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hand, terminal part of the forelimb in primates. The human hand consists of the wrist, palm, four fingers, and thumb. In humans and other primates, the thumb is opposable, i.e., it can be moved into a position opposite to the other four digits. Opposable thumbs make possible precise movements such as grasping small objects. In vertebrates other than humans, the primary function of the hand is locomotion; the human hand, due to the evolutionary development of bipedalism, is freed for manipulative tasks. There are 27 bones in the human hand. The wrist, which joins the hand to the forearm, contains eight cubelike bones arranged in two rows of four bones each. The metacarpus, or palm, is composed of five long metacarpal bones. Fourteen phalangeal bones constitute the four fingers and thumb (three in each finger, two in the thumb). Ligaments interconnect the bones of the hand. The bones of the digits are anchored to muscles in the hand and to muscles in the arms and shoulders, through connections to tendons, permitting a wide range of movements. Among humans, the undersides of the fingers and palms have distinctive ridges, which improve grip and can be used as identification marks.
the terminal section of the upper extremity (arm) in man, capable of performing extremely delicate and differentiated movements.
The hand consists of the carpus, the metacarpus, and the digits. Of the eight bones of the carpus, which are arranged in two rows, three articulate with the bones of the forearm (the radiocarpal joint) and with those of the metacarpus, which make up the base of the hand. The basal phalanges of the fingers articulate with the metacarpal bones.
The fingers have great mobility. The first digit, or thumb, can be opposed to the remaining four digits. This is especially important for grasping and holding objects. Movement of the hand and fingers is made possible by muscles located both in the hand itself and in the forearm. The tendons of the hand muscles pass through the bone-fiber canals and are surrounded by sheaths that are longer in the first and fifth digits.
The muscles that move the hand and fingers are innervated by branches of the ulnar, radial, and median nerves. The hand receives its blood supply from the radial and ulnar arteries, which form deep and superficial arterial arches and plexuxes on the hand’s palmar surface. The deep and superficial venous networks pass into the antebrachial veins.
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Between the 't' and the 's'. HTH. HAND.