve egg production and growth of young animals.

The internal parts and the chicken carcass itself are sources of a variety of food products and are very popular among the average consumer.

This material examines the body systems that function in the bird’s body and provides general descriptions of activities and internal processes.

The main feature of the bird's anatomy is the bones, which are empty inside. This is explained by the fact that, like all other birds, theoretically a chicken can fly, but in practice this is not done regularly. Chickens rise in height briefly and infrequently, but at the same time their skeletal system resembles those who are quite active in this regard. Due to the air sinuses, the weight of the bones decreases.

In the first 2 months, the main growth of the chicken skeleton occurs and this continues until the individual reaches six months of age. Most of the body weight (up to 70%) is also gained in the first 60 days.

The total weight of the skeletal system rarely exceeds a tenth of the total mass.

The second distinguishing feature of the chicken skeleton is the absence of teeth. They are replaced by a dense beak, which is a standard horny process. This is the difference between chickens and humans and mammals.

Also, animals and people have an increased bone marrow mass (about 5% of the total) compared to chicken - its bone marrow accounts for 2 percent of body weight.

It is believed that the ancestors of birds and mammals were reptiles that lived during the era of dinosaurs. If you carefully examine the appearance of laying hens, you will notice characteristic scales on their legs, characteristic of an extinct group of living creatures.

The internal structure of birds is simple

Skeletal system

The skeletal system combines the head, trunk and limbs. Sometimes it seems that the head looks disproportionate against the background of a more voluminous body, but this is a feature of the skeleton.

The cervical region includes 13 or 14 vertebrae, the thoracic region - 7 pieces, the tail consists of 5-6 movable vertebral parts. In the thoracic spine there is a specific component called the keel. The largest pectoral muscles in the chicken’s body are attached to it, which can be easily felt when assessing the fatness of the bird.

1. The coracoid system.
2. Scapular region.
3. Collarbone.
4. That area of ​​the wing that is free and combines several sections - radial, humeral, ulnar.

Chicken wings do not perform the function of frequent flights, but are still necessary
The wings are the forelimbs, which include:

From the back, the legs of chickens are paws with claws. Roosters additionally have structures such as spurs. The paws are in close contact with the pelvic region and include the shins, tibias, tibias, as well as the femurs and that part of the body that is commonly called the tarsus. The latter is located between the fingers and ankle. Most chickens have four toes, but there are also breeds with more.

Young, growing laying hens have medullary bone, which is not characteristic of roosters. It is involved in the formation of the shell around eggs and begins to function at puberty.

Features of bones

Chicken bones mainly contain the following microelements: calcium, phosphorus (99% and 90%, respectively - poultry bones are storage reservoirs). In addition, they include thin collagenous fibrous elements closely intertwined with each other. The skeleton of a chicken is as reliable as a human one, and this is due to its structural features.

It is important for poultry to receive vitamin D. This brings the chicken skeleton into proper shape and condition. If, as a result of vitamin deficiency, calcium ceases to be absorbed, the egg shells will become soft or stop forming altogether.

The extreme stage of lack of the “sunshine vitamin” is manifested in the suspension of laying.

If we are talking about cellular metabolism, then calcium also manifests itself in a deficient form. Characteristic signs are osteoporosis, muscle weakness and related disorders, including paralysis. To cure a bird, you need to plant it on the ground and give it dietary calcium as a dietary supplement.

There are two types of bones in a chicken's body.

Table 1. Types of chicken bones

It must be said that the neck and spinal column of a chicken are quite flexible. The latter includes 39 bone elements. And the neck is long enough to search for food everywhere.

The largest bone in the system is the sternum, which covers half the body. The wings are attached to the sternum by special muscles.

The legs of laying hens and roosters are similar in structure to the legs of people. The only difference is that the human hip is in close connection with the spine. Thanks to this, it is securely and rigidly attached. This position strengthens the powerful muscle corset.

Internal anatomy of a domestic chicken

In comparison with the usual scheme relevant for mammals, the anatomy of chickens has a number of specific features.

Digestive tract

Food ends up in the bird's beak. The intermediate link of movement is the goiter, and the final section of the digestive system is the cloaca.

The bird takes food into its beak, swallowing it; the crop is needed for primary fermentation, since birds do not have teeth. This is due to the fact that teeth would weigh down the skeletal structure and make the bird's structure more bulky.

The crop is a “stop” where the nutrient mass accumulates and from where it enters the stomach, gradually moving forward for digestion in the glandular and muscular parts.

The chicken esophagus is a long muscular tube. During the movement of food particles along it, they are not fermented and are not affected by juices. The glandular part of the stomach begins digestion, since it is in this section that the acids and enzymes necessary for digestion are secreted.

After gastric digestion, food enters the duodenum. Then the resulting mass goes further into the thin section. In both, it begins to be absorbed, providing the organs and systems with complete nutrition with vitamins and microelements. Untreated residues enter the environment in the form of feces through the cloaca. The large intestine is responsible for timely bowel movements.

Digestion in chickens is rapid. The only exception is the coarse parts of the grain, which may take longer to digest.

An interesting fact is that chicken intestines are 180 centimeters long. This figure is 6 times greater than the same figure for the body. Due to the fact that digestion takes place quickly, laying hens are in an eternal search for food.

In general, a young bird digests food in about 4 hours. When a clutch is observed, the process takes 8 hours; brood hens digest and absorb nutrients for 12 hours.

Respiratory system

When flying, an ordinary bird consumes a lot of oxygen. This is due to the atypical structure of the respiratory system. Chickens are no exception, although they fly in exceptional cases. The first link is the nostrils. After getting inside, the air passes through the nasal cavity, then along the laryngeal part and, finally, into the trachea, so that, having divided into streams, it goes to the bronchi.

In this place, where the trachea is divided into parts, the characteristic vocal “accompaniment” of each bird, including chickens, is formed

It is noteworthy that in birds, including domestic chickens, the bronchi continue outside the lungs and are tightly connected to the air sacs, which are located directly in the body. This property unites them with ancient reptiles that went extinct millions of years ago. According to scientists, dinosaurs breathed using similar air sacs, where up to 75% of the inhaled air could settle.

Chicken lungs hardly change in volume when breathing, since they do not have the ability to stretch, like mammals. There are no valves in this system of the avian body. Any movement occurring inside it is subject to thermodynamic laws. Additional functions of the respiratory organs are thermoregulation and gas exchange.

Circulatory organs

The chicken circulatory system includes organs:

1. Heart system with 4 chambers.
2. Pulmonary circulatory system.
3. Systemic circulatory system.

Both circles are disconnected. This means that venous blood always moves through the vessels separately from arterial blood. The first collects in the right side of the heart muscle, called the atrium, to then enter the ventricle on the right side. The enriched blood then passes through the lung into the left atrium. So it moves in a small circle.

As for the large circle of motion, it looks like this:

1. This part of the circulatory system originates in the left side of the heart - the ventricle.
2. Next, from the aorta, blood fluid is supplied to organs and systems through a network of small blood vessels.

The heart muscle of a chicken is quite large if you compare it as a whole with the dimensions of a bird. Externally it is asymmetrical. This is due to the functional work of the organ, the left side of which pumps more blood.

High heart rates and blood pressure are considered normal in chickens. Thanks to this, the chicken’s body has a fast metabolism, as well as a high temperature.

