Біоморфологія м’язів, діючих на плечовий суглоб чорнодзьобої гагари

The article presents the results of studies of the biomorphological features of muscles acting on shoulder joint of some representatives of order Gaviiformes. Shoulder joint is a multifaceted joint, movements of which are provided not only by the muscles of the shoulder joint itself, but also some muscles of the shoulder girdle and elbow joint. It should be noted that the main muscles of the flight of birds are muscles of the shoulder girdle, in particular: thoracic and m. supracoracoideus. Also important are some of the muscles of the elbow, in particularm.coraco-radialis and m. scapula-triceps This is confirmed both by the points of fixation, and the degree of their development.The degree of development and differentiation of muscles acting on the shoulder joint is different, which is due to the peculiarities of the wing operation during the flight, and in waterfowl – peculiarities of underwater swimmingusing wings. The aim of this biomorphological study was understanding of development degree, and the main, mechanisms of differentiation and transformation of muscles acting on the shoulder joint of birds adapted to the aquatic habitat.Material for research was obtained from the funds of the Department of anatomy of Animals named after acad. V.G. Kasyanenko of the National University of Life and Environmental Sciences of Ukraine, where the muscle structures of the shoulder joint were studied on  black-tailed gagar Gavia immer in number of 3 individuals. Birds of Gaviiformes order are characterized by a rapid, but little maneuverable flight. They are extremely well adapted to the aquatic environment and spend most of their lives in the water, leaving on land only during breeding. These birds perfectly swim and dive, and during diving use not only the pelvic fins but also the wings. This, in turn, imposes certain imprints on the degree of development and differentiation of the studied muscle groups. It was found that among the studied groups of muscles (shoulder girdle, shoulder and elbow joints) the most developed group of muscles is shoulder girdle – 86%. The muscle groups of the elbow – 8.5% and the shoulder – 5.4% of the joints are significantly less. In addition, for the first time, we have found that the largest in its development among all the muscles examined - the thoracic muscle (the group of muscles of the shoulder girdle) has significant differences in comparison with other species of birds. These differences consist in the fact that this muscle is clearly differentiated into two separate layers, in fact two separate muscles – superficial and deep, most of which are developed superficial. Such a differentiation is due to biomorphological adaptations to the habitat.