The respiratory system of birds is peculiar, it is adapted to regular flights. The best gas exchange in the body of birds is promoted by double breathing, which has developed as a result of evolutionary transformations.
Upper respiratory tract
The path of air in the body of birds begins with the laryngeal fissure, through which it enters the trachea. The part of it located on top is the larynx. It is called the top, it does not play any role in sound formation. The voice of birds originates in the lower larynx, which is unique to birds. It is located where the trachea divides into two bronchi, and is an extension that is supported by rings of bones.
Inside the larynx itself there are vocal membranes attached to the walls. Under the action of the singing muscles, they change their configuration, which leads to a wide variety of sounds produced. The internal vocal membranes are below where the trachea divides.
The upper respiratory tract is important for the regulation of body temperature. The heat causes the bird to breathe quickly and shallowly. The blood vessels located in the mouth and pharynx dilate. As a result, the bird's body cools, giving off heat to the exhaled air.
Light and air bags
The structure of the lungs of birds is different from amphibians and reptiles, in which they resemble empty bags. In feathered representatives of the fauna, this organ is attached to the back of the chest. In composition, it resembles a dense sponge. Branched bronchi have bridges - parabronchi with a large number of dead-end canals (bronchioles), which are braided with a dense network of capillaries.
Some bronchi, after branching, become large air sacs with thin walls. Their volume is much larger than that of the lungs. Birds have multiple air sacs:
- 2 neck,
- interclavicular,
- 4-6 infants,
- 2 abdominal.
The channels go under the skin and connect with pneumatic bones.
Double breathing exists precisely because of the air sacs. With their help, the mechanism of breathing is determined during the flight.
Double Breath
A resting bird that sits renews the air in the lungs through the work of the muscles. As the sternum descends, oxygen-rich gas is sucked into the respiratory organ. By the reverse movement of the muscles, the air is pushed out. The lungs also help pump oxygen.
A bird that walks or climbs uses the air sacs located in the peritoneum to work. The upper parts of the legs put pressure on them.
In flight, the importance of air sacs increases many times, because the process of double breathing of the bird takes place. Step by step it looks like this:
- Wingsrise, stretching the air sacs.
- Air is forced into the lungs.
- Part of the gas, without lingering, passes into the air bags, without losing oxygen. Gas exchange does not occur in this organ.
- Wings descend, as you exhale, oxygen-rich gas from the air sacs passes through the lungs.
The phenomenon in which the blood is saturated with oxygen during inhalation and exhalation is called double breathing. It is of great importance in the life of birds. Breathing speeds up as the intensity of the wing beat increases.
Other features of breathing
Double breathing is typical for birds, but in some the number of strokes and respiratory movements do not match. However, certain stages of these processes correspond in time. The presence of air sacs helps prevent birds from overheating in flight because cold air flows around the body from the inside. With their help, the density of the body and the friction of organs against each other are reduced. The frequency of respiratory movements differs in different species. Air sacs are an order of magnitude larger than lungs.
