No two hands are alike, not even our left hand and our right.
Children learn about the world around them by using their hands to "grasp" things. All of us come into contact with our environment via our hands - we grasp, pick up, touch and feel. Our brains and our hands have a very close relationship.
Many of the disorders that can affect the hand are so different in nature that they require special consideration in the context of a specialist medical field.
In functional terms, the hand represents a highly complex interaction of individual bones, tendons, ligaments, muscles, nerves and joints that is unparalled on the earth. The wrist (carpus) is made up of eight carpal bones (trapezium, trapezoid, capitate, hamate, scaphoid, lunate, triquetrum, pisiform) that are joined to one another by the midcarpal and intercarpal joints in two-row arrangement. The wrist joint, the point at which it hinges, is the joint between the proximal row of carpal bones and the distal end of the radius and ulna of the forearm. The middle hand (metacarpus), which is attached to the top of the distal row of carpal bones, consists of 5 long bones known as the metacarpals. The five fingers with their 14 bones (2 in the thumb and 3 each in the remaining 4 fingers) represent the free-moving part of the human hand.
While the muscles of the hand are very complex, they account for only a part of the hand's mobility. Most of the 33 muscles involved in hand movement are located in the forearm and exercise their control over the hand via their tendons that extend into the hand. The main groups of powerful muscles in the hand itself include the thenar eminence on the palm of the hand just below the thumb and the hypothenar eminence on the side of the little finger. Small muscles are located between the bones of the middle hand (metacarpals).
The hand is supplied by three nerves: the ulnar nerve, the median nerve, and the radial nerve. Blood is supplied to the hand via the radial and the ulnar arteries.
The palm of the hand is protected by a sturdy sheath of thickened tissue known as the palmar aponeurosis. This gives us a powerful grip. The remarkable precision of the human hand is achieved via numerous sensors in the tips of the fingers. The inside of the hand is outfitted with around 17,000 sensory receptors (140 per cm²) that allow us to perceive slight degrees of pressure, movement and vibration.
The enormous complexity of the hand as an instrument and sensory organ also makes it susceptible to nerve and tendon disorders. Owing to the important role played by our hands in our daily lives, these disorders may entail significant disability.
