home Investment What part of the respiratory system of birds. Respiratory system of birds. The cords consist of

What part of the respiratory system of birds. Respiratory system of birds. The cords consist of

The respiratory organs of birds are characterized by: 1) the simplicity of the structure of the nasal cavity. 2) the presence of an independent area in the trachea for producing sound (singing larynx), 3) a completely unique structure of the lungs, occupying a very small space in the chest, but complicated by the development of special air sacs. They provide a versatile service for birds with the original ability to ventilate their gas exchange areas during flight.
Nasal cavity-cavum nabi-narrow and short, divided by the nasal septum -septum nasi-into the right and left halves. The nostrils are either rounded or oval, and at the entrance to them, chickens have a small fixed tire-nasal valve, and around the nostrils there is a corolla of short bristle-like feathers. The edges framing the nostrils consist of wax. Geese and ducks have through, i.e., communicating with each other, nostrils that lie in front of the nasal septum.
In each half of the nasal cavity there are three small cartilaginous shells. There is no labyrinth of the ethmoid bone. The sense of smell in birds is poorly developed; their olfactory nerve branches in the dorsal concha and nasal septum. Near the medial corner of the eye in the frontal bone lies a package of nasal glands-gl. nasalis, the excretory duct of which opens into the nasal cavity.
Larynx-larynx (upper larynx - larynx superior) - located at the bottom of the pharynx, where the entrance to the larynx is visible in the form of a slit-like opening, surrounded by a rim of mucosal papillae.

The skeleton of the larynx (Fig. 274) consists only of the annular and arytenoid cartilages. The ring-shaped cartilage - cartilago cricoidea - is complex and is built from plates: an unpaired ventral (1, 1"), paired lateral (2, 2') and an unpaired dorsal section (3, 3'). The ventral plate, concave into the larynx, ossifies early. Posterior a section of the dorsal edge of the plate is attached to the lateral plates (in geese it fuses). The lateral plates on the dorsal side are closed by the early ossifying dorsal portion of the annular cartilage, thus connecting motionlessly. On it in front there are two articular surfaces for articulation with the arytenoid cartilages.
The arytenoid cartilages—cartilagines arytaenoideae—consist of cartilaginous dorsal and bony ventral sections (Ar. d, Ar. v).
In front of the entrance to the larynx, at the bottom of the pharynx, the mucous membrane forms a transverse fold, which plays the role of the epiglottis. The inner surface of the larynx is lined with ciliated epithelium and does not form the vocal lips.
The skeleton of the larynx is quite mobile and is controlled by the muscles: a) annular-arytenoid medial-m. cricoarytaenoideus medialis - functioning as a constrictor of the larynx; b) ring-arytenoid lateral - m. cricoarytaenoideus lateralis, - expanding the larynx; c) laryngohyoid-m. laryngohyoideus, - pushing the larynx forward, and d) sterno-laryngeal - m. sternolaryngeus, - returning the larynx to its resting position.
Trachea-trachea (Fig. 273-2) - relatively long, round or transversely oval in cross-section. Its skeleton consists of cartilaginous rings that ossify in old geese and ducks. The mucous membrane of this section of the airway is nothing special. The trachea is mobile and controlled by two muscles: a) m. ypsilotrachealis goes to the trachea from the clavicle (or from the lower larynx) and accompanies the trachea along its entire length; b) m. Bternotrachealis runs from the sternum to the sides of the trachea.
The singing, or lower, larynx-syrinx s. larynx inferior (Fig. 275) - in poultry it lies at the place where the trachea branches into the bronchi (syrinx bronchotrachealis). Its anatomical parts are: the drum, the bridge with the semilunar membrane and the eardrums (external and internal).
Drum-tympanum (2) is a local modification of the windpipe in the form of the growth of several tracheal rings thickened on the sides. In geese they merge with each other. At the apex of the division of the trachea into bronchi, a cartilaginous, often ossifying bridge formation acts sagittally as a drum amplifier (3). It separates the entrance from the trachea to the bronchi and is complemented by the semilunar fold of the mucous membrane - membrane semilunaris. The drum contains devices that can be considered similar to the vocal lips of mammals.
There are two identically constructed pairs of such vocal devices - right and left. Each pair consists of an inner and outer tympanic membrane lying opposite each other.

Internal tympanic membranes - membranes tympaniformes internae (5) - extend on the sides of the bridge and the adjacent medial wall of each bronchus. They are formed by the mucous membrane in the form of elastic folds protruding into the corresponding bronchus.
External tympanic membranes - membranes tympaniformes externae (4) - protrude from the outer walls of each bronchus, also in the form of elastic folds. The vibration of these membranes produces sound. In ducks, in the area where the vocal organ is located on the left side, a special bone tympanic bladder is developed - bulla tympaniformis (Fig. 276), which plays the role of a resonator.
Female birds have a less differentiated singing larynx compared to males. Songbirds have special muscles to tension and relax membranes.
Lungs-pulmones (Fig. 277-8) are constructed in a unique way and, despite their small size, are adapted to a very perfect exchange of gases, especially during flight. Birds are also characterized by the presence of a number of specific protrusions of some bronchi beyond the lungs with the formation of huge air sacs. They play different roles in the life of birds.
The right and left lungs, small in volume and pink in color, are located directly under the spine and in the recesses between the vertebral ends of the ribs, due to which their dorsal surface is uneven (it is wedged into the niches between the protruding edges of the ribs). The ventral surface of the lungs is adjacent to the already described rudimentary diaphragm.
Along the length of the body, the lungs occupy the space from the 1st rib to the location of the kidneys.
The structure of the lungs is very complex due to the unique course and branching of the bronchi. In general, the distribution of the bronchi is as follows. The main bronchus (b) enters each lung from the ventral side and stretches caudally through the organ to the posterior edge.
However, it does not end here, but continues beyond the lung, expanding into the vast abdominal air sac (7) (see below).
Soon after its entry into the lung, the main bronchus expands slightly in a fusiform manner into the vestibulum. Two rows of secondary bronchi, the dorsal and ventral, branch off from the main bronchus.