Table 2. Norms of heart rate and body temperature

Excretory organs of chickens

The excretory system combines paired kidneys, as well as ureters, which connect the main organs to the cloaca. This is how urine is removed.

Birds do not have a bladder, like in humans and animals. Water, saturating the body, is processed and exits directly into the cloaca.

This is associated with the atypical appearance of chicken urine. It is thick and resembles a mushy substance. It is not so easy to distinguish the liquid secretions of chickens from their feces. In addition, a chicken urinates much more often than a mammal - urination occurs as often as stool.

Nature has provided birds with ease of movement, including through a unique system for removing fluid from the body and forming feces.

Reproductive organs and reproductive system

Like other birds, chickens reproduce by laying and incubating eggs. Their body is perfectly adapted for this.

Males fertilize females with the help of testes located near the kidneys, from where, during the breeding season, sperm enter the chicken’s body through the spermatic ducts. Chickens do not have external genitalia - the process occurs directly when the cloacas come into contact.

During the breeding season, the testes reach more impressive sizes.

As for females, only their left ovary has proper development. The right one atrophies by the time the chicken reaches adulthood. It is located in the area of ​​the kidneys, like the testes of roosters. Then it passes into the left oviduct. The structure of the chicken's reproductive system is completed by an expanded funnel. It, in turn, turns into a twisted thick-walled pipe, which has an outlet into the cloaca.

Eggs, like those in humans and mammals, appear in the ovary. The peculiarity of reproduction is that only the left ovary has this function. Eggs are a very valuable product, as they contain all the essential nutrients needed for the process of gestation and birth of chicks.

The oviduct is divided into sections in its structure. The first of these is the fallopian tube, followed by the uterus. In many ways, the system resembles the human and animal reproduction systems. The length of the oviduct is from 35 to 86 centimeters.

If oviposition occurs intensively and for a long time, the ovary reacts immediately and externally becomes 10 times larger.

The pattern of birth of offspring in chickens is more primitive compared to humans and animals.

From the time the egg is released into the oviduct, from half a day to two days will pass. The oviduct performs another important function - the egg itself is formed in it.

The breeding scheme is as follows:

1. Before becoming a real egg, the embryo moves from the ovary and gradually builds up protein.
2. Then, after four hours, the egg becomes its usual shape and then enters the oviduct. The appearance of a dense shell of the egg occurs here. This happens within 24 hours or a little less time.

A baby chicken can move independently and stand almost immediately after birth.

When mating occurs, the hen can store the rooster's sperm in the pockets of the oviduct and remove them from there if necessary. Sperm viability is 1 month. It can be used to fertilize eggs within the specified period.

Organs of the nervous system

Chickens have a brain and a spinal cord. Their nervous system also includes special processes and fibers that allow nerve impulses to travel throughout the body.

The body of chickens is designed in such a way that nerve impulses can travel through the internal organs and systems for some time after the death of the bird.

In the brain, the system is represented by the anterior, intermediate sections, as well as the middle section and the cerebellum. Chicken hemispheres are not large in size. They are responsible for orientation in space, as well as the implementation of the bird’s basic instincts. In the cerebellum, impulses are processed properly, turning into coordinated movements.

An interesting feature is that the parts of the brain are located relative to each other like humans. Their functionality is also identical, despite the minimal number of convolutions in the hemispheres.

Conclusion

Chickens are important objects in the economic and production part. Their meat is extremely popular, but few people understand how poultry's body systems work and how it affects performance. To do this, it is necessary to expand knowledge about the internal structure and delve a little deeper into the anatomical component.

Video - How a chicken egg is formed

Video - Opening a chicken

When the structure of the internal organs of a chicken is considered, the main attention is paid to what can be eaten - the stomach, liver, heart. While in the body of any living creature the most important organ is the brain. But these birds were not lucky here either. The common expression “chicken brains” belittles the level of intelligence of these birds.

Although the brain size relative to the body size of these birds is indeed small, they are not as brainless as is attributed to them. There are some things chickens know and can do.

The chickens' heads also contain sensory organs - eyes, tongue, nostrils, and auditory openings that come out.

The sense of smell in birds is poorly developed, so the nostrils are used mainly for breathing. But other ways of perceiving the environment are in perfect order. Chickens can see at a distance of 50 meters, hear the faintest squeak of their chickens, and also distinguish all tastes due to the numerous taste buds on the tongue and palate. In addition, all birds have an excellent sense of touch due to the presence of sensory nerves at the base of their feathers.

The internal structure of the chicken in the neck area is rather “classic”. There is the esophagus, trachea, jugular vein, carotid artery and the spinal cord, located inside the spine. The larynx, which blocks the access of food to the respiratory tract of the bird, is in a lower position, next to the lungs.

An interesting feature of the chicken digestive system is the presence of a crop, in which food (up to 100 grams of grain) accumulates before entering the stomach. The organ is located in the lower part of the esophagus. As food passes through it, it undergoes certain changes. It softens and sometimes changes chemically. From there, after 3-4 hours, the food passes into the glandular section of the stomach, where it is exposed to gastric juice, and then mechanically processed in the muscular section.

In addition to the lungs, the chest contains the heart. Compared to human ones, it works very quickly - from 200-300 beats per minute in adult birds, to 400-500 in young birds, providing a body temperature of 40-42 degrees. The reproductive organs in roosters are the testes, and in chickens - the ovary, facial tube, uterus and cloaca. In addition, each bird has a coccygeal gland near the tail, which produces fats to lubricate the feathers.

The anatomical structure of the chicken is such that the process of assimilation of nutrients from the feed occurs very quickly. Intestinal juices are similar in composition to the juices of mammals. Also involved in the process of digesting food are the liver, gallbladder, pancreas, kidneys and ureter. But birds of this species do not have a bladder.

A chicken is an interesting living creature, with its own characteristics of vital activity and structure. The information presented in our article contains complete data on the anatomy of this useful bird. Such data can be useful to representatives of various professions.

Biological characteristics of birds

The most characteristic features of birds that distinguish them from other vertebrates are the ability to fly and the intensity of life processes.

The ability to fly affected the entire organization of birds. In flight, the bird makes a huge number of movements, which is accompanied by large expenditures of energy and intense metabolism, which also determines a high constant body temperature (an average of 42 o C), which requires intense work from the heart. The number of heart beats in chickens is 128-340 beats per minute.

The lungs of birds are relatively small, despite this, the enrichment of the body with oxygen is quite intense due to the action of the air sac system; their volume is several times greater than the volume of the lungs. Air sacs play an important role in thermoregulation; moisture evaporates from their surface through the respiratory tract, which prevents the possibility of overheating of the body. Since birds do not have sweat glands and moisture evaporates through the respiratory system, chickens always open their mouths at high temperatures. Birds' food is crushed in the stomach, which has powerful muscles and is lined on the inside with a dense film - the cuticle.

Grinding of feed is enhanced by gravel and coarse sand eaten by the bird.

Birds have good eyesight and excellent hearing. The chicken's field of view is 300°.
Poultry has completely or partially lost the ability to fly. Her productivity has increased exponentially.
There is no seasonality of egg laying.

Skeleton

During evolution, birds developed a light and very strong skeleton.

The chicken skeleton is made up of bones and cartilage connected by ligaments and provides the solid foundation of the body.

