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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]
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 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] The other two muscles that influences movement of the thumb are the adductor pollicis and the first dorsal interosseous muscle.
The intrinsic muscle groups are the thenar and hypothenar (little finger) muscles; the interossei muscles (four dorsally and three volarly) originating between the metacarpal bones; and the lumbrical muscles arising from the deep flexor (and which are special because they have no bony origin) to insert on the dorsal extensor hood mechanism.
Motor function tests focus on examining the use of the thenar muscles within the hand most affected by median nerve injury. Common functional tests include the evaluation of grip and pinch strength using dynamometry and gross and fine motor coordination ability using the Purdue pegboard, 9-hole peg test, and other assessment tools.
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.
The opponens pollicis is a small, triangular muscle in the hand, which functions to oppose the thumb. It is one of the three thenar muscles . It lies deep to the abductor pollicis brevis and lateral to the flexor pollicis brevis .
In human anatomy, the adductor pollicis muscle is a muscle in the hand that functions to adduct the thumb. It has two heads: transverse and oblique. It is a fleshy, flat, triangular, and fan-shaped muscle deep in the thenar compartment beneath the long flexor tendons and the lumbrical muscles at the center of the palm.