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The muscles allow for flexion, extension, adduction, abduction and opposition of the thumb. The muscles acting on the thumb can be divided into two groups: The extrinsic hand muscles, with their muscle bellies located in the forearm, and the intrinsic hand muscles, with their muscles bellies located in the hand proper.
Abduction of the thumb is defined as the movement of the thumb anteriorly, a direction perpendicular to the palm. The abductor pollicis brevis does this by acting across both the carpometacarpal joint and the metacarpophalangeal joint. It also assists in opposition and extension of the thumb.
The flexor pollicis longus (/ ˈ f l ɛ k s ər ˈ p ɒ l ɪ s ɪ s ˈ l ɒ ŋ ɡ ə s /; FPL, Latin flexor, bender; pollicis, of the thumb; longus, long) is a muscle in the forearm and hand that flexes the thumb. It lies in the same plane as the flexor digitorum profundus.
Abduction is an anatomical term of motion referring to a movement which draws a limb out to the side, away from the median sagittal plane of the body. It is thus opposed to adduction . Upper limb
(The flexor pollicis longus, which is inserted into the distal phalanx of the thumb, is not considered part of the thenar eminence.) Opponens pollicis lies deep to abductor pollicis brevis. As its name suggests it opposes the thumb, bringing it against the fingers. This is a very important movement, as most of human hand dexterity comes from ...
Cutaneous innervation of the upper limbs is the nerve supply to areas of the skin of the upper limbs (including the arm, forearm, and hand) which are supplied by specific cutaneous nerves. Modern texts are in agreement about which areas of the skin are served by which cutaneous nerves, but there are minor variations in some of the details.
An accessory abductor pollicis longus (AAPL) tendon is present in more than 80% of people, and a separate muscle belly is present in 20% of people. In one study, the accessory tendon was inserted into the trapezium (41%); proximally on the abductor pollicis brevis (22%) and opponens pollicis brevis (5%); had a double insertion on the trapezium and thenar muscles (15%); or the base of the first ...
The lateral portion supplies a short, stout branch to certain of the muscles of the ball of the thumb, viz., the abductor pollicis brevis, the opponens pollicis, and the superficial head of the flexor brevis, and then divides into three proper palmar digital nerves of median nerve (proper volar digital nerves):