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Image: “Intrinsic Muscles of the Hand” by Phil Schatz. License: CC BY 4.0
Muscles of the Hand
Many of the muscles that move the hand and fingers are reviewed in the Anatomy of the Upper Limb – Muscles of the Arm lecture.
The other muscles of the hand are divided into 3 groups: the intrinsics, the thenars, and the hypothenars.
Intrinsic muscles of the hand
Lumbricals
| Muscles | Origin | Insertion | Nerve supply | Function |
| Lumbricals (I-II) | Lateral two tendons of FDP (unipennate) | Lateral surfaces of extensor expansions of digits 2-5 | Median nerve (T1) | Flex metacarpophalangeal and extend interphalangeal joints of digits 2-5 |
| Lumbricals (III-IV) | Medial two tendons of FDP (bipennate) | Deep branch of ulnar nerve (T1) |
The lumbricals are four narrow muscle bellies which have no direct bony anchoring. They also stabilize the metacarpophalangeal joints and prevent an ulnar deviation.
Interossei muscles
| Muscle | Origin | Insertion | Nerve supply | Function |
| Dorsal interossei | Dorsal sides of all metacarpals (bipennate) | Base of proximal phalanges and extensor expansions (digits 2-4, dorsal; digits 2, 4 and 5, palmar) | Deep branch of ulnar nerve (T1) | Abduct digits 2-4 away from axial line |
| Palmar interossei | Palmar sides of metacarpals 2, 4 and 5 | Adduct digits 2, 4 and 5 toward axial line |
The radial artery passes through between the two heads of the dorsal interosseous muscle I. There are three palmar interossei muscles and they are one-headed and lie between the metacarpal bones.
Thenar muscles
| Muscles | Origin | Insertion | Nerve supply | Function |
| Opponens policis | Flexor retinaculum and tubercles of scaphoid and trapezium | Lateral side of first metacarpal | Recurrent branch of median nerve (C8) | Oppose thumb |
| Abductor pollicis brevis | Lateral side of proximal phalanx of digit 1 | Abducts thumb; supports opposition | ||
| Flexor pollicis brevis | Flexes thumb | |||
| Adductor pollicis | Oblique head: Base of second and third metacarpals and capitate Transverse head: anterior surface of third matacarpal |
Medial side of proximal phalanx of thumb | Deep branch of ulnar nerve (C8) | Adducts thumb |
Hypothenar muscles
| Muscles | Origin | Insertion | Nerve supply | Function |
| Palmaris brevis | Transverse carpal ligament and palmar aponeurosis | Ulnar palm | Ulnar nerve | Wrinkles the skin of the medial palm |
| Abductor digiti minimi | Pisiform | Medial side of proximal phalanx of fifth digit | Deep branch of ulnar nerve (T1) | Abducts fifth digit |
| Flexor digiti minimi brevis | Hook of hamate and flexor retinaculum | Flexes proximal phalanx of fifth digit | ||
| Opponens digiti minimi | Medial border of fifth metacarpal | Rotates and draws anteriorly fifth metacarpal |
Popular Exam Questions on the Muscles of the Thumb and Fingers
The solutions can be found below the references.
1. Which of the following structures does not serve as the origin of the extensor digitorum muscle?
- Lateral epicondyle humeri
- Radial collateral ligament
- Os hamatum
- Annular ligament of the radius
- Antebrachial fascia
2. Which of the following muscles does not belong to the group of thenar muscles?
- Abductor pollicis longus muscle
- Flexor pollicis brevis muscle
- Abductor pollicis brevis muscle
- Adductor pollicis muscle
- Opponens pollicis muscle
3. Which of the following muscles passes through the 3rd tendon compartment?
- Extensor pollicis longus muscle
- Extensor pollicis brevis muscle
- Abductor pollicis longus muscle
- Abductor pollicis brevis muscle
- Adductor pollicis muscle
