When birds acquired the ability to fly, their structure underwent noticeable changes compared to that which was characteristic of their ancestors - reptiles. In order to reduce the body weight of the animal as much as possible, some of the organs became more compact, while others were completely lost. As for the scales, feathers have taken their place.
Those heavy structures that were vital were moved closer to the center of the body to improve its balance. In addition, the controllability, speed and efficiency of all physiological processes have increased markedly, which provided the flight power that the animal required.
bird skeleton
For the bird skeleton, the characters are unique rigidity and lightness. The lightening of the skeleton was achieved due to the fact that a number of elements were reduced (primarily in the limbs of birds), and also due to the fact that air cavities appeared inside some bones. Rigidity was provided by the fusion of a number of structures.
For convenience of description, the bird skeleton is divided into the axial skeleton of the limbs. The latter includes the sternum, ribs, spine and skull, and the latter consists of arched shoulder and pelvic girdle with bones attached to them of the hind and anterior hips.
The structure of the skull in birds
The eye sockets of a huge size are characteristic of a bird's skull. Their size is so large that the brain box adjacent to them from behind is, as it were, pushed back by the eye sockets.
The bones protruding very strongly forward form a toothless upper and lower jaws, which correspond to the upper and lower mandibles. Under the lower edge of the eye sockets and almost close to them are the ear openings. Unlike the upper jaw in humans, the avian upper jaw is mobile due to the fact that it has a special, hinged attachment to the braincase.
The spine of birds consists of many small bones called vertebrae, which are located one after another, starting from the base of the skull to the end of the tail. The cervical vertebrae are isolated, highly mobile, and at least twice as many as in most mammals, including humans. Due to this, birds can tilt their heads very strongly and turn it in almost any direction.
The vertebrae of the thoracic region articulate with the ribs and in most cases are firmly fused to each other. In the pelvic region, the vertebrae are fused into one long bone called the compound sacrum. Such birds are characterized by an unusually stiff back. The remaining tail vertebrae are quite mobile, except for the last few, fused into a single bone called the pygostyle. In their form, they resemble the plow share and are the skeletal support for the long tail feathers.
Thoracic cage in birds
The heart and lungs of birds are externally protected and surrounded by ribs and thoracic vertebrae. Fast-flying birds are characterized by an extremely wide sternum, which has grown into a keel. This ensures efficient attachment of the major flight muscles. In most cases, the larger the keel of a bird, the stronger its flight. Birds that do not fly at all have no keel.
The shoulder girdle connecting the wings with the skeletal skeleton is formed on each side by three bones, which are arranged like a tripod. One leg of this design (crow bone - coracoid) rests against the sternum of the bird, the second bone, which is the shoulder blade, lies on the ribs of the animal, and the third (collarbone) merges with the opposite clavicle into a single bone called the "fork". The scapula and coracoid in the place where they converge form the articular cavity, in which the head of the humerus rotates.
The structure of the wings of birds
In general, the bones of a bird's wings are the same as the bones of a human hand. Just like in humans, the only bone in the upper limb is the humerus, which articulates at the elbow joint with the two bones (ulna and radius) of the forearm. Below the brush begins, many elements of which, unlike their human counterparts, are merged or completely lost. As a result, only two carpal bones remain, one buckle (metacarpal bone of a large size) and four phalanges, which correspond to three fingers.
The bird's wing is much lighter than the limb of any other terrestrial vertebrate similar in size to a bird. And this is not only due to the fact that the bird brush includes fewer elements. The reason is also that the long bones of the forearm and shoulder of the bird are hollow.
Moreover, in the humerus there is a specific air bag, which belongs to the respiratory system. Additional relief to the wing is given by the fact that there are no large muscles in it. Instead of muscles, the main movements of the wings are controlled by the tendons of the very developed musculature of the sternum.
Flying feathers extending from the hand are called primary (large) flight feathers, and those that are attached in the region of the ulnar bones of the forearm are called secondary (small) flight feathers. In addition, three more wing feathers are spilled, which are attached to the first finger, as well as covering feathers, which smoothly, like a tile, lean on the bases of the flight feathers.
As for the pelvic girdle of birds, on each side of the body it consists of three bones fused together. These are the ilium, pubic and ischium bones, and the ilium is fused with the sacrum, which is complex in structure. This complex design protects the kidneys from the outside, while providing a strong connection between the legs and the shoulder skeleton. Where the three bones belonging to the pelvic girdle converge with each other, there is a significant depth of the acetabulum. It rotates the head of the femur.
The device of the legs in birds
Like humans, the femur of birds is the core of the upper section. lower extremities. At the knee joint, the lower leg is attached to this bone. But if in humans the small and large tibia are included in the lower leg, then in birds they are fused with each other, as well as with one or several tarsal bones. Together, this element is called tibiotarsus. As for the fibula, only a short thin rudiment remained visible from it, which is adjacent to the tibiotarsus.
Bird foot arrangement
In the intratarsal (ankle) joint, the foot, which consists of one long bone, the bones of the fingers and the tarsus, is attached to the tibiotarsus. The latter is formed by elements of the metatarsus, which are fused together, as well as by several tarsal lower bones.
Most birds have four fingers, each of which is attached to the tarsus and ends with a claw. The first finger of birds is turned back. The remaining fingers in most cases are directed forward. Some species have a second or fourth finger facing backwards (like the first). It should be noted that in swifts the first finger, like the rest of the fingers, is directed forward, while in the osprey it can turn in both directions. The tarsus of birds does not rest on the ground, and they walk only on their toes, not resting on the ground with their heels.
Muscular system in birds
The legs, wings, and other parts of the bird's body are driven by approximately 175 different skeletal striated muscles. These muscles are also called voluntary, since their contractions can be controlled by consciousness and, accordingly, they can be voluntary. As a rule, these muscles are paired, located symmetrically on the right and left sides of the body.
The main muscles that provide flight are the pectoral muscle and the supracoracoid. Both muscles start on the sternum. The largest muscle is the chest. She pulls the wing down, causing the movement of the bird in the air up and forward. And the supracoracoid muscle lifts the wing up, in the direction opposite to the work of the pectoral muscle, preparing it for the next stroke. I must say that in turkey and domestic chicken, these two muscles are considered "white meat", while the rest of the muscles are "dark meat".
In addition to skeletal voluntary muscles, birds, like other vertebrates, have smooth muscles, which lie in layers in the walls of the organs of the genitourinary, digestive, vascular and respiratory systems. In addition, there are smooth muscles in the skin. It is they who determine the movement of feathers. There are also smooth muscles in the eyes: thanks to it, the image is focused on the retina. Such muscles, in contrast to the striated muscles, are called involuntary muscles, since they work without volitional control.
Nervous system in birds
Central nervous system birds consists of a spinal cord and brain formed by many neurons nerve cells.
The most prominent part of the brain in birds are the cerebral hemispheres, which are the center in which higher nervous activity takes place. The surface of these hemispheres has neither convolutions nor furrows typical of many mammals, and its area is quite small, which coincides with the relatively low intelligence of the majority of birds. Inside the cerebral hemispheres are the centers of coordination of those forms of activity that are associated with instinct, including the instincts of feeding and singing.
Of particular interest is the avian cerebellum, which is located immediately behind the cerebral hemispheres, and is covered with convolutions and furrows. Its large size and structure correspond to those complex tasks, which are associated with maintaining balance in the air and coordinating the many movements necessary for flight.
The cardiovascular system in birds
In relation to body size, the heart of birds is noticeably larger than that of mammals of the same size. It was observed that the smaller specific view birds, the larger will be his heart (of course, relative to the size of her body). For example, in a hummingbird, the mass of the heart is 2.75% of the mass of the entire body. This is necessary so that all perennial birds can provide rapid blood circulation. The same applies to those species of birds that live at high altitudes or in cold areas. And, just like mammals, birds have a four-chambered heart.
