Morphofunctional studies of the respiratory, digestive and urinary systems in birds

Of all the diversity of the animal world, birds are the most mobile vertebrates. As a result of mastering flight as a perfect form of movement associated with increased gas exchange, the bird developed complex respiratory organs, represented by lungs, ecto- and endobronchi, parabronchi, and cranial and caudal air sacs. The anterior group (expirators) of the air sacs, occupying the smallest volume, is located in the craniodorsal section of the thoracoabdominal cavity, and the caudal (inspirators), constituting the largest volume, lie in the caudodorsal section. Providing the body with nutrients left an imprint on the structure of the digestive system, consisting of the esophagus, crop, glandular and muscular stomachs, small intestine and two caeca. Increased metabolism, which is characteristic of birds, is associated with the functioning of the kidneys, consisting of cranial, middle and caudal lobes. The caudal lobe has the greatest mass, lying in deep pits of the pelvic bone and repeating its shape. The study examined the structural and adaptive features of the structure of the internal organs of the respiratory, digestive and urinary systems in birds adapted to terrestrial and aquatic habitats. The functions of the lungs with their complex bronchial system and air sacs, parietal gland, glandular and muscular stomachs, and kidneys were analyzed. The revealed adaptations of the internal organs in birds allow them to maintain high life support in certain habitat conditions.