The bones of the chicken skeleton also serve as a place for the accumulation of mineral salts necessary for the life of the body and, in particular, for the formation of eggs. At the same time, mineral substances are constantly consumed and at the same time replenished due to substances received by chickens with food. Therefore, to ensure good and long-term egg laying in chickens, it is necessary that before mass production begins, skeletal ossification in pullets is completely completed and the necessary reserves of mineral substances accumulate inside the body. Without this, the chicken will not be able to have high productivity for a long time.

Connecting to each other, all the bones of the chicken are combined into a single skeleton. The bones of the skeleton serve as levers when the bird moves; they protect the brain and spinal cord, heart and other internal organs from harmful mechanical influences and damage. The purpose of individual bones of the skeleton is different, and therefore their structure and shape are not the same. On the outside, the bone is covered with a special membrane, the so-called periosteum. It contains blood vessels and nerves. There are also special cells - bone-forming cells. In a young body, due to the proliferation of these cells from the periosteum, bones grow in thickness.

The bird skeleton is divided into axial and peripheral. The axial skeleton includes the bones of the head, torso and tail, and the peripheral skeleton includes the bones of the limbs.

Chickens have a small head skeleton. It consists of the brain and facial sections. The brain section forms the cranium. It contains the brain. The facial section is more complex. Its upper part also consists of fused bones and forms the beak, which is fixedly connected to the skull. The lower part of the face is the jaw. It has a movable connection to the skull.

The skeleton of the body is divided into cervical, thoracic and lumbosacral (pelvic) sections. The cervical region of chickens is the largest. It has 13-14 vertebrae, movably connected. Thanks to this, chickens have a long and very mobile neck, which is of great importance for obtaining food, cleaning and lubricating feathers. The thoracic region is the rib cage, consisting of the vertebrae, the ribs attached to them, and the breastbone. Chickens have seven thoracic vertebrae and, accordingly, the same number of pairs of ribs.

The thoracic vertebrae from the second to the fifth are fused, and the last (seventh) is fused to the lumbosacral region. Five pairs of ribs are fused to the sternum and, thanks to this, form a fairly large thoracic cavity, protected from mechanical stress, where the most vital organs are located - the lungs and heart. The ribs are connected to each other by intercostal hook-shaped processes, which significantly strengthens the chest. The breast bone of chickens has a highly developed ridge, or keel. Powerful pectoral muscles are attached to it, driving the wings. Lack of minerals in the diet of chickens, especially calcium, as well as vitamin D, causes thinning or curvature of the breast bone.

There are 11-14 vertebrae in the lumbosacral region of chickens, but it is not easy to distinguish them. Even at a young age, the birds grow tightly together not only with each other, but also with the last thoracic and also the first caudal vertebra, forming, as it were, one lumbosacral bone. This bone is also tightly connected to the bones of the pelvis. There are only 5-6 vertebrae in the tail section of chickens. They have low-moving joints. The last caudal vertebra is the largest and has a special shape. It is called the coccyx (pygostyle).

The wing skeleton consists of the bones of the shoulder girdle and the bones of the wing itself. The shoulder girdle includes the scapula, clavicle and caracoid bone. They serve to movably connect the wing with the skeleton. The wing itself contains the following bones: the humerus, two forearm bones - a thicker ulna and a thinner radius, two wrist bones, a metacarpal bone and three poorly developed finger bones.

The pelvis consists of paired lamellar bones: ilium, ischium and pubis. The iliac bones of the pelvis are immovably connected to the sacrum. Unlike mammals, birds' pubic bones are not connected to each other. In laying hens, they seem to soften, become elastic and diverge from each other to a considerable distance. By the size of this distance you can judge whether the chicken is laying eggs or not. The more intense the chicken’s egg laying and the higher the weight of the eggs, the greater the distance between these bones. The difference between the skeleton of a chicken and a rooster is the presence of a medullary bone in chickens; it is involved in the formation of eggshells.

The skeleton of the pelvic limb consists of the femur, tibia, two metatarsal bones and four fingers. Of these, the hind finger has two segments, the inner - three, the middle - four and the outer - five. The end of each last segment has a claw. Most chickens have 4 toes, however, there are breeds that are characterized by the presence of a fifth toe. The femurs of the legs are connected by movable joints to the pelvis.

Digestive system

The chicken digestive system has its own characteristics. The digestive organs include the beak, oral cavity, pharynx, esophagus, crop, glandular and muscular stomachs, intestines and cloaca. The beak and oral cavity are intended exclusively for capturing food, as well as transporting it to the esophagus and further to the stomach. A chicken can swallow food in any position of its head, even if it is lowered down. This is ensured by the horny teeth present on the tongue and palate of the chicken. But she swallows water only with her head raised. Knowing this is very important, since when keeping chickens in cages and transporting them in boxes, the latter must have a certain height and design that allows the chickens to raise their heads above the drinker to a height sufficient to swallow water.

From the mouth, food enters the esophagus through the pharynx. As a result of wave-like contraction of the muscles of its walls, the feed masses, bypassing the crop (elastic expansion of the esophagus), pass directly into the stomach. If the stomach is already full, then the food enters the crop, and then into the stomach as it is cleared of its contents. The transition of food from the crop to the stomach is also caused by contraction of the muscles of the crop walls. When feeding chickens loose or granular feed, when it is in front of them throughout the day, their crops may always be empty or poorly filled, but this does not mean that the chickens do not eat enough feed. Since they peck at it constantly, but little by little, the food, bypassing the crop, goes directly into the stomach.

The lack of teeth in chickens is compensated by the presence of two stomachs (glandular and muscular). The esophagus is a long tube leading from the mouth to the first stomach. The walls of the esophagus do not secrete any digestive juices; it is intended solely for transporting food to the stomach, and also quite often for its temporary storage.

Chickens swallow unchewed food, and its processing begins directly in the stomach. From the esophagus, food enters the glandular stomach. Its walls secrete strong acid and some enzymes in abundance, which trigger the process of digestion of food, which soon passes into the second stomach, which is a cavity formed by extremely strong and durable muscular walls. Working on the principle of a millstone, the walls of the muscular stomach, vigorously contracting, grind and grind food, preparing it for further digestion. The process of grinding food is facilitated by the presence of gastroliths - small pebbles or grains of sand that birds swallow specifically for this purpose.

The midgut, or small intestine, consists of the duodenum, jejunum, and ileum. In its wall lie the parietal - general intestinal - glands. The wall glands are the liver and pancreas. Birds do not have duodenal glands. The intestines contain long villi, and its mucous membrane is collected in folds, increasing the path of food through the intestines.

The duodenum emerges from the anterior portion of the muscular part of the stomach and goes to the pelvis, and then returns, forming a loop of two knees. The pancreas is located in this loop.

The jejunum and ileum are suspended on a thin mesentery, touching each other and forming spiral curls. Ileum - opens into the hindgut at the border of the cecum with the rectum.

The liver is quite large, divided into two lobes and occupies a significant part of the ventral half of the thoraco-abdominal cavity. The gallbladder is located on the right lobe of the liver.

The pancreas is located in a loop of the duodenum; in chickens it has three lobes and three ducts.