Most of the secondary bronchi remain within the lung parenchyma, but three bronchi, like the main bronchi, extend from each lung outside the organ, also forming air sacs (5, 6). Those of the secondary bronchi that branch within the lung are called internal bronchi-endobronchi, and those extending their ends outside the lung are called external bronchi-entobronchi. In the thickness of the lung, all secondary bronchi are connected to each other by numerous smaller bronchi-parabronchi. A large number of protrusions with respiratory surfaces already branch off from the parabronchi,” i.e., the respiratory areas of the lung. The system of bronchial branches in the lung has a huge number of anastomoses.
Air sacs. As mentioned above, a number of through bronchi open into air sacs. They are thin-walled protrusions of the mucous membrane, tightly covered with a serous membrane and relatively poor in blood vessels, and give off branches that penetrate the bones (with the exception of the skull bones), which therefore become pneumatized. There are nine such bags in both lungs, one of them is unpaired, and the rest are paired.
1) The interclavicular sac - saccus interclavicularis (1) - develops into an unpaired organ due to the fusion along the midsagittal line of two initially separated protrusions from both lungs. The protrusion originates from the clavicular ventral ectobronchi. This sac is divided into intrathoracic and extrathoracic sections.
The intrathoracic region lies between the clavicles and covers the heart from the ventral, dorsal and lateral sides. The extrathoracic section forms a number of outgrowths, among which the axillary diverticulum - diverticulum axiliaro (2) - communicates with the humerus (3). This diverticulum plays an important role in gas exchange during bird flight.
2) Cervical (paired) sacs - sacci cervicales (4) - develop from the cervical ventral ectobronchi of each lung. They are located above the trachea and esophagus. An air passage originates from the anterior end of the cervical sac, leading to the neck and pneumatizing the cervical vertebrae. There is also a passage that conducts air into the thoracic vertebrae and ribs.
3) Cranial thoracic (or intermediate) sacs - sacci thoracici (intermedii) craniales (5) - originate from the caudoventral ectobronch. They lie under the lungs and extend back to the last rib,
4) Caudal thoracic (or intermediate) sacs - sacci thoracici (intermedii) caudales (6) - derived branches of the posterior section of the main bronchus, i.e. they depart in the same way as the next abdominal sac. They are adjacent to the liver, stomach, intestines and abdominal pouches.
5) The abdominal sacs - sacci abdominales (7) - are the most voluminous, with very elastic walls and start from the posterior end of the main bronchus. They lie freely in the body cavity and have a number of diverticula. The latter pneumatize the lumbar and sacral vertebrae, pelvic bones and femur.
The posterior thoracic and abdominal sacs are characterized by a specific feature, namely that the sac bronchi (saccobronclii) (d, e) are separated from them. These bronchi also enter the lung, branch in its thickness and connect with the respiratory areas of the lungs.
The importance of air sacs is varied, but their role in gas exchange is in the foreground. Firstly, the bags serve as reserve reservoirs for inhaled air, which is of great importance for birds; Thus, ducks and geese have the ability to keep their heads submerged in water for a long time, looking for food. Secondly, thanks to the bags, the very act of gas exchange rises to a very advanced level, since the gas exchange field of the lungs can receive fresh portions of oxygen from two opposite sides: a) when inhaling, from the trachea in the usual way, b) when exhaling, from the two rear air sacs through the sac bronchi. Due to this device, the oxidative process in the body of birds, and consequently the manifestations of their life, proceeds very intensively, with the release of a significant amount of heat. The body temperature of birds exceeds that of mammals. Thirdly, during the flight of birds, the axillary diverticula of the interclavicular sacs act as bellows, replacing the movements of the chest. During rest and forward movements on land, in other words, with folded wings, respiratory movements occur through the expansion and contraction of the chest, especially the movement of the sternum (Fig. 278). During flight, the chest, as a supporting place for the muscles of the wings, is firmly fixed. Ventilation of the lungs under these conditions is carried out passively as a result of compression and expansion of the axillary diverticula by flapping the wings during contraction and relaxation of the pectoral muscles.

Overcoming air currents with great ease, birds perform various smooth movements, alternating the direction of flight. You might be interested to know that birds perform such maneuvers thanks to their respiratory system. Birds skillfully catch the oncoming wind. According to scientists, the mechanism of flying creatures responsible for the passage of air is exceptionally fine-tuned and much more complex than that of other animals.

Great opportunities for birds

It is interesting that birds, when flying long distances, expend a minimal amount of energy. Many of them, having flown several thousand kilometers, make practically no special effort. It has been proven that planning techniques help birds. Birds' skill lies in the fact that they can extract energy from the wind. First, they fly high into the air in a headwind, and then, turning around at a certain point, they fly along with the same air stream. In this case, the anatomical structure of the respiratory system of birds also plays an important role. A detailed examination of bird organs and their functions will help us uncover the secret of the amazing capabilities of birds.

General information

If we talk briefly about the respiratory system of birds, it has the following features:

The simple structure and small size of the nasal cavity.
At the branch of the trachea (at the bifurcation), where it passes into the two main bronchi, there is a mechanism for producing sounds - the singing larynx.
The optimal location of the lung, allowing the bronchi to enter inside it and form a spongy branch of bronchioles entangled in a web of capillaries. Some thicker bronchi do not form forks and are strongly elongated, protruding beyond the organ in the form of thin-walled sacs.

The diagram of the respiratory system of birds is a kind of well-coordinated potential, consisting of the following sections:

The structure of air passages

The starting point of the respiratory system of birds is the nostrils. They open the way for air to pass into the nasal cavity and through the upper larynx into the trachea. The structure of the trachea itself is very different in all birds and mainly depends on the length and number of rings consisting of cartilaginous tissue. At the site of the trophy bifurcation there is a syrinx, which represents the vocal apparatus of birds. This special organ is located in the lower part of the larynx. In the same place, the trachea forms a fork from two bronchi that enter the lung. Having transformed into secondary bronchi, these organs partially emerge from the lung, forming air sacs in various areas of the bird’s body. In the body of birds there are many parabronchi, entangled with blood capillaries, interacting with secondary ones.

Lungs

This organ has an elongated shape, is almost inelastic and is not located freely. The lungs are tightly secured between the ribs by pressing with the upper dorsal surface. On them you can see traces of ribs in the form of grooves. Organs of the respiratory system of birds, such as the lungs and bronchi, have a unique structure. Merging with each other, they form a dense sponge consisting of small branches. Upon entering the lungs, the bronchi diverge into smaller structures. Due to the secondary and tertiary forks of the bronchi, the lungs of birds have a spongy structure. They are light red in color and perform a vital function in gas exchange. Small respiratory tubes located in the lungs pass atmospheric air into the blood through epithelial cells. Oxygen saturation also occurs through the endothelium of the capillaries.

