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The thenar eminence is the mound formed at the base of the thumb on the palm of the hand by the intrinsic group of muscles of the thumb. [1] The skin overlying this region is the area stimulated when trying to elicit a palmomental reflex. The word thenar comes from Ancient Greek θέναρ (thenar) 'palm of the hand'. [2]
The intrinsic muscles of the thumb can be divided into two groups; the thenar eminence and other muscles. The thenar eminence refers to the group of muscles on the palm at the base of the thumb. The three muscles composing the thenar eminence are the abductor pollicis brevis, flexor pollicis brevis and opponens pollicis. [5]
In the thenar eminence, the recurrent branch of the median nerve provides motor innervation to: [4] opponens pollicis muscle; abductor pollicis brevis muscle; superficial part of flexor pollicis brevis muscle; A separate, more proximal branch of the median nerve additionally provides motor innervation to the 1st and 2nd lumbricals of the hand.
The muscles of hypothenar eminence are from medial to lateral: Opponens digiti minimi; Flexor digiti minimi brevis; Abductor digiti minimi; The intrinsic muscles of hand can be remembered using the mnemonic, "A OF A OF A" for, Abductor pollicis brevis, Opponens pollicis, Flexor pollicis brevis (the three thenar muscles), Adductor pollicis, and the three hypothenar muscles, Opponens digiti ...
It also supplies the muscles of the thenar eminence by a recurrent thenar branch. [8] The rest of the intrinsic muscles of the hand are supplied by the ulnar nerve. The median nerve innervates the skin of the palmar (volar) side of the index finger, thumb, middle finger, and half the ring finger, and the nail bed.
Once in the hand, the nerve splits into a muscular branch and palmar digital branches. The muscular branch supplies the thenar eminence while the palmar digital branch supplies sensation to the palmar aspect of the lateral 3 + 1 ⁄ 2 digits and the lateral two lumbricals. [5]
The abductor pollicis brevis is a flat, thin muscle located just under the skin. It is a thenar muscle, and therefore contributes to the bulk of the palm's thenar eminence. It originates from the flexor retinaculum of the hand, the tubercle of the scaphoid bone, and additionally sometimes from the tubercle of the trapezium.
It is one of three thenar muscles. [1] [2] ... (as can the other muscles of the thenar eminence). [6] Additional images. The muscles of the left hand. Palmar surface ...