The respiratory system of birds is peculiar, it is adapted to regular flights. The best gas exchange in the body of birds is facilitated 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 gap through which it enters the trachea. 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 arises in the lower larynx, which is exclusively in birds. It is located where the trachea is divided into two bronchi, and is an extension that is supported by rings of bones.
Inside the larynx there are voice membranes attached to the walls. Under the influence of the singing muscles, they change their configuration, which leads to a wide variety of sounds made. The inner vocal membranes are below the place where the trachea divides.
The upper respiratory tract is important for regulating body temperature. The heat causes the bird to breathe often and shallowly. The blood vessels located in the mouth and throat expand. As a result, the bird's body cools, giving off heat to the exhaled air.
Light and air bags
The structure of light 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 jumpers - parabronchuses with a large number of blind channels (bronchioles), which are braided by a dense network of capillaries.
Some bronchi, after branching, pass into large thin-walled air sacs. Their volume is much larger than that of the lungs. Birds have several air sacs:
- 2 cervical,
- interclavicular
- 4-6 breast,
- 2 abdominal.
The channels go under the skin and connect to the pneumatic bones.
Double breathing exists precisely thanks to air sacs. With their help, during the flight, the respiratory mechanism is determined.
Double breath
The resting bird, which sits, carries out the renewal of air in the lungs through the work of muscles. When lowering the sternum, oxygen-rich gas is sucked into the respiratory organ. By the reverse movement of the muscles, air is pushed out. Lungs also help pump oxygen.
A bird that walks or climbs connects air sacs located in the peritoneum to work. The upper parts of the legs exert pressure on them.
In flight, the importance of air sacs increases many times, because the process of double breathing of the bird occurs. In stages, it looks like this:
- The wings rise, stretching the air sacs.
- Air is pumped into the lungs.
- Part of the gas, not lingering, passes into the air sacs without losing oxygen. In this body, gas exchange does not occur.
- The wings drop, while exhaling through the lungs passes a gas rich in oxygen from air sacs.
The phenomenon in which blood is saturated with oxygen during inhalation and exhalation is called double breathing. He has great importance in the life of birds. Breathing becomes more frequent with increasing intensity of wing flaps.
Other breathing features
Double breathing is characteristic of birds, but in some the number of strokes and respiratory movements do not coincide. However, certain stages of these processes correspond in time. The presence of air bags 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 the organs against each other are reduced. Respiratory rate is different for different species. The volume of air bags is an order of magnitude greater than light.