Complex breathing process

The main feature of the structure of the respiratory system of birds is the lung wrapped around the chest, which is not subject to stretching. Bone tissue does not allow the bird to change its configuration in this area, so the lung allows air to pass through the bronchi. Next come the air sacs, which allow the passage of air by changing their volume. Stretchable containers are able to pass most of the oxygen (75%) that enters the secondary bronchi, while the rest is retained by the lungs. When a bird is in flight, the air sacs constantly expand and contract. Moreover, the faster its wings flap, the more intense the breathing will be. When making upward flaps, air is rapidly drawn into the lungs and thin-walled formations, and when the bird lowers its wings, as it exhales, the air from the bags re-passes through the lungs.

The feature described above is triggered in birds only in a state of flight. When they are at rest, the chest gains the ability to contract and expand.

Due to the close relationship between breathing and the movement of wings, the bird will not die in flight. It is worth paying attention to one more important detail when performing this process - enhanced gas exchange.

Double Breathing

The respiratory system of birds is designed in such a way that oxygen saturation of the blood does not occur in the air sacs. As already mentioned, a smaller volume of air is retained in the lungs (25%) and a small part of it is used to oxidize the blood. To replenish the missing supply of oxygen, at the exit, a stream of air from the bags again passes through the lungs. Thus, both when inhaling and exhaling, the lungs are enriched with oxygen, and the process of blood saturation occurs in this organ. In order for more saturated air to communicate with arterial blood, their flows move opposite to each other. This gas exchange process is commonly called second wind.

The role of air sacs

When you inhale, the main bronchi deliver vital air to the lungs and posterior air sacs. On the way back, the air that has passed through the lungs enters the front reservoirs. The fact is that the exhaust air does not immediately leave the bird’s body. As a result of the first exhalation, it lingers in the anterior sac, and only after the second does it leave it. Making its way through the central bronchi and trachea, it exits in the form of carbon dioxide. In its place, the next portion of air immediately enters from the posterior sac, passing through the lungs. The flow moves in one direction. As you can see, thin-walled structures play an important role in the breathing process of birds.

Birds have enough air capacity to ensure a comfortable flight. Due to them, the bird's body becomes lighter and its density decreases. Well-filled bags located between the organs protect the birds from overheating during travel.

Classification of air sacs

Birds have 9 thin-walled air-bearing formations, which are classified as the main ones. In addition to them, the respiratory system of birds is endowed with intermediate growths and bags located at the back of the body.

The main ones are divided into 4 paired formations and one separate one: cervical, prothoracic, abdominal, metathoracic and unpaired clavicular. Inside, the mucous membrane of the sac is covered by a layer of ciliated epithelium. Their walls are quite elastic and have a capillary network. Air-bearing formations are placed between the internal organs and muscles. Some of them are even visible in the cavities of some long bones.

Due to the presence of a whole set of respiratory sacs, in the body of birds they can perform the following roles:

take part in the gas exchange process;
set the correct body position in flight;
ensure timely cooling of the body;
create protection for internal organs, acting as shock absorbers;
lighten body weight;
serve as a reservoir for air.

Voice apparatus

One of the most interesting functions of the respiratory system of birds is the ability to sing. Such skill is again determined by the design of the unique mechanism of the air-conducted apparatus. The superior fissure, located behind the tongue, leads to the upper part of the larynx, called the pharynx. This area consists of typical cartilage and does not act as a vocal apparatus in birds (as is typical for other land animals from the vertebrate class).

The syrinx, located on the lower part of the larynx, is responsible for the pleasant singing of birds. The cartilaginous rings of the trachea maintain optimal expansion of the wall of this organ. The vocal membranes extend from its outer part and flow into the syrinx. In the region of the trophy bifurcation, another membrane enters the larynx, called the internal glottis. When the singing muscles begin to contract, the membranes become tense. When you exhale, air from the lungs enters the glottis and vibrates the membranes, as a result of which they begin to make sounds. In this case, the trachea serves as a resonator and expands in volume at the moment of singing.

Due to the special property of the vocal apparatus to change its shape, birds can reproduce various sounds, and some of them are able to imitate human speech. In order for this organ to function normally, it is given enough space in the bird’s body. Based on this, in small birds almost the entire body is involved in the singing process.

In small birds, the frequency of breathing acts is much higher than in large birds. For example, the godwit covers a distance of up to 10,000 thousand kilometers in about 9 days. He has the ability to sense the approach of vortices and tries to catch a tailwind.

The smallest bird, the hummingbird, performs up to 80 movements of its wings in one second. At the same time, she skillfully performs her dance in the air, flying to the sides and vice versa. It weighs just over one gram and is the same size as a bee. It is noteworthy that this miniature bird is a close relative of common swifts.

The respiratory system of birds allows some of them to talk. The most famous talker was the Jaco parrot. He was also a representative of the Red Book. He was able to pronounce complete sentences in different languages. The parrot's vocabulary was about 400 words.

For the black swift, the sky serves as a home. A bird can stay in the air for several years without returning to the ground. She fulfills all her needs in flight.

In addition to the anatomical structure, the flight of large birds is carried out thanks to a special design: the feathers of eagles and storks at the edges of their wings turn upward, forming a vertical bend. This feature allows you to multiply the lifting force of birds with a small wing size, which greatly facilitates their flight.

The peregrine falcon is one of the fastest representatives in the whole world, which can reach up to 300 km/h. In addition, the bird's body reaches 1 m in length. Their females are usually larger than their males.

Conclusion

Having examined the features of the respiratory system of birds, we can safely conclude that this is one of the most complex mechanisms found in nature. For example, the presence of two larynxes allows birds to communicate with each other in their own language and perform beautiful melodies for people.

Birds are the youngest in evolutionary terms, highly developed animals, which are characterized by walking on two legs, feather cover, wings and beak, warm-bloodedness with an intense metabolism, a well-developed brain and complex behavior. All these features of birds allowed them to spread widely across the globe and occupy all habitats - land, water, air; they inhabit any territory from high polar latitudes to the smallest oceanic islands.

