Humerus Bone

Proximal End Anatomy

The head of the humerus is at its proximal end. This is the large, round, smooth region that faces medially. The head articulates with the glenoid cavity of the scapula to form the glenohumeral (shoulder) joint.

An expanded bony area, the greater tubercle, is located on the lateral side of the proximal humerus. A smaller, lesser tubercle is found on the anterior aspect of the humerus. The anatomical neck connects the tubercles to the tubercular head. The greater and lesser tubercles are attachment sites for muscles that act across the shoulder joint.

The intertubercular groove (sulcus) passes between the greater and lesser tubercles. This narrow depression is also known as the bicipital groove because it provides passage for the biceps brachii muscle tendon. The proximal end of the humerus narrows to form the surgical neck, a common site of arm fractures.

Middle Portion Anatomy

The middle portion of the humerus is referred to as the shaft or body. A roughened, V-shaped elevation called the deltoid tuberosity is located on the mid-lateral side of the shaft. The name is applied to this structure because it is where the deltoid muscle attaches.

Just above these bony areas are two small depressions. These spaces accommodate the forearm bones when the elbow is fully bent (flexed). Superior to the trochlea is the coronoid fossa, which receives the coronoid process of the ulna, and above the capitulum is the radial fossa, which receives the head of the radius when the elbow is flexed. Similarly, the posterior humerus has the olecranon fossa, a larger depression that receives the olecranon process of the ulna when the forearm is fully extended.

Distal End Anatomy

The smooth, rounded distal end of the humerus is referred to as the humeral condyle. It is divided into two surfaces that articulate with the radius and ulna of the forearm to form the elbow joint. The pulley-shaped trochlea (L. pulley) is on the medial side and articulates with the ulna bone. Immediately lateral to the trochlea is the capitulum (L. head), a knob-like structure located on the anterior surface of the distal humerus. The capitulum articulates with the radius bone of the forearm.

Just above these bony areas are two small depressions. These spaces accommodate the forearm bones when the elbow is fully bent (flexed). Superior to the trochlea is the coronoid fossa, which receives the coronoid process of the ulna, and above the capitulum is the radial fossa, which receives the head of the radius when the elbow is flexed. Similarly, the posterior humerus has the olecranon fossa, a larger depression that receives the olecranon process of the ulna when the forearm is fully extended.

Superior to (proximal) the humeral condyle are two prominent bony projections. On the medial side is the medial epicondyle, and on the lateral side is the much smaller lateral epicondyle. A roughened ridge of bone, the lateral supracondylar ridge, is located above the lateral epicondyle. These areas are attachment points for muscles that act on the forearm, wrist, and hand. The powerful grasping muscles of the anterior forearm arise from the medial epicondyle, which is thus larger and more robust than the lateral epicondyle, giving rise to the weaker posterior forearm muscles.