Abductor pollicis brevis muscle
Encyclopedia
The abductor pollicis brevis is a muscle in the hand that functions as an abductor of the thumb
.
.
It originates from the flexor retinaculum of the hand
, the tubercle of the scaphoid bone, and additionally sometimes from the tubercle of the trapezium.
Running lateralward and downward, it is inserted by a thin, flat tendon into the lateral side of the base of the first phalanx of the thumb
and the capsule of the metacarpophalangeal joint
.
. C8/T1
and the metacarpophalangeal joint
.
It also assists in opposition and extension of the thumb.
Thumb
The thumb is the first digit of the hand. When a person is standing in the medical anatomical position , the thumb is the lateral-most digit...
.
Structure
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 eminenceThenar eminence
The thenar eminence refers to the group of muscles on the palm of the human hand at the base of the thumb...
.
It originates from the flexor retinaculum of the hand
Flexor retinaculum of the hand
The flexor retinaculum is a strong, fibrous band that arches over the carpus, converting the deep groove on the front of the carpal bones into a tunnel, the carpal tunnel, through which the Flexor tendons of the digits and the median nerve pass.It is attached, medially, to the pisiform and the...
, the tubercle of the scaphoid bone, and additionally sometimes from the tubercle of the trapezium.
Running lateralward and downward, it is inserted by a thin, flat tendon into the lateral side of the base of the first phalanx of the thumb
Thumb
The thumb is the first digit of the hand. When a person is standing in the medical anatomical position , the thumb is the lateral-most digit...
and the capsule of the metacarpophalangeal joint
Metacarpophalangeal joint
The metacarpophalangeal joints are of the condyloid kind, formed by the reception of the rounded heads of the metacarpal bones into shallow cavities on the proximal ends of the first phalanges, with the exception of that of the thumb, which presents more of the characters of a ginglymoid joint...
.
Innervation
The abductor pollicis brevis is innervated by the recurrent branch of the median nerveMedian nerve
The median nerve is a nerve in humans and other animals. It is in the upper limb. It is one of the five main nerves originating from the brachial plexus....
. C8/T1
Actions
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 jointCarpometacarpal joint
The carpometacarpal joints are five joints in the wrist that articulates the distal row of carpal bones and the proximal bases of the five metacarpal bones....
and the metacarpophalangeal joint
Metacarpophalangeal joint
The metacarpophalangeal joints are of the condyloid kind, formed by the reception of the rounded heads of the metacarpal bones into shallow cavities on the proximal ends of the first phalanges, with the exception of that of the thumb, which presents more of the characters of a ginglymoid joint...
.
It also assists in opposition and extension of the thumb.