The humerus (; pl. humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a rounded head, a narrow neck, and two short processes (tubercles, sometimes called tuberosities). The body is cylindrical in its upper portion, and more prismatic below. The lower extremity consists of 2 epicondyles, 2 processes (trochlea & capitulum), and 3 fossae (radial fossa, coronoid fossa, and olecranon fossa). As well as its true anatomical neck, the constriction below the greater and lesser tubercles of the humerus is referred to as its surgical neck due to its tendency to fracture, thus often becoming the focus of surgeons. Etymology
The word "humerus" is derived from Latin: humerus, umerus meaning upper arm, shoulder, and is linguistically related to Gothic ams shoulder and Greek ōmos. Structure
Upper extremity
The upper or proximal extremity of the humerus consists of the bones large rounded head joined to the body by a constricted portion called the neck, and two eminences, the greater and lesser tubercles. Head
The head (caput humeri), is nearly hemispherical in form. It is directed upward, medialward, and a little backward, and articulates with the glenoid cavity of the scapula to form the glenohumeral joint (shoulder joint).
There may be genetic causes in some cases, and there may be environmental factors to which the mother is exposed during pregnancy.Risk factors include the mother being young, and use of alcohol or tobacco. Pathophysiology
During the fourth week of human embryonic development, the lateral body wall folds of the embryo meet at the midline and fuse together to form the anterior body wall. However, in gastroschisis and other anterior body wall defects, this fails to occur by either one or both of the lateral body wall folds not moving properly to meet with the other and fusing together. This incomplete fusion results in a defect that allows abdominal organs to protrude through the abdominal wall, and the intestines typically herniate through the rectus abdominis muscle, lying to the right of the umbilicus.