Intrinsic Muscles of the Hand PDF Winter 2025

Unit 1: Lecture 8 of 8 Intrinsic Muscles of the Hand MSAK 1 Lecture...

Unit 1: Lecture 8 of 8 Intrinsic Muscles of the Hand MSAK 1 Lecture Laurence Muir Readings: Muscolino T&D: sections 11.18 Course notes are created for exclusive use at WCCMT Victoria.  LESSON OBJECTIVES ❑Describe movements of the thumb and fingers ❑List the intrinsic muscles of the hand and their relative location ❑Discuss the Origin, Insertion, and Actions of the muscles ❑What is the extensor expansion? ❑Describe the anatomy and contents of the carpal tunnel Course notes are created for exclusive use at WCCMT Victoria.  Thumb Movements Course notes are created for exclusive use at WCCMT Victoria.  Midline of the hand is a line through the 3rd digit. Course notes are created for exclusive use at WCCMT Victoria.  Intrinsic Muscles of the Hand Course notes are created for exclusive use at WCCMT Victoria.  Intrinsic Muscles of the Hand Are muscles that originate/insert in the hand Act upon the fingers 3 hypothenar muscles 1 superficial muscle Attach onto flexor retinaculum Palmaris brevis and carpals then into 5th finger ABductor digiti minimi manus 3 thenar muscles Flexor digiti minimi manus Attach onto flexor retinaculum and Opponens digiti minimi carpals then into the thumb Abductor pollicis brevis 4 central compartment muscles Flexor pollicis brevis Deep layer of musculature Opponens pollicis Adductor pollicis Lumbricals manus Palmar interossei Dorsal interossei manus Course notes are created for exclusive use at WCCMT Victoria.  Palmaris Brevis Origin: Flexor retinaculum Palmar aponeurosis Insertion: Dermis of the ulnar border of hand Actions: Wrinkles the skin of the palm Thought to slightly contribute to strength/security of palmar grip Is superficial to the hypothenar eminence Course notes are created for exclusive use at WCCMT Victoria.  Intrinsic Muscles of the Hand “All For One And One For All” Orientation from lateral to medial: A: Abductor pollicis brevis (thenar) F: Flexor pollicis brevis (thenar) O: Opponens pollicis (thenar) A: Adductor pollicis (central) O: Opponens digiti minimi (hypothenar) F: Flexor digiti minimi manus (hypothenar) A: Abductor digiti minimi manus (hypothenar) Course notes are created for exclusive use at WCCMT Victoria.  Abductor Pollicis Brevis (2) (Most superficial of the 3 Thenar muscles) Origin: Tubercle of scaphoid Tubercle of trapezium Flexor retinaculum Insertion: Lateral side of base of proximal phalanx of thumb Dorsal digital expansion Actions: Abducts the thumb at CMC joint Flexes the thumb MCP joint Extends CMC and IP joint of thumb Course notes are created for exclusive use at WCCMT Victoria.  Flexor Pollicis Brevis (3) Origin: Trapezium Flexor retinaculum Insertion: Lateral side of base of proximal phalanx of thumb Actions: Flexes thumb at CMC and MCP joints Abducts thumb at CMC joint Sesamoid bone found in distal tendon Course notes are created for exclusive use at WCCMT Victoria.  Opponens Pollicis (1) (Deepest of the 3 Thenar Muscles) Origin: Tubercle of trapezium Flexor retinaculum Insertion: Anterior surface and radial border of 1st metacarpal Actions: Opposes thumb at the CMC joint Opposition is a combination of flexion, medial rotation, and abduction of the metacarpal of the thumb at the CMC joint Course notes are created for exclusive use at WCCMT Victoria.  Adductor Pollicis Origin: Transverse head: Metacarpal III Distal 2/3 anterior surface Oblique head: Capitate, anterior base of metacarpals II + III Insertion: Base of medial proximal phalanx I Dorsal digital expansion (oblique head) Actions: Adducts thumb at CMC joint Flexes the thumb at the CMC and MCP joints Extends the thumb at the IP joint Sesamoid bone found in tendon Course notes are created for exclusive use at WCCMT Victoria.  See it Feel it Say it ❖ Where is the thenar eminence? Do it Teach it ❖ What 3 muscles make up the thenar eminence? ❖ Can you name the 4th intrinsic muscles that acts upon the thumb? ❖ Where are you most likely to find sesamoid bones in the thumb? Course notes are created for exclusive use at WCCMT Victoria.  Opponens Digiti Minimi (Deepest of the 3 Hypothenar muscles) Origin: Hook of hamate Flexor retinaculum Insertion: 5th metacarpal Anterior surface and ulnar border Actions: Opposes little finger at CMC joint Opposition is a combination of flexion, lateral rotation, and adduction of the metacarpal of the little finger at the CMC joint Course notes are created for exclusive use at WCCMT Victoria.  Flexor Digiti Minimi Manus Origin: Hook of hamate Flexor retinaculum Insertion: 5th proximal phalanx Actions: Flexes digit V at MCP joint Flexes digit V at CMC joint Course notes are created for exclusive use at WCCMT Victoria.  Abductor Digiti Minimi Manus (Most superficial of the 3 Hypothenar muscles) Origin: Pisiform And tendon of flexor carpi ulnaris Insertion: Medial side of base of proximal phalanx of digit V Dorsal digital expansion Actions: Abducts digit V at the MCP joint Abducts digit V at the CMC joint Flexes the little finger at the MCP and CMC joints Extends the little finger at the PIP and DIP joints Course notes are created for exclusive use at WCCMT Victoria.  See it Feel it Say it Do it Teach it ❖ Where is the hypothenar eminence? ❖ Can you name the 3 muscles than make up the hypothenar eminence? Course notes are created for exclusive use at WCCMT Victoria.  Dorsal Digital Expansion (aka Extensor Expansion or Dorsal Hood or Extensor Hood) Course notes are created for exclusive use at WCCMT Victoria.  Dorsal Digital Expansion (aka Extensor Expansion or Dorsal Hood or Extensor Hood) Is a fibrous aponeurotic expansion of the extensor digitorum muscle Serves as a movable “hood” during finger flexion/extension Terminates into middle and distal phalanges on the dorsal aspect Any muscle attaching into the extensor expansion will cause finger extension at the PIP and DIP joints Course notes are created for exclusive use at WCCMT Victoria.  Lumbricals Manus (4) Origin: Distal tendons of flexor digitorum profundus in the palm Insertion: Lateral side of extensor expansion Actions: Flexes digits 2-5 at MCP joints Extend digits 2-5 at PIP and DIP joints Course notes are created for exclusive use at WCCMT Victoria.  Palmar Interossei (3) “PAD” Origin: Metacarpals II, IV, and V Insertion: Proximal phalanges (base and dorsal digital expansion) of digits II, IV, and V on the “middle finger side” Actions: ADduct fingers II, IV, and V toward middle finger at MCP joints Flex fingers II, IV, and V at MCP joint Extend fingers II, IV, and V at PIP and DIP joint Course notes are created for exclusive use at WCCMT Victoria.  Dorsal Interossei Manus (4) “DAB” Origin: Metacarpals I-V Insertion: Proximal phalanges (base and dorsal digital expansion) of digits II, III, IV on the side that faