Humerus

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

• Upper extremity of humerus
• Body of humerus
• Lower extremity of humerus

Articulations

A bursa lies between the scapula and the chest wall, allowing for smooth movement between the two. 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 of the humerus and the head of the radius, which allows the hand to pronate and supinate.

Muscle attachments

A variety of muscles attach to the humerus, enabling movement at the elbow and at the shoulder. The rotator cuff muscles attach at the proximal end of the humerus, allowing for the movement of the arm at the shoulder. Some of the forearm muscles, such as pronator teres and the flexors and extensors of the wrist, attach to the distal end.

Actions

• Deltoid has a variety of actions on the top of the arm.

• Pectoralis major, teres major and latissimus dorsi, which all insert at the intertubercular groove of the humerus, adduct and medially rotate the humerus.

• Biceps brachii, brachialis, coracobrachialis, and brachioradialis (which attaches very distally), act to flex the elbow. Biceps however does not attach to the humerus.

• Triceps brachii and anconeus extend the elbow, and attach to the posterior side of the humerus.

Clinical considerations

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).

Popular culture

Since "humerus" is the homonym of "humorous", 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.

The humerus is also notable because it is the longest bone in the human arm (the femur is the longest bone in the human body).

In an episode of the television series CSI ("To Halve and To Hold"), the skeletal humerus is used to determine a man\'s original height by multiplying the length of his humerus by five.

Leaning on both the medical and "funny bone" definitions, a Hollywood design firm took the name Humerus LLC and released a series of Zombie related products, and features an x-ray of the humerus bone in their logo.

Additional images

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.

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