Humerus

'Humerus' measures about 30 cm, it is a typical long bone. It can be divided into:


 * caput − the head,
 * corpus − the body of the bone,
 * condylus − the distal part.

The head
Caput humeri (1) s covered by cartilage on the medial part and forms the head of the shoulder joint. Just below the edges of the cartilage is the collum anatomicum (anatomical neck). There are two bumps on the front under the head:


 * tuberculum majus (3) − laterally,
 * tuberculum minus (4) − ventrally.

Between the tubercles is the sulcus intertubercularis (2) and the tendon of the long head of the biceps passes through it. Below the level of both bumps is the site of the most frequent fractures of the humerus, the, collum chirurgicum (5, není anatomická struktura). The head of the humerus is turned dorsally by 30° relative to the axis of the condyles, which is in the frontal plane (retroversion).

Body
The triangular body of the humerus connects to the head. At the point of attachment of the deltoid muscle the tuberositas deltoidea is visible (7). The sulcus nervi radialis can be seen at the place where the radial nerve runs (the nerve can be injured in the case of a humerus fracture in this place). In the middle of the length of the body there is a foramen nutricium (6), through which nourishing vessels enter the bone.

Condyles
It forms the most distal part of the humerus. The articular surfaces located on it participate in the elbow joint. The ovoid condyles extend into:


 * epicondylus lateralis (10),
 * epicondylus medialis (13) − behind it is the sulcus nervi ulnaris (14, for nervus ulnaris, popularly know as the „funny bone“; in case of fractures of the condyles, this nerve can therefore be injured).

Just above the articular surfaces are three depressions:


 * fossa radialis (9) − ventrally, laterally;
 * fossa coronoidea (15) − entrally, medially, fits into it at the bend of the processus coronoideus of the Ulna;
 * fossa olecrani − on the dorsal side, the olecranon fits into it.

On the most distal part there are two articular surfaces:


 * capitulum humeri (11) − head, laterally, articulated with the radius;
 * trochlea humeri (12) − pulley, medially, articulated with the ulna.

Ossification
From the 3rd week of pregnancy, ossification begins in the diaphysis and both epiphyses of the humerus. Proximal growth cartilage is more active than distal. Smaller ossification nuclei are also formed (for example in bumps). Around the age of 20, the last growth spurts disappear.

Related articles

 * Bones of the upper limb
 * Muscles of the upper limb