thenar

The thenar refers to the thenar eminence, the fleshy mass at the base of the thumb on the palm side. It is formed by three intrinsic hand muscles: abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis. The adductor pollicis lies in the midpalmar region and is not considered part of the thenar group.

Innervation is primarily by the median nerve through its recurrent branch, with the exception that the deep head of the flexor pollicis brevis receives innervation from the ulnar nerve. The blood supply to the thenar region comes mainly from branches of the radial artery, including the princeps pollicis and associated vessels, with additional contribution from the superficial palmar arch.

Functionally, these muscles coordinate thumb movements essential for grip and manipulation. They enable opposition (the thumb’s ability to touch the digits), as well as flexion and abduction of the thumb. This combination allows precision gripping and fine motor control of the hand.

Clinical relevance includes the appearance of thenar atrophy or weakness in conditions that affect the median nerve, such as carpal tunnel syndrome, which impairs thumb opposition. In contrast, motor deficits involving the ulnar nerve can affect the deep head of the flexor pollicis brevis and the adductor pollicis, altering thumb strength in other directions. Overall, the thenar eminence is central to the functional versatility of the thumb.