The habitat was a selection factor in the evolution of birds (body structure, wings, limbs, methods of movement, food production, features of breeding).

Birds are characterized by seasonal cycles, which are most noticeable in migratory birds and less pronounced in migratory or sedentary birds. The greatest species diversity of birds is concentrated in the tropical zone. Almost every bird species can live in several different biogeocenoses.

The most numerous group of forest birds includes carnivores, herbivores and omnivores. They nest in hollows, on branches, on the ground. Birds of open places - meadows, steppes, deserts - build nests on the ground; Coastal birds nest on rocks, forming bird colonies, where several species of birds not only live together, but also protect themselves from enemies.

Birds are characterized by clearly defined dynamics of population changes. Thus, the maximum of birds on Earth (up to 100 billion individuals) is observed after the emergence of the young, the minimum - by the beginning of next summer (decrease in number up to 10 times). Human economic activity plays a major role in changing the number of birds. The areas of forests, swamps, meadows, and natural reservoirs are being reduced, and some birds are simply exterminated.

The role of birds in food chains is great, since they represent the final links of many food chains.

Birds are of great importance in the distribution of fruits and seeds. In human economic activity, the importance of birds is mainly positive: they exterminate rodents, insect pests, and weed seeds, which can be considered as biological protection of fields and gardens. Birds must be protected and protected, fed, especially in winter, and their nests must not be destroyed. Without birds - so bright, mobile, loud-voiced - our forests, parks, meadows, and reservoirs become joyless and dead.

The damage caused by birds is incomparably lower than their benefit. They devastate orchards and vineyards, peck out sown seeds, pull out seedlings, so they have to be scared away. Cases of bird collisions with airplanes have become more frequent. Birds carry infectious diseases - influenza, encephalitis, salmonellosis, and spread ticks and fleas.

A person is engaged in poultry farming, raising poultry, as well as ornamental and songbirds.

80 species of birds are listed in the Red Book of the USSR.

There are about 8,600 species of birds in the world fauna, of which approximately 750 species are found within the territory of our country. Birds are common on all continents of the globe with the exception of the interior regions of Antarctica; some of them spend most of their lives on the open sea. On land, different species of birds are found everywhere where there is plant or animal food for them - in forests, bushes, parks, shelterbelts, meadows, swamps, deserts, mountains and tundra.

Class characteristics

Birds are very similar in structure to reptiles and represent their progressive branch, the evolution of which followed the path of adaptation to flight. Birds are often combined with reptiles into the group of lizards (Sauropsida). Birds are bipedal amniotes whose forelimbs have developed into wings; the body is covered with feathers, the body temperature is constant and high.

The organization of birds is adapted to flight conditions. The body is compact, the skeleton is extremely lightweight. The spread wings and tail form an area much larger compared to the area of the body. In the body structure of birds, one can note not only features characteristic of birds, but also features common to reptiles. Thus, there are no glands in the skin of birds, with the exception of the coccygeal gland above the root of the tail. Some birds also lack this gland.

Coverings of the body. The skin is very thin. There are horny sheaths on the beak, horny scales on the limbs, and claws on the fingers. Derivatives of the skin are feathers, phylogenetically related to scaly formations (this is indicated by the similarity in the development of feathers and scales in the early stages). Feathers cover the outside of a bird's body, help retain heat (thermal insulation function), provide streamlining of the body, protect it from damage, and form load-bearing planes in flight (wings, tail).

There are contour and down feathers.

Outline feathers consist of a strong and elastic hollow horny trunk (rod) and a soft fan. The fan is formed by a dense network of thin horny plates - barbs. The first-order barbules extend parallel to one another from the rod, on both sides of which numerous thinner second-order barbs extend, the latter interlocking with small hooks. There are long and especially strong feathers - flight feathers - they form the plane of the wing; long and strong tail feathers form the plane of the tail, the remaining integumentary contour feathers provide a streamlined body shape. 9-10 primary flight feathers are attached to the rear edge of the skeleton of the hand; during flight they form a thrust that carries the bird forward, and to a lesser extent - a lifting force. The secondary flight feathers are attached to the forearm and form the main load-bearing surface of the wing. On the leading edge of the latter there is a small wing with several short feathers that make it easier for the bird to land. Tail feathers take part in flight control and braking.

Down feathers have a thin short shaft and a soft fan with thinner and fluffy beards, without hooks (i.e. not connected to each other). Down feathers increase thermal insulation and help reduce heat transfer.

Birds molt periodically (once or twice a year), and new feathers grow in place of old feathers.

Skeleton. The bones of the skeleton are filled with air (pneumatic) and are lightweight. The thickness of the bones is small, the tubular bones are hollow inside, except for air, they are partially filled with bone marrow. Many bones fuse together. Thanks to these features, the bird's skeleton is light and strong. The spine is divided into five sections: cervical, thoracic, lumbar, sacral and caudal. The cervical vertebrae (there are from 11 to 25) are movably connected to each other. The vertebrae of other sections are fused to each other and are motionless, which is necessary during flight. The thoracic vertebrae are almost motionless; the ribs are attached to them. The ribs have hook-shaped processes that overlap the adjacent posterior ribs. The thoracic vertebrae, ribs, and broad breastbone, or sternum, form the rib cage. The sternum has a high ridge at the bottom - the keel. Powerful muscles that move the wing are attached to it and the sternum.

All lumbar and sacral (there are two) vertebrae are fused with each other and with the iliac bones; several caudal vertebrae join them, forming the complex sacrum characteristic of birds. It serves as a support for a pair of hind limbs, which bear the entire weight of the body. There are 5-9 free caudal vertebrae, the terminal caudal vertebrae are fused into the coccygeal bone, to which the tail feathers are attached.

The forelimb girdle consists of three paired bones: coracoids, scapulae and clavicles. The skeleton of the forelimb, which turned into a wing, is significantly modified. The wing skeleton consists of one humerus, two forearm bones (ulna and radius), several hand bones (most of them fused to form one bone) and three fingers. The skeleton of the fingers is sharply reduced.

When moving on land, the entire weight of the body is transferred to the pelvic girdle and hind limbs, and therefore they are also transformed. The hind limb girdle consists of three pairs of bones that fuse to form the pelvis. Along the midline of the body, the pelvic bones do not fuse together; this is the so-called open pelvis, which allows birds to lay large eggs. The skeleton of the hind limb is formed by long and strong tubular bones. The total length of the leg exceeds the length of the body. The skeleton of the hind limb consists of one femur, fused bones of the lower leg and foot bones that form the tarsus, and four toes.

