Flexor pollicis brevis muscle
Encyclopedia
The flexor pollicis brevis is a muscle in the hand that flexes the thumb. It is one of three thenar muscles. It has both a superficial part and a deep part.
and the tubercle of the trapezium
, a bone in the wrist. It passes along the radial side of the tendon of the flexor pollicis longus
, and, becoming tendon
ous, is inserted into the radial side of the base of the proximal phalanx
of the thumb
; in its tendon of insertion there is a sesamoid bone.
The deeper (and medial) portion of the muscle is very small, and arises from the ulna
r side of the first metacarpal bone between the oblique part of the adductor pollicis
and the lateral head of the first dorsal interosseous muscle
, and is inserted into the ulnar side of the base of the first phalanx with the adductor pollicis.
The deep (medial) part of the flexor brevis pollicis is sometimes described as the first palmar interosseous muscle
. When this muscle is included, the total number of palmar interossei is four. Otherwise, there are only three palmar interossei.
(C8, T1). The deep part is often innervated by the deep branch of the ulnar nerve
.
Origin and insertion
The muscle's superficial part arises from the distal edge of the flexor retinaculumFlexor 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...
and the tubercle of the trapezium
Trapezium
The word trapezium has several meanings:* - a quadrilateral with one pair of parallel sides ....
, a bone in the wrist. It passes along the radial side of the tendon of the flexor pollicis longus
Flexor pollicis longus muscle
The flexor pollicis longus is a muscle in the forearm and hand that flexes the thumb...
, and, becoming tendon
Tendon
A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other...
ous, is inserted into the radial side of the base of the proximal phalanx
Phalanx bones
In anatomy, phalanx bones are those that form the fingers and toes. In primates such as humans and monkeys, the thumb and big toe have two phalanges, while the other fingers and toes consist of three. Phalanges are classified as long bones.The phalanges do not have individual names...
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...
; in its tendon of insertion there is a sesamoid bone.
The deeper (and medial) portion of the muscle is very small, and arises from the ulna
Ulna
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...
r side of the first metacarpal bone between the oblique part of the adductor pollicis
Adductor pollicis muscle
In human anatomy, the adductor pollicis muscle is a muscle in the hand that functions to adduct the thumb. It has two heads: transverse and oblique....
and the lateral head of the first dorsal interosseous muscle
Dorsal interossei of the hand
The dorsal interossei of the hand are muscles that occupy the space between the metacarpals.-Structure:There are four dorsal interossei in each hand...
, and is inserted into the ulnar side of the base of the first phalanx with the adductor pollicis.
The deep (medial) part of the flexor brevis pollicis is sometimes described as the first palmar interosseous muscle
Palmar interossei muscles
The palmar interossei are small muscles in the hand that lie on the anterior aspect of the metacarpals. They are smaller than the dorsal interossei of the hand, which lie between the metacarpals.-Structure:...
. When this muscle is included, the total number of palmar interossei is four. Otherwise, there are only three palmar interossei.
Innervation
The flexor pollicis brevis is mostly 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). The deep part is often innervated by the deep branch of the ulnar nerve
Ulnar nerve
In human anatomy, the ulnar nerve is a nerve which runs near the ulna bone. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest unprotected nerve in the human body , so injury is common...
.