2. The muscles that act on the hand can be divided into two groups:
Extrinsic muscles
located in the anterior and
posterior compartments of the
forearm. They control crude
movements and produce a forceful
grip.
Intrinsic muscles
located within the hand itself.
They are responsible for the
fine motor functions of the
hand.
3. Thenar Muscles
The thenar muscles are three short
muscles located at the base of the
thumb. The muscle bellies produce a
bulge, known as the thenar
eminence. They are responsible for
the fine movements of the thumb.
4. Thenar
Muscles
1. Opponens
Pollicis
Origin Tubercle of trapezium bone, flexor
retinaculum
Insertion Radial border of metacarpal bone 1
Action Carpometacarpal joint 1: Thumb
opposition
Innervation Recurrent branch of median nerve(C8,
T1)
Blood
supply
Superficial palmar branch of radial
artery
Action
5. Abductor pollicis brevis
Origin Tubercles of scaphoid and trapezium
bones, Flexor retinaculum
Insertion Lateral aspect of base of proximal
phalanx 1 (via radial sesamoid bone)
Action Carpometacarpal joint 1: Thumb
abduction
Innervation Recurrent branch of median nerve (C8,
T1)
Blood
supply
Superficial palmar branch of radial
artery
6. Flexor pollicis brevis
Origin Superficial head: Flexor retinaculum, tubercle of
trapezium bone
Deep head: Trapezoid and capitate bones
Insertion Lateral aspect of base of proximal phalanx 1 (via
radial sesamoid bone)
Action Carpometacarpal and metacarpophalangeal joint
1: Thumb flexion
Innervation Superficial head: Recurrent branch of median
nerve
Deep head: Deep branch of ulnar nerve (C8, T1)
Blood supply Superficial palmar artery, princeps pollicis artery
and radialis indicis artery
7. Adductor pollicis muscle
Origin Transverse head: Palmar base of
metacarpal bone 3
Oblique head: Capitate bone, palmar
bases of metacarpal bones 2 & 3
Insertion Medial base of proximal phalanx 1 (via
ulnar sesamoid bone)
Action Carpometacarpal joint 1: Thumb
adduction
Innervatio
n
Deep branch of ulnar nerve (C8, T1)
Blood
supply
Deep palmar arch
8. Hypothenar Muscles
The hypothenar muscles form
the hypothenar eminence – a muscular
protrusion on the medial side of the
palm, at the base of the little finger.
These muscles are similar to the thenar
muscles in both name and organisation.
The ulnar nerve innervates the muscles
of the hypothenar eminence.
9. Opponens Digiti
Minimi
Origin Hook of hamate bone, flexor
retinaculum
Insertion Ulnar aspect of metacarpal bone 5
Action Carpometacarpal joint 5: Finger flexion,
finger lateral rotation/opposition
Innervation Deep branch of ulnar nerve (C8, T1)
Blood
supply
Deep palmar branch of ulnar artery,
deep palmar arch
10. Abductor Digiti
Minimi
Origin Pisiform bone (Pisohamate ligament,
Tendon of flexor carpi ulnaris)
Insertion Ulnar side of base of proximal phalanx
of digit 5, Extensor expansion of digit 5
Action Metacarpophalangeal joint 5: Finger
abduction and flexion;
Interphalangeal joints: Finger extension
Innervation Deep branch of ulnar nerve (C8, T1)
Blood
supply
Palmar branch of ulnar artery, palmar
digital artery, superficial palmar arch
11. Flexor digiti minimi
brevis
Origin Hook of hamate, flexor retinaculum
Insertion Base of proximal phalanx of digit 5
Action Metacarpophalangeal joint 5: Finger
flexion (+ finger lateral
rotation/opposition)
Innervation Deep branch of ulnar nerve (C8, T1)
Blood
supply
Deep palmar branch of ulnar artery
12. Lumbricals
There are four lumbricals in the hand, each associated
with a finger. They are very crucial to finger movement,
linking the extensor tendons to the flexor tendons.
Denervation of these muscles is the basis for the ulnar
claw and hand of benediction.
•Attachments: Each lumbrical originates from a tendon of
the flexor digitorum profundus. They pass dorsally and
laterally around each finger, and inserts into the extensor
hood.
•Actions: Flexion at the MCP joint and extension at the
interphalangeal (IP) joints of each digit.
•Innervation: The lateral two lumbricals (of the index and
middle fingers) are innervated by the median nerve. The
medial two lumbricals (of the little and ring fingers) are
innervated by the ulnar nerve.
13. INTEROSSEI
The interossei muscles are located between the
metacarpal bones of the hand. They can be divided into
two groups – dorsal and palmar.
In addition to their actions of abduction (dorsal interossei)
and adduction (palmar interossei) of the fingers, the
interossei also assist the lumbricals in flexion at the MCP
joints and extension at the IP joints.
Dorsal Interossei
The most superficial of all dorsal muscles, these can be
palpated on the dorsum of the hand. There are four dorsal
interossei muscles.
•Attachments: Each interossei originates from the lateral
and medial surfaces of the metacarpals. They attach into
the extensor hood and proximal phalanx of each finger.
•Actions: Abduction of the digits. Assists in flexion at the
metacarpophalangeal joints and extension at the
interphalangeal joints.
•Innervation: Ulnar nerve.
14. PALMAR INTEROSSEI
These are located anteriorly on the hand. There are three
palmar interossei muscles (although some texts describe
a fourth muscle at the base of the proximal phalanx of the
thumb).
•Attachments: Each interossei originates from a medial or
lateral surface of a metacarpal, and attaches into the
extensor hood and proximal phalanx of same finger.
•Actions: Adduction of the digits. Assists in flexion at the
metacarpophalangeal joints and extension at the
interphalangeal joints.
•Innervation: Ulnar nerve.
15. Other Muscles in the Palm
There are two other muscles in the palm that are not lumbricals or interossei and do not fit in the
hypothenar or thenar compartments:
Palmaris Brevis
The palmaris brevis is a small, thin muscle, found
superficially in the subcutaneous tissue of the
hypothenar eminence.
•Attachments: Originates from the palmar
aponeurosis and flexor retinaculum, attaches to the
dermis of the skin on the medial margin of the
hand.
•Actions: Wrinkles the skin of the hypothenar
eminence and deepens the curvature of the hand,
improving grip.
•Innervation: Ulnar nerve.
16. ADDUCTOR POLLICIS
The adductor pollicis large triangular muscle with two
heads. The radial artery passes anteriorly through the
space between the two heads, forming the deep palmar
arch.
•Attachments: One head originates from metacarpal III.
The other head originates from the capitate and adjacent
areas of metacarpals II and III. Both attach into the base
of the proximal phalanx of the thumb.
•Actions: Adductor of the thumb.
•Innervation: Ulnar nerve.
