anatomy 12.1 pt 5

Actions of the extensor digitorum

Extends the wrist, Extends the MP joints, Extends the PIP joints, Extends the DIP joints of fingers 2–5.

Action of the extensor digiti minimi

Extends the little finger (finger 5) and assists in wrist extension.

Actions of the extensor carpi ulnaris

Extends the hand, Adducts the hand (ulnar deviation).

Muscles in the deep posterior forearm compartment (lateral to medial)

Supinator, Abductor pollicis longus, Extensor pollicis brevis, Extensor pollicis longus, Extensor indicis.

Primary action of the abductor pollicis longus

Abducts the thumb (and weakly extends the wrist).

Action of the extensor pollicis brevis

Extends the metacarpophalangeal (MP) joint of the thumb.

Actions of the extensor pollicis longus

Extends the MP joint of the thumb, Extends the IP joint of the thumb, Weakly extends the wrist.

Action of the extensor indicis

Extends the index finger (finger 2) at the MP, PIP, and DIP joints.

Intrinsic muscles of the hand

Small muscles whose origin and insertion are both within the hand.

Three groups of intrinsic muscles of the hand

Thenar group, Hypothenar group, Midpalmar group.

Formation of the thenar eminence

The thenar group at the base of the thumb.

Formation of the hypothenar eminence

The hypothenar group at the base of the little finger.

Muscles of the thenar group

Flexor pollicis brevis, Abductor pollicis brevis, Opponens pollicis.

Action of the flexor pollicis brevis

Flexes the thumb.

Action of the abductor pollicis brevis

Abducts the thumb.

Action of the opponens pollicis

Produces opposition of the thumb.

Muscles of the hypothenar group

Flexor digiti minimi brevis, Abductor digiti minimi, Opponens digiti minimi.

Action of the flexor digiti minimi brevis

Flexes the little finger.

Action of the abductor digiti minimi

Abducts the little finger.

Action of the opponens digiti minimi

Produces opposition of the little finger.

Muscle groups of the midpalmar region

Lumbricals, Dorsal interossei, Palmar interossei, Adductor pollicis.

Actions of the lumbricals

Flex the MP joints, Extend the PIP joints, Extend the DIP joints of fingers 2–5.

Actions of the dorsal interossei

Abduct fingers 2–5, Flex the MP joints, Extend the PIP and DIP joints.

Actions of the palmar interossei

Adduct fingers 2–5, Flex the MP joints, Extend the PIP and DIP joints.

Action of the adductor pollicis

Adducts the thumb.

Muscles producing hand (radial) abduction

Flexor carpi radialis, Extensor carpi radialis longus, Extensor carpi radialis brevis (Weakly: extensor indicis, extensor pollicis longus, extensor pollicis brevis, abductor pollicis longus).

Muscles producing hand (ulnar) adduction

Flexor carpi ulnaris, Extensor carpi ulnaris.

Muscles producing finger abduction

Dorsal interossei, Abductor pollicis longus, Abductor pollicis brevis, Abductor digiti minimi.

Muscles producing finger adduction

Palmar interossei, Adductor pollicis.

Mnemonic for actions of the interossei muscles

PAD-DAB: Palmar interossei ADduct, Dorsal interossei ABduct.