The heart rate depends on the size of the heart and the animal itself, as well as on the degree of load. For example, the heart rate of a resting ostrich is about 70 beats per minute, while in a hummingbird it rises to 615 beats per minute during flight. At the same time, excessive fright can frighten the bird so much that the increased pressure can cause the arteries to burst and the bird to die.
Like mammals, birds are warm-blooded animals. At the same time, the range of normal temperatures of their bodies is higher than that of humans and ranges from 37.7 to 43.5 degrees. As a rule, avian blood contains more red blood cells than the bulk of mammals. Thanks to this, the bird's blood can carry more oxygen per unit of time, which is very important for flight.
Respiratory system in birds
In almost all birds, the nostrils lead to the nasal cavities located at the base of the beak. But there are exceptions: gannets, cormorants and some other species of birds do not have nostrils and therefore are forced to breathe through their mouths. Air entering the nose or mouth moves into the larynx, behind which the trachea begins.
Unlike mammals, the larynx of birds does not produce sounds, being only a valve apparatus that protects the lower respiratory tract from water and food entering them.
Closer to the lungs, the trachea divides into two bronchi, which enter one each lung. At the point where they separate, the lower larynx is located, which serves as the bird's vocal apparatus. It is formed by ossified dilated bones of the trachea and bronchi, as well as internal membranes. Pairs of special singing muscles are attached to them. When the air exhaled from the lungs passes through the lower larynx, it causes the membranes to vibrate, which produces sounds. Those birds that are characterized by a wide range of emitted tones have more singing muscles that strain the vocal membranes than those species that sing frankly poorly.
Each bronchus divides at the entrance to the lungs into thin tubes. The walls of these tubes are permeated with blood capillaries, which receive oxygen from the air and give carbon dioxide back into it. These tubes are sent to thin-walled air sacs, resembling soap bubbles not penetrated by capillaries. These bags are located outside the lungs - in the region of the pelvis, shoulders, neck, around the digestive organs and lower larynx, and even stick into the large bones of the wings and legs.
When the bird inhales, air enters these same sacs through the tubes, and when it is exhaled, it travels from the sacs through the tubes through the lungs, where gas exchange occurs again. Thanks to this double breathing, the supply of oxygen to the body increases, which creates more favorable conditions for flight.
In addition, air sacs humidify the air and also regulate body temperature. This is achieved due to the fact that as a result of evaporation and radiation, the surrounding tissues can lose heat. As a result, birds acquire the ability, as if to sweat from the inside, which is a worthy compensation for the absence of sweat glands in birds. In addition, air sacs help remove excess fluid from the body.
The structure of the digestive system in birds
In general, we can say that the digestive system of birds is a hollow tube extending from the beak up to the opening of the cloaca. This tube performs many functions at once, taking in food, secreting juices with enzymes that break down food, absorb substances, and also remove undigested food residues. However, despite the fact that all birds have the same structure of the digestive system, as well as its functions, there are differences in some details that are associated with feeding habits, as well as with the diet of a particular group of birds.
The process of digestion begins with the entry of food into the mouth. The majority of birds have salivary glands that secrete saliva that wets food, and digestion of food begins with it. In some birds, such as swifts, the salivary glands secrete a sticky fluid that is used to build nests.
The functions and shape of the tongue, however, as well as the beak of a bird, depend on the lifestyle of a particular species of birds. The tongue can be used both for holding food in the mouth and for handling it in the mouth, as well as for tasting and feeling food.
Hummingbirds and woodpeckers have a very long tongue that they can protrude far beyond their beak. Some woodpeckers have notches pointing backwards at the end of their tongue, thanks to which the bird can pull insects and their larvae to the surface that are in the bark. But the tongue, as a rule, is bifurcated at the end and rolled into a tube, which helps to suck nectar from the flowers.
In pheasants, grouses, and turkeys, as well as in some other birds, part of the esophagus is permanently enlarged (called a goiter) and is used to store food. In many birds, the esophagus is sufficiently distensible and can accommodate a significant amount of food for some time before it enters the stomach.
The stomach in birds is divided into a glandular and muscular ("navel") part. The glandular part secretes, splitting food into substances suitable for subsequent absorption, gastric juice. The muscular part of the stomach is characterized by thick walls and hard internal ridges that grind food that is obtained from the glandular stomach, which performs a compensatory function for these toothless animals. Muscular walls are especially thick in those birds that feed on seeds and other solid foods. Since some of the food that has entered the stomach may be undigested (for example, solid parts of insects, hair, feathers, parts of bones, etc.), in many birds of prey, rounded flat pellets are formed in the “navel”, which burp from time to time.
The digestive tract continues with the small intestine, which immediately follows the stomach. This is where the final digestion of food takes place. The large intestine in birds is a thick straight tube leading to the cloaca. In addition to it, the ducts of the genitourinary system also open into the cloaca. As a result, both fecal matter and sperm, eggs and urine enter the cloaca. And all these products leave the body of the bird through this one hole.
The genitourinary system in birds
The genitourinary complex consists of excretory and reproductive systems which are very closely related. The excretory system functions continuously, while the second one is activated only at certain times of the year.
The excretory system consists of a number of organs, among which, first of all, two kidneys should be mentioned, which extract waste products from the blood and form urine. Bladder birds do not, so urine through the ureters enters directly into the cloaca, where the bulk of the water is again absorbed into the body. The white porridge-like residue left after that, together with the dark-colored feces that came from the large intestine, is thrown out.
The reproductive system in birds
This system consists of the sex glands (gonads) and the tubes that extend from them. Male gonads are represented by a pair of testes, in which gametes (male sex cells) are formed - spermatozoa. The shape of the testes is either elliptical or oval, with the left testis usually larger than the right. The testicles are located in the body cavity near the anterior end of each kidney. With the approach of the mating season, the pituitary hormones, due to their stimulating effect, increase the testes by several hundred times. The spermatozoa from each testicle enter the seminal vesicle through the vas deferens, which is thin and tortuous. It is there that they accumulate, remaining until copulation and the ejaculation that occurs at that moment. At the same time, they enter the cloaca and go out through its opening.
The ovaries (female gonads) produce eggs (female gametes). The bulk has only one (left) ovary. The egg cell, when compared with a microscopic sperm cell, has a huge size. In terms of mass, its main part is the yolk, which is a nutrient material for the embryo that began to develop after fertilization. The egg from the ovary enters the oviduct, the muscles of which push the egg past all kinds of glandular areas located in the walls of the oviduct. With their help, the yolk is surrounded by protein, shells under the shell and consisting mostly of calcium shell. At the end, pigments are added that color the shell in one color or another. It takes about a day for an egg to develop an egg ready for laying.
Birds are characterized by internal fertilization. During copulation, sperm enter the female's cloaca and then move up the oviduct. Female and male gametes (that is, fertilization itself) occurs at the upper end of the oviduct even before the egg is covered with protein, shell membranes and shells.
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It is useful for every farmer to know the anatomy of chickens and roosters, the structure of their skeleton, features internal organs and basic life systems. Such knowledge will help not only score correctly, but also recognize certain diseases and start 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 the skin, and the beak acts as a mouth cavity. From humans and other animals, chickens are also distinguished by the absence 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 is about 10% of the total weight of the bird. In the first two months of life, the development of the skeleton progresses rapidly, and the bones are able to grow only the first six months.
Important. Unlike roosters, the anatomy of laying hens suggests the presence of a medullary bone, which directly affects the formation of the shell around the egg when the hen reaches puberty.
The chicken skeleton can be formally divided into three parts:
- head office;
- torso;
- limbs.
The head of birds is small and often looks ridiculous on a voluminous body. The skull, in turn, consists of 10 parts: the nasal bone and square-zygomatic, articular and lacrimal, dentary and incisive, palatine, pterygoid and ethmoid, as well as the nasal opening.
The chicken wing consists of the coracoid bone, clavicle, shoulder blade and free wing. On the cervical region of the spine there are 13-14 vertebrae, in the thoracic region - 7, the last of which is motionless, and in the mobile caudal region - 5-6 elements. hallmark the thoracic region is considered to have a specific protrusion - the keel, to which the most developed chest muscles are attached. They are perfectly palpable, which helps poultry farmers determine the fatness of their livestock.