The hindgut, or large intestine, does not have a colon in birds. Chickens have two cecums. Their apices face cranially, and are delimited from the ileum by a circular fold. The rectum passes into the cloaca, which is divided into three sections by two transverse folds: anterior, middle and posterior. The rectum opens into the anterior section, and the ureters, vas deferens (in males) and oviducts (in females) into the middle section. The posterior section of the cloaca ends with the anus, through which undigested food remains mixed with urine, and in females eggs are also thrown out. The sperm of males also passes through this same section during mating. On its dorsal wall in young birds there is a protrusion - a fibrous (bursa of Fabricius), which is reduced in adult birds.

Chicken stomach outside

Sectional view of chicken stomach

The length of time that feed remains in the chicken’s digestive tract depends on many conditions, and primarily on its preparation for feeding. Whole grains spend the longest time in the digestive organs, and feedstuffs with low fiber content last the longest. The time it takes for food to pass through the digestive organs of chickens also depends on their physiological state and the intensity of the body’s work. Thus, in young chickens, grain feed passes through the intestines in about 4 hours, and in non-laying adult chickens - in 8 hours, in laying but low-productive chickens - in 3 hours, and in highly productive chickens in only 2. These features must be taken into account when organizing feeding the bird. That is why it is advisable to feed highly productive chickens with compound feed without restrictions during the day. For the same reason, the best food is considered to be a loose or granulated compound feed that is balanced in all nutrients, and the chicken spends significantly less time and energy on digesting it.

Excretory system

With the help of the digestive organs, the chicken provides itself with nutrients to maintain life, body growth and the formation of eggs. But in the process of constant metabolism occurring in the body, decay products are formed - chemical substances harmful to the body, which are the result of the activity of cells, various tissues and organs. These substances must be removed from the body. This task is performed by the so-called excretory organs, which include the kidneys and ureters (urinary system); the bird does not have a bladder. Chickens have fairly large kidneys; they are located on both sides of the lumbar vertebrae. Inside them there are so-called renal glomeruli, enveloped in a dense network of the finest blood vessels - capillaries. Here, passing through the capillaries, the blood releases excess fluid and substances harmful to the body, which are then released into the urinary tubules of the kidneys, forming urine.

Urine does not accumulate in the excretory organs, but is excreted from the cloaca, first flowing from the kidneys into the ureters, then through the urinary tubules into the cloaca. The excretion product is uric acid (up to 80% of the total urine nitrogen), which precipitates in the form of crystals into the solution, forming a white mushy mass. In addition to the kidneys, harmful substances are released from the blood into the stomach and intestines, from where they are then released in the droppings. The liver also plays a major role in this, neutralizing toxic substances entering the blood from the intestines.

Reproductive system

Males have two testicles located inside the body. Sperm descend through the vas deferens into the cloaca and exit the body. Fertilization occurs when the cloacal openings of the male and female come into contact during mating. Males do not have an organ that penetrates the female's body. In females, only the left ovary and oviduct are usually functional. The eggs travel through the reproductive tract from the ovary. The sperm passes through this path and fertilizes the egg at the very beginning of the process. Sometimes sperm can remain viable in the female's body for three weeks after mating.

The time a pullet hen lays her first egg is considered the time of her puberty. It may occur earlier or later, depending on the breed, as well as the individual characteristics of the chicken. In chickens of egg breeds, sexual maturity is usually observed at the age of about five months, and in chickens of meat and egg breeds about a month later. The timing of puberty is greatly influenced by the conditions of feeding and keeping the bird.

With abundant feeding and a long daylight hours - more than 14 hours a day, chickens of egg breeds can lay eggs at the age of about 130 days, having not yet completed their growth and general physiological development. As a result, such chickens subsequently become poor laying hens. They lay smaller eggs and reduce egg production quite quickly. Therefore, it is not recommended to artificially induce early puberty in chickens. It should occur only after the pullet has largely finished growing, has fully developed, and its bones and organs have accumulated sufficient reserves of minerals, nutrients and vitamins.

At the beginning of laying, hens lay smaller eggs, then their weight gradually increases and reaches a normal value by 10-12 months of age. Therefore, to characterize chickens, the weight of eggs is determined at one year of age. Chickens lay the largest number of eggs in the first year of life. In the second year (after molting), their egg production decreases by about 12-15%, and sometimes more.

Therefore, in commercial farms, chickens are kept only for a year or a little more - 13-15 months. The productive period of chickens begins at 5 months of age; usually, to obtain eggs, they are kept until 17-18 months, and sometimes 19-22 months of age. Egg laying may stop prematurely if the hen begins to exhibit the brooding instinct - clucking. But in egg-laying chickens, especially Leghorns, thanks to the long-term selection work carried out with them, this instinct has almost disappeared.

Chickens usually lay eggs intermittently. For example, a hen lays eggs for 3-5 days, and then does not lay eggs for one or two days. The period of continuous egg laying (for several days in a row) is called a cycle. If 4-5 or more eggs are obtained during a cycle, then cyclicity is considered good. Record hens during the period of highest egg laying produce up to 25 or more eggs per cycle. Chickens lay eggs mainly in the morning or in the first half of the day. But some chickens can lay eggs at later times of the day.

Chicken reproductive system

Rooster reproductive system

Nervous system

In birds, the relationship between the structure of the brain and the sense organs and their functions is clearly visible. The relatively insignificant role of smell in the life of birds is directly dependent on the small size of the olfactory lobes of the brain. The perfection of the visual organs is due to the increased size of the visual thalamus of the well-developed midbrain.

The nervous system plays a leading role in all life processes of any organism. The nervous system communicates the body with the environment. All irritations coming from the outside are perceived by her through the senses. In response to these irritations, the functions of various organs change and the body adapts to the environment. Sufficiently strong irritation in any part of the nervous system usually causes numerous reflexes, which determine the reaction of the body as a whole.

A reflex is the body’s response to irritation of nerve receptors (endings) located both on the surface of the body and inside it, carried out through the central nervous system. Reflexes are divided into conditioned and unconditioned. Acquired reflexes are called conditioned; they can occur throughout the life of the bird. Unconditioned reflexes are those that are innate and are inherited. Unconditioned reflexes include the sexual reflex, the defensive reflex and many others. Conditioned reflexes are strictly individual and unstable, that is, they can disappear without a systematic stimulus and appear again.

Sometimes, under the influence of extreme stimuli, a state of general tension in the body, called stress, can occur. Stress can have both positive and negative effects on the bird’s body, up to its complete disorganization.

Circulatory system

Blood plays an important role in the life of the body. It, like lymph, delivers oxygen and nutrients to cells and tissues, carrying away decay products from them. Blood helps regulate body temperature and maintain a certain chemical composition in it. The secretions of the endocrine glands, which regulate all processes in the body, are carried with the blood. Special substances (immune bodies) accumulate in the blood, which ensure the body's immunity (immunity) to infectious diseases.

The total amount of blood in chickens is 8-9% of body weight. But during slaughter, only about half of this amount comes out, and the rest of the blood is retained in the tissues.

A bird's heart works like a pump, pumping blood throughout the body and supplying its cells with oxygen. The heart of birds resembles the heart of mammals, although it is asymmetrical: its left half is more developed than the right because it performs more work. The heart of birds beats faster than that of mammals of approximately equal size.

