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Thenar eminence: location, the thenar muscles and their nerve supply

Where is the thenar eminence?

Turn your palm up and look at the base of the thumb. The rounded mound there is the thenar eminence. Under the skin lie short muscles that move the thumb, stacked in layers, and their bulk makes the mound. The view below has one of these muscles selected: abductor pollicis brevis.

teamLabBody with the right abductor pollicis brevis (yellow) selected, palm view, with flexor pollicis brevis, opponens pollicis and adductor pollicis beside it
Abductor pollicis brevis, one of the thenar muscles (right hand, palm side)Screen from teamLabBody Pro, an anatomy app ›

The view above shows the right hand from the palm side. The yellow muscle is abductor pollicis brevis, the most superficial. Next to it are flexor pollicis brevis and opponens pollicis, and toward the middle of the palm the fan-shaped adductor pollicis. The mound at the base of the little finger is the hypothenar eminence; between the two lies the palmar aponeurosis.

The muscles

・Abductor pollicis brevis: most superficial; lifts the thumb away from the palm

・Flexor pollicis brevis: flexes the thumb at its base; has a superficial and a deep head

・Opponens pollicis: under abductor pollicis brevis; turns the thumb to face the fingers

・Adductor pollicis: deepest; draws the thumb toward the index finger; has an oblique and a transverse head

The first three arise from the flexor retinaculum and the nearby carpal bones (scaphoid and trapezium). Abductor and flexor pollicis brevis insert on the proximal phalanx of the thumb, while opponens pollicis inserts on the first metacarpal, which is why it can rotate the whole thumb. Adductor pollicis arises from the capitate and the second and third metacarpals and inserts on the proximal phalanx.

Counts differ between textbooks. Many English-language texts list three thenar muscles and treat adductor pollicis separately; Japanese textbooks usually include it and count four.

Nerve supply

teamLabBody showing the thenar muscles with the median nerve and its thenar branch, the flexor retinaculum and the hypothenar muscles
The thenar muscles with the median nerve, the flexor retinaculum and the hypothenar musclesScreen from teamLabBody Pro, an anatomy app ›

Abductor pollicis brevis, opponens pollicis and the superficial head of flexor pollicis brevis are supplied by the recurrent (thenar) branch of the median nerve, which leaves the nerve just beyond the carpal tunnel and curves back into the thenar muscles. Adductor pollicis and the deep head of flexor pollicis brevis are supplied by the deep branch of the ulnar nerve. Descriptions of the supply of flexor pollicis brevis vary slightly between textbooks.

Terms

Thenar refers to the base of the thumb; hypothenar to the little-finger side. Pollicis is Latin for of the thumb. The mound at the base of the big toe is the ball of the foot, a different structure with the same reading in Japanese (母趾球).

See it in the app

Four muscles overlap in a small space, so flat drawings hide the deeper ones. In the 3D anatomy app teamLabBody you can hide the superficial muscles one at a time and watch opponens pollicis and adductor pollicis appear. The app lists the two heads of flexor pollicis brevis and of adductor pollicis as separate parts.

FAQ

Where is the thenar eminence?
On the palm at the base of the thumb. It is the mound formed by the short thumb muscles.
How many thenar muscles are there?
Three in many English-language textbooks: abductor pollicis brevis, flexor pollicis brevis and opponens pollicis. Some texts add adductor pollicis and count four.
Which nerve supplies the thenar muscles?
Mainly the recurrent branch of the median nerve. Adductor pollicis and the deep head of flexor pollicis brevis are supplied by the ulnar nerve.

Related articles

・Abductor pollicis muscles: abductor pollicis brevis and longus

・Median nerve: gives the thenar branch beyond the carpal tunnel

・Ulnar nerve: supplies adductor pollicis

・Flexor retinaculum of the hand: origin of the thenar muscles

・Anatomy by body system

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