The humerus bone is the long bone that extends between the shoulder and elbow joints, supporting the upper arm. It consists of three main parts: the proximal end, the shaft, and the distal end.
The head of the humerus extends medially from the most proximal end of the bone. Its rounded, ball-like surface articulates with the glenoid cavity of the scapula to form the glenohumeral (shoulder) joint.
Inferior to the head is the greater tubercle. This large, lateral projection is a site of attachment for several muscles that abduct (move away from the body’s midline), flex, and rotate the glenohumeral joint. The lesser tubercle is a smaller projection located on the anterior side of the humerus and is an area of attachment for one of the rotator cuff muscles. A narrow groove called the anatomical neck separates the head of the humerus from the tubercles.
The intertubercular groove (bicipital groove or sulcus) is an elongated indentation between the greater and lesser tubercles on the bone’s anterior surface. The groove serves as a passageway for a tendon of the biceps brachii muscle. It is also an attachment site for several muscles that adduct (move toward the body’s midline) and rotate the glenohumeral joint.
Inferior to the tubercles, the bone narrows to form the cylindrical shaft. The term surgical neck is applied to this region because it is a frequent site of fractures.
The shaft or body of the humerus bone is the long, cylindrical portion that extends between the proximal and distal ends. The deltoid tuberosity is a rough, V-shaped bump located on the lateral margin of the humerus, approximately one-third of the way down from the shoulder. It serves as the insertion point for the deltoid muscle. On the posterior side of the shaft is the radial groove (radial sulcus; spiral groove). This shallow depression runs diagonally towards the elbow and serves as a passageway for the radial nerve.
Two eminences form a condyle (articulation site) at the distal end of the humerus. On the lateral side is the smooth rounded capitulum, which articulates with the depressed surface on the head of the radius bone. Medial to capitulum is the trochlea. This pulley-shaped structure articulates with the trochlear notch of the ulna. On the lateral side is the smooth rounded capitulum, which articulates with the depressed surface on the head of the radius bone. Medial to capitulum is the trochlea. This pulley-shaped structure articulates with the trochlear notch of the ulna.
Directly superior to the distal articular surfaces are two small, slight depressions. Above the capitulum is the radial fossa, which accommodates the head of the radius during elbow flexion. Above the trochlea is the coronoid fossa. During elbow flexion, this slightly larger depression allows for the ulna’s coronoid process.
Superior to the fossae are two bump-like prominences called epicondyles. The medial epicondyle is an attachment for several muscles that flex the elbow joint. The lateral epicondyle is a similar projection located on the lateral side of the humerus. It is a site of attachment for several muscles that extend the elbow joint.
On the bone’s distal posterior end is a deep depression called the olecranon fossa. It provides room for the olecranon process of the ulna during full extension of the elbow.
Anterior Bone Markings:
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Posterior Bone Markings:
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References and Attributions
Cleveland Clinic – “Humerus.”
NIH: National Library of Medicine – “Anatomy, Shoulder and Upper Limb, Humerus.”
OpenStax – “Bones of the Upper Limb” (Access for free at https://openstax.org/books/anatomy-and-physiology-2e/pages/1-introduction).