Abductor pollicis longus muscle
Encyclopedia
The abductor pollicis longus muscle (APL) is one of the extrinsic muscles of the hand
. It lies immediately below the supinator muscle
and is sometimes united with it.
below the insertion of the Anconæus, from the interosseous membrane
, and from the middle third of the dorsal surface of the body of the radius
.
Passing obliquely downward and lateralward, it ends in a tendon, which runs through a groove on the lateral side of the lower end of the radius, accompanied by the tendon of the Extensor pollicis brevis, and is inserted into the radial side of the base of the first metacarpal bone.
It occasionally gives off two slips near its insertion: one to the greater multangular bone and the other to blend with the origin of the Abductor pollicis brevis.
, which is a continuation of the deep branch of the radial nerve
after it passes through the supinator muscle
. The posterior interosseous nerve
is derived from spinal segments C7 & C8.
, thereby moving the thumb anteriorly.
By its continued action it helps to abduct
the wrist.
Hand
A hand is a prehensile, multi-fingered extremity located at the end of an arm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs...
. It lies immediately below the supinator muscle
Supinator muscle
In human anatomy, the supinator is a broad muscle in the posterior compartment of the forearm, curved around the upper third of the radius. Its function is to supinate the forearm.-Terminology:...
and is sometimes united with it.
Origin and insertion
It arises from the lateral part of the dorsal surface of the body of the ulnaUlna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...
below the insertion of the Anconæus, from the interosseous membrane
Interosseous membrane
An interosseous membrane is a broad and thin plane of fibrous tissue that separates many of the bones of the body. It is an important component of many joints.Interosseous membranes in the human body:* Interosseous membrane of the forearm...
, and from the middle third of the dorsal surface of the body of the radius
Radius
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...
.
Passing obliquely downward and lateralward, it ends in a tendon, which runs through a groove on the lateral side of the lower end of the radius, accompanied by the tendon of the Extensor pollicis brevis, and is inserted into the radial side of the base of the first metacarpal bone.
It occasionally gives off two slips near its insertion: one to the greater multangular bone and the other to blend with the origin of the Abductor pollicis brevis.
Innervation
The abductor pollicis longus muscle is innervated by the posterior interosseous nervePosterior interosseous nerve
The posterior interosseous nerve is a nerve in the forearm. It is the continuation of the deep branch of the radial nerve, after this has crossed the supinator muscle. It is considerably diminished in size compared to the deep branch of the radial nerve...
, which is a continuation of the deep branch of the radial nerve
Radial nerve
The radial nerve is a nerve in the human body that supplies the upper limb. It supplies the medial and lateral heads of the triceps brachii muscle of the arm, as well as all 12 muscles in the posterior osteofascial compartment of the forearm and the associated joints and overlying skin.It...
after it passes through the supinator muscle
Supinator muscle
In human anatomy, the supinator is a broad muscle in the posterior compartment of the forearm, curved around the upper third of the radius. Its function is to supinate the forearm.-Terminology:...
. The posterior interosseous nerve
Posterior interosseous nerve
The posterior interosseous nerve is a nerve in the forearm. It is the continuation of the deep branch of the radial nerve, after this has crossed the supinator muscle. It is considerably diminished in size compared to the deep branch of the radial nerve...
is derived from spinal segments C7 & C8.
Action
The chief action of abductor pollicis longus is to abduct the thumb at 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....
, thereby moving the thumb anteriorly.
By its continued action it helps to abduct
Abduction (kinesiology)
Abduction, in functional anatomy, is a movement which draws a limb away from the median plane of the body. It is thus opposed to adduction.-Upper limb:* of arm at shoulder ** Supraspinatus** Deltoid* of hand at wrist...
the wrist.
Variations
More or less doubling of muscle and tendon with insertion of the extra tendon into the first metacarpal, the greater multangular, or into the Abductor pollicis brevis or Opponens pollicis.See also
- Anatomical snuffbox
- Extensor pollicis longusExtensor pollicis longus muscleIn human anatomy, the extensor pollicis longus is a skeletal muscle located dorsally on the forearm. It is much larger than the extensor pollicis brevis, the origin of which it partly covers, and acts to stretch the thumb together with this muscle....