Intrinsic Muscles Flashcards
What are the muscles of the thenar eminence
> flexor pollicis brevis
abductor pollicis brevis
opponens pollicis
adductor pollicis
What are the muscles of the hypothenar eminence
> abductor digiti minimi
flexor digiti minimi
Opponens digiti minimi
Palmaris brevis
What are the intermediate muscles of the hand
> Dorsal interossei (4)
Palmar interossei (4)
Lumbricals (4)
Flexor Pollicis Brevis
- Position: most medial of thenar eminence
- Origin: Superficial head: flexor retinaculum
: trapezium
: Deep head: Trapezoid
: Capitate - Insertion: Radial base of proximal phalanx of thumb (involved with sesamoid bone)
- Action: Flexion of MCP joint of thumb
: assists flexion of CMC joint of thumb
: assists medial rotation of thumb - Innervation: Superficial: Median Nerve T1
: Deep: Ulnar nerve T1
Abductor Pollicis Brevis
- Position: most lateral + superficial of thenar muscles
- Origin: Flexor retinaculum
: Scaphoid
: Trapezium - Insertion: Radial base of proximal phalanx of thumb
- Action: abduction at CMC + MCP joints of thumb
- Innervation: Median Nerve T1
Opponens Pollicis
- Position: deep, covered by both FPB + AbPB
- Origin: flexor retinaculum
: trapezium - Insertion: whole lateral 1/2 of anterior 1st metacarpal
- Action: Opposition of thumb (abd, med rot, flex, add)
- Innervation: Median Nerve T1
Adductor Pollicis
- Position: Web space of thumb
- Origin: Oblique head: Tendon of FCR
: bases of metacarpals 2-3
: trapezoid
: capitate
: Transverse head: anterior shaft of 3rd MC - Insertion: Medial base of proximal phalanx of thumb
(associated with sesamoid bone) - Action: Strong adductor of thumb
- Innervation: Ulnar nerve C8-T1
Abductor Digiti Minimi
- Position: most superficial
- Origin: Pisiform
: Pisohamate ligament
: Pisometacarpal ligament
: Tendon of flexor capir ulnaris - Insertion: Ulna side of proximal phalanx of little finger
: (slip to extensor hood of little finger) - Action: Abducts little finger
: flexion at mcp joint of little finger - Innervation: Ulnar nerve T1
Flexor digiti Minimi
- Position: lateral to ADM
- Origin: hook of hamate
: flexor retinaculum - Insertion: base of proximal phalanx of little finger
- Action: flexes MCP of little finger
- Innervation: Ulnar nerve T1
Opponens digiti minimi
- Position: Deep to ADM
- Origin: hook of hamate
: flexor retinaculum - Insertion: palmar shaft of 5th MC
- Action: Opposition of 5th digit
- innervation: Ulnar nerve T1
Palmaris Brevis
- Origin: Flexor retinaculum
: Palmar aponeurosis
- Insertion: skin of palm into dermis
- Action: steadies + corrugates skin of palm to aid grip
- Innervation: Ulnar nerve C8-T1Dorsal Interossei
DAB
- abduct digits 2-4
- assists flexion of MCP of digits 2-4 (+ limit hyperextension)
- assists extension of PIP/DIP of digits 2-4
- Important for grip
- Innervated by Ulnar nerve C8-T1
- 2 points of insertion then insert on to medial/lateral side of own MC
- 1 + 5 have own powerful abductors
- middle finger can be abducted in either direction as has 2 dorsal interossei
Palmar Interossei
PADD
- Actions: Adduct digits 1,2,4,5
(middle finger has 2 dorsal interossei so doesn’t need a palmar one)
: assists flexion of MCP of digits 1,2,4,5
: assists extension of PIP/DIP of digits 2,4,5
(via insertion into extensor hood)
* single point of origin from metacarpal base
- Innervation: Ulnar nerve C8-T1
Lumbricals
- Origin: digits 2+3 = unipennate (single origin) from lateral edge of own FDP tendon
: digits 4+5 = bipennate (two origins) from lateral edge of own FDP tendon and medial edge of lateral FDP tendon - Insertion: lateral edge of extensor hood
- Action: flexion of MCP of digits 2-5
: extension of PIP/DIP of digits 2-5 - Innervation: Index + Middle = median C7-8
: Ring + little = ulnar C7-8
