mão

The hand, or mão in Portuguese, is the distal portion of the upper limb in humans and many primates. It consists of the wrist, the palm, and the fingers, and is capable of complex manipulation of objects. The word mão is feminine (a mão) and has plural mãos.

Anatomically, the hand contains 27 bones: eight carpal bones in the wrist, five metacarpal bones in the palm, and 14 phalanges in the fingers. Joints include the radiocarpal joint, midcarpal joints, metacarpophalangeal joints, and interphalangeal joints. The thumb is opposable due to its carpometacarpal joint.

Muscles are split into extrinsic (forearm-origin muscles that move the wrist and fingers) and intrinsic (muscles within the hand such as thenar, hypothenar, interossei, and lumbricals). Innervation comes mainly from the median and ulnar nerves, with the radial nerve supplying dorsal skin; arterial supply from the radial and ulnar arteries. Sensation is distributed across the palmar surfaces via median, ulnar, and radial nerves.

Functionally, the hand enables grip and manipulation, tactile exploration, and communication, including sign languages. The opposable thumb allows precise grip and object manipulation, while the fingertips provide high tactile acuity.

Clinically relevant aspects include fractures of the distal radius, metacarpals, or phalanges; carpal tunnel syndrome; tendinopathies; and arthritis. The hand also features prominently in art, culture, and everyday tool use.

Etymology: mão derives from Latin manus; plural mãos follows irregular form.