Wings act as forelimbs. The components of the chicken wing are the coracoid bone, clavicle, shoulder blade and free wing, which can cover several types of bones: chumen, humerus, ulna, metacarpal, carpal and fingers.
There are four fingers on the legs of the crocodile, the basis of which is the pelvic girdle, and the feathered cavaliers also have sharp spurs. There are breeds in the world that have a different number of fingers. The constituent elements of the legs are the tibia, femur, tibia and fibula, and tarsus.
Internal organs
The anatomy of chickens is somewhat different from the structure of mammals, because birds have not only the esophagus, stomach, heart and liver, but also special internal organs that are unique to birds.
The digestive system originates from the beak and ends with the cloaca. A separate intermediate organ is the goiter, in which the preliminary fermentation of food is carried out - its wetting and processing. Since chickens do not have teeth, the process of feed processing cannot take place 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. Often, for good grinding of food, birds 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, the assimilation of useful elements and vitamins from food is carried out, after which it takes the form of feces in the large intestine and is excreted using the cloaca.
Due to the absence of teeth in chickens, the process of feed processing does not begin in the beak. Interesting. The intestines of chickens have a size of 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 the clovers are constantly in search of food.
Respiratory system
Full description internal structure chickens is impossible without a respiratory system, which is characterized by an unusual structure of organs. 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 region of the divergence of the trachea, the lower larynx is located, which performs the functions of sound production. The bronchi protrude beyond the edges of the lungs and are in 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
Domestic birds, including chickens, have a well-developed nervous system. It is demonstrated by the brain and spinal cord, as well as by the nerve processes of the fiber, through which nerve impulses propagate throughout the body of the quok. It is well known that when slaughtered, chickens can still run without a head for some time, which is due to nerve impulses coming even after death.
Chickens have a well developed nervous system. Conventionally, the brain consists of several sections:
- cerebellum;
- forebrain;
- midbrain;
- intermediate brain.
The hemispheres of the brain are small in size and deprived of convolutions, which is probably why the proverb about chicken brains has become widespread among the people. The hemispheres are responsible for the implementation of instincts and orientation in space, and the cerebellum is responsible for controlling movements.
Selection system
Chickens have large pelvic paired kidneys. The chicken isolation 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, which makes up to 80% of the total urine nitrogen, which precipitates into solution in the form of crystals.
The bladder itself is absent in birds, which affects the atypical form of urine, which has a thick and mushy consistency, not much different from feces. Despite this, stools in birds are regular and much more frequent than in 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 disconnected and in no way can merge with each other.
The circulatory system of chickens is represented by a four-chambered heart, small and large circles of blood circulation. In the right atrium of the cloves, venous blood is collected, which, in the process of contraction, penetrates into the right ventricle. Further, moving along the pulmonary artery, it passes into the lung for oxygenation, and when saturated, it goes to the left atrium. This cycle is called the pulmonary circulation.
The systemic circulation starts in the left ventricle, from which blood enters the aorta and is distributed to all organs and systems with the help of 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 have high blood pressure and a rapid pulse. These phenomena are associated with fast exchange substances and high temperature bodies that require a high rate of blood circulation through the vessels.
reproductive system
Reproduction of chickens is carried out 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 increase significantly in size during the breeding season. The continuation of the testis is the vas deferens, which passes into the seminal vesicle, where the spermatozoa are located.
Important. Feathered cavaliers do not have a genital organ, therefore fertilization is carried out by contact between the male and female cloacae. 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 useful nutrients, which play an important role in the full development of the embryo. Outwardly, the ovary resembles a bunch of grapes, and with prolonged oviposition, it can increase tenfold.
The right ovary of a chicken atrophies as it grows older. The oviduct is an elongated tubular organ, the length of which can reach 35-86 cm. It is a place of accumulation of sperm from the moment of intercourse until fertilization, and an 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;
- protein part - an area up to 37 cm long, which produces protein during the passage of the yolk through it;
- funnel neck (isthmus) - a narrow tube connecting the funnel and the protein part;
- uterus - a muscular organ, which is the widest part of the oviduct, in which the shell is laid;
- vagina - an organ up to 3-5 cm long, into which a ready-made egg enters from the uterus through the sphincter and is brought out.
You can learn more about the structure of the skeleton and muscles of birds from this video.
Introduction
The class of birds is divided into keeled and keeled. The latter include detachments of anseriformes and chickens.
The structure of the organism in representatives of the class of birds is associated with their peculiarity of movement, which consists in adaptability to flight. For example, a change in the structure of the pectoral limbs, the relief of most organ systems, the presence of feathers, the presence of large air sacs, etc.
Skeleton.
The skeleton of birds is especially light due to pneumatic bones (that is, containing air cavities), as well as structural features. The spinal column, as in mammals, is represented by the cervical, thoracic, lumbar, sacral and caudal regions.
The cervical region is represented by a greater number of vertebrae than in mammals (chickens 13-14, ducks 14-15, swans 23-25, geese 17-18, ostrich 18-20), it is S-shaped. The spinous processes are poorly developed or completely absent, the ventral crests are well developed, and the transverse processes show rudiments of ribs directed caudally. The transverse openings form the cervical canal, in which the artery, vein and sympathetic nerve pass. The vertebral bodies are connected by saddle joints with cartilaginous layers, which ensures high mobility of the cervical spine.
The thoracic region is formed by 7 (hens) or 9 (ducks and geese) departments. From the second to the fifth vertebrae fused into a single whole. The first 1-3 ribs in birds are asternal, i.e. do not reach the sternum. Each complete rib is divided into vertebral and sternal bone sections. The vertebral sections of the ribs are carried along the uncinate process (processus uncinatus), which is directed caudally and joins the subsequent rib, which ensures the strength of the chest. The lower ends of the vertebral sections are connected to the sternal ones through the joints, located almost at a right angle. The sternum is very strongly developed, its inner surface is concave, and the outer convex surface has a massive keel, or crest of the sternum (carina s. crista sterni), on the sagittal plane. The pectoral muscles are attached to it, thanks to which flight is carried out. Running birds do not have a crest. The posterior edge of the sternum has a different different types paired tenderloin length.
The pelvic region consists of 11-14 segments, fused into one lumbosacral bone.
The tail section consists of 5 (hens) or 7 (ducks, geese) vertebrae, to which the coccyx, or pygostil, is attached at the very end, but to which the steering wings are strengthened.
The skull of birds consists of the facial and brain sections. The medulla consists of early fused bones. The occipital bone has only one occipital tubercle for articulation with the atlas, the sphenoid bone has only temporal wings, in the temporal bone the petrous bone and scales are fused. The interparietal bone is absent. Ethmoid bone without a developed labyrinth. The orbits are wide, deep, separated from each other by an interorbital bone plate.
The facial section of the skull is more complex, but its volume is relatively small. Its lightness is ensured by the absence of teeth and a special structure. upper jaw, which merged into a whole formation, mobile in relation to the brain section. The mandibular bone consists of two sections: cranial (dentary - os dentale) and caudal (articulated bone - os articulare). The square bone (os quadratum) is located inside the jaw joint, so the complex jaw joint and the system of movable bones of the skull create a mechanism for wide opening of the oral cavity.
The thoracic limb is greatly modified in comparison with mammals and is called the wing. The shoulder girdle is represented by the scapula, clavicle and coracoid. Due to this, the bird can make large and strong swings of the free part of the wing during flight. The scapula is devoid of scapular cartilage and has the appearance of a narrow plate. The coracoid bone (os coracoideum) is the most powerful, it connects to the scapula, humerus and clavicle. The clavicles fuse with the distal bones, forming a fork, or bow (furula). On the medial surface of the humeral wing there is a pneumatic opening leading to the air cavity of the bone (foramen pneumaticum). The ulna is more developed than the radius, there is a significant interosseous space between them. The bones of the hand are reduced. The wrist is represented by the carpal radius and ulna. The metacarpus is reduced to three segments, merged into one formation, to which the distal row of the carpus has grown. The phalanges of the fingers are reduced, only the third finger with two phalanges is clearly preserved.
