External and internal structure of birds. Internal organs of birds

What is the external and internal structure of birds? How do they differ from other classes of animals? What signs are peculiar only to birds? You will find answers to these questions in this article.

General characteristics of birds

Birds are a class of animals, whose body is covered with feathers. They have a constant and high body temperature and are active at any time of the year. Ability to fly is characteristic of most representatives of this class. The external and internal structure of birds is subject to this feature.

Feathers can easily change their place of residence depending on the conditions. Due to the ability to fly a class is widespread, it occurs in a wide variety of conditions throughout the planet. There are about 9000 species of birds.

Birds also have a pronounced concern for their own offspring. Reproduction occurs with the help of large, lime-coated eggs.

External structure of birds

The body of the bird consists of a head, a movable neck, a teardrop-shaped body and limbs. The skin is thin and dry due to lack of cutaneous glands. Most birds have gland serving to lubricate feathers - the coccygeal gland. It is especially well developed in waterfowl. The secret secreted by the gland serves to maintain the elasticity of the feathers and prevents their wetting. In some species (ostriches, parrots, pigeons, bustards), the function of lubrication is carried out by special powder feathers, with breakdown forming a powder.

The birds can have various growths on the beak, legs, head. In some species of birds (for example, predators and parrots), the base of the beak is covered with a soft wax. On the legs can be plates, fimbria, membranes.

The external and internal structure of birds directly depends on the way of life. The shape of the body, head, paws and tail, wings can be very diverse. All this depends on the habitat and the way of obtaining food.

External structure of birds. Plumage

Only the bird class has a feather cap, so they are also called birds. The plumage tightly adjoins to a body and gives to it a streamlined form. The cover is light and keeps the heat well, which helps incubate the eggs. Some feathers, thanks to their structure, provide the possibility of flight (steering and flywheel).

The feathers themselves are derivatives of the skin, akin to the scales of reptiles. The structure of the pen is as follows: its trunk consists of a dense stem, ending with a clearing (hollow end). To the core are joined the fan. They consist of horny plates - a fistula. From the rod go beards, having branches, called borodochkami. Some of them are studded with hooks, by which they are connected with neighboring barbules without hooks. A large feather can consist of a million barrels.

This structure ensures the density of the fan. During the flight, very little air can pass through the pen. If the beard disconnects, the bird will correct it with its beak when cleaning the feathers.

By functionality, feathers can be divided into two groups: down and outline. The feathers feathers were loose. Also there are simply feathers - feathers, consisting almost of one barrel, with an undeveloped stem. There are also setiform feathers, which, on the contrary, consist of rods, practically without beards. There are also hair-like feathers, on which the function of touch is entrusted. Contour feathers can be divided into mahovye, helmsman, covering and coverslips. Each kind of pen performs its function. A variety of color feathers due to the presence of pigments.

Musculoskeletal system

Features of the internal structure of birds are associated with a characteristic inherent only to birds - the ability to fly. The bird's skeleton is light, but at the same time it has great strength, consists of thin hollow bones. It includes a skull, a spine, belts of limbs and bones of extremities. The skeleton protects internal organs.

The internal structure of birds assumes a large volume of the skull. The eyes are enlarged, the jaws form a beak, the teeth are absent. The spine is divided into 5 divisions: cervical, thoracic, lumbar, sacral, caudal. The vertebrae of the cervical section have a special structure, thanks to which the bird can turn its head 180 degrees.

The thoracic vertebrae join together and form a single bone, to which ribs are attached. In flying birds on the sternum there is a keel. This is a large growth, which is attached to the powerful muscles of the wing. The vertebrae of the lumbar and sacral region also coalesce to serve as a reliable support for the pelvis, and the tail fuses into a single coccygeal bone to become a support for the steering pens.

The humerus consists of three pairs of bones: the clavicle, the scapula and the crow's bones. The wing consists of a humerus, a forearm and bones of a brush. The pelvic bones coalesce with the vertebrae and serve as a support for the lower limbs. The leg consists of the hip, shank, forelock (several fused bones of the foot) and fingers.

Muscles of the bird, located from the keel to the shoulder, ensure the operation of the wings. In flying feathered musculature in this part is particularly well developed. Neck muscles provide movement of the head. The internal structure of birds in the field of the muscles and tendons of the lower limbs is interesting. Through the joints of the legs tend tendons, which end in the fingers. When the bird sits on a tree and flexes its legs, the tendons stretch and the fingers wrap around the branch. Thanks to this feature, birds can sleep on branches, their fingers do not unclench.

Digestive system

We continue to study the internal structure of birds. The general characteristic begins with the first department of the digestive system - the beak. It represents the bones of the jaws, covered with horny covers. The shape of the beak depends on the method of obtaining food. There are no teeth for birds. The food is swallowed whole, from a large piece with the help of a beak the bird can tear off the appropriate pieces.

Esophagus feathery can significantly stretch. Some species of birds can fill it with food and do not experience discomfort. At the end of the esophagus, there may be a goiter, a special extension adapted to store food.

