Extensor pollicis brevis muscle
Encyclopedia
In human anatomy
, the extensor pollicis brevis is a skeletal muscle
on the dorsal side of the forearm
. It lies on the medial side of, and is closely connected with, the abductor pollicis longus
.
distal to the abductor pollicis longus
, from the interosseous membrane
, and from the dorsal surface of the radius
.
Its direction is similar to that of the abductor pollicis longus, its tendon passing the same groove on the lateral side of the lower end of the radius, to be inserted into the base of the first phalanx of the thumb
.
and metacarpophalangeal joint
s.
Human anatomy
Human anatomy is primarily the scientific study of the morphology of the human body. Anatomy is subdivided into gross anatomy and microscopic anatomy. Gross anatomy is the study of anatomical structures that can be seen by the naked eye...
, the extensor pollicis brevis is a skeletal muscle
Skeletal muscle
Skeletal muscle is a form of striated muscle tissue existing under control of the somatic nervous system- i.e. it is voluntarily controlled. It is one of three major muscle types, the others being cardiac and smooth muscle...
on the dorsal side of the forearm
Forearm
-See also:*Forearm flexors*Forearm muscles...
. It lies on the medial side of, and is closely connected with, the abductor pollicis longus
Abductor pollicis longus muscle
The abductor pollicis longus muscle is one of the extrinsic muscles of the hand. It lies immediately below the supinator muscle and is sometimes united with it.-Origin and insertion:...
.
Origin and insertion
The extensor pollicis brevis arises from the radiusRadius
In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...
distal to the abductor pollicis longus
Abductor pollicis longus muscle
The abductor pollicis longus muscle is one of the extrinsic muscles of the hand. It lies immediately below the supinator muscle and is sometimes united with it.-Origin and insertion:...
, from the interosseous membrane
Interosseous membrane of the forearm
The interosseous membrane of the forearm is a fibrous sheet that connects the radius and the ulna...
, and from the dorsal surface of the radius
Radius (bone)
The radius is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna, which exceeds it in length and size. It is a long bone, prism-shaped and slightly curved longitudinally...
.
Its direction is similar to that of the abductor pollicis longus, its tendon passing the same groove on the lateral side of the lower end of the radius, to be inserted into 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...
.
Action
In a close relationship to the abductor pollicis longus, the extensor pollicis brevis both extends and abducts the thumb at the carpometacarpalCarpometacarpal 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 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...
s.