Avian Physiology

The musculoskeletal structure of birds can vary tremendously based on whether they fly or not. The avian skeleton evolved to support flight, locomotion, and protection of the organs. Bone and cartilage parts are interconnected by joint structures, including synovial joints that connect between limb elements, intervertebral discs that confer pliability on the vertebral column, and fibrous joints to minimize movement between skull bones. As in other animals, the respiratory system functions to exchange oxygen and carbon dioxide in the lungs. The integument is the external surface of the bird composed of skin, feathers, and other derivatives. The surface of the skin, especially areas of feathered skin, beak or bill, toes and claws, contain cutaneous nerve receptors. Feather growth occurs in the feather follicle, which appears as a pocket or socket visible on the skin surface.