Hardly any other muscle group has so many small intricate complexes as those of the thumb and fingers and causes such a headache to medical students. And yet, the muscles and their functions can be very easily remembered on the basis of their denominations and the majority of them is innervated by the deep branch. It is, therefore, advisable for aspiring doctors to study with the help of mnemonics in order to be able to go relaxed into their next exam.
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Hands and Fingers

Image : “The front and back of a human right hand” by Evan-Amos. License: CC BY-SA 3.0

diese abbildung zeigt die muskeln die die hand bewegen

Image: “Titel” by philschatz. License: CC BY 4.0

Many of the muscles that move the hand and fingers are reviewed in the Anatomy of the Upper Limb – Muscles of the Arm article.

The other muscles of the hand are divided into 3 groups: the intrinsics, the thenars, and the hypothenars.

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 the ulnar nerve (T1)

The lumbricals are four narrow muscle bellies that 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 the ulnar nerve (T1) Abduct digits 2—4 away from the axial line
Palmar interossei Palmar sides of metacarpals 2, 4 and 5 Adduct digits 2, 4 and 5 toward the 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 pollicis Flexor retinaculum and tubercles of scaphoid and trapezium Lateral side of the first metacarpal Recurrent branch of the median nerve (C8) Oppose thumb
Abductor pollicis brevis Lateral side of proximal phalanx of digit 1 Abducts thumb; supports the opposition
Flexor pollicis brevis Flexes thumb
Adductor pollicis  Oblique head: Base of second and third metacarpals and capitate
Transverse head: anterior surface of the third metacarpal		 Medial side of proximal phalanx of thumb Deep branch of the 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 the fifth digit Deep branch of the ulnar nerve (T1) Abducts the fifth digit
Flexor digiti minimi brevis Hook of hamate and flexor retinaculum Flexes proximal phalanx of the fifth digit
Opponens digiti minimi Medial border of the fifth metacarpal Rotates and draws anteriorly fifth metacarpal

Review Questions

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?

  1. Lateral epicondyle humeri
  2. Radial collateral ligament
  3. Os hamatum
  4. Annular ligament of the radius
  5. Antebrachial fascia

2. Which of the following muscles does not belong to the group of thenar muscles?

  1. Abductor pollicis longus muscle
  2. Flexor pollicis brevis muscle
  3. Abductor pollicis brevis muscle
  4. Adductor pollicis muscle
  5. Opponens pollicis muscle

3. Which of the following muscles passes through the 3rd tendon compartment?

  1. Extensor pollicis longus muscle
  2. Extensor pollicis brevis muscle
  3. Abductor pollicis longus muscle
  4. Abductor pollicis brevis muscle
  5. Adductor pollicis muscle
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References plus_icon

Bayes, M. C. (2013). Hand and Fingers. Basics of Musculoskeletal Ultrasound,29-34. doi:10.1007/978-1-4614-3215-9_6.

Bell, C. (n.d.). Of the muscles of the arm and hand—Their vital action—Their mechanical adaptation to the motions of the hand and fingers—Form of the human hand. The Hand: Its Mechanism and Vital Endowments, as Evincing Design (7th Ed. Rev.).,81-93. doi:10.1037/12269-004.

Boscheinen-Morrin, J., & Conolly, W. B. (2001). The hand: Fundamentals of therapy. Oxford: Butterworth-Heinemann.

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