The ilium fuses with the lumbosacral region and extends over the ends of the last ribs on the thoracic limb. The pubic bones do not fuse, the ventral wall of the pelvic cavity consists of muscles, connective tissue and skin. Femur shorter than the bones of the lower leg, has one trochanter. The body of the bone is curved to the dorsal side. The tibia is long, the proximal tarsus fuses with its distal segment, forming the tibio-tarsal bone (tibiotarsus). The fibula is greatly reduced and fused with the tibia. The bones of the tarsus fuse with the 2nd, 3rd, and 4th metatarsal bones, forming the tarsal-metatarsal joint, or tarsus. The first metatarsal is small and articulates with the first toe. Proximal to it, the roosters have a spur process. The skeleton of the fingers has 4 rays. The number and size of phalanges varies from species to species. 
Musculature.
In non-flying birds or with difficulty flying, which include chickens, the muscles are pale, it has less than red blood vessels, less myoglobin, glycolytic enzymes predominate, due to which they are rapidly reduced, but fatigue occurs rather quickly.
The skin muscles are well developed, as some of them end on the feather sheaths. Mimic muscles absent, but well developed chewing muscles. The dorsal muscles of the thoracic and lumbar spine are very poorly developed due to the immobility of these departments. The abdominal muscles are represented by thin and weak layers. The neck muscles in birds are well developed and differentiated. Rather complex musculature of the wing and pelvic limbs, the muscles of the thigh are especially massive.
Skin and its derivatives.
The skin of birds consists of the epidermis, the base of the skin and the subcutaneous layer. The skin does not contain sweat and sebaceous glands, the epidermis is constantly flaky. Above the last sacral vertebrae there is a coccygeal gland (glandula uropigii), which functions like a sebaceous gland and serves to lubricate the feather cover (with the help of a beak). Feathers are of great importance during flight and for thermoregulation, touch, protection and sexual demorphism. In poultry, contour (integumentary), filamentous, downy and brush feathers are distinguished.
Moulting in birds is juvenile (once in a lifetime) and seasonal (once a year). For the period of molting in poultry, egg production stops.
Digestive organs.
The oropharynx of birds consists of the oral cavity and pharynx. The oral cavity lacks teeth, gums, cheeks and lips. The jaws are covered with a horn cover - the beak, which consists of the mandible and mandible.
The esophagus has a wide lumen and passes into a goiter (ingluves), presented in chickens before entering the thoracic region by a unilateral protrusion of the esophagus on the right side. It accumulates and macerates solid nutrient material.
The stomach consists of glandular and muscular parts. The glandular part is located between the lobes of the liver as a continuation of the esophagus, contains glands. Tapering, it passes into a muscular, more pronounced in granivorous, rounded large part. Its walls are formed by four large muscles from smooth muscle tissue. Shiny white tendon mirrors are visible on the outer surfaces. This part of the function is correlated with the goiter. The tubular glands of the muscular stomach of many birds form a cuticle: a hard keratin sheath that also helps to mechanically process food (grind). 
The duodenum exits from the right side of the cranial edge of the muscular part of the stomach, forming a loop, between the knees of which the pancreas is located, fixed by the pancreaticoduodenal ligament. The gland has two (ducks, geese) or three (chickens) lobes, from which a corresponding number of ducts depart.
Next comes the jejunum, about 1 meter long. In chickens, on the intestinal wall, there is a remnant of the former yolk sac in the form of a small diverticulum. In 50% of chickens, it is invisible, but it persists in most geese and ducks. The ileum lies between the right and left caecum and ends in the large intestine.
The liver of birds is relatively large, divided into two lobes, held by a falciform ligament. On its right lobe, most birds have gallbladder. From the left lobe, the hepatic duct begins, which from the right lobe goes to the gallbladder, from which the cystic duct is sent to the duodenum.
The large intestine is separated from the small intestine by a fold of mucous membrane, behind which are two blind intestines. Further under the spine is the rectum, which flows into the cloaca.
Cloaca (cloaca) - the final part of the digestive tract. Two folds, it is divided into three sections: cranial (coprodeum), middle (urodeum) and final (proctodeum). The ureters and excretory tracts of the genital organs open into the middle section. Defecation and excretion occur simultaneously with the help of the muscles of the intestinal wall and the pressure of the air sacs.
Respiratory system.
The lungs of birds do not contain alveoli, as in mammals, but consists of millions of thin parabronchi, connected at the ends to the dorsobronchi and ventrobronchi. A capillary runs along each parabronchi. The blood in them and the air in the parabronchi move in opposite directions. Gas exchange occurs through the air-blood barrier
In connection with the way of life, the respiratory organs of birds have several characteristic features, allowing birds to ventilate their respiratory organs during flight:
1) the simplicity of the structure of the nasal cavity;
2) the presence of a singing larynx;
3) a peculiar structure of the lungs, which occupy a small volume in the chest;
4) complicated development of air sacs.
The nasal cavity is divided by a septum into two halves, each of which contains the upper and lower nasal conchas. There is no ethmoid labyrinth. The nasal cavity is connected by a fissure with the infraorbital cavity, in the wall of which the lacrimal-nasal canal passes.
In birds, the upper cranial larynx and the lower sound (singing) larynx, located in the bifurcation region, are distinguished. The singing larynx consists of parts: a drum, a bridge with a semilunar membrane and eardrums (external and internal). The entrance to the larynx is covered by a mucous fold that replaces the epiglottis.
The trachea in the neck lies ventral to the spine, enters the chest cavity between the collarbones. Tracheal rings are solid. The bifurcation is located above the base of the heart.
The lungs are light pink in color, have a specific structure. In the lung tissue, gas exchange occurs through the walls of the air capillaries. The main bronchi pass through the lungs and end in the air sacs: when you inhale, air enters the lungs and fills the chest and abdominal sacs; when you exhale, the air from these sacs passes through the lungs into the cervical and subclavian sacs. In the pleural cavity of the lungs are thin fibers of connective tissue that connect the surface of the lungs to the chest wall. There are also 6 types of bronchi: the main bronchus, second-order bronchi (without cartilage in the walls), ectobronchi (pass into the air sacs), recurrent sac bronchi (lead back to the lungs), endobronchus (directed dorsally and laterally inside the lungs), parabronchi (from they branch off the respiratory sections of the lung). A number of airy bronchi open into air sacs, represented by protrusions of the mucous membrane, tightly dressed with a serous membrane. They give branches that penetrate into the bones (with the exception of the skull). There are nine of them in both lungs: interclavicular (unpaired) sac (saccus interclaviculares), cervical (sacci cervicales), cranial and caudal thoracic, or intermediate (sacci thoracici craniales et caudales), abdominal sacs (sacci abdominales). The bags serve as additional reservoirs for air, and also improve the act of breathing itself: birds receive oxygen not only when they inhale, but also when they exhale, which significantly increases the metabolic rate. Also, the axillary diverticula of the interclavicular sacs during flight act as bellows that replace the movements of the chest. They also play a role in making sounds, emptying the cloaca, when swimming, and, very importantly, protect the body from overheating during flight.
Urinary organs.
The excretory system in birds is noticeably simpler than in mammals. The kidneys do not have renal cups, pelvis, and there is not even a clear distinction between the urinary and efferent zones. They lie in the ventral recesses of the lumbosacral spine and ilium. Urinary tubules, approaching the ventral (medial) edge of the kidney, are connected into short branches, which open into the ureter. The ureter passes along the medial edge backwards and opens into the middle part of the cloaca. Birds do not have a bladder.
Sexual organs of the male.
