Why do birds fly so high without being deprived of oxygen?

When the bird is at rest, the respiratory movement, like other terrestrial vertebrates, is accomplished by the lifting of the ribs and the upward and downward movement of the sternum to change the volume of the thoracic cavity. However, when flying, because the sternum is the fixed place and support point of the pecternus (pecternus) muscle, it cannot move up and down, and the vigorous breathing movement is mainly completed by the expansion and contraction of the air sac caused by the rhythm of the fanning wings. When a bird flies, when the wings are raised, the air sac expands, and due to the imbalance of air pressure inside and outside the bird, a part of the air quickly enters the posterior air sac along the primary bronchi.

This part of the air is oxygen-rich because it is not exchanged with gases in the lungs. The other part of the air enters the lungs at the same time, where gas exchange takes place directly at the bronchioles; When the wings are fanned, the air in the lungs that has undergone gas exchange is expelled from the body through the anterior air, and at the same time, the posterior air sacs are compressed and contracted, and the stored oxygen-rich air is pressed into the lungs, where the gas exchange is carried out again. As a result, the bird body is able to exchange gases in the lungs during both inhalation and exhalation.

This breathing phenomenon is called double breathing. It can be seen that the emergence of air sacs and the generation of double respiration are the excellent adaptation of birds to flying life, which ensures the smooth completion of vigorous breathing movements when birds fly, and thus also ensures the need for high energy, high oxygen consumption and constant body temperature when birds fly.

The bird has a lot of air sacs that allow him to breathe a second time, and there is enough oxygen in the air sacs for him to fly. He can breathe while collecting oxygen for begging.

The respiratory organs of birds are very different from those of humans - except for the lungs, there are several "air sacs" in the body that can store air - when breathing, part of the inhaled air enters the lungs, and the other part does not have time to exchange gases with the blood and enters the "air sacs" for storage, and there is no respiration here; During exhalation, the air in the "air sac" is pressed out of the body, passing through the lungs and allowing oxygen to enter the bloodstream, making up for a gas exchange – meaning that oxygen can be absorbed even when exhaling!

It can be seen that every time a bird such as a swan makes a breathing activity, the lungs exchange gas twice, a phenomenon called "double breathing".

"Airbags" and "double breathing" are very important when flying, especially at high altitudes; The significance is that such a continuous supply of oxygen** enables swans and other birds to breathe fully and freely all the time!

Birds have air sacs in addition to their lungs, and flapping their wings to drive the air sacs can carry out double breathing, and the oxygen uptake is higher.

Part of the inhaled air enters the lungs, and the other part does not have time to exchange gas with the blood and enters the "air sac" for storage, and there is no respiration here. When you exhale, the air in the "air sac" is forced out of the body, and it passes through the lungs, allowing oxygen to enter the bloodstream, and a gas exchange is performed. That's how it works.

The main reason why the birds migrate and fly so high is that the air at high altitude is relatively stable and not as turbulent as the convection at low altitude, so the birds will fly at high altitude with a lot less effort, and of course the consumption will be smaller. Then, depending on its snout growing on a pointed beak, it may be able to glide at high speed and breathe enough oxygen.

This is purely a personal opinion.

You are really talented, according to the knowledge learned in junior high school biology, birds use their unique "air sacs" to exchange gases with the lungs, so as to achieve the so-called "double breathing".

The special structure of the bird's respiratory system is adapted to the high oxygen consumption required for flight life. Experiments have shown that a bird in flight consumes 21 times more oxygen than at rest. The airbag is also a device that ensures that the bird has enough oxygen when flying.

When birds are resting, they mainly rely on the movement of the sternum and ribs to change the volume of the thoracic cavity, causing the expansion and contraction of the lungs and air sacs to complete gas metabolism. When flying, the sternum stabilizes as the starting point of the winging muscles, so it mainly relies on the expansion and contraction of the air sacs to assist the lungs to complete breathing.

In addition to aiding breathing, the air sac also helps to reduce the specific gravity of the body, reduce friction between muscles and internal organs, and is a cooling system for rapid heat metabolism (someone calculates that 3 4 of the air intake is used for cooling in a flying pigeon).