Which two bones comprise the shoulder girdle?

The shoulder girdle is primarily composed of the clavicle and scapula. The clavicle, commonly known as the collarbone, serves as a connection point between the arm and the body, providing support and stability to the shoulder area. It articulates with the sternum at its medial end and with the acromion of the scapula at its lateral end.

The scapula, or shoulder blade, is a flat, triangular bone that anchors the muscles of the shoulder and provides a surface for the attachment of muscles that facilitate arm movement. Together, the clavicle and scapula form a system that allows for a wide range of motion of the shoulder, making them integral to upper limb mobility and function.

The other choices include bones that do not directly compose the shoulder girdle. The humerus is the upper arm bone, the radius is one of the forearm bones, and the sternum is part of the ribcage rather than the shoulder girdle. Thus, the correct identification of the shoulder girdle bones is crucial for understanding anatomy related to upper limb function and movement.