The testicles are bean-shaped or ovoid, their size depends on the sexual cycle. Anchored in abdominal cavity with a short mesentery. There are small appendages on the medial surface. Semen ducts meander and lead to the middle section of the cloaca, where they open on a small papilla in roosters. The drake has an analogue of the external genital organ. There are no adnexal sex glands in birds.
Sexual organs of the female.
The right ovary is reduced during embryonic development. The deep layer of the ovary is the deep zone. With age, the ovary becomes more and more tuberous due to maturing follicles. The eggs grow unevenly, the most mature sag on the stem-like outgrowths of the serous membrane. After leaving the egg, a hollow cup (calyix) remains on the stalk for some time.
The oviduct consists of a funnel (fundibulum), a protein part, an isthmus (istmus), a bird's uterus and a vagina that opens into the middle section of the cloaca. In the process of passing through the oviduct, a protein shell is formed, and then a leathery, and finally, a calcareous shell.
The system of organs of blood and lymph circulation.
The heart of birds is four-chambered, completely divided into right and left halves. There are no papillary muscles in the right ventricle. The atrioventricular orifice has a double muscular plate that serves as a valve for this orifice.
The aortic arch is preserved on the right. Also a feature is the presence of two cranial vena cava.
Lymph nodes are rare and are located in two places: in the area of the entrance to the chest at the end of the jugular veins and in the lumbar region above the spine. On the dorsal side of the cloaca there is a pouch of Fabricius, an organ significantly reduced in adult birds (starting from 8-9 months of age), but functioning normally in young birds. The bag of Fabricius forms lymphocytes and oxyphilic leukocytes.
The spleen is small, rounded, lies on the right side of the stomach.
endocrine apparatus.
Represented by the pituitary gland, epiphysis, thyroid gland, parathyroid glands, thymus, adrenal glands and ultimobronchial glands.
Nervous system.
The medulla oblongata is strongly convex.
The cerebellum consists of a well-developed vermis and small lobes.
The midbrain consists of a well-defined colliculus and a wide cavity. The diencephalon has small optic tubercles.
The large hemispheres are characterized by the fact that they do not have convolutions and furrows (except for the Sylvian). The corpus callosum is absent, there are no ammon horns, the lateral ventricles are wide. All cranial nerves are present, but some are poorly developed due to underdeveloped facial and some other musculature.
Sense organs.
The eyeball is relatively large. In the sclera there is a cartilaginous plate, ossified during the transition to the cornea, and bone tissue in the area where the optic nerve exits. On the choroid near the exit of the optic nerve there is a ridge in the form of a wedge-shaped protrusion, the top of which is attached to the lens capsule. In the lower eyelid there is a cartilaginous plate. Developed third eyelid. The lacrimal gland is small with one excretory duct. Between the orbit and periorbita lies Garder's gland.
The outer ear does not have an auricle, the inlet is covered with a fold of skin and feathers. The tympanic membrane is attached to the bone ring. There is only one auditory ossicle in the middle ear - the column. The cochlea has an auditory papilla (an analogue of the cortico organ).
The olfactory analyzer is represented by cells in the dorsal turbinate. There are no taste buds on the tongue. There are taste endings in the mucous membrane of the tongue of chickens and taste buds in ducks and geese. Chicks have more taste buds.
Skin analyzers are represented by free nerve endings in the skin. There are especially many of them in the cerome on the border of the beak with the scalp. In ducks and geese, there are also many of them in the plates of the ramfoteka and in the wax that covers the surface of the beak.
Veterinarian Kazakov Artem Arkadievich
General characteristics of the bird
Birds, in connection with their adaptability to flight, have a number of specific features in the structure of the body. In their development, they are closer to reptiles and unite with them into a common superclass of lizards. Birds, like reptiles, do not have skin glands, strongly developed horny skin derivatives (feathers, scales, horny beak, claws), a typical lower zygomatic arch, compound sphenoid and mandibular bones, a single occipital condyle, a movable square bone, a complex sacrum, the presence of hook-shaped processes of the ribs, a metatarsal articulation on the pelvic limb, a similar structure of the kidney, etc. In birds, the following are better developed than in reptiles: the brain, organs of vision and hearing. They are distinguished by warm-bloodedness and other features associated with the peculiarities of their ecology.
A special mode of transportation - flight - left its mark on their entire organization. These features were dictated by the need to subordinate the form and structure of the body to the requirements of aerodynamics. The structural features of the system of organs of movement and the feather cover create a streamlined contour of the body, the thoracic limb has turned into a wing - a specialized aircraft. The bones are strong and light, often pneumatized, the head is lightened due to the absence of teeth. The cervical region is elongated and very mobile, together with the head acting as a front rudder, grasping limb and providing a circular view. The thoracolumbar section is short and inactive, the tail section is turned into the basis for tail feathers. The muscles are located extremely unevenly, providing mainly flight and walking.
The internal organs are located in such a way that the most massive (liver, stomach) lie near the center of gravity of the body. The intestine is short while maintaining high activity of secretory (large parietal glands) and absorption (villi in the large intestine) functions. Increased aeration due to the development of air sacs (double breathing), which contributes to the intensification of metabolic processes and the vital activity of birds. Facilitation of the excretory system - the absence of the bladder, reproduction - one ovary and oviduct, external development of the embryo.
Features of the structure of the apparatus of movementSKELETON. The lightness of the bird skeleton is created due to the greater mineralization of the compact bone substance, the porosity of the spongy substance, pneumatization and early bone fusion. In females, before oviposition, spongy medullary bone accumulates in the bone marrow cavities of the tubular bones, which, with a sufficient calcium content in the diet, fills the entire bone cavity. During oviposition, the medullary bone is used to form the shell. With a lack of calcium, the compact substance becomes thinner and the bones become brittle.
Scull . The brain region of the skull is formed by unpaired occipital, sphenoid, ethmoid and paired temporal, parietal, and frontal bones. The seams between the bones of the skull are visible only in the first days after hatching. In adult birds, the boundaries between the bones are completely invisible. The shape of the bird's skull is greatly influenced by large eyes. Under their pressure, the orbital wings of the sphenoid bone fuse with each other and with the perpendicular plate of the ethmoid bone and become the interorbital septum. As a result, the brain region of the skull does not extend rostrally beyond the orbits. The occipital bone has one condyle, which greatly increases the mobility of the head.
The front section is more complicated. It is formed by paired incisive (intermaxillary), maxillary, nasal, lacrimal, palatine, zygomatic, pterygoid, square, mandibular and unpaired openers, hyoid bones. The incisive, maxillary and nasal bones form the bony skeleton of the upper beak - the upper beak. The nasal bones have the appearance of a thin springy plate, which joins (in goose joints) to the frontal and lacrimal bones and allows you to raise the upper beak. This movement takes place simultaneously with the lowering of the lower jaw - the mandible - due to the development of the lower zygomatic arch and the mobility of the quadrate bone. This bone of an irregular quadrangular shape forms 4 joints: with the temporal, pterygoid, zygomatic and mandibular bones. The movable connection of the pterygoid, zygomatic, palatine, square, mandibular bones, with the combined work of several joints formed by them, form a good grasping mechanism of the bird's beak.
stem skeleton . cervical in birds of different species it has a different number of vertebrae: in chickens and turkeys - 13-14, in ducks - 14-15, in geese - 17-18. The cervical vertebrae are mobile, have short spinous and well-developed transverse processes, rudiments of ribs in the form of costal processes. The complex relief of the heads and pits of the vertebrae provides not only flexion and extension, but also abduction to the sides, and limited rotation.
