BONES OF THE DAY (MONDAY): Humerus The humerus is the both the largest bone in the arm and the only bone in the upper arm. Many powerful muscles that manipulate the upper arm at the shoulder and the forearm at the elbow are anchored to the humerus. Movement of the humerus is essential to all of the varied activities of the arm, such as throwing, lifting, and writing. At its proximal end, the humerus forms a smooth, spherical structure known as the head of the humerus. The head of the humerus forms the ball of the ball-and-socket shoulder joint, with the glenoid cavity of the scapula acting as the socket. The rounded shape of the head of the humerus allows the humerus to move in a complete circle (circumduction) and rotate around its axis at the shoulder joint. Just below the head, the humerus narrows into the anatomical neck of the humerus. Two small processes, the greater and lesser tubercles, extend from the humerus just below the anatomical neck as attachment points for the muscles of the rotator cuff. The humerus narrows below the tubercles again in a region known as the surgical neck before extending toward elbow joint as the body of the humerus. About a third of the way to the elbow, the humerus swells into a small process known as the deltoid tuberosity, which supports the insertion point of the deltoid muscle.
Posted on: Mon, 19 Jan 2015 04:30:01 +0000
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