forearm to form the elbow. Its anatomical portions
include a head (a rounded portion that fits into a recess
of the scapula) called the glenoid fossa; the shaft,
which is the main part of the humerus; and the distal
end, which includes the prominence (called an
epicondyle) and the surfaces that articulate with the
bones of the forearm.
Radius and Ulna.When the arm is in the
anatomical position with the palm turned forward, the
radius is on the lateral (thumb) side and the ulna is on
the medial (little finger) side of the forearm (fig. 1-22).
When the hand is pronated (with the palm turned
downward), the bones rotate on each other and cross in
the middle. This pronation makes it possible to turn the
wrist and hand (as when opening doors). The ulna and
the radius articulate at their proximal ends with the
humerus, at their distal ends with some of the carpal
bones, and with each other at both ends.
Carpal.There are eight carpal bones, arranged
in two rows, forming the wrist.
Metacarpal.The metacarpal bones are
numbered one to five, corresponding with the five
fingers, or digits, with which they articulate. The
f i n g e r s a r e n a m e d a s f o l l o w s : 1 s t t h u m b ;
2ndindex; 3rdmiddle; 4thring; and 5thlittle.
Phalanges.The small bones of the fingers are
called phalanges, and each one of these bones is called
a phalanx. Each finger has three phalanges, except the
thumb (which has two). The phalanges are named for
their anatomical position: The proximal phalanx is the
bone closest to the hand; the distal phalanx is the bone
at the end of the finger; and the middle phalanx is the
bone located between the proximal and distal
LOWER EXTREMITY.The lower extremity
includes the bones of the hip, thigh, leg, ankle, and
foot. The bones that form the framework of the lower
extremities are listed in table 1-2.
HEAD OF HUMERUS
Figure 1-22.Left arm: A. Frontal view of left arm with hand supinated; B. Frontal view of left arm with hand pronated.