According to the structure of the respiratory system of turtles is not too different from other animals. They have well developed lungs with which they breathe and exhale air.But turtles have no chest. They breathe not through the convergence and divergence of the ribs, as this prevents the shell, and using the muscle bundles going to the plastron from the shoulder and pelvic girdle, and dorsal-ventral muscles, which are located on the edge of the shell. Movement of the involved muscles changes the volume of the body cavity to decrease or increase and, consequently, to change the volume of the lungs, resulting in inhalation or exhalation.
At the front end of the head of a turtle located external nostrils, through which it breathes air. Then it gets into the mouth, which is the output of the internal nostrils-hoani adjacent to the glottal gap. The air enters the trachea, then the bronchi, and from there into the lungs.
Turtles don't have gills so they cannot breathe oxygen dissolved in water. As water and land animals need air for normal functioning. Here are just a breath of turtles is not same intensive, as people. Tortoise in the period of activity makes only 4-6 breaths per minute. Water is even scarcer, it may float to the surface to gasp for air only once in twenty minutes. During hibernation, when the animals metabolism slows down, the need of oxygen they have noticeably reduced.
During the evolution of turtles has received some highly original devices that facilitate the process of breathing. For example, soft-shelled turtles not only breathe with lungs, but also able to absorb oxygen through the skin. And turtles that live in fresh water part of the gas exchange occurs in the anal pouches that open into the cloaca.