Final answer:
The attachments for locomotory and respiratory muscles in birds, uncinate processes, and elements that resist compression are the bones. These structures are particularly adapted in birds to support the demands of flight, with sternum modifications like a keel for muscle attachments.
Step-by-step explanation:
In birds, the attachments for the locomotory and respiratory muscles, uncinate processes, and elements that resist compression are the bones. The skeletal system, which includes bones, cartilage, and ligaments, supports the weight of the body, facilitates body movements, and protects internal organs. The muscles of the body, which enable movement and respiration, are attached to the skeleton via structures called tendons. Particularly in birds, bones such as the sternum have unique adaptations like a keel for the attachment of their powerful flight muscles, and their bones are lighter with air-filled spaces to aid in flight.