humanhand

The human hand is the distal part of the upper limb, specialized for grasping, manipulating objects, and sensing the environment. It comprises the wrist, palm, and fingers, and houses bones, joints, muscles, tendons, nerves, and vessels that enable a wide range of precise movements and tactile perception.

Bones: a total of 27 bones form the hand. The wrist contains eight carpal bones; the palm contains five metacarpal bones; the fingers contain 14 phalanges (two in the thumb and three in each of the other fingers). Joints include the radiocarpal and intercarpal joints of the wrist, carpometacarpal joints of the palm, and the metacarpophalangeal and interphalangeal joints of the fingers.

Muscles and nerves: extrinsic muscles in the forearm generate most grip force, while intrinsic muscles within the hand (thenar, hypothenar, interossei, and lumbricals) refine position and fine motor control. The median, ulnar, and radial nerves provide motor and sensory innervation; arterial supply comes mainly from the radial and ulnar arteries, with connecting palmar arches.

Function: the hand performs various grips and manipulations. A power grip encircles or grips an object; a precision grip uses the fingertips and thumb. The thumb's opposition to the fingers is a key feature enabling complex manipulation and tool use.

Clinical and evolutionary context: the hand's evolution emphasizes an opposable thumb and versatile tendon arrangements. Common clinical issues include carpal tunnel syndrome (median nerve compression), tendinopathies, fractures, and Dupuytren's contracture. Hand health involves ergonomics, rehabilitation, and appropriate treatment after injury.