The thenar eminence is the mound formed at the base of the

thumb The thumb is the first digit of the hand, next to the index finger. When a person is standing in the medical anatomical position (where the palm is facing to the front), the thumb is the outermost digit. The Medical Latin English noun for thumb ...

on the palm of the hand by the intrinsic group of muscles of the thumb. The skin overlying this region is the area stimulated when trying to elicit a palmomental reflex. The word thenar comes .θέναρ
/ref>

Structure

The following three muscles are considered part of the thenar eminence: * Abductor pollicis brevis abducts the thumb. This muscle is the most superficial of the thenar group. *

Flexor pollicis brevis 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. Origin and insertion The muscle's superficial head arises from the distal edge of the ...

, which lies next to the abductor, will flex the thumb, curling it up in the palm. (The flexor pollicis longus, which is inserted into the distal phalanx of the thumb, is not considered part of the thenar eminence.) * Opponens pollicis lies deep to abductor pollicis brevis. As its name suggests it opposes the thumb, bringing it against the fingers. This is a very important movement, as most of human hand dexterity comes from this action. Another muscle that controls movement of the thumb is

adductor pollicis In human anatomy, the adductor pollicis muscle is a muscle in the hand that functions to Adduction, adduct the thumb. It has two heads: transverse and oblique. It is a fleshy, flat, triangular, and fan-shaped muscle deep in the Thenar eminence, ...

. It lies deeper and more distal to flexor pollicis brevis. Despite the name, adductor pollicis is chiefly responsible for rotation and opposition. This muscle is not in the thenar group of muscles, and is supplied by the

ulnar nerve The ulnar nerve is a nerve that runs near the ulna, one of the two long bones in the forearm. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest in the human body unprotected by muscle or ...

instead.

Nerve supply

The opponens pollicis and abductor pollicis brevis are normally innervated by the recurrent branch of the median nerve. The flexor pollicis brevis has two heads: a superficial and a deep head. The superficial head is usually innervated by the recurrent branch of the

median nerve The median nerve is a nerve in humans and other animals in the upper limb. It is one of the five main nerves originating from the brachial plexus. The median nerve originates from the lateral and medial cords of the brachial plexus, and has cont ...

. The deep part is often innervated by the

deep branch of ulnar nerve The deep branch of the ulnar nerve is a terminal, primarily motor branch of the ulnar nerve. It is accompanied by the deep palmar branch of ulnar artery. Structure It passes between the abductor digiti minimi and the flexor digiti minimi brevis ...

( C8 and T1 roots).

Gray's Anatomy ''Gray's Anatomy'' is a reference book of human anatomy written by Henry Gray, illustrated by Henry Vandyke Carter and first published in London in 1858. It has had multiple revised editions, and the current edition, the 42nd (October 2020 ...

37th British Edition, p. 630 There are normal variations. In a Cannieu-Riche anastomosis, fibers from the deep branch of ulnar nerve innervate the opponens pollicis and/or abductor pollicis brevis. Regardless of their final innervation, the nerves that reach the thenar muscles arise from the C8 and T1 roots, pass through the lower trunk of the

brachial plexus The brachial plexus is a network of nerves (nerve plexus) formed by the anterior rami of the lower four Spinal nerve#Cervical nerves, cervical nerves and first Spinal nerve#Thoracic nerves, thoracic nerve (cervical spinal nerve 5, C5, Cervical spi ...

, and then through the medial cord of the plexus. The adductor pollicis is typically innervated by the

. The ulnar nerve is exclusively responsible for the innervations of the hypothenar eminence. Both nerves contribute to the innervations of the midpalmar group. Print. The innervation of these muscles by the median nerve is unusual, as most of the intrinsic muscles on the palm of the hand are supplied by the ulnar nerve. The lateral two lumbrical muscles are the other exception.

Additional images

File:Slide8PPP.JPG, Thenar eminence File:Hand dissection 5.jpg, Carpal tunnel and thenar and hypothenar eminences File:Thenar eminence comparison anterior.jpg, Comparison, anterior File:Thenar eminence comparison posterior.jpg, Comparison, posterior File:Thenar eminence comparison thumbs.jpg, Comparison facing thumbs

References

External links

* {{DEFAULTSORT:Thenar Eminence Hand Muscles of the upper limb

Structure

Nerve supply

Additional images

See also

References

External links