Final answer:
The humerus has various posterior structures such as the medial and lateral epicondyles and the olecranon fossa, which attach to muscles extending the forearm. The infraglenoid tubercle of the scapula serves as the origin for the triceps brachii muscle, lying posteriorly on the humerus.
Step-by-step explanation:
Anatomy of the Humerus
The humerus is the long bone in the upper arm. On its posterior side, particularly at the posterior shaft distal to the radial groove, the humerus provides attachment points for muscles that control movement of the arm and forearm. Posteriorly, the humerus features regions such as the medial epicondyle, which serve as attachment points for the powerful grasping muscles of the anterior forearm, and the smaller lateral epicondyle for extensor muscles of the wrist and hand. Moreover, the olecranon fossa accommodates the olecranon process of the ulna when the forearm is extended, which is commonly associated with muscles that extend the forearm at the elbow.
The infraglenoid tubercle of the scapula is another important structure as it serves as the origin for the long head of the triceps brachii muscle, which lies posteriorly on the humerus and is most common in this context. This muscle extends the forearm at the elbow and is critical for the movement of the upper limb.