The average temperature of birds is 42 o C. With all the undoubted advantages that birds are given by their warm-bloodedness, which allows them to overcome any vicissitudes of the climate, it should be noted that it is very expensive. After all, the warm body of a bird continuously cools, and the faster, the higher the difference between the physiologically best tissue temperature for birds and the external temperature surrounding them. This difference must be constantly compensated by spending additional energy to continuously warm up the body.

Respiratory system

The structure of the respiratory system of birds differs from all other vertebrates. The lungs of birds resemble a sponge, completely permeated with numerous thin branching canals - parabronchi. The lungs of birds are connected to many special thin-walled cavities - air sacs, penetrating literally into all corners of the bird's body and in total volume exceeding the lungs by 3-4 times. There is no gas exchange in the air sacs; they are intended solely for storing and redistributing air in the bird’s respiratory system.

It is the presence of these volumetric reservoirs that provides the main feature of bird breathing - the continuous flow of air through the parabronchi rich in blood vessels, where the blood is enriched with oxygen and releases carbon dioxide. This eliminates the inevitable pause in gas exchange that occurs immediately after exhalation. In birds, the movement of air through the parabronchi occurs continuously and always in the same direction due to its independent influx not only from the outside through the trachea, but also from the inside from different air sacs, the rhythmic emptying and filling of which is coordinated by complex nervous mechanisms and is carried out largely independently from the rhythm of inhalation and exhalation. This breathing system ensures almost continuous saturation of the blood with oxygen and its uninterrupted flow to the tissues. The lungs of chickens practically do not change in size and do not have the same ability to stretch as the lungs of mammals.

It is useful for every farmer to know the anatomy of chickens and roosters, the structure of their skeleton, features of internal organs and basic vital systems. Such knowledge will help not only to score correctly, but also to recognize certain diseases and begin their treatment in a timely manner.

The skeleton of these farm birds has a number of features, one of which is a large number of hollow bones. Thanks to this, birds are endowed with the ability to fly, although they do not often practice this method of movement.

One of the features of the chicken skeleton is a large number of hollow bones.

They have practically no glands on their skin, and their beak acts as a mouth cavity. Chickens are also distinguished from humans and other animals by their lack of teeth.

In its structure, the chicken skeleton, regardless of whether it is a broiler or an egg breed, is very similar to the skeleton of well-flying birds. The bone mass of adults accounts for about 10% of the total weight of the bird. In the first two months of life, skeletal development progresses rapidly, and bones are only able to grow in the first six months.

Important. Unlike roosters, the anatomy of laying hens involves the presence of a medullary bone, which directly affects the formation of the shell around the egg when the hen reaches sexual maturity.

The skeleton of chickens can be formally divided into three parts:

• head section;
• torso;
• limbs.

The birds' heads are small and often look awkward on a voluminous body. The skull, in turn, consists of 10 parts: the nasal bone and quadratozygomatic, articular and lacrimal, dental and incisive, palatine, pterygoid and ethmoid, as well as the nasal opening.

The chicken wing consists of the coracoid bone, clavicle, scapula and free wing.

There are 13-14 vertebrae in the cervical region of the spine, 7 in the thoracic region, the last of which is immobile, and in the movable caudal region there are 5-6 elements. A distinctive feature of the thoracic region is the presence of a specific protrusion - the keel, to which the most developed chest muscles are attached. They can be easily palpated, which helps poultry farmers determine the fatness of their flock.

The wings act as the forelimbs. The components of a chicken wing are the coracoid bone, the clavicle, the scapula and the free wing, which can include several types of bones: the gurus, humerus, ulna, metacarpals, carpals and fingers.

There are four toes on the legs of quons, the basis of which is the pelvic girdle, and the feathered cavaliers also have sharp spurs. There are breeds in the world with a different number of fingers. The constituent elements of the legs are the tibia, femur, tibia, fibula, and tarsus.

Internal organs

The anatomy of chickens is somewhat different from the structure of mammals, because birds have not only an esophagus, stomach, heart and liver, but also special internal organs that are unique to birds.

The digestive system begins with the beak and ends with the cloaca. A separate intermediate organ is the crop, in which preliminary fermentation of food is carried out - its wetting and processing. Since chickens have no teeth, the process of processing food cannot occur in the beak.

Moving along the esophagus, food enters the stomach, where in the glandular section, under the influence of gastric juice, the process of complete fermentation begins. To ensure good grinding of food, birds often swallow sand and stones, which are found in the stomach after slaughter.

Having completed its functions, the stomach redirects processed food to the small intestine. Here, beneficial elements and vitamins from food are absorbed, after which in the large intestine it takes the form of feces and is excreted through the cloaca.

Due to the lack of teeth in chickens, the process of processing food does not begin in the beak.

Interesting. The intestines of chickens measure up to 160-180 cm, which is almost six times the length of their body. Despite this, the digestive process is quite fast and comfortable, so black whales are constantly in search of food.

Respiratory system

A complete description of the internal structure of chickens is impossible without the respiratory system, which is characterized by an unusual organ structure. The beginning of the respiratory system is the nostrils, after which the air enters the nasal cavity and larynx, and finally reaches the trachea, which divides the air into two bronchi.

In chickens, the lungs cannot greatly transform their size.

In the area of ​​divergence of the trachea, the lower larynx is located, which performs sound production functions. The bronchi protrude beyond the edges of the lungs and come into contact with a large number of air sacs located in the body of feathered workers. They are responsible for the implementation of gas and heat exchange processes. Approximately 75% of the air entering the body settles in these air sacs.

The lungs of chickens cannot radically transform their size and stretch like the lungs of mammals. In addition, the breathing system cannot boast of special valves, because air circulation is subject only to the basics of thermodynamics.

Nervous system

Poultry, including chickens, have a well-developed nervous system. It is demonstrated by the brain and spinal cord, as well as the nerve fibers through which nerve impulses spread throughout the quonk’s body. It is well known that when slaughtered, chickens can run around without their heads for some time, which is due to nerve impulses arriving even after death.

Chickens have a well-developed nervous system.

Conventionally, the brain consists of several sections:

• cerebellum;
• forebrain;
• midbrain;
• diencephalon.

The hemispheres of the brain are small in size and lack convolutions, which is perhaps why the proverb about chicken brains has become widespread among people. The hemispheres are responsible for implementing instincts and orientation in space, and the cerebellum is responsible for controlling movements.

Extraction system

Chickens have large paired pelvic kidneys.

The chicken selection system also has its own characteristics. It is represented by rather large pelvic paired kidneys, which open into the cloaca through the ureter. When these elements interact, uric acid is released, constituting up to 80% of the total urine nitrogen, which precipitates into the solution in the form of crystals.

The bladder itself is absent in birds, which affects the atypical appearance of urine, which has a thick and mushy consistency, not much different from feces. Despite this, birds have regular bowel movements and much more often than mammals. This allows them to lighten their body weight for a comfortable flight.

Circulatory system

The circulatory system of chickens is represented by a four-chambered heart, a small circle of blood circulation and a large one, while both circles are separated and in no way can merge with each other.

The circulatory system of chickens is represented by a four-chambered heart, a small and large circle of blood circulation.

Venous blood collects in the right atrium of the quotation, which penetrates into the right ventricle during contraction. Further moving along the pulmonary artery, it passes into the lung to be saturated with oxygen, and when saturated, it goes to the left atrium. This circulation is called the pulmonary circulation.

