Thenar and Hypothenar Muscles Of The Hand

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Introduction

Thenar and Hypothenar eminence

The complex integrity of the human hand is one of the factors that set our spices apart from the primates. The movement of opposition played an important role in the human evolution and this was made possible as more muscles go to the thumb in modern humans than our ancestral primates. Although the muscles of the human hand and forearm are found in one or more extant non –human primates, it is the combination of such what makes up for the uniqueness. 

In this article, Thenar and Hypothenar muscles of the hands will be discussed.

Description

When the human hand is viewed from the palmar side, 2 'fleshy' mounds can be noted.

• Thenar eminence - fleshy part at the base of the thumb, made of 3 muscles which control the thumb movements.
• Hypothenar eminence - fleshy part at the base of the fifth digit (little finger), made of 4 muscles which contract to manifest motion through the little finger.

The muscles of the thenar and the hypothenar eminence along with the addcutor compartment make up the intrinsic muscles of the hands as their origin and insertion is within the carpal and metacarpal bones, ligaments, and fascia of the hand. They help with fine motor movements of the hands.

The extrinsic muscles of the hand originate outside the hand, commonly the forearm, and insert into hand structures.

Thenar Eminence (TE) Muscles

File:Thenar Eminence.jpg

Thenar Muscles

The muscles of the TE are -

• Opponens Pollicis the largest of the 3 muscles

Origin - at the tubercle of the trapezium

Insertion - lateral margin of the metacarpal of the thumb

Nerve - recurrent branch of the median nerve.

Artery - Superficial palmar arch from the radial artery

Function - perform opposition by flexing and medially rotating the metacarpal on the axis of the trapezium.

• Abductor Pollicis Brevis positioned anteriorly to the opponens pollicis

Origin - tubercles of the scaphoid and trapezium

Insertion - lateral aspect of the proximal phalanx of the thumb.

Nerve - recurrent branch of the median nerve.

Artery - Superficial palmar arch from the radial artery

Function - primary muscle providing opposition. Also leads to abduction of the thumb which is drawing the thumb away from the midline

• Flexor Pollicis Brevis

Origin - tubercle of the trapezium via the deep head, and the associated flexor retinaculum via the superficial head

Insertion - lateral aspect of the proximal phalanx of the thumb.

Nerve - dual innervation with fibers from both the median ( superficial head) and ulnar ( deep head) nerves

Artery - branches of the radial artery; superficial palmar artery, branches of the princeps pollicis artery and radialis indicis artery.

Function - flexion at the metacarpophalangeal and carpometacarpal joints leading to opposition of the thumb and, if continued, produces the medial rotation of thumb.

Hypothenar Eminence (HE) Muscles

The HE muscles are -

• Opponens Digiti Minimi

Origin - the hook of hamate and associated transverse carpal ligament

Insertion - lateral aspect of the proximal phalanx of the thumb.

Nerve - Deep branch of ulnar nerve (C8, T1)

Artery - Ulnar artery

Function - flex and laterally rotate the 5th metacarpal about the 5th carpometacarpal joint.

• Abductor digiti minimi

Origin - pisiform bone and the tendon of flexor carpi ulnaris

Insertion - the ulnar base of the proximal phalanx of the small finger

Nerve - Deep branch of ulnar nerve (C8, T1)

Artery - Ulnar artery

Function - abduction of the 5th finger, as well as flexion of its proximal phalanx

• Flexor digiti minimi brevis

Origin - the hook of hamate and associated transverse carpal ligament

Insertion - the base of the proximal phalanx of the small finger

Nerve - Deep branch of ulnar nerve (C8, T1)

Artery - Ulnar artery

Function - flexes the little finger at the metacarpophalangeal joint

• Palmaris brevis 

Origin - the transverse carpal ligament

Insertion - on the skin of the medial palm

Nerve - Deep branch of ulnar nerve (C8, T1)

Artery - Ulnar artery

Function - tenses the skin of the palm on the ulnar side during a grip action and deepens the hollow of the palm.