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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]
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 can also be palpated in the volar (palmar) hand/wrist. Its position is the intersections of the long axes of the four fingers while in a fist, or the base of the thenar eminence. When palpated in this position, the bone will be felt to slide forward during radial deviation (wrist abduction) and flexion.
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 ...
6 Additional images. ... muscles of the thenar eminence). [6 ... public domain from page 461 of the 20th edition of Gray's Anatomy (1918) This page ...
Symptoms of Bennett fracture are instability of the CMC joint of the thumb, accompanied by pain and weakness of the pinch grasp. Characteristic signs include pain, swelling, and ecchymosis around the base of the thumb and thenar eminence, and especially over the CMC joint of the thumb.