The systemic circulation starts in the left ventricle, from which blood enters the aorta and spreads to all organs and systems through small veins, arteries and capillaries.

The chicken heart has impressive dimensions and stands out for its asymmetry. The left side is larger and takes on more load. Like all birds, chickens experience high blood pressure and increased heart rate. These phenomena are associated with rapid metabolism and high body temperature, which require high blood circulation through the vessels.

Reproductive system

Chickens reproduce by laying fertilized eggs, from which chickens will hatch in the future. Roosters have paired and symmetrical reproductive organs - testes, which are located near the kidneys and significantly increase in size during the breeding season. A continuation of the testis is the vas deferens, which passes into the seminal vesicle, where the sperm are located.

Important. Feathered cavaliers do not have a genital organ, so fertilization occurs by contact of the cloaca of the male and female. As a rule, the formation of an egg in the oviduct takes from 12 to 48 hours.

The reproductive system of chickens is represented by the oviduct and only the left ovary, since the right one atrophies as the bird grows older. In the ovary, eggs are formed, represented by yolks and beneficial nutrients, which play an important role in the full development of the embryo. Externally, the ovary resembles a bunch of grapes, and with prolonged egg laying it can increase tenfold in volume.

The hen's right ovary atrophies as she gets older.

The oviduct is an elongated tube-shaped organ, the length of which can reach 35-86 cm. It is a place where sperm accumulate from the moment of sexual intercourse until fertilization, and the egg is formed here.

There are 5 components of the oviduct:

• funnel – located in the upper part and opens with a wide opening into the abdominal cavity near the ovary;
• the protein part is an area up to 37 cm long that produces protein as the yolk passes through it;
• neck of the funnel (isthmus) - a narrow tube connecting the funnel and the protein part;
• the uterus is a muscular organ that is the widest part of the oviduct, in which the shell is laid;
• vagina - an organ up to 3-5 cm long, into which the finished egg enters from the uterus through the sphincter and is released out.

You can learn more about the structure of the skeleton and muscles of birds from this video.

Skeleton

In the cervical region Chickens have 13-14 vertebrae, ducks have 14-15, and geese have 17-18. The spinous processes are weak, the articular surfaces are saddle-shaped (movement along two planes - sagittal and frontal). On the atlas, the articular surface is in the form of a fossa, corresponds to one condyle of the occipital bone, the joint is multi-spinous.

Thoracic department. Chickens have 7, ducks have 9. The 1st-2nd ribs, less often the 3rd, are sternal, the rest are sternal. From the posterior edge of the vertebral part of the rib, uncinate processes extend caudodorsally and connect to the next rib. Sternum well developed, lamellar; in the caudal region the notch is well defined in chickens, less so in ducks, and is closed into a hole in the goose; on the ventral side there is a ridge (keel) which normally ossifies in laying hens by day 240; if not, there is a metabolic disorder; at the cranial end there is an articular surface for connection with the caracoid bone.

Lumbosacral region. They merge to form the common pelvic region. 11-14 vertebrae fuse, and the ilium and the first caudal vertebrae fuse with them. The intervertebral foramen is visible only from the ventral side. The tail vertebrae are movably connected, in chickens 5, in ducks and geese 7; together form the coccyx to which the tail feathers are attached

Scull Lightweight, bones grow together. Facial department- smaller in size, but more complex than the brain. There is a mandible and a mandible. Upper beak- connects with the medulla movably by 3 bones (1st - quadratic - 4 articular surfaces for the temporal, pterygoid, quadratozygomatic and mandibular. 2nd - paired palatine - limits the choanae, connects with the pterygoid and maxillary. 3rd - pterygoid - connects to the palatine, sphenoid and quadrate). The beak contains the incisive bone (the largest, unpaired, fused in the egg), the maxillary (weakly developed) and the nasals (lying between the incisive, palatine and maxillary). The nasal cavity is divided by a septum. The palatine bones are mobile and limit the choanae, the basis of the hard palate. Square bones are quadrangular. Mandible- formed by the paired lower jaw, connected by a joint to the quadrate bone, and when the mouth opens, the mandible simultaneously descends and the mandible rises.

Limb skeleton

Shoulder girdle- how reptiles have 3 bones preserved: the scapula, the clavicle and the coracoid. Spatula- in the form of a curved narrow plate, along the spinal column, there are articular surfaces for connection with the humerus, scapula and coracoid. There is no cartilage. Coracoid bone - the largest, the upper end connects to the humerus, scapula and collarbone, as well as to the sternum. Clavicle (Clavicularia) - steam room, grows together distally to form a fork.

Pelvic girdle- the pubic and ischial bones are not connected along the pelvic suture, but rather a pelvis with wide open ventral surfaces (facilitates egg laying). Ischium - fuses with the lumbosacral, participates in the formation of the roof of the pelvic cavity, on the ventral surface there are depressions in which the kidneys are located. Ilium - lamellar, the largest of the pelvic bones, fuses with the lumbosacral region. pubic bone- long, narrow, located ventral to the ischium.

Free thoracic limb (wing). Brachial bone. The proximal end medially has a pneumatic opening that leads into the pneumatic cavity of the humerus. The head is oval, at the distal end there are 2 articular surfaces (one for the ulna, the other for the radius). Forearm- the ulna is better developed, the radius is thin and straight. The interosseous space is well developed between them. Brush changed at all levels. The proximal row of the wrist is only the 2nd bones, the carpal radius is fused with the intermediate, and the carpal ulna with the accessory. The distal row is completely fused with the proximal ends of the metacarpals. There are 3 rays preserved in the metacarpus (2, 3, 4), fused into one bone. Among the fingers of the hand, 2 phalanges are developed in the 3rd finger and worse in the 2nd and 4th fingers - one phalange each.

Free pelvic limb. Femur- short, curved. At the proximal end there is a head and 1 trochanter, at the distal end there are condyles for the tibia and a block for the patella. The tibia is better developed in the lower leg. The fibula is greatly reduced, thin, disappears in the middle of the lower leg, and fuses with the tibia. Foot- the tarsus is absent, because its proximal row fuses with the tibia, and the distal and central bones fuses with the bones of the metatarsus. Metatarsus - 2, 3, 4 fused together to form a long, powerful bone. Together with the bones of the tarsus - the tarsus. At the distal end it is divided into 3 rays, where there are 3 articular blocks for the 2nd, 3rd and 4th fingers. Roosters have a process on their tarsus. Birds usually have 4 fingers: 1st - posterior and hanging (2 phalanges), 2nd - 3 phalanges, 3rd - 4 phalanges, 4th - 5 phalanges. The number of fingers and phalanges varies from bird to bird. In migratory birds, the femur may be pneumatized to reduce weight. There are no serious differences in the connection of bones from mammals.

Skeletal muscles

Unevenly expressed. The muscles of those who fly poorly are pale pink, those of those who fly are dark red. Cutaneous muscles Well developed, ending on the feather sheaths, helping to relax the feathers and tighten the wing membrane. Facial muscles Absent. Jaw muscles More differentiated than in mammals. There are muscles that push and pull the quadrate bone. In addition to the 4 chewing muscles, there are the quadratomaxillary, sphenoid-maxillary, levator quadrate, sphenoid-maxillary muscles, the muscles of the thoracic and lumbosacral column are poorly developed, the cervical and caudal muscles are well developed and highly differentiated. Muscles of the chest- external and internal intercostal, levator ribs, transverse pectoral, scalene, no diaphragm (a poorly developed tendon fold remains). Abdominal muscles The same, but poorly developed. Muscles of the pelvic limb Numerous and similar to mammals.