Thoracic short and immobile. Consists of 7-9 thoracic vertebrae, the same number of pairs of ribs and sternum. Vertebrae from the 2nd to the 5th fused into a single vertebral, or dorsal, bone. The 1st and 6th vertebrae are free. The 7th fused with the first lumbar. The ribs of chickens consist of two bone parts - vertebral and sternal. 2–3 anterior and one posterior are sternal, the rest are sternal. At the vertebral ends of the ribs are uncinate processes strengthening the chest wall. Between the vertebral and sternal parts of the rib, between the rib and the sternum - joints. The sternum is a flat bone, concave at the top. Her body is elongated in the caudal direction and on the ventral surface bears a crest - keel. The body of the sternum in waterfowl is wide, the keel is not as high as in chickens. On the front edge of the body there are surfaces for articulation with the coracoid bone, on the sides there are 2 processes - lateral (thoracic) and posterior (abdominal), separated by deep notches. The most powerful muscles are attached to the sternum.
lumbosacral and tail sections. The last thoracic, lumbar, sacral, and first caudal vertebrae fuse into a single lumbosacral bone. It has 11-14, in goose - 16-17 bone segments. The pelvic bones grow to it from both sides, which is why the entire department is called the pelvic. In the caudal region, there are 5 non-fused vertebrae. The last 4–6 vertebrae fuse into pygostyle- a flat triangular bone to which tail feathers are attached.
Skeleton of the chest. In connection with the adaptability to flight, the thoracic limb turned into a wing, the skeleton of which consists of a belt and a free limb. Shoulder skeleton birds consists of three bones: scapula, clavicle and coracoid bone. The scapula is a flat, long, narrow, saber-curved bone. Lies parallel to the spine at the vertebral ends of the ribs. The clavicle is a paired bone in the form of a thin rounded stick. The distal ends of both clavicles fuse, resulting in a fork. The coracoid bone is the most powerful of the bones in the girdle. It is located almost at right angles to the scapula and parallel to the collarbone. The bone is pneumatized. The proximal end articulates with the scapula, clavicle and humerus, the distal end with the sternum.
Skeleton of the free thoracic limb consists of the bones of the shoulder, forearm and hand. The humerus is long, tubular, pneumatized, with a wide proximal epiphysis. Of the bones of the forearm, the ulna is better developed - long, slightly curved. It is the main support of flight feathers. On the distal epiphysis, there are two articular surfaces for articulation with the bones of the wrist and one with the radius. The radius is smaller than the ulna and looks like a cylindrical rod. There is a wide interosseous space between them.
The bones of the hand are greatly reduced. Of the carpal bones, only the carpal radius and carpal ulna have been preserved. Intermediate bone fused with the radial carpal, additional with the ulna carpal. The brushes of the distal row are fused with the bones of the metacarpus, which are also partially reduced and fused. II, III and IV metacarpals and bones of the distal row of the wrist fused into a single metacarpal bone or buckle. In the buckle, the largest part is formed by the III metacarpal bone. II bone looks like a small tubercle. Between the III and IV bones of the pastern is the interosseous space. Of the fingers, III is more developed, the skeleton of which consists of two phalanges, the II and IV fingers have one phalanx each. II finger is the bone base of the winglet.
Skeleton of the pelvic limb. Skeleton of the pelvic girdle consists of the ilium, pubic and ischium bones, fused into the pelvic bone. All three bones take part in the formation of the articular cavity. The ilium lies along the lumbosacral bone, with which it fuses. Strongly inclined down. The cranial part of the bone is concave, here lie the gluteal muscles. The caudal part is convex, below it are the kidneys. The pubic and ischium bones grow to the caudal edge of the ilium. The ischium has the form of an elongated triangle. The pubic bone is in the form of a long thin curved stick running along the edge of the pelvic bone. The pubic and ischial bones do not fuse together. The basin has a wide entrance with soft walls - a device for laying eggs.
Free limb skeleton Consists of thigh, leg and foot bones. The femur is long, tubular, pneumatized. Of the bones of the lower leg, the tibia is better developed, which, moreover, fuses with the bones of the tarsus and forms a tibio-tarsal or running bone- the longest and most powerful bone of the skeleton. The fibula is reduced, its distal end fuses with the tibia-tarsal bone. The bones of the foot, except for the toes, are fused. The tarsus doesn't exist. The proximal row of the tarsus became part of the tibio-tarsal bone, the distal and central rows merged with the bones of the metatarsus, and those, as a result of fusion of the II, III and IV metatarsal bones, formed the metatarsal bone, or tarsus.
At the distal end is a triple block for articulation with the bones of the fingers. At the distal end of this bone, an independent first metatarsal bone lies in the form of a pea. Roosters have a spur process on the plantar surface of the tarsus. The fingers are well developed. I finger is turned back and has two phalanges, II finger - three, III finger - four, IV finger - five phalanges.
MUSCLE. The skeletal muscles in birds are unevenly distributed on the body. The subcutaneous muscles are well developed, gathering the skin into folds, which allows you to ruffle, lift and turn contour feathers.
Muscles of the head . Facial mimic muscles missing. Chewing muscles more differentiated than in mammals, and well developed. There are special muscles that act on the quadrate and other movable bones of the skull. Muscles of the stem bodies are well developed in the neck and tail. There are many short and long muscles on the neck, arranged in several layers. The peculiarities of the structure of the vertebrae, the mobility and the large length of the neck contribute to the extension, abduction and some rotation not only of the whole neck, but also of its individual sections, as a result of which the neck of the bird takes on an S-shape. The muscles of the thoracic and lumbosacral spine are not developed due to their immobility. Muscles of the chest and abdominal wall the same as in mammals, with the exception of the diaphragm, which has the form of a connective tissue film that does not completely separate the lungs from other organs.
Muscles of the chest highly developed and differentiated. These include several dozen muscles. The thoracic limb of birds is connected to the body not only by joints, but also by muscles in the area of the shoulder girdle and shoulder. These are the most powerful muscles in the body. They make up to 45% of the mass of the muscles and perform the main work during the flight, raising, lowering, supinating, penetrating the wing, depending on the maneuver performed by the bird. These are such muscles as the superficial (large) pectoral muscle, subscapularis, coracoid-brachial and others.
Muscles of the pelvic limb are also numerous. In the pelvis and thigh area, there are muscles of various functions that act on hip joint. Of the muscles acting on the distal links of the limb, extensors and flexors are developed. Their tendons are usually ossified. During movement, due to the combined action of muscles on 2–3 joints, simultaneous extension and flexion of the joints occurs. Flexion is always accompanied by adduction of the fingers, extension by abduction. In chickens, the mechanism of sitting on a branch is well developed without the expenditure of muscle energy. This is a kind of tendon system, which begins with the tendon of the slender muscle, spreads over the patella, where it is attached to the tendon of the pectineal muscle, then passes to the lateral side of the lower leg, is fixed on the fibula, turns to the plantar surface and fuses with the tendons of the flexors of the fingers. This mechanism binds the joints so that when the knee joint is bent, the fingers are also bent.
Skin and its derivativesThe skin of birds, like that of mammals, consists of the epidermis, dermis, and subcutaneous tissue. The skin of birds is thin, dry (as a result of the absence of sweat and sebaceous glands), forms longitudinal folds. The subcutaneous tissue is well developed. In different parts of the body, the skin has an unequal thickness - from 0.3 to 3 mm. On pterylia- areas of the body where feathers grow, the skin is thinner than on aptery, - places where covering feathers do not grow. In land birds, the skin on the back is thicker than on the stomach, in waterfowl - on the contrary. The thickest skin on the soles and interdigital membranes.
Skin derivatives can be divided into several groups: horny formations of the epidermis- feathers, scales, claws, beak; skin folds- comb, earrings, lobes, corals, flying membranes; skin glands- coccygeal. Horn formations of the epidermis perform a protective function.
The feather cover protects the bird's body from mechanical influences, maintains body temperature, creates an aerodynamic contour of the body, creates bearing surfaces that make flight possible. Depending on the form and function, feathers are divided into contour, down, semi-down, filiform, brush, bristles, powdery. contour feathers the most common, they determine the outlines of the bird's body. Among them, coverts, fly and tail feathers are distinguished. The mature contour pen consists of trunk and fan. Bottom part the trunk to the fan is called by the way. Rays (beards) of the first order depart from the rod in both directions, in total forming a fan. From rays of the first order, numerous rays of the second order, covered with cilia and hooks, depart in both directions. The rays are connected to each other by hooks into a single elastic plate.
