Humerus

The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow. Anatomically, it connects the scapula and the ulna, and consists of the following three sections:

Upper extremity of humerus
Body of humerus
Lower extremity of humerus

Anatomy of the Humerus

Upper Extremity

The upper extremity of the humerus (proximal humerus) consists of a large rounded head joined to the body by a constricted portion called the neck, and two eminences, the greater and lesser tubercles:

• The head - It is directed upward, medial ward, and a little backward, and articulates with the glenoid cavity of the scapula,
• The anatomical neck - It affords attachment to the articular capsule of the shoulder-joint, and is perforated by numerous vascular foramina. Fracture of the anatomical neck rarely occurs.
• The greater tubercle,
• The intertubercular groove, and
• The surgical neck - Is a narrow distal to the tubercles that is a common site of fractures

Body of the Humerus

The body or shaft of the humerus is almost cylindrical in the upper half of its extent, prismatic and flattened below, and has three borders and three surfaces.

The borders include the anterior, lateral and medial borders. The surfaces include the antero-lateral surface and the posterior surface.

Lower Extremity of the Humerus

The lower extremity of the humerus is flattened from before backward and curved slightly forward; it ends below in a broad, articular surface, which is divided into two parts by a slight ridge.

Nerves of the Humerus

The Axillary Nerve

The most common type of shoulder dislocation is an anterior or inferior dislocation of the humerus of the glenohumeral joint. This dislocation has the potential to injure the axillary nerve or axillary artery. Signs and symptoms of this dislocation include a loss of the normal shoulder contour and a palpable depression under the acromion.

The Ulnar Nerve

The ulnar nerve at the distal end of the humerus near the elbow is sometimes referred to in popular culture as 'the funny bone'. Striking this nerve can cause a tingling sensation ("funny" feeling), and sometimes a significant amount of pain.

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