Skin covering.

There are no glands on the skin; there is a coccygeal gland under the last sacral vertebrae (works like a sebaceous gland, better developed in waterfowl, for lubricating feathers). Derivatives include the beak, scales, claws, spurs of a rooster, combs, wattles, beard, feathers, wax and membranes in waterfowl. There are few blood vessels in the skin (except for the ridge and catkins).

Feathers needed for flight and preservation of heat, they have a rod and a fan. On the stem there is a quill (a part of the feather placed in the bag) and a stem from which branches go in different directions, and from them rays with hooks. There are integumentary feathers (over the entire surface), down feathers (lie under the integumentary feathers, a fan without hooks), flight feathers (a wide fan) and tail feathers. Throughout the body there are feather zones (pteria) and bald zones (apteria) - they act as thermoregulation, are not visible outwardly, most of all in the axillary region, chest and abdominal walls. In the area of ​​the wing, from the body to the shoulder and forearm there is a large fold of skin - a flying membrane between the leaves of which there is an elastic membrane and for example. muscle membrane. When the wing expands, the membrane contracts and pulls the wing towards the body.

Digestive apparatus

Oropharynx - There is no velum palatine, so there is no division into the oral cavity and pharynx. The entrance to the oropharynx is the beak, in chickens it is hard and cone-shaped, in ducks and geese it is flattened, softer, covered with a wax that contains many tactile bodies; in male guinea fowl the wax is large and convex. Along the edges of the oropharynx in geese and ducks there are many membranous plates with nerve endings (straining water and retaining edibles).

Solid sky - In chickens, there remains a narrow palatine slit in the middle, and across it there are papillae, i.e., the oropharynx communicates with the nasal cavity. On the sides on the hard palate there are openings of the salivary glands, at the bottom of the oropharynx there is a tongue (the shape corresponds to the beak). Filiform papillae are across the base of the tongue in chickens and on the sides in geese. There are no taste buds; their role is played by corpuscles at the base of the tongue and on the hard palate. The area of ​​the oropharynx, which can be called the pharynx, is lined with stratified squamous epithelium, from which there is an entrance to the larynx. No teeth.

Foregut - Goiter and 2-chamber stomach. Esophagus- mucous membrane is longitudinally folded. Before entering the chest cavity in chickens, a protrusion forms (an expansion of the wall of the esophagus - a goiter; in waterfowl it is spindle-shaped). The mucous membrane of the crop contains numerous glands; pre-wetting and pre-processing of the feed occurs. Stomach- first glandular, then muscular. The glandular layer lies between the lobes of the liver, and when passing into the muscular part it narrows to form an isthmus. The muscular lining of the glandular stomach consists of a thin outer layer (longitudinal fibers) and a developed inner annular layer; the mucous membrane contains glands - gastric juice. Food passes through it in transit and is only wetted. The muscular stomach compensates for the lack of teeth, is well developed in granivores, worse in carnivores, all muscles are connected into a single whole, the mucous membrane is folded, contains glands that produce a secretion that immediately hardens and forms a protective layer - the cuticle.

Small intestine - Duodenum, jejunum, ileum. Longer in granivores. Age affects length DPK which is in the form of a long loop in which the pancreas lies. The pancreas in chickens opens into 3, and in ducks and geese, 2 ducts into the duodenum. The hepatic and bile ducts also flow here. The liver has 2 lobes, on the right there is a gallbladder from which the bile duct goes, and from the left there is the hepatic duct. Some wild birds do not have a gall bladder. Jejunum on the long mesentery between the air sacs. Ileum goes between the blind bags.

Large intestine. Consists of 2 cecums and a rectum (the rectum does not correspond to the structure of mammals). Rectum short, flows into the cloaca. It is separated from the cloaca by a sphincter; the mucosa contains lymphoid formations. The cloaca is an expanded part of the intestine, divided into 3 sections by 2 ring-shaped folds: cranial (the bursa of Fabricius opens, with the onset of puberty it is reduced, reaching its maximum size by the 90th day; in the folds of the mucous membrane of the bursa of Fabricius there are lymphoid elements that produce B-lymphocytes (stimulate the production of antibodies)), the middle section (the ureters and excretory genital tract open) and the final section (ends at the anus). The drake, gander, swan, guinea fowl, and ostrich have a penis in their cloaca. In chickens, the intestines are 160-170 cm, six times the length of the body, in ducks and geese it is 4-5 times, in raptors it is 1.5-2 times.

Breathing apparatus

Features: 1. Small size and simple structure of the nasal cavity. 2. The presence of a voice-forming organ in the area of ​​tracheal bifurcation - the singing larynx. 3. Insignificant size and position of the lungs, the bronchi of which communicate with the cavity of the air sacs.

The nasal cavity has three cartilaginous conchae in each half; there is no ethmoid labyrinth. The olfactory nerve branches in the conchae and nasal septum.

The larynx lies at the bottom of the pharynx, opening into it with a narrow slit. Lined with ciliated epithelium. There is no voice box. Consists of annular and arytenoid cartilages, there is no thyroid cartilage and epiglottis. The cartilages are mobile, controlled by the muscles of the larynx, instead of the epiglottis there is a transverse fold of the mucous membrane.

The trachea is formed by cartilaginous rings; in old geese and ducks they ossify. The mucosa is rich in alveolar-type glands. In the area of ​​bifurcation - the singing larynx - is represented by a drum (thickening of the tracheal ring), a semilunar fold and tympanic membranes (replace the vocal cords). The air flow vibrates under the influence of the membranes and produces sound signals.

The lungs are light pink. Left and right are not divided into parts. The walls protrude into the intercostal spaces. They lie from the 1st rib to the legs. Differences from mammals:

1. In lung tissue, gas exchange occurs not through the wall of the alveoli, but through the walls of the air-bearing capillaries.

2. The main bronchi pass through the lungs and end in the air sacs. When you inhale, air passes through the lungs and fills the chest and abdominal sacs. When exhaled, it passes through the lungs into the cervical and interclavicular sacs.

3. The pleural cavity contains thin fibers of connective tissue that connect the lungs to the chest wall.

4. There are 6 types of bronchi:

4.1. The main bronchus enters the lungs and divides within them.

4.2. Bronchi of the 2nd order - a wall without cartilage.

4.3. Ectobronchi - arise from 4.2., pass through the lungs into the bags.

4.4. Returning sac bronchi - go from the sacs to the lungs.

4.5. Endobronchi - do not pass into bags, they divide inside the lungs.

4.6. Parabronchi - d=0.5-2 mm., conduct air into the air capillaries from 4.3. and 4.5., are lined with flat epithelium, underneath there are muscle bundles and elastic tissue that changes the d of the bronchi.

5. Air capillaries - short, flat epithelium, surrounded by a dense network of capillaries, gas exchange takes place, air passes during inhalation and exhalation.

