Alec Titan
The thumb is controlled by nine skeletal muscles located in the hand and forearm. These muscles allow for flexion, extension, adduction, abduction, and opposition of the thumb. The extensor pollicis longus (EPL) is one of the deep forearm extensors that controls the movement of the thumb. The EPL muscle is an extrinsic thumb muscle that extends and adducts the thumb metacarpophalangeal (MCP) and interphalangeal (IP) joints. The abductor pollicis brevis and adductor pollicis muscles, which are attached to the EPL tendon, can also extend the thumb's interphalangeal joint to the neutral position.
| Characteristics | Values |
|---|---|
| Muscle Extending the Thumb | Extensor pollicis longus |
| Alternative Names | EPL, Extensor pollicis brevis, Abductor pollicis longus, Flexor pollicis longus |
| Muscle Group | Extrinsic thumb muscles |
| Muscle Belly Location | Forearm |
| Function | Extension of the thumb at the metacarpophalangeal and interphalangeal joints |
| Innervation | Posterior interosseous nerve, continuation of the deep branch of the radial nerve |
| Blood Supply | Anterior interosseous artery, posterior interosseous artery, radial artery, ulnar artery |
| Tendon Length | 6.7 to 9.7 centimetres |
| Tendon Sheath | Synovial sheath |
| Variants | Rare, with a prevalence of 1% |
Explore related products
What You'll Learn
Extensor pollicis longus
The extensor pollicis longus (EPL) is a skeletal muscle located on the dorsal surface of the forearm. It is one of the extrinsic thumb muscles, along with the extensor pollicis brevis, abductor pollicis longus, and flexor pollicis longus. The EPL is much larger than the extensor pollicis brevis, the origin of which it partly covers and works together with to stretch the thumb.
The EPL arises from the dorsal surface of the ulna and the interosseous membrane, near the origins of the abductor pollicis longus and extensor pollicis brevis. It passes through the third tendon compartment, moving through a narrow, oblique groove on the back of the lower end of the radius. The EPL then crosses the wrist close to the dorsal midline before turning towards the thumb, using Lister's tubercle on the distal end of the radius as a pulley.
The EPL tendon is associated with pathologies such as stenosing tenosynovitis and spontaneous tendon rupture. These conditions may be linked to medical comorbidities like rheumatoid arthritis or trauma, such as distal radius fractures. The EPL tendon can also become inflamed or rupture, leading to a condition known as "drummer's paralysis," commonly seen in individuals who repeatedly stress their wrists, including drummers, sculptors, blacksmiths, or waiters.
The main function of the EPL is to extend the thumb at the metacarpophalangeal and interphalangeal joints. It is the only muscle that can achieve full hyperextension at the interphalangeal joint. Additionally, when the thumb is fully extended or abducted, the EPL assists in adduction. The EPL also contributes to the supination of the forearm and the extension and abduction of the wrist joint.
Measuring Muscle Stiffness: Techniques for Understanding Your Body
You may want to see also
Explore related products
Extensor pollicis brevis
The extensor pollicis brevis originates from the posterior surface of the radius, below the origin of the extensor pollicis longus. The origin area extends to the adjacent interosseous membrane. The muscle then runs downwards towards the wrist, ending in a tendon proximally to the wrist. This tendon passes deep through the extensor retinaculum and between the tendons of the abductor pollicis longus and extensor carpi radialis longus. After passing under the retinaculum, the tendon moves laterally to insert onto the dorsal surface of the base of the proximal phalanx of the thumb.
The extensor pollicis brevis is a deep extensor of the thumb, lying deep to the extensor digitorum muscle. It is involved in extending the thumb in the carpometacarpal and metacarpophalangeal joints, as well as in the extension and abduction of the wrist joint. This movement is crucial in the anatomy of grip, allowing for the release of objects. The EPB is innervated by the posterior interosseous nerve, a continuation of the deep branch of the radial nerve (C7 and C8).
In terms of blood supply, the extensor pollicis brevis receives blood from the posterior interosseous artery and perforating branches from the anterior interosseous artery, which are both branches of the common interosseous artery. The common interosseous artery arises from the ulnar artery, just below the tuberosity of the radius.
Massage Therapy: Friend or Foe to Muscle Strength?
You may want to see also
Explore related products
Abductor pollicis longus
The abductor pollicis longus (APL) is a muscle found in the posterior compartment of the forearm. It is one of the five deep extensors in the forearm, along with the supinator, extensor pollicis brevis, extensor pollicis longus, and extensor indicis. The abductor pollicis longus is an extrinsic muscle of the hand, and its primary function is to abduct the thumb at the carpometacarpal joint, allowing the thumb to move anteriorly. It also assists in extending and rotating the thumb, abducting the wrist, and flexing the hand.
The abductor pollicis longus is innervated by the posterior interosseous nerve (C7, C8), which is a continuation of the deep branch of the radial nerve. The radial nerve originates from the posterior cord of the brachial plexus. The blood supply to the abductor pollicis longus comes from the interosseous branches of the ulnar artery, with the proximal part of the muscle supplied by the lateral branch of the posterior interosseous artery and the distal part vascularised by a perforating branch of the anterior interosseous artery.
