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The thenar muscles are a group of four intrinsic muscles of the thumb. They include the abductor pollicis, adductor pollicis, opponens pollicis, and flexor pollicis brevis. The recurrent branch of the median nerve, which typically arises distal to the carpal tunnel, supplies these muscles. The abductor pollicis brevis, opponens pollicis, and flexor pollicis brevis muscles are all innervated by the recurrent branch of the median nerve. Thumb movement is made possible by the coordination of these intrinsic muscles.
| Characteristics | Values |
|---|---|
| Definition | The four thenar muscles make up the intrinsic muscles of the thumb. |
| Types | Abductor pollicis, adductor pollicis, opponens pollicis, and flexor pollicis brevis. |
| Function | Thumb motion is facilitated through the coordination of these intrinsic muscles. |
| Innervation | The recurrent branch of the median nerve. |
| Nerve Roots | C8 and T1. |
| Exceptions | In a Cannieu-Riche anastomosis, fibers from the deep branch of the ulnar nerve innervate the opponens pollicis and/or abductor pollicis brevis. |
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What You'll Learn
- The thenar muscle is one of the four intrinsic muscles of the thumb
- The recurrent branch of the median nerve supplies the thenar muscles
- The abductor pollicis brevis muscle is also involved with the thenar muscles
- The adductor pollicis is another muscle that controls the movement of the thumb
- The hypothenar muscles are similar to the thenar muscles in name and organisation
The thenar muscle is one of the four intrinsic muscles of the thumb
The hypothenar muscles, which are similar to the thenar muscles in name and organisation, form the hypothenar eminence, a muscular protrusion on the medial side of the palm at the base of the little finger. The palmaris brevis is a small, thin muscle found superficially in the subcutaneous tissue of the hypothenar eminence. It improves grip by deepening the curvature of the hand and wrinkling the skin of the hypothenar eminence. The abductor digiti minimi is the most superficial of the hypothenar muscle group and abducts the little finger.
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The recurrent branch of the median nerve supplies the thenar muscles
The thenar muscles are a group of four intrinsic muscles of the thumb. These include the abductor pollicis, adductor pollicis, opponens pollicis, and flexor pollicis brevis. Thumb movement is facilitated through the coordination of these intrinsic muscles.
The recurrent branch of the median nerve is a small motor branch of the median nerve in the hand that supplies the thenar muscles. It usually arises distal to the flexor retinaculum and the carpal tunnel, and then curls proximally and laterally around the distal border of the ligament to supply the thenar muscles. The recurrent branch of the median nerve is also referred to as the thenar branch of the median nerve or the thenar muscular branch of the median nerve.
The recurrent branch of the median nerve provides motor innervation to the thenar muscles, which are associated with fine movements of the thumb. These muscles include the abductor pollicis brevis, opponens pollicis, and the larger superficial head of the flexor pollicis brevis. The recurrent branch of the median nerve may be affected by carpal tunnel syndrome or peripheral neuropathies.
The origin of the recurrent branch of the median nerve can vary within the population, with two recognised variations. The first variation, sub-ligamentous, arises within the carpal tunnel and courses underneath the flexor retinaculum before reaching the thenar muscles. The second variation, trans-ligamentous, arises within the carpal tunnel and pierces the flexor retinaculum to reach the thenar muscles.
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The abductor pollicis brevis muscle is also involved with the thenar muscles
The thenar muscles are a group of three or four muscles located within the hand. They form an elevation on the radial (lateral) aspect of the palm, known as the thenar eminence. These muscles are responsible for fine motor functions and thumb movement. The three muscles are: abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis. However, some sources include the adductor pollicis as a fourth thenar muscle.
The abductor pollicis brevis is the most lateral and superficial of the thenar muscles. It is located directly superior to the opponens pollicis and flexor pollicis brevis muscles. It originates from the tubercles of the scaphoid and trapezium carpal bones and the flexor retinaculum, attaching to the lateral aspect of the proximal phalanx of the thumb.