6. Air sacs - the inside is mucous, and the outside is serous. There are few vessels in the walls, i.e. they weakly participate in gas exchange. Functions - air reserve when flying or diving under water, air enters the lungs both when inhaling and when exhaling, since the metabolism is intense, during flight the clavicular and cervical bags expand and contract under the influence of the muscles of the wings, the expansion of the abdominal bags creates pressure on intestines and cloaca (excretion of droppings), as well as on the ovary and oviduct (promotes oviposition), the change of air in the bags is involved in thermoregulation, in waterfowl it lightens the body, when making a sound, the air stream during exhalation increases. There are 4 paired and 1 unpaired bags:

6.1. Cervical - a continuation of the cervical ectobronchi, lie under the trachea and esophagus, the cervical and thoracic vertebrae and ribs are pneumatized.

6.2. Cranial thoracic - lie under the lungs.

6.3. Caudal thoracic - they include branches of the main bronchus, cover the liver, stomach and intestines.

6.4. The abdominal ones are the largest, they contain the main bronchus, cover the internal organs, pneumatize the lumbosacral vertebrae, pelvic bones, and femur. From the caudal thoracic and abdominal bronchi, the recurrent sac bronchi run into the lungs next to the ectobronchi.

6.5. Unpaired interclavicular - consists of two parts, acts as bellows replacing the movement of the chest during flight.

6.5.1. The intrathoracic part lies between the collarbones and covers the heart.

6.5.2. The extrathoracic part forms a series of diverticula; the largest diverticulum, the axillary one, communicates with the humerus.

Urination apparatus.

Buds range from pale pink to dark red. They lie in the recesses of the pelvic region. There are cranial, middle and posterior lobes of the kidneys. No fat capsule. The border between the cortical and medulla layers is not pronounced. There is no pelvis or bladder. The right and left ureters open in the middle section of the cloaca. The urine is thick, whitish-gray in color, contains a lot of uric acid (specific odor) and urate salts (uric acid salts). Together with feces, it is excreted from the cloaca (litter).

Male reproductive apparatus.

Represented by testes, tubules, vas deferens, appendages, seminal ampoules and organ of copulation (genital tubercles or penis).

The testes are laid and develop in the abdominal cavity because there is no scrotum. They are located semimetrically on both sides near the anterior end of the kidneys, suspended on a short mesentery, bean-shaped or ovoid in shape, whitish-yellow in color. The left one is bigger than the right one. Weight depends on the species, age and physiological state. In egg roosters - 45 g, in meat - 70 g, in drakes - 70. Mature testes have large convoluted tubules and contain sperm at different stages of development. From the wall of the tubule to the lumen there are spermatogonia, spermatocytes of the 1st and 2nd orders, and sperm. Also on the wall and in the lumens of the tubules there are feeding cells (Sertolli cells) to which sperm are attached. In the connective tissue between the tubules - Leydig cells - secrete hormones.

The testicular appendages are poorly developed and visible during sexual activity. In mammals, sperm maturation occurs in the epididymis, and in birds, sperm from the testis immediately enters the vas deferens. The vas deferens are thin convoluted tubes; during sexual activity the walls are thicker, the lumen is wider, the number of convolutions increases, it opens into the cloaca, and before entering it forms small thickenings - seminal vesicles. The vesicles are filled with sperm - the role of the epididymis.

The penis is absent in most birds; it is better developed in drakes and ostriches, and less so in ganders and guinea fowl. Formed by a fold of the ventral part of the posterior wall of the cloaca. It has voids that are filled with lymph during an erection. On the surface is the mucous membrane, which forms a fold in the form of a groove. During an erection, the gutter turns into a canal, the penis lengthens to 7-15 cm and emerges from the cloaca. Ostriches have a bone in their penis. In roosters and guinea fowls, for copulation, there is a copulatory organ, which, during an erection, protrudes from the cloaca in the form of a small protrusion; sperm flows through the gutter.

Female reproductive organs.

Ovary - eggs (egg yolks) enriched with nutrients are formed. Only the left ovary and, accordingly, the left oviduct develop. The right one is reduced on the 7-8th day of incubation. Suspended on the mesentery, not formed, tuberous. Most of the ovary is formed by follicles at different stages of development (from a grain of sand to a full yolk and resembles a bunch of grapes). The outside is covered with an epithelial and connective tissue membrane, under which lies the follicular layer, under it is the vascular layer - the serous membrane is rich in blood vessels.

Oviduct - sperm live and remain for up to 3 weeks (from insemination to fertilization). This is a long convoluted organ - in chickens up to 60 cm, 10 cm in diameter. The wall is elastic and changes dimensions. Consists of sections in which egg shells are formed:

1. Oviduct funnel - L=4 cm, d=8-10 cm, thin, ciliated epithelium, fertilization occurs here, the egg is located for 15-20 minutes, attached by a ligament to the abdominal wall near the ovary. The ligament is mobile and ensures the capture of mature follicles from the ovary after ovulation.

2. Narrowing of the funnel - transition to the white part.

3. Tunica albuginea - L=30-35 cm, folded mucosa, many glands, secretes protein secretion. In 3-3.5 hours, the yolk is enveloped in protein.

4. Isthmus - 8-10 cm, thick layer of circular muscles. In the mucous membrane, the glands (keratinoids) that form the subshell film (thin protein and thick fibrous) are a leathery shell. At the blunt end it stratifies, forming an air chamber. Without visible boundaries it passes into the uterus.

5. Bird's uterus - thick-walled, wide, L=8-10 cm, folded mucosa, at the end of the uterus there is a strong sphincter. A finely porous, hard, sometimes pigmented calcareous shell is formed.

6. Vagina - the final section of the oviduct, 8-10 cm, the mucous membrane contains glands, forms an under-shell film, then the finished egg passes into the middle section of the cloaca.

The heart bag is connected by ligaments to the spine and liver. The apex of the heart is located between the lobes of the liver. Blood vessels like those of mammals. From the brachiocephalic trunk the carotid trunk extends to the head and the subclavian trunk to the wing. In the caudal direction there is the caudal aorta, from which the sciatic, lateral pelvic, intercostal, internal spermatic, renal, glandular and muscular parts of the stomach, duodenum, anterior and posterior mesenteric arteries depart. Veins - 2 cranial vena cava and 1 caudal vena cava. The liver contains 2 portal veins.

There are no lymph nodes, but there is an accumulation of lymphoid tissue in the form of follicles in the wall of the respiratory, digestive, and skin organs. There are pharyngeal and esophageal tonsils. The cecum contains plaques and tonsils. Geese and ducks have several formed lymph nodes near the jugular veins at the entrance to the chest cavity. The intercellular substance contains lymphatic capillaries that pass into lymphatic vessels. Lymph flows into the jugular veins. The spleen is small, round in shape. The thymus produces T-lymphocytes and lies under the skin from the 2nd cervical to the chest.

Endocrine glands.

Adenohypophysis - the large and posterior lobes are smaller, there is no intermediate lobe.

The pineal gland is greatly enlarged during the period of egg production.

The thyroid gland is round in shape, its structure is similar to that of mammals.

The adrenal glands are located on the sides of the aorta near the cranial lobe of the kidneys. In males the left one is covered by the testes, in females the left one is covered by the ovary. Yellow-brown color. Hormones regulate metabolism, water and sexual cycles.

Features of the NS.

The cerebellum is well developed, instead of the quadrigemone there is a colliculus (there is no auricle). The corpus callosum is weakly expressed. There are few convolutions on the mantle, there is no facial nerve (no facial muscles).