The skull is characterized by complete fusion of all bones until the sutures disappear, extreme lightness and large eye sockets close to each other. The jaws of birds are represented by a light beak, devoid of teeth.

Musculature well developed, its relative mass is greater than that of reptiles. At the same time, the abdominal muscles are weaker than the pectoral muscles, which make up 10-25% of the total mass of the bird, i.e. approximately the same as all other muscles combined. This is due to the fact that the paired pectoralis major and minor muscles, starting on the sternum and its keel, lower and raise the wings during flight. In addition to the pectoral muscles, the complex work of the wing in flight is controlled by several dozen small muscles attached to the body and forelimbs. The muscles of the neck and legs are very complex. Many birds have a special device on the tendon of the deep toe flexor muscle that automatically secures the toes in a compressed state when the bird wraps them around a branch. Therefore, birds can sleep sitting on branches.

Digestive system. The digestive organs are characterized by the complete absence of teeth in modern birds, which greatly facilitates the body for flight. In granivorous birds they are replaced by a muscular stomach, which serves for mechanical grinding of food, while the glandular stomach serves for enzymatic action.

The digestive organs begin with the beak - this is the main organ for capturing food. The beak consists of an upper part (the mandible) and a lower part (the mandible). The shape and structural features of the beak are different in different birds and depend on the method of feeding. The tongue is attached to the bottom of the oral cavity; its shape and structural features depend on the nature of the food. The ducts of the salivary glands open into the oral cavity. Some birds have the enzyme amylase in their saliva and digestion of food begins in the oral cavity. Swallows and some swifts use sticky saliva when building nests; woodpeckers have insects stuck to their long tongue moistened with sticky saliva. Food moistened with saliva is easily swallowed and enters the esophagus, the lower part of which in many birds forms an extension - a crop (in which the food is soaked and partially digested). Further along the esophagus, food enters the thin-walled glandular stomach, in which numerous glands secrete digestive enzymes. Enzymatically processed food passes into the gizzard. The walls of the latter have well-developed strong muscles, thanks to the contraction of which food is ground. The ground food enters the duodenum, into which the ducts of the pancreas and gall bladder flow (birds have a two-lobed liver). The food then passes into the small intestine and then into the hind intestine, which is not differentiated into the colon and rectum and is significantly shortened. Through the hind intestine, undigested food remains are excreted into the cloaca.

Birds are characterized by high digestion intensity. For example, sparrows digest caterpillars in 15-20 minutes, beetles in about 1 hour, and grain in 3-4 hours.

Respiratory system. The respiratory organs begin with the nostrils, located at the base of the beak. From the mouth, the laryngeal fissure leads into the larynx, and from it into the trachea. In the lower part of the trachea and the initial sections of the bronchi there is the vocal apparatus of birds - the lower larynx. The source of sounds is the membranes that vibrate as air passes between the last cartilaginous rings of the trachea and the semi-rings of the bronchi. The bronchi penetrate into the lungs, branching into small tubes - bronchioles - and very thin air capillaries, which form an air-carrying network in the lungs. Blood capillaries are closely intertwined with it, gas exchange occurs through the walls of the latter. Some of the bronchial branches are not divided into bronchioles and extend beyond the lungs, forming thin-walled air sacs located between internal organs, muscles, under the skin and even inside hollow bones. The volume of the air sacs is almost 10 times the volume of the lungs. The paired lungs are small, are densely spongy bodies, and not bags, like in reptiles, and have little extensibility; they grow into the ribs on the sides of the spine.

In a calm state and while moving on the ground, the act of breathing is carried out due to the movement of the chest. When inhaling, the chest bone lowers, moving away from the spine, and when exhaling, it rises, approaching it. During flight, the sternum is motionless. When the wings are raised, inhalation occurs due to the fact that the air sacs stretch and air is sucked into the lungs and sacs. When the wings lower, exhalation occurs, oxygen-rich air moves from the air sacs into the lungs, where gas exchange takes place. Thus, oxygenated air passes through the lungs both during inhalation and exhalation (so-called double breathing). Air sacs prevent the body from overheating, as excess heat is removed with air.

Excretory system. The excretory organs are represented by two large kidneys, constituting 1-2% of body weight; they lie deep in the pelvis on both sides of the spine. There is no bladder. Through two ureters, uric acid in the form of a white mushy mass flows into the cloaca and is excreted out along with excrement without remaining in the body. This reduces the bird’s body weight and is important during flight.

Circulatory system. The heart of birds is relatively large, its mass making up 1-2% of body weight. The intensity of the heart is also high: the pulse at rest is 200-300 beats per minute, and in flight - up to 400-500 (in medium-sized birds). The large volume of the heart and rapid pulse ensure rapid blood circulation in the body, intensive oxygen supply to tissues and organs and removal of metabolic products.

In the structure of the heart, noteworthy is the complete division of the heart by a longitudinal continuous septum into the right venous and left arterial halves. Of the two aortic arches, only the right one, originating from the left ventricle, is preserved. The large and small circles of blood circulation are completely separated. The systemic circulation begins from the left ventricle and ends in the right atrium; arterial blood is carried through the arteries throughout the body (all organs are supplied only with arterial blood), venous blood through the veins enters the right atrium, and from it into the right ventricle. The pulmonary circulation begins from the right ventricle and ends in the left atrium. Venous blood through the pulmonary arteries enters the lungs, is oxidized there, and arterial blood through the pulmonary veins enters the left atrium, and from it into the left ventricle and into the systemic circulation. As a result of the fact that arterial and venous blood do not mix, the organs receive arterial blood. This enhances metabolism, increases the vital activity of the body, and causes a very high and constant body temperature of birds (42-45 ° C). The constancy of body temperature and its independence from environmental temperature is an important progressive feature of birds and mammals compared to previous classes of animals.

Nervous system. The brain has relatively large hemispheres and optic lobes, a well-developed cerebellum, and very small olfactory lobes. This is associated with more complex and varied behavior and the ability to fly. All 12 pairs of cranial nerves arise from the brain.

