Human Anatomy Vol 1

Fig. 9.18: Dupuytren's contracture

Feolures

The intrinsic muscles of the hand serve the function of
adjustingthe hand during grippingand also for carrying
out fine skilled movements. The origin and insertion of
these muscles is within the territory of the hand.

There are 20 muscles in the hand. These are:
'I. a. Three muscles of thenar eminence

i. Abductor pollicis brevis (Fig. 9.19).

ii. Flexor pollicis brevis.

iii. Opponens pollicis.

b. One adductor ofthumb: Adductor pollicis.

Flexor retinaculum

Tubercle of scaphoid

Abductor pollicis brevis

Flexor pollicis brevis

Opponens pollicis

Crest of trapezium

Adductor pollicis (oblique head)

Opponens pollicis

Abductor pollicis brevis

and flexor pollicis brevis

Adductor pollicis and first

palmar interosseous

Adductor pollicis (transverse head)

FOREARM AND HAND

2 Four Lrypothenar muscles

i. Palmaris brevis.

ii. Abductor digiti minimi.

iii. Flexor digiti minimi (Fig. 9.20).

iv. Opponens digiti minimi (Fig.9.22).

Muscles (ii) to (iv) are muscles of hypothenar

eminence.

3 Four lumbricals (Fig. 9.21).

4 Four palmar interossei (Figs 9.23 and9.24b).

5 Four dorsal interossel (Figs 9.23 and 9.24a).

These muscles are described in Tables 9.5 and9.6.

Actions of Thenor Muscles

Lr studying the actions of the thenar muscles, it must

be remembered that the movements of the thumb take

place in planes at right angles to those of the other digits

because the thumb (first metacarpal) is rotated medially

through 90 degrees. Flexion and extension of the thumb

take place in the plane of the palm; while abduction

and adduction at right angles to the plane of palm.

Movement of the thumb across the palm to touch the

other digits is known as "opposition". This movement

is a combination of flexion and medial rotation.

Aclions of Dorso! lnlerossei

All dorsal interossei cause abduction of the digits away

from the line of the middle finger. This movement

Palmaris longus

Palmaris brevis

Pisiform bone

Abductor digiti minimi

Flexor digiti minimi

Opponens digiti minimi

Hook of hamate

Opponens digiti minimi

Abductor digiti minimi and

flexor digiti minimi

Fig. 9.19: The origin and insertion of the

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and hypothenar muscles (n