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Intrinsic Muscles of Hand (Thenar Muscles (Abductor pollicis brevis (I:…
Intrinsic Muscles of Hand
Thenar Muscles
Abductor pollicis brevis
I: Lateral side of base of proximal phalanx of thumb
A: abducts thumb; helps oppose it
O: Flexor retinaculum and tubercles of scaphoid and trapezium
Flexor pollicis brevis
Superficial head
Deep head
I: Lateral side of base of proximal phalanx of thumb
A: Flexes Thumb
O: Flexor retinaculum and tubercles of scaphoid and trapezium
Opponens pollicis
I: lateral side of 1st metacarpal
A: oppose thumb, draws 1st metacarpal medially to center of palm and rotates it medially
O: Flexor retinaculum and tubercles of scaphoid and trapezium
Adductor pollicis
oblique head
I: Medial side of base of proximal phalanx of thumb
A: adducts thumb toward lateral border of palm
O: Bases of 2nd and 3rd metacarpals, capitate, and adjacent carpals
Transverse head
O: Anterior surface of shaft of 3rd metacarpal
I: medial side of base of proximal phalanx of thumb
Adducts thumb toward lateral border of thumb
Hypothenar Muscles
Flexor digiti minimi
I: Medial border of 5th metacarpal
A: Flexes proximal phalanx of 5th digit
O: Hook of hamate and flexor retinaculum
Opponens digiti
I: Medial border of 5th metacarpal
A: Draws 5th metacarpal anterior and rotates it, bringing 5th digit into opposition with thumb
O: Hook of hamate and flexor retinaculum
Abductor digiti minimi
I: Medial side of base of proximal phalanx of 5th digit
A: Abducts 5th digit; assists in flexion of its proximal phalanx
O: Pisiform
Short Muscles
Dorsal Interossei, 1st-4th
I: Bases of proximal phalanges; extensor expansions of 2nd to 4th digits
A: Abducts 2nd to 4th digits from axial line; act with lumbricals in flexing MCP joints and extending the IP joints
O: Adjacent sides of two metacarpals (as bipennate msucles)
Palmar Interossei, 1st-3rd
I: Base of proximal phalanges; extensor expansions of 2nd, 4th, and 5th digits
A: Adducts 2nd, 4th, and 5th digits toward axial line; assists lumbricals in flexing MCP joints and extending IP joints; extensor expansions of 2nd to 4th digits
O: Palmar surfaces of 2nd, 4th, and 5th metacarpals (as unipennate muscles)
Lumbricals
1st and 2nd
I: Lateral sides of extensor expansions of 2nd to 5th digits
A: Flex the MCP joints; extend the IP joints of 2nd to 5th digits
O: lateral two tendons of flexor digitorum profundus
3rd and 4th
I: lateral sides of extensor expansions of 2nd to 5th digits
A: Flex the MCP joints; extend the IP joints of 2nd to 5th digits
O: medial three tendons of flexor digitorum produndus