The arm is that portion of the upper extremity which is situated between the shoulder and the elbow. Its skeleton consists of a single bone, the humerus.
The Humerus
The Humerus is the longest and
largest bone of the upper extremity; it presents for examination a shaft and
two extremities.
The Upper Extremity presents a large, rounded head,
joined to the shaft by a constricted portion, called the neck, and
two other eminences, the greater and lesser tuberosities.
The head, nearly hemispherical in form/ is'
directed upward, inward, and alittle
backward, and articulates with the glenoid cavity of the scapula; its surface
is smooth and coated with cartilage in the recent state. The circumference of
its articular surface is slightly constricted, and is termed the anatomical
neck, in contradistinction to the constriction which exists below the
tuberosities. The latter is called the surgical neck, from its often
being the seat of fracture.
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