The stomach of the bird consists of a glandular and muscular division. In the first there is a secretion of gastric juice, which softens the food, and in the second it is rubbed. This process is promoted by pebbles that swallow the birds. The stomach follows the intestine, ending in a cloaca. In the cloaca also open the ureters and excretory pathways of the reproductive organs.

Respiratory system

We continue to study the internal organs of birds. The internal structure of birds is subject to the need to provide flight. It also concerns the respiratory system, which is represented not only by light, but also by air bags located in the free space between internal organs. These bags are connected to the lungs, and they are entrusted with an important function of providing breathing during the flight. At rest the bird breathes lungs, working with the thorax.

In flight, thanks to the operation of the wings, air bags increase and contract, delivering air into the lungs. The faster the bird flaps its wings, the more frequent the reduction of air bags. For example, the dove alone makes 26 breaths, and in flight - up to 400. Due to the active circulation of air, the bird's body cools. Oxygen-enriched air from the respiratory bags enters the lungs, which prevents the bird from suffocating.

The circulatory system of birds

Features of the internal structure of birds can be found and studying the circulatory system, which is represented by two circles of blood circulation and a four-chambered heart. Large and small circles of blood circulation are completely disconnected, that is, arterial and venous blood do not mix. The heart consists of two atria and two ventricles.

The heart muscle can accelerate its work dozens of times, for example at rest the heart of a dove is reduced 165 times per minute, and during the flight 550 times. Features of the structure of the circulatory system of birds are caused by a high level of metabolism. The heart has a large volume, the pulse is frequent, the blood is saturated with oxygen and sugars - all this ensures both intensive supply of all organs with the necessary substances and rapid removal of metabolic products.

Sense organs

The organs of smell in the birds are poorly developed. Most birds are unable to distinguish smells. The internal structure of birds, especially the organs of hearing, is more developed than in reptiles. Hearing organs are represented by the inner, middle and outer ear. The latter consists of a deep external auditory canal framed by skin folds and special feathers.

Birds have well developed vision organs. Eyes large and complex structure, good sensitivity. Color vision is better developed than in many other animals. Birds distinguish a large number of shades. With high speed during the flight, vision allows you to assess the situation from a long distance, but the objects that are in a few centimeters are clearly seen by the bird.

Nervous system

In flight birds perform complex movements, so the cerebellum responsible for coordination is large. The visual bumps are also well developed. The hemispheres of the forebrain are enlarged. The internal structure of birds, their brain and nervous system is associated with the complex behavior of birds.

Most of the actions are instinctive - building a nest, pairing, caring for the offspring. But with age, birds are able to learn. If the chicks do not fear a person, then adults of people are afraid. They can distinguish the hunter from the unarmed, and crows can understand that it is in the hand of a person - a stick or a gun.

Some species of birds recognize people who often feed them, can be trained and are able to imitate various sounds, including human speech.

Excretory and reproductive systems

Consider the excretory and sexual systems, their internal structure and reproduction of birds. Since the metabolism of birds is accelerated, the kidneys are large. These paired metanephric organs are divided into three lobes and are under the dorsal walls of the pelvis. The ureters leaving them open in the cloaca. There is no urinary bladder in birds. Wastes, consisting mainly of uric acid, are quickly removed from the body.

The majority of birds do not have a copulatory organ. Testes enlarged in size during the reproduction period lead the contents out through the canal into the seminal vesicle located in the cloaca.

The internal structure of birds, more precisely, of the reproductive organs of females, has interesting features. They have only the left ovary and oviduct, the right ones are usually rudimentary. Most likely this is due to the lack of space for the simultaneous formation of large eggs. From the ovary leaves the oviduct, which is divided into several sections: a long fallopian tube, a thin-walled and broad uterus and a narrow vagina that opens into the cloaca. To carry out fertilization, the male presses his cloaca against the cloaca of the female.

Reproduction and care of the offspring

We examined the internal structure of birds. Biology not only studies anatomy, but also analyzes the behavior of animals. Let's talk about such a complex process as reproduction and care for the offspring of birds.

The breeding season occurs when enough food appears. Our birds - in the spring and summer. But the reproduction of birds, contained in captivity, for example, decorative, stimulate at any time of the year, increasing the amount and nutritional value of feed.

Most small and medium sized birds form pairs for the season, while large ones often have long-term alliances. They can form flocks where temporary pairs are formed. Choosing a partner is not accidental. Males are puffing to attract the attention of females: they spread feathers, make special sounds, enter fights.

Most species lay eggs in the nest, which can be located on the ground, on trees, bushes, hollows, holes. Eggs protect a strong shell, often having a masking color.

In brood species (domestic birds, ducks, geese, black grouses, swans) the chicks appear from the egg with open eyes and covered with down. Very quickly they begin to eat on their own and leave the nest. In nesting birds (pigeons, crows, titmouses, sparrows, rooks, parrots, birds of prey) the young appear blind and naked, completely helpless.

For birds is characterized by a long care for the offspring. Feathers warm and nourish their chicks, protect them.