Skin folds, in addition to flying membranes, perform a thermoregulatory function. Powerful vascular networks and plexuses lie in their dermis. The flying membranes are stretched between the chest and shoulder - back and between the shoulder and forearm - front. They increase the surface of the bird's support on the air during flight.
The coccygeal gland lies on the tail vertebrae. In chickens it is the size of a pea, in gooses it is a hazelnut. This is a complex tubular sebaceous gland, its excretory duct in the form of a high papilla with brush feathers on top. The bird squeezes out the fatty secret with its beak and lubricates the feathers with it.
Features of the structure of internal organsDIGESTIVE SYSTEM. Birds have a relatively short digestive tract: 6–11 times longer than the body. Food passes through it in 2.5–4 hours. Like in mammals, the digestive system of birds is divided into the oropharynx, esophago-gastric region, small and large intestines.
Oropharynx includes the oral cavity and pharynx, which are not separated from each other due to the absence of the palatine curtain. Birds also lack lips, cheeks, gums, and teeth; the vestibule of the oral cavity is also absent. The jaws have changed into a beak. beak various kinds birds of different shapes and densities. Chickens have a rather short beak, cone-shaped, with a convex back and a pointed tip. At the base it is covered with soft wax, rich in sensitive nerve endings. Goose beaks are long, wide and flat, with small transverse plates for filtering food. The hard palate is the roof of the oral cavity. It has a longitudinal fissure, which passes aborally into the choanae. In the palate of chickens, there are 5–7 rows of cone-shaped palatine papillae that perform the function of retaining food. In goose papillae lie longitudinally.
The tongue occupies the bottom of the oral cavity and repeats its shape. The salivary glands are located in the own plate of the tongue. Their ducts are associated with taste buds located in a small number (30–120 pieces) in the epithelium of the tongue. The muscles of the tongue are poorly developed. The mobility of the tongue is provided mainly by the muscles of the hyoid apparatus. The caudal edge of the tongue is framed by papillae, which, together with the last row of palatine papillae, are considered the boundary between oral cavity and throat. The pharynx of birds corresponds to the oropharynx of mammals. Holes in its roof are choanae, more aborally, pharyngeal-tympanic tubes. A large number of small salivary glands lie in the walls of the pharynx.
Esophageal-gastric department consists of the esophagus, crop and stomach. Esophagus in chickens, the goiter is divided into pre-goiter and post-goiter parts. Goose do not have goiter. Their esophagus in the middle part has a spindle-shaped thickening. In the mucous membrane of the esophagus there are mucous tubular glands. Goiter- bag-like expansion of the esophagus at the entrance to the chest cavity. In it, the food is accumulated, macerated, moistened with the mucous secretion of the glands lying in the dorsal and lateral walls of the crop. There are many lymphoid elements in the mucous membrane of the goiter.
Stomach consists of two chambers: glandular and muscular. The glandular section of the stomach is spindle-shaped, 2–6 cm long. Its wall is thickened, filled with complex deep glands that produce all the components of gastric juice. On the surface of the mucous membrane of the glandular stomach, 30–75 cone-shaped elevations are noticeable - papillae, surrounded by concentric folds. The ducts of the deep glands open at the apex of the papillae. Food, wetted by the juice of the glands, enters the muscular department. The muscular section of the stomach has powerfully developed muscles, the alternate contraction of which leads to grinding of the contents of the stomach. In the mucous membrane lie simple tubular glands that produce a secret. The latter, at the exit from the ducts, turns into a dense keratinoid substance - cuticle protecting the wall of the stomach from injury and abrasion.
Intestines starts from the outlet from the muscular stomach - the pylorus, and ends with the opening of the cloaca. The intestine exceeds the length of the body by 4-6 times and is divided into thin and thick. Small intestine consists of the duodenum with obstructive glands - the liver and pancreas, jejunum and ileum. The duodenum forms a loop that runs from the stomach to the pelvis and back. The pancreas lies in the loop. The wall of the duodenum does not have its own glands. The jejunum forms 6-9 loops in geese, 10-12 loops in chickens, suspended on a long mesentery. Despite this, they are rather limited in their position by the abdominal fat pad, the air sacs, and the ligaments that connect the intestinal loops. The ileum is short and lies above the duodenum. It ends at the confluence of the blind and rectum. The pancreas consists of 2-3 elongated lobes. The liver is large and consists of two lobes. The guinea fowl, pigeon and ostrich do not have a gallbladder.
Colon consists of two blind, rectum and cloaca. The caecum with their apices turned cranially. They lie on the sides of the ileum, connected to it by ligaments. Their tops are expanded. When they enter the rectum, their mucous membrane is strongly thickened and contains an accumulation of lymphoid tissue - tonsil of the caecum. The rectum, like the cecum, has villi. Ends with an ampulla-shaped extension - cloaca. There are 3 chambers in the cloaca: anterior - coprodeum- a cavity for feces, the rectum opens into it; medium - urodeum- a cavity for urine, the ureters, vas deferens or oviduct open into it; proctodeum- the final cavity into which the cloacal (fabrician) bag opens. The proctodeum ends with an anus. cloacal bag- lymphoepithelial organ in which differentiation and specialization of lymphocytes occurs.
RESPIRATORY SYSTEM. In birds, this system has features that allow gas exchange both on inhalation and exhalation.
nasal cavity located at the top of the beak. It is divided into two halves by the nasal septum. Each contains three small turbinates. The nostrils are located at the base of the beak, in chickens they have a nasal valve, in gooses they communicate with each other. The exit from the nasal cavity is the choanae, with a closed beak, they are located above the larynx.
Upper larynx It is formed by three cartilages: two arytenoids and a cricoid. The fold of the mucous membrane in front of the laryngeal fissure acts as an epiglottis. The laryngeal fissure is framed by pharyngeal papillae that prevent food from entering the respiratory tract.
Trachea consists of 140–200 closed osteocartilaginous rings united by connective tissue into a gaping tube. Before bifurcation, the trachea narrows - it forms lower, or chanting, larynx. In males, it is better developed.
Lungs small, do not divide into lobes, penetrate deeply into the intercostal spaces, which is why notches form on the lungs. The airways are presented endobronchus I, II and III orders branching in the lungs, and ectobronchi ending in air sacs. Respiratory sections are formed by pulmonary lobules. Gas exchange takes place in air capillaries. 5 pairs of air sacs are connected with the lungs: cervical, interclavicular, anterior and posterior thoracic and abdominal. Interclavicular always grow together, cervical - often. The rest are always in pairs. These are thin-walled formations, the wall of which is formed by the mucous and serous membranes. Their functions are varied. They are additional reservoirs of air, contribute to an increase in the level of gas exchange, participate in thermoregulation, water exchange, lighten body weight, are resonators, shock absorbers and heat insulators.
URINARY AND REPRODUCTION SYSTEMS. Both systems are greatly simplified and lighter in comparison to mammals. urinary system consists of the kidneys and ureters. The kidneys are large, lie in the form of three lobes in the fossa of the ilium and the recesses of the lumbosacral bone. The kidney is not divided into cortex and medulla, but consists of microscopic lobules, each of which has cortical and medulla zones. Only a small number of nephrons have a developed nephron loop. The rest do not have it and correspond to the nephrons of reptiles. The ureter runs along the medial edge of the kidney and opens into the cloacal urodeum.
reproductive system male consists of testes with appendages and vas deferens. The testicles of an adult male are bean-shaped and lie in the body cavity. Their size increases during the rut. On the medial concave surface is a small appendage of the testis. The duct of the appendage passes into a long, highly convoluted vas deferens, which ends in the cloacal urodeum with the papilla. The organs of copulation are a fold of the cloacal proctodeum and are developed differently in different species.
