various movements and is very sensitive to sensations constantly sending sensory nerve impulses to the brain. The hand can be divided into several layers including the skin, subcutaneous tissue, pal-mar aponeurosis, superficial palmar arch of blood vessels, nerves, tendons, deep palmar arch of blood vessels, metacarpal bones and interosseous muscles from superficial to the deepest layer. The palmar skin is covered with a thick layer of keratinized epithelium. The central part of the palmar skin is less movable because it is fixed by tense subcutaneous tissue and many fibrous septa, connected with the palmar aponeurosis. Thereby things can be held tightly in the hand. The palmar aponeurosis is a white, firm, triangular plate of dense connective tissue, tightly connected with the skin and subcutaneous tissue to assist wrist extension and finger flexibility. The hand is sup-plied with nuerous blood vessels and nerves.
The superficial and deep palmar arches are mutually connected and send forth arterioles to supply nutrients to the parts of the hand. Although blood circulation through the superficial arch is blocked when something is held tightly in the hand, blood can still pass through the deep arch to the tips of the fingers without interfering with the blood supply to the rest of the hand. The nerves of the hand originate from the median, radial and ulnar nerves of the arm to innervate the hand muscles and skin. The numerous nerve endings gathered on the fingertips are very sensitive to pain and tactile sensations.
There are many fibrous bundles in the subcutaneous tissue firmly connecting the skin of the distal phalanx with its periosteum. The central canaliculi of fibrous bundles are filled with fatty tissue and the arterioles passing through the fibrous bundles nourish the distal phalanx. Themspaces in joints between the bones are filled with synovial fluid to facilitate nimble hand movement (Fig. 2-2).
1-median nerve 2-radial artery, vein and nerve 3-ulnar artery, vein and nerve 4-superficial palmar arch 5-deep palmar arch 6-proper artery and nerve beside finger.