Of the sense organs, vision is the best developed. The eyeballs are large, allowing the retina to capture large images with clear detail. The eye has three eyelids - the upper, lower and transparent inner, or nictitating membrane. Accommodation (focusing the eye) is carried out by changing the shape of the lens and simultaneously changing the distance between the lens and the retina, as well as some changing the curvature of the cornea. All birds have color vision. The visual acuity of birds is several times higher than the visual acuity of humans. This property is associated with the enormous importance of vision during flight.

The hearing organ is anatomically similar to the hearing organ of reptiles and consists of the inner and middle ear. In the inner ear, the cochlea is better developed, and the number of sensitive cells in it is increased. The cavity of the middle ear is large, the only auditory bone - the stapes - is of a more complex shape, it is more mobile when the dome-shaped eardrum vibrates. The eardrum is located deeper than the surface of the skin; a canal leads to it - the external auditory canal. Birds have very acute hearing.

Compared to reptiles, birds have an increased surface area of the nasal cavity and olfactory epithelium. Some birds (ducks, waders, carrion-eating predators, etc.) have a well-developed sense of smell and are used when searching for food. In other birds, the sense of smell is poorly developed.

The taste organs are represented by taste buds in the mucous membrane of the oral cavity, on the tongue and at its base. Many birds distinguish between salty, sweet and bitter.

Reproductive organs. The male has two testes, the vas deferens form a small expansion in the lower part - the seminal vesicle - and flow into the cloaca. The female has only one left ovary and a left oviduct, which flows into the left side of the cloaca. Fertilization is internal and occurs in the initial part of the oviduct. Due to the contraction of the walls of the oviduct, the fertilized egg moves towards the cloaca. In the oviduct there are protein glands and glands that form on the egg a two-layer leathery subshell shell, a porous calcareous shell and a thin supershell shell. The latter protects the egg from microorganisms.

The egg moves through the oviduct for 12-48 hours and is successively covered with a thick albumen, subshell, shell and supra-shell membranes. At this time, the development of the embryo occurs. At the moment the egg is laid, it looks like a germinal disc, which is located on the surface of the yolk. Two convoluted protein cords - chalazae - go from the inner shell to the yolk and support the yolk so that the embryonic disk is on top, closer to the body of the bird that incubates the egg. For egg development, a temperature of 38-39.5 °C is required. The duration of incubation varies among different birds: from 12-14 days for small passerines to 44-45 days for the golden eagle and almost two months for large penguins, albatrosses, and vultures. In different species of birds, the eggs are incubated by the female, the male, or both in turn. Some birds do not incubate eggs: the sandpiper in Turkmenistan buries its eggs in hot sand, the weedy (or big-footed) chickens of Australia and the Malay Archipelago lay them in heaps of sand and rotting plants; during decay, the heat necessary for the development of the embryo is generated.

Most birds incubate their eggs in a nest. Most often, birds build or weave nests from twigs, grass, moss, often fastening them with some additional material (hair, wool, clay, mud, etc.). The nest usually has raised edges and a recessed interior - a tray that holds the eggs and chicks. Thrushes, finches, and goldfinches strengthen their nests in the forks of branches on bushes and trees. In the wren and long-tailed tit, the nest has the form of a dense ball with thick walls and a side entrance, fixed in the fork of the branches. Larks and wagtails make nests on the soil, in a hole lined with grass. Woodpeckers, nuthatches, tits, flycatchers, and whirligigs nest in hollows, kingfishers, bee-eaters, and shore swallows nest in holes along river banks. Many swallows make a nest out of lumps of clay and mud, held together by sticky saliva. Rooks, crows, storks, and many daytime predators build nests from large twigs and branches. Seagulls, guillemots, and loons lay eggs in the sand and in depressions on rock ledges. Female ducks, geese, and eiders pluck the fluff on their abdomen and line their nest with it. Temperature fluctuations in nests are significantly less than in the environment; this improves incubation conditions.

According to the degree of physiological maturity of the chicks at the time of hatching, all birds are divided into two groups - brood and nestlings. In brood birds, immediately after hatching, the chicks are covered with down, sighted, can move around and find food independently. Adult birds protect the brood, periodically warm the chicks (this is especially important in the first days of life), and help in searching for food. This group includes Galliformes (grouse, hazel grouse, pheasants, partridges, quails, chickens), Anseriformes (geese, ducks, swans, eiders), cranes, bustards, ostriches. In nestling birds, the chicks are initially blind, deaf, naked or slightly pubescent, cannot move, and remain in the nest for a long time (in passerines - 10-12 days, in some birds - up to 2 months). All this time, their parents feed and warm them. This group includes pigeons, parrots, passerines, woodpeckers and many others. First, parents feed the chicks soft, nutritious food (for example, tits feed the chicks spiders in the first days). The chicks leave the nest feathered, almost reaching the size of adult birds, but with uncertain flight. For 1-2 weeks after departure, the parents continue to feed them. At the same time, the chicks learn to search for food. Thanks to various forms of caring for their offspring, the fertility of birds is much lower than the fertility of reptiles, amphibians and fish.

Extinct forms and phylogeny. All the features of birds that distinguish them from reptiles are primarily adaptive in nature. It is quite natural to believe that birds evolved from reptiles. Birds originate from the most ancient reptiles - pseudosuchians, whose hind limbs were built in the same way as those of birds. A transitional form - Archeopteryx - in the form of fossil remains (imprints) was discovered in Upper Jurassic deposits. Along with the features characteristic of reptiles, they have the structural features of birds.

Taxonomy. Modern forms of birds are divided into three groups: ratites (South American, African, Australian ostriches and kiwis), penguins and keels; the latter unite a huge number of species. There are about 30 orders of keelbirds. Of these, the most important are passerines, chickens, diurnal predators, Anseriformes, pigeons, etc.

Flights

Sedentary birds live in certain territories throughout the year, for example sparrows, tits, magpies, jays, crows. After the breeding season, nomadic birds make migrations over hundreds of kilometers, but do not leave a certain natural zone, for example, waxwings, bullfinches, redpolls, crossbills, and many owls. Migratory birds regularly fly to wintering grounds thousands of kilometers from their nesting sites along clearly defined flyways to other natural areas.

