The bone of the upper arm is called the humerus. It articulates with the scapula at the shoulder joint, and the radius and ulna at the elbow.
The proximal end of the humerus is dominated by a half-spherical articular surface, called the head, that forms the ball of the ball-and-socket joint of the shoulder. The head points medially into the shoulder joint. On the lateral side, a bump called the greater tubercle projects proximally.
The distal end of the humerus has two articular surfaces. The first of these, called the trochlea, is a pulley-shaped surface that accommodates the ulna. The other, called the capitulum, is a small spherical structure lateral to the trochlea that articulates with the head of the radius. The capitulum is on the lateral side, the trochlea is medial.
On the posterior surface, above the trochlea is a large dent, called the olecranon fossa. The proximal end of the ulna fits into this fossa when the elbow is extended.
What to do: At this station are many right and left humeri, including some fragmentary bones. Work on telling right and left humeri from each other. You will find the distal end of the bone very helpful, with the trochlea medial and capitulum lateral, and the olecranon fossa on the posterior aspect.