Birds spend enormous amount of energy during flight. Their way of movement had a great influence on all systems of bodies. Birds are not able to afford large and heavy bodies therefore emphasis was put on efficiency of their work. As a result the respiratory system of birds which constantly improved during evolution is one of the most difficult among all vertebrata today.
Instruction
1. Air comes to an organism of a bird through two nostrils located over a beak. After that through a throat it comes to a long trachea. Passing into a chest cavity, the trachea is divided into two bronchial tubes. In the place of a branching of a trachea the birds have an expansion – a so-called lower throat. Here vocal chords are located. Lungs at birds are located in a body cavity not as at the person. They are strongly attached to edges and a spine column, maloelastichna also cannot stretch, being filled with oxygen.
2. Air goes through lungs as transit goods. In this body there are only about 25% of the arrived oxygen. The main part directs further – in air bags. Birds have five couples of air bags which are outgrowths of branches of bronchial tubes. Air bags are capable to stretch at intake of air in them. It will also be a breath of a bird.
3. At an exhalation air from air bags directs back in lungs, and then comes to light. Thus, though it is possible to call work of easy birds insufficiently hard in comparison with lungs of the person, thanks to double breath the bird receives amount of oxygen, sufficient for it.
4. At rest birds breathe thanks to expansion and narrowing of a thorax. During flight the thorax of birds remains almost motionless, and process of breath is carried out already at the expense of other mechanisms. When raising wings the air bags of a bird stretch, and air is involuntarily sucked in in lungs, and then and in bags. When the bird lowers wings, air from air bags is pushed out. The more intensively the bird waves wings, the more often she breathes.