The abductor pollicis brevis muscle is responsible for the abduction of the thumb at the carpometacarpal and metacarpophalangeal joints. This movement occurs in synergy with the abductor pollicis longus muscle. The abductor pollicis brevis also facilitates the movement of the thumb towards the fingertips in the carpometacarpal joint (opposition) and flexion in the metacarpophalangeal joint.
The abductor pollicis brevis muscle is innervated by the recurrent (thenar) branch of the median nerve (root value C8 and T1). It is vascularized by the superficial palmar branch, which arises from the radial artery. The radial artery runs across the superficial aspect of the abductor pollicis brevis.
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The adductor pollicis is another muscle that controls the movement of the thumb
The thenar muscle group is made up of four muscles that control the movement of the thumb. These are the abductor pollicis, adductor pollicis, opponens pollicis, and flexor pollicis brevis. The adductor pollicis is a large, triangular, intrinsic muscle of the hand, with two heads: the oblique head and the transverse head.
The adductor pollicis muscle is found in the thenar region of the hand, but it is the sole muscle of the adductor compartment of the hand and does not form part of the thenar muscle group. It is a fleshy, flat, and fan-shaped muscle, located deep in the thenar compartment beneath the long flexor tendons and the lumbrical muscles at the center of the palm. It overlies the metacarpal bones and the interosseous muscles.
The two heads of the adductor pollicis originate from different locations. The transverse head originates from the palmar base of the third metacarpal bone, while the oblique head originates from the capitate bone and the palmar bases of the second and third metacarpals. The two heads then merge as the fibers travel laterally, forming the tendon of the adductor pollicis, which often contains a sesamoid bone. The muscle ends in a tendon that inserts into the base of the first proximal phalanx, as well as its extensor hood.
The adductor pollicis is the most powerful of the intrinsic muscles of the hand. Its main function is the adduction of the thumb, which is the movement of the thumb towards the index finger from an abducted position. This action is essential for functions that require pinching and gripping. The adductor pollicis also aids in the later stages of opposition of the thumb, which is a combination of adduction, medial rotation, flexion, and adduction of the thumb so that it can touch each fingertip of the same hand.
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The hypothenar muscles are similar to the thenar muscles in name and organisation
The human hand is a complex structure, with its unique anatomy setting our species apart from other primates and animals. The thenar muscles are three short muscles located at the base of the thumb, forming a bulge known as the thenar eminence. These muscles are responsible for the fine movements of the thumb and include the abductor pollicis, adductor pollicis, opponens pollicis, and flexor pollicis brevis. Thumb motion is facilitated through the coordination of these intrinsic muscles.
Both the thenar and hypothenar muscles are intrinsic muscles of the hand, located within the hand itself and responsible for fine motor functions. They are innervated by the median nerve and the ulnar nerve, respectively. The ulnar nerve is particularly important for the hypothenar muscles, as compromise at the Guyon's canal can cause weakness in finger abduction and adduction, flexion, and extension. Similarly, Carpal Tunnel Syndrome (CTS) can lead to thenar muscle wasting due to median nerve compromise.
The complex interplay of these muscles and their respective nerve innervations contribute to the unique dexterity of the human hand, setting us apart from other species. Understanding the anatomy of these muscles is vital for surgical procedures and physiotherapy interventions aimed at optimising hand function.
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Frequently asked questions
The four thenar muscles are the intrinsic muscles of the thumb. They include the abductor pollicis, adductor pollicis, opponens pollicis, and flexor pollicis brevis.
The thenar muscles are associated with fine movements of the thumb and facilitate thumb motion through the coordination of the intrinsic muscles.
The thenar muscles are innervated by the recurrent branch of the median nerve, which is a small motor branch of the median nerve in the hand.
The thenar muscles are associated with the thumb, while the hypothenar muscles form the hypothenar eminence, a muscular protrusion on the medial side of the palm at the base of the little finger.
