tumme

Tumme is the Swedish word for the human thumb, the short, thick first digit of the hand. It is one of the least long digits, but it plays a central role in grip and manipulation, enabling opposability with the other fingers.

Anatomy and joints: The thumb has two phalanges (proximal and distal) and is connected to the hand by the first metacarpal. Its Carpometacarpal joint is a saddle joint that allows a wide range of motion, including opposition, which brings the thumb to touch the other fingers. The thumb also has a metacarpophalangeal joint and an interphalangeal joint. The muscles of the thumb group together in the thenar eminence, including the abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis; these are mainly innervated by the median nerve. The adductor pollicis, which brings the thumb toward the palm, is innervated by the ulnar nerve. Sensation from the thumb is primarily via the median nerve, with the dorsal side supplied in part by other nerves.

Function and significance: The opposable thumb allows precision grip and power grip, facilitating object manipulation, writing, and tool use. Its range of motion supports pinching, opposition, and fine motor control that are characteristic of human hand dexterity. The degree of thumb opposability varies among primates, with humans possessing highly developed capabilities that underpin skilled manipulation.

Clinical notes: Thumb injuries are common in sports and accidents, including fractures of the proximal or distal phalanx and ligament injuries such as skier’s thumb (ulnar collateral ligament injury at the MCP joint). Conditions like De Quervain’s tenosynovitis affect thumb tendons, while nerve injuries can alter sensation and movement.

See also: Pollex, opposable digit, thenar eminence.