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Features of the internal structure and life of birds
Features of the skeleton of a bird. In the process of adaptation for flight in birds has been relieved of the skeleton (most bones are filled with air) and increase its strength (many bones are fused among themselves in the early stages of embryonic development). The spine, as in reptiles, is composed of 5 departments. The cervical spine comprises from 11 to 25 vertebrae, it is long and mobile (birds can usually rotate the head 180 degrees). Thoracic vertebrae were fused together. Along with the ribs and breastbone, and they form the rib cage.
Most modern birds have sternal outgrowth Kil. It increases the area of attachment of the pectoral muscles. The last thoracic vertebrae, all lumbar, sacral, and anterior caudal vertebrae fused and created a complex sacrum that serves as a strong pillar of the rear limbs. The tail section consists of several flexibly jointed vertebrae and vertebrae, coccygeal bone is formed, which serves as a point of attachment of caudal feather. Sternum and waist of the front legs. Muscles birds
In the skeleton of the forelimbs of the changes in the brush. It survived 3 hypoplastic thumb, a few small bones were fused and formed a single complex bone. The reduction in the number of fingers and fusion of small bones secured a modification of the brush. Because it carries the biggest load when flying, giving it strength. The belt of the front legs consists of a pair of blades, the clavicles, fused together at the bottom, crow bones and creates a sturdy support for the wings.
In the skeleton of the hind limbs specially modified foot, multiple small bones which are fused into a single bone — bobbin, which gives the strength of the legs of the bird. The lower end of the stuffing horn articulates with the bones of the fingers. Belt rear legs — pelvis. It is formed by two hip bones (each formed by the fusion of three bones) fused bones of the sacrum difficult.
The skull of birds consists of fused bones forming the skull with the upper and lower jaws. It is characterized a large amount of brain boxes and large orbital cavities, which is associated with strong development of the brain and eyes.
The musculature of birds. Due to the complex movements, especially in flight, when walking, the muscles in birds is highly developed, particularly large breast muscles that draw the wings.
Good flyers pectoral muscles make up 1/5 of the body weight. Under the pectoralis muscles are large subclavian muscle, raising the wings. Strongly developed in birds and the muscles of the hind limbs.
On the feet of birds are the muscles with long tendons. When the bird sits on a branch, the tendons stretch and compress the fingers.
Features of structure of organs of the body cavity. The differences of the digestive system of birds are primarily associated with the esophagus, stomach and colon. The esophagus in many birds, especially seed-eating (pigeons, grouse, wood grouse), which forms an extension of the goiter . It received the food under the special influence of the secretions of glands softens and partially digested. The stomach consists of two sections: glandular and muscular. In the glandular Department of food processed by the digestive juices. Contraction of the muscular walls of the stomach causes movement of food, rubbing her Horny lining, small stones and swallowing the bird. Turned into mush food enters the small intestine where the ducts of the pancreas, liver and gallbladder. Food is digested in birds at high speed. The mouse swallowed the brownie owl, for example, is digested for 4 h, and juicy fruit eaten by waxwings, for 8-10 min, the large intestine in birds is short, the remains of undigested food in it do not stay long and are removed through the cloaca to the outside. Frequent bowel movements — adaptation of birds to the relief of body weight.
Birds consume a lot of food quickly digest and therefore provide your body with plenty of nutrients.
Respiratory system of birds has a more complex structure than that of reptiles. The lungs of birds are spongy dense body (Fig. 270). Constituent bronchi branching. Many of the branches end with the finest bubbles, the walls of which are penetrated by a dense network of capillaries. Part of the large bronchi branches outside the lungs and forms an air bag ; some of them settled in the cavity of the tubular bones, pass between the muscles under the skin . Air bags protect the internal organs from overheating during the flight, reduce the density of the body. The primary role of air bags is involved in the mechanism of breathing during the flight. When lifting the wings away from the sternum to the spine, the chest expands, air bags stretch and the breath. When lowering the wings the thorax is compressed, the internal organs put pressure on the air bags and there is an exhalation.
Each time the first breath of atmospheric air in the trachea and bronchi takes place in air sacs and partly into the lungs . When you first exhale the air from posterior air sacs enters the lungs, and are experiencing intensive gas exchange: oxygen through the walls of the capillaries passes into the blood and from the blood into the lungs is carbon dioxide.
During the second inhalation, air passes into the front bags. His stock needed to reduce body density birds that facilitate flight. During the second exhalation the air passes from the lungs through the front of the bags and is removed by breathing out.
Thus, air enters the lungs at the first breath and first breath. The more flying, the more air rich in oxygen, passes through the lungs. When traveling by land and alone respiration in birds occurs without air bags.
In the circulatory system of birds has undergone significant changes in the structure of the heart: it was four chambers: two Atria and two ventricles. Large and small circles of blood circulation are fully separated. Due to such changes the blood through the body of the bird flows unmixed in the systemic circulation from the heart enters the arterial blood, and in small venous. The speed of blood circulation in birds is extremely high, due to the great frequency of the heartbeat. The bullfinch, for example, the heart is reduced to 730 times a minute.The structure of the heart birds the excretory Organs of birds — the bean-shaped kidneys. Formed in them the urine flows down the ureters into the cloaca together and the stool is expelled.
Metabolism. Improved breathing, providing a significant oxygen saturation of blood, consumption of large quantities of food and rapid digestion, high heart rate and faster supply of organs and tissues of nutrients and oxygen, and the release of bodies from unnecessary waste products has provided the birds with a high level of metabolism. In the process of oxidation of complex organic substances in the cells of the body started to get free a lot of energy needed to work the muscles, warming the body and other processes.
Thanks feather cover decreased significantly the return of heat to the external environment. Body temperature in birds have been high (up to 43 0 C) and a constant.
The nervous system of birds differs significantly to the development of the brain. Especially strongly developed hemispheres of the forebrain and the midbrain and cerebellum . With the high development of the anterior hemispheres of the brain involves the rapid creation of a variety of conditioned reflexes, with the average brain — improvement of the organs of vision, the cerebellum — coordination of complex movements, especially while flying.
The complexity of bird behaviour, in particular the care of offspring, so high that sometimes leads people to the idea of conscious towards the bird parents to their offspring. However, experiments conducted by scientists over the guillemots, gulls and other birds, showed that the basis of their behavior are instincts. Guillemots — waterfowl, nesting colonies. They do not build nests and lay one egg on ledges of bare rocks. Returning after feeding, Kaira postponed it unerringly finds the egg, although a number are hundreds of eggs laid by other individuals. When the place of the eggs put the potato, the bird “was naviwala” her, but it was enough to move the egg on 22-30 cm, Kaira sat on the space where lay the egg, and naviwala it. In place of the nestling guillemots in her absence had placed the bird the snowy owl. Kyra took it and fed as a chick.