Humerus bone

Humerus

Anterior view of the humerus
Latin	Humerus
Articulations	Scapula, Radius, Ulna
Precursor	Limb bud
System	Skeletal system

The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow. It connects the scapula (shoulder blade) to the radius and ulna (the bones of the forearm) and consists of three sections: the proximal humerus, the shaft, and the distal humerus.

Anatomy

Proximal Humerus

The proximal end of the humerus includes the head, anatomical neck, greater and lesser tubercles, and the surgical neck.

• Head: The head of the humerus is a large, rounded structure that articulates with the glenoid cavity of the scapula to form the glenohumeral joint.
• Anatomical Neck: This is a slight constriction immediately below the head.
• Greater Tubercle: Located laterally, it serves as the attachment site for the supraspinatus, infraspinatus, and teres minor muscles.
• Lesser Tubercle: Located anteriorly, it serves as the attachment site for the subscapularis muscle.
• Surgical Neck: This is a common site of fractures and is located just below the tubercles.

Shaft

The shaft of the humerus is cylindrical in the upper half and more triangular in the lower half. It features the deltoid tuberosity and the radial groove.

• Deltoid Tuberosity: A roughened area on the lateral surface where the deltoid muscle attaches.
• Radial Groove: A shallow groove that runs obliquely down the posterior aspect of the shaft, accommodating the radial nerve and deep brachial artery.

Distal Humerus

The distal end of the humerus is expanded and forms the elbow joint with the radius and ulna. It includes the capitulum, trochlea, medial and lateral epicondyles, and the olecranon fossa.

• Capitulum: A rounded eminence on the lateral side that articulates with the head of the radius.
• Trochlea: A spool-shaped structure that articulates with the trochlear notch of the ulna.
• Medial Epicondyle: A prominent projection on the medial side, serving as an attachment for the ulnar collateral ligament and forearm flexor muscles.
• Lateral Epicondyle: A smaller projection on the lateral side, serving as an attachment for the radial collateral ligament and forearm extensor muscles.
• Olecranon Fossa: A deep depression on the posterior surface that accommodates the olecranon of the ulna during elbow extension.

Function

The humerus serves as a structural support for the arm and provides attachment sites for muscles that move the shoulder and elbow joints. It plays a crucial role in the movement and function of the upper limb.

Clinical Significance

Fractures of the humerus are common and can occur at any of its three main parts: proximal, shaft, or distal. Proximal humerus fractures are often seen in elderly patients with osteoporosis, while shaft fractures can result from direct trauma. Distal humerus fractures are less common but can be complex due to the involvement of the elbow joint.

Also see

• Scapula
• Radius
• Ulna
• Glenohumeral joint
• Elbow joint