Migration is a seasonal phenomenon in the life of birds, which arose in the process of evolution under the influence of periodic changes in weather conditions associated with the change of seasons, intensive processes of mountain building over vast areas and sharp cold snaps in the Quaternary period. The long northern day and a large amount of animal and plant food contribute to the feeding of offspring. In the second half of summer in the northern regions, the length of daylight hours decreases, the amount of animal food (especially insects) decreases, the conditions for its production worsen, the birds' metabolic patterns change, which, with increased nutrition, leads to the accumulation of fat reserves (in American tree warblers before flying over sea fat reserves account for up to 35% of the mass of birds). Many birds begin to unite in flocks and migrate to wintering areas. During migrations, birds fly at normal speeds, small passerines move 50-100 km per day, ducks - 100-500 km. The migrations of most birds take place at an altitude of 450-750 m. In the mountains, flocks of flying cranes, waders, and geese were observed at an altitude of 6-9 km.

Migration in some species occurs during the day, in others at night. The flight alternates with stops for rest and feeding. Migrating birds are capable of celestial navigation, i.e. to select the desired flight direction based on the position of the sun, moon and stars. The selected correct general direction of flight is adjusted according to visual landmarks: when flying, birds adhere to river beds, forests, etc. The direction and speed of migrations, wintering places and a number of other characteristics of birds are studied using their mass ringing. Every year, about 1 million birds are ringed in the world, including about 100 thousand in the USSR. A light metal ring with the number and symbol of the institution that carried out the ringing is put on the bird’s leg. When a ringed bird is caught, the ring is removed and sent to Moscow to the Ringing Center of the USSR Academy of Sciences.

The meaning of birds

Birds are of great economic importance, as they are a source of meat, eggs, down, and feathers. They destroy pests of fields, forests, orchards and vegetable gardens. Many species of domestic and wild birds suffer from psittacosis, a viral disease that can also infect humans. Birds living in the taiga, along with mammals, represent a natural reservoir of the taiga encephalitis virus. Birds living in Central Asia, along with mammals and reptiles, can be a natural reservoir of tick-borne relapsing fever pathogens.

However, not a single bird can be considered only useful or only harmful; it all depends on the circumstances and time of year. For example, sparrows and some granivorous birds feed on the seeds of cultivated plants and can peck juicy fruits in gardens (cherries, cherries, mulberries), but feed their chicks on insects. Feeding chicks requires a particularly large amount of food. The great tit brings food to the chicks up to 400 times a day, while destroying up to 6 thousand insects. The pied flycatcher collects 1-1.5 kg of insects, preferably small caterpillars, to feed six chicks over 15 days. During the autumn migration, the blackbird destroys a lot of blackbird bugs in forest belts and bushes: blackbird bugs during this period make up up to 74% of the total number of insects in the stomachs of blackbirds. Especially many harmful insects on agricultural crops and in forest plantations are destroyed by tits, flycatchers, nightingales, swallows, nuthatches, swifts, shrikes, starlings, rooks, woodpeckers, etc. Insectivorous birds eat many mosquitoes, midges, and flies that carry pathogens. Many birds (larks, pigeons, tap dancers, goldfinches, partridges, quails, bullfinches, etc.) feed on weed seeds, clearing fields of them. Birds of prey - eagles, buzzards, falcons (falcons, saker falcons, kestrels), some harriers, as well as owls destroy large numbers of mouse-like rodents, some feed on carrion and, thus, are of no small sanitary importance.

Under certain conditions, some bird species can be harmful. In particular, the bee-eater near apiaries feeds on bees, but in other places it destroys many harmful insects. The hooded crow eats the eggs and chicks of small birds, but also feeds on insects, rodents, and carrion. The goshawk, sparrowhawk, and marsh harrier destroy a large number of birds, in particular, the marsh harrier - chicks of waterfowl. One rook eats more than 8 thousand larvae of cockchafers, click beetles, and beet weevils per season, but in the spring, rooks pull out seedlings of corn and some other crops, so crops have to be protected from them.

Bird strikes sometimes cause serious accidents in jet and propeller-driven aircraft. In the areas of airfields, birds have to be scared away (in particular, by broadcasting recorded distress calls or alarm calls).

By making transcontinental flights, birds contribute to the spread of pathogens of certain viral diseases (for example, influenza, ornithosis, encephalitis, etc.). However, most birds can be considered beneficial. Many birds serve as objects of sport or commercial hunting. Spring and autumn hunting is permitted for hazel grouse, wood grouse, black grouse, pheasants, partridges, ducks and other birds. On the islands and coasts of the Arctic Ocean, light and warm eider down is collected, which eiders use to line their nests. Down is used to insulate the clothing of pilots and polar explorers.

Poultry farming

Poultry farming is an important branch of agriculture, developing rapidly. Chickens are bred at poultry factories and poultry farms (egg-laying breeds - Leghorn, Russian White, Oryol; egg-meat breeds - Zagorsk, Leningrad, Moscow), geese, ducks, and turkeys. Tens of thousands of eggs are laid in incubators at a time. Feeding, collecting eggs, maintaining the required temperature and light, cleaning processes, etc. mechanized and automated.

Bird conservation

To increase the number of beneficial birds, it is necessary to create favorable conditions for their nesting, for example, mixed forest plantations with a varied shrubby undergrowth, planting clumps of shrubs in parks and gardens. By hanging artificial nesting boxes (birdhouses, nest boxes, etc.), you can increase the number of tits, flycatchers, starlings and other birds by 10-25 times. In winter, it is recommended to feed sedentary birds by installing feeders on window sills, in front gardens, gardens, and parks. You should not disturb birds during the nesting period, destroy nests or collect eggs. During the hatching period, bird hunting is prohibited. Birds should also be protected in their wintering areas. State reserves and sanctuaries are of great importance in the protection of birds. For some rare and endangered bird species (for example, the white crane, etc.), measures are being developed for artificial maintenance and breeding in nature reserves.

The respiratory system of birds is considered the most complex of all animals.

This is understandable: the flying lifestyle requires an exceptionally developed respiratory mechanism and its well-functioning operation.

Airway diagram

The respiratory tract of birds is a complex system consisting of several parts:

Nasal and oral cavities;
Upper and lower larynx (pharynx and syrinx);
Trachea;
Bronchi;
Air bags.

The bronchi form the basis of the lungs. However, birds have only one trachea, unlike mammals. Inhalation and exhalation with such a system are carried out in a more complicated way. The lungs of birds are designed so that air passes through them.