Reproductive system of the female consists of the left ovary and oviduct. The ovary is grape-shaped, weighing 50–60 g. Sex cells in the stage of rapid growth reach 3–4 cm in diameter. The oviduct is a tube-shaped organ, lies in the left half of the body cavity, is suspended on wide ligaments, reaches 60 cm in a chicken, 80 in a duck, 100 cm in a turkey and a goose. Several sections are distinguished in it in a laying hen. The mucous membrane of the oviduct forms folds filled with glands. closest to the ovary funnel. In it, fertilization and the formation of the chalase protein occur. Next - protein department 25–40 cm long. In its mucosa there are many glands that secrete a protein secret. The egg passes through it in 3 hours and is covered with a protein coat. isthmus- the next section, where the shell membranes are formed. Then comes uterus or shell department bag-shaped, where the egg lingers for 16-19 hours and is covered with a shell. The last department vagina- a muscular tube that protrudes into the cloaca during the passage of the egg and covers it with a bactericidal shell film.
CARDIOVASCULAR SYSTEM AND GLANDS. Heart birds have four chambers. There are no papillary muscles in the right ventricle; instead of an atrioventricular valve, there is a muscular plate extending from the wall of the ventricle. Right aortic duct. There are two cranial pudendal veins - right and left. The caudal vena cava is short, formed by the confluence of two common iliac veins. There are two portal systems in the body of birds: the liver and the kidneys. The blood from these systems eventually drains into the caudal vena cava.
Endocrine glands. The thyroid gland has the form of two oval amber bodies lying on both sides of the trachea at the entrance to the body cavity. adrenal glands triangular shape, ocher, lie on the medioventral surface of the anterior lobe of the kidneys. The left one is closed by the ovary. thymus- brownish-yellowish in color, flattened lobes lie on the neck. In adults, 1-2 lobes are barely preserved. The parathyroid gland, in the form of two reddish grains of millet, lies near the thyroid gland. Often it is enclosed with her in a common capsule.
NERVOUS SYSTEM AND SENSORS. The brain has the same 5 sections as the mammalian brain. In the telencephalon, the hemispheres do not have convolutions, there is only one furrow. Instead of the corpus callosum, there are few transverse fibers. There is no transparent septum, the lateral ventricles are large and communicate with the cavity of the olfactory bulbs. There is no mastoid body in the diencephalon, the visual tubercles do not merge. In the midbrain there is a double colliculus instead of a quadrigemina, the Sylvian aqueduct is wide. In the sympathetic nervous system, there are significant features in the branching of the nerves.
Sense organs. The sense of smell is poorly developed. The olfactory epithelium covers the dorsal nasal concha. Taste poorly developed. Taste buds lie in the epithelium of the tongue in the amount of 30–170 pieces. hearing organ consists of the outer, middle and inner ear. In the outer ear, the role of the auricle is performed by small feathers that close the entrance to the wide and short external auditory meatus. In the middle ear, there is only one auditory ossicle - the column. In the inner ear, the spiral organ looks like the auditory papilla. Organ of vision consists of the eyeball, protective and auxiliary formations. The eyes of birds are very large, but inactive. The third eyelid is mobile, the lacrimal gland is poorly developed. The sclera contains cartilage, and at the transition to the cornea, 12–16 bone plates lie like a diaphragm in a camera. They are the backbone of large eyes. In the thickness of the vitreous body there is a ridge - a vascular-connective tissue plate extending from the wall of the eyeball deep into. Its function is unknown. organ of touch- receptor field of the skin. Nerve endings are associated not only with the skin, but also with its derivatives: beak, feathers, scales.
Good afternoon, dear subscribers and readers of the site "All about laying hens and broilers." In our new material, the anatomy of a laying hen in pictures, see interesting video. So let's go!
Skeleton structure
Knowing the anatomy of a laying hen, the structure of the skeleton, the location and size of the internal organs is not only interesting, but also useful in slaughtering and processing. Such knowledge may also be needed to identify and treat certain chickens.
A feature of the chicken skeleton is a lot of hollow bones. This is due to the possibility of flight of chickens, although they do not often practice this type of movement.
Hollow bones are so light that on average, the mass fraction of the chicken skeleton is 10% of the total body weight. Another feature is the presence of a beak and the absence, in turn, of teeth.
The skeleton of a chicken can be divided into three parts: the main section, the trunk and limbs. The head, set on a long neck with 13-14 vertebrae, is small compared to the body. The thoracic part of the spine has 7 vertebrae and 5-6 tail section.
A feature of the thoracic region is the presence of a keel, and the forelimbs of chickens are wings. Components The chicken wing is the coracoid bone, shoulder blade, clavicle and free wing.
The hind limbs are paws crowned with sharp claws, and the roosters also have dangerous spurs. Mostly chickens have 4 fingers, but there are breeds that are characterized by the presence of a different number.
The difference between the skeleton of a chicken and a rooster is that the hens have a medullary bone, it is involved in the formation of the eggshell.
Digestive system
Laying hen anatomy. Digestive system begins with the beak and ends with the cloaca. A separate intermediate station is the crop intended for the primary fermentation of feed. As mentioned above, chickens do not have teeth, so this process cannot occur in the beak.
The movement of food occurs through the esophagus and this is its only function. Fermentation begins to take place in the stomach. Often chickens swallow stones and sand, which then end up in the stomach after slaughter. This is useful and correct, such foreign objects help grind large feed.
From the stomach, food enters the duodenum and small intestine, where absorption from it and other useful substances takes place, and undigested food forms stool in the large intestine, which exits through the cloaca.
Respiratory system
Laying hen anatomy. Respiratory system has a number of features due to the possibility of chicken flight. It begins with the nostrils, continues with the nasal cavity and larynx, passes into the trachea, lower larynx and bronchi, which extend beyond the lungs and combine with many air sacs located in the body. About 75% of the air that the chicken inhales settles in these bags.
It is the air sacs that are responsible for the implementation of the processes of gas exchange and thermoregulation. The lungs of chickens practically do not change size and do not have the same ability to stretch as the lungs of mammals.
Circulatory system
Laying hen anatomy. The circulatory system is a four-chambered heart and two circles of blood circulation: large and small. In the right atrium, venous blood accumulates, which passes into the right ventricle, then into the pulmonary artery, enters the lungs, is saturated with oxygen from them and enters the left atrium. This is the pulmonary circulation.
The systemic circulation originates in the left ventricle, from where the blood passes into the aorta and is carried to all organs and systems. In this case, numerous blood vessels serve as transport routes.
Regarding the size of the chicken, its heart is quite large and has an asymmetrical shape, the left side is larger and does more work. The pulse of chickens is frequent, and blood pressure is high, like all birds.
excretory system
The excretory system of a chicken consists of two kidneys, ureters and cloaca. Chickens do not have a bladder, and this causes an atypical appearance of their urine, which is thick and cloudy, and often does not differ from feces.
The stool occurs often enough that it is necessary for lightening the body weight and easy flight.
reproductive system
Laying hen anatomy. Chickens reproduce by laying eggs. The reproductive organs of roosters are the testes, which are located near the kidneys. During the breeding season, they greatly increase in size.
From the testis comes the vas deferens, which passes into the seminal vesicle, where the spermatozoa are placed. Roosters do not have an external genital organ, and the process of fertilization occurs when the cloacae of a rooster and a chicken touch.
The reproductive system of the chicken includes the ovary, and only one, the left one, which is properly developed, the oviduct, which expands and passes into the cloaca. Between the moment when the egg enters the oviduct and when the chicken lays the egg, it takes from 12 to 48 hours.
Nervous system
The nervous system of a chicken is represented by the brain and spinal cord, nerve processes and fibers. It is through them that nerve impulses are transmitted through the body of the chicken. The brain is conditionally divided into anterior, intermediate, middle and cerebellum. The hemispheres of the brain are small and devoid of convolutions, hence the numerous sayings about "chicken brains".
The functions of orientation in space and the realization of instincts are assigned to the hemispheres. The cerebellum is responsible for coordinating movements.
Autopsy of a chicken by a pathologist:
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