The abductor pollicis longus originates from the posterior surface of the proximal half of the radius, ulna, and intervening interosseous membrane, just inferior to the insertion of the anconeus muscle. The muscle then courses inferolaterally towards the radial side of the hand, becoming more superficial as it enters the distal third of the forearm. Near the wrist, the muscle gives off a narrow tendon, which passes through a groove on the lateral surface of the distal end of the radius, accompanied by the tendon of the extensor pollicis brevis. The abductor pollicis longus tendon then passes beneath the extensor retinaculum.
The abductor pollicis longus tendon forms the lateral border of the anatomical snuff box, a triangular space found at the base of the thumb, distal and posterior to the styloid process of the radius. The margins of this space are completed by the extensor pollicis longus and brevis, while the floor is comprised of the scaphoid and trapezium bones. The abductor pollicis longus tendon crosses the radial artery, along with the tendons of the extensor pollicis brevis and longus.
Reversing Muscle Atrophy: Is It Possible?
You may want to see also
Explore related products
Flexor pollicis longus
The flexor pollicis longus (FPL) is a muscle in the forearm and hand that flexes the thumb. It is unique to humans, being either rudimentary or absent in other primates. It is classified as an extrinsic muscle of the hand because, although it lies in the forearm, its function is seen in thumb movement.
The flexor pollicis longus arises from a broad area on the radius and adjacent structures, crosses three joints, and finally inserts onto the distal phalanx of the thumb. It originates from the mid-half of the anterior surface of the radius and the adjacent half of the interosseous membrane. Its origin point often also includes the adjacent anterior surface of the interosseous membrane and/or the lateral border of the coronoid process of the ulna. The muscle tapers into a flat tendon near the wrist and inserts into the base of the distal phalanx of the thumb on the palmar surface.
The main function of the flexor pollicis longus is flexion of the thumb at the interphalangeal joint, which is essential for gripping. It is the only muscle that flexes the interphalangeal joint of the thumb, making it vital for activities that require hand gripping.
The flexor pollicis longus is supplied by the anterior interosseous (C8-T1) branch of the median nerve (C5-T1). It receives dual blood supply: its medial part is supplied by the anterior interosseous artery, an indirect branch of the ulnar artery, and its lateral part receives blood from the radial artery. The flexor pollicis longus may also receive contributions from the median artery if the muscle is well-developed.
TENS Units: Muscle Development or Relaxation?
You may want to see also
Explore related products
Intrinsic thumb muscles
The muscles of the thumb are nine skeletal muscles located in the hand and forearm. The muscles are responsible for flexion, extension, adduction, abduction, and opposition of the thumb. The muscles acting on the thumb are divided into two groups: extrinsic hand muscles and intrinsic hand muscles. The extrinsic hand muscles have their muscle bellies located in the forearm, while the intrinsic hand muscles have their muscle bellies located in the hand.
The intrinsic thumb muscles are further divided into two groups: the thenar eminence and other muscles. The thenar eminence refers to the group of muscles on the palm at the base of the thumb. The three muscles composing the thenar eminence are the abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis. The abductor pollicis brevis originates on the scaphoid tubercle and the flexor retinaculum, and it inserts into the radial sesamoid bone and the proximal phalanx of the thumb. It is innervated by the median nerve (C8 and T1). The flexor pollicis brevis is a two-headed muscle, with the superficial head arising on the flexor retinaculum and the deep head originating from three carpal bones: the trapezium, trapezoid, and capitate. The muscle is inserted onto the radial sesamoid bone of the metacarpophalangeal joint, allowing it to flex, adduct, and abduct the thumb. The opponens pollicis originates on the tubercle of the trapezium and the flexor retinaculum and is inserted onto the radial side of the first metacarpal. It opposes the thumb and assists in adduction.
The other two muscles that influence thumb movement are the adductor pollicis and the first dorsal interosseous muscle. The adductor pollicis has two heads: a transversal head and an oblique head. The transversal head originates along the entire third metacarpal bone, while the oblique head originates from the carpal bones proximal to the third metacarpal. The adductor pollicis lies deeper and more distal to the flexor pollicis brevis. Despite its name, its main action is rotation and opposition rather than adduction. The first dorsal interosseous, one of the central muscles of the hand, extends from the base of the thumb metacarpal to the radial side of the proximal phalanx of the index finger.
How HDH Influences Muscle Growth and Performance
You may want to see also
Frequently asked questions
The extensor pollicis longus (EPL) muscle is the primary muscle responsible for extending the thumb at the metacarpophalangeal and interphalangeal joints.
The extensor pollicis longus muscle is a deep muscle of the forearm that controls the movement of the thumb, allowing for extension, abduction, and adduction of the thumb.
Yes, the extensor pollicis brevis muscle works in conjunction with the extensor pollicis longus to fully extend and abduct the thumb. Additionally, the abductor pollicis brevis and adductor pollicis muscles, which attach to the extensor pollicis longus tendon, can extend the thumb's interphalangeal joint to a neutral position.
The extrinsic thumb muscles are the EPL (extensor pollicis longus), extensor pollicis brevis, abductor pollicis longus, and flexor pollicis longus. These muscles are located in the forearm and contribute to various movements of the thumb.
