shoulder(redirected from shoulders arms)
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of man, the segment of the upper extremity closest to the trunk.
The shoulder is bounded above by the shoulder joint and below by the elbow joint. The base of the shoulder is formed by the humeral bone, which has a body, an upper joint surface (caput, or head) to unite with the shoulder blade, and a lower joint surface (trochlea of the humerus) to unite with the bones of the forearm. The part of the bone under the head is called the neck of the shoulder. The shoulder bone is surrounded by longitudinally situated muscles—biceps and brachialis in front and triceps in back. The muscles are covered by a layer of connective tissue, subcutaneous fatty tissue, and skin. Deep in the soft tissues of the muscles are the blood vessels and nerves—the humeral artery and veins and the radial, ulnar, and median nerves. Superficial nerves, arteries, and veins are situated in the subcutaneous tissue.
Traumata of the shoulder include injuries to muscles, tendons, nerves, and blood vessels, as well as fractures—most commonly of the neck of the humerus.