In this case, only 25 percent of the air remains in them, the rest is collected in the air sacs. When you exhale, the rest of the oxygen enters the lungs. This system is called double breathing and is a distinctive feature of birds.

The air sacs of a bird are the main “carrier of oxygen” and resolve the “avian paradox”, which consists in the fact that birds need to breathe much more than mammals and humans, but their lungs have significantly smaller relative sizes, are inactive and are attached to the bones of the spine and ribs.

Birds do not have a diaphragm, and air movement is created by changes in pressure in the air sacs, which are stretched and compressed by the pectoral muscles. The air bag plays the role of a pump.

structure of the respiratory system of birds photo

By expanding it, the bird forces external air into it (some of which, as already mentioned, settles in the lungs through a branch in the trachea); then she compresses it, and the air passes through another path - through the lungs, from where it exits into the trachea and out.

This breathing becomes more intense during flight; air is independently pumped into and out of the air sac during the flapping of the wings. The more intensely a bird flaps its wings, the more deeply it breathes.

In addition to the respiratory function, the air sacs perform additional functions: they lighten body weight, promote the release of excess heat, and in waterfowl they also provide buoyancy.

Efficiency

The described structure of the respiratory tract of birds allows for more efficient gas exchange compared to the lungs of mammals, and even more so of reptiles and amphibians. Fresh air enters the lungs both during inhalation and exhalation.

At the same time, the waste air cannot immediately leave the body: there is an anterior air sac between the lungs and the trachea, and during the first exhalation, the unnecessary air remains there. During the second exhalation, the air from there finally comes out, and its place is filled by a new portion that has passed from the main, posterior air sac through the lungs.

The set of air sacs in birds is quite extensive and is not limited to the two considered. There are cranial sacs, which include the clavicular, cervical and cranial. The abundance of these cavities provides the bird with a light body capable of long flight.

However, the functions of the respiratory system of birds are not limited to breathing itself. She is also responsible for singing. The air passes through the lower larynx - the syrinx, which is also a distinctive feature of the class of birds. The trachea plays the role of a resonator and can increase in volume during singing.

These and other changes in the shape of the vocal apparatus allow birds to reproduce a huge number of sounds, including imitating human speech. Based on the size of the trachea, we can say that in small birds the entire body is responsible for resonance.

Respiratory system of birds differs sharply from the respiratory systems of other terrestrial vertebrates in a number of features that intensify respiration and thereby ensure a high level of oxygen consumption.

Through the paired nostrils, air is sucked into the nasal cavity and passes through the choanae into the oral cavity. The larynx, supported by three laryngeal cartilages, opens here through a narrow slit. Unlike mammals, the upper larynx of birds does not have vocal folds and does not serve as a source of sounds. Behind the larynx is the trachea - a flexible tube, the lumen of which is supported by cartilaginous tracheal rings located in its walls. In the body cavity, the trachea splits into two bronchi, each of which enters the corresponding lung and branches there. The lower part of the trachea and the initial sections of the bronchi form the lower larynx, a vocal apparatus characteristic only of birds, the structural details of which vary greatly. The source of sounds is the membranes that vibrate as air passes, located between the last rings of the trachea and the semi-rings of the bronchi. Special muscles change the tension of the vocal membranes, changing the nature of the sounds produced. Often the lower rings of the trachea grow, forming a thin-walled bone drum, amplifying sounds and changing their modulation. In other species, the resonator can be an elongated trachea, forming loops lying under the skin in the crop area or even protruding into the carina of the sternum (cranes, etc.).

The paired lungs are relatively small in size, quite dense and have little extensibility; they grow onto the ribs on the sides of the spinal column. Having entered the lung, the bronchus breaks up into 15-20 secondary bronchi, most of which end blindly, and some communicate with the air sacs. The secondary bronchi communicate with each other by numerous smaller parabronchi, from which arise many bronchioles - radially located cellular outgrowths, densely entwined with pulmonary blood capillaries. This is where the blood is oxygenated. The total respiratory surface of the lungs of birds significantly exceeds the respiratory surface of the lungs of reptiles and is quite comparable to the respiratory surface of the lungs of mammals. Associated with the lungs of birds are air sacs - transparent, elastic, thin-walled outgrowths of the mucous membrane of the secondary bronchi. The volume of the air sacs is approximately 10 times the volume of the lungs.

Bird air sacs

One of the air sacs - interclavicular - unpaired, four paired - cervical, anterior and metathoracic, abdominal. Air sacs are located between the internal organs, and their processes penetrate under the skin and into the cavities of large bones (shoulder, hip, etc.). The act of breathing is carried out due to the expansion and contraction of the chest. When you inhale, when the sternum moves away from the spinal column, the volume of the body cavity increases and the elastic air sacs expand, sucking in air. In this case, air from the lungs is sucked into the anterior air sacs, and air from the external environment goes through the trachea, bronchi and their branches into the lungs and into the posterior air sacs, metathoracic and abdominal.

When exhaling, the sternum moves towards the spinal column, the volume of the body cavity decreases and; under pressure from internal organs, air is squeezed out of the air sacs. Air containing a lot of oxygen from the rear air sacs is pumped into the lungs, and air from the anterior sacs - interclavicular, cervical and prothoracic, containing little oxygen but a lot of carbon dioxide, is pushed into the trachea and expelled out. Thus, oxygen-saturated air passes through the lungs almost continuously, both during inhalation and exhalation, enriching the blood with oxygen (the so-called double breathing). More complete; Blood saturation with oxygen is also facilitated by the movement of blood in the lungs towards the flow of air (the counterflow principle). With intense movement, especially in flight, the frequency of respiratory movements increases. Thus, a mallard duck takes 10-16 breaths per minute at rest, and 90-120 during takeoff. In small birds, breathing is rapid - up to 60-100 breaths per minute at rest.

In addition to intensifying breathing, air bags prevent the body from overheating during intense movement, since excess heat is removed by constantly changing air. An increase in intra-abdominal pressure during exhalation promotes defecation. Diving birds, by increasing the pressure in the air sacs, can reduce the volume and thereby increase the density, which makes it easier to dive into water.

Literature: Zoology of vertebrates. Part 2. Reptiles, birds, mammals. Naumov N.P., Kartashev N.N., Moscow, 1979