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The humerus is a long bone in the arm or fore-legs (animals) that runs from the shoulder to the elbow. On a skeleton, it fits between the scapula and the ulna. It consists of the following three sections:
A bursa lies between the scapula and the chest wall, and allows the scapula to move over the chest wall. Movements of the shoulder are actually often combined movements of the glenohumeral joint as well as movement of the scapula on the chest wall.
The distal end of the humerus (at the elbow) creates a hinge joint with the ulna, allowing only flexion and extension. This happens on the trochlea of the humerus. Two pits at this end of the humerus (the coronoid fossa and the olecranon fossa) allow the ulna room to move, but prevent it from over-flexing/extending.
There is also a pivot joint between the capitulum (sometimes called the capitellum) of the humerus, and the head of the radius. This allows the hand to pronate and supinate (turn to face downwards or upwards).
A variety of muscles attach to the humerus. These enable movement at the elbow and at the shoulder.
The rotator cuff muscles attach at the proximal humerus, and can rotate and abduct the arm at the shoulder.
Some of the forearm muscles, (such as pronator teres, and the flexors and extensors of the wrist) also attach to the distal humerus.
The most common type of shoulder (glenohumeral joint) dislocation is an anterior or inferior dislocation of the humerus. This dislocation has the potential to injure the axillary nerve or axillary artery. Signs and symptoms of this dislocation are: a loss of the normal contour of the shoulder, a depression under the acromion that you can feel, and being able to feel the head of humerus in the axilla (armpit).
Since 'Humerus' is the homonym of 'humorous', it is sometimes referred to in popular culture as 'the funny bone'. However, the funny bone is actually not a bone, but refers to the ulnar nerve situated at the end of the humerus near the elbow. Accidentally hitting the funny bone can cause a tingling sensation (or 'funny' feeling), and possibly a significant amount of pain. Humerus is a Latin word meaning 'upper arm'.
This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Humerus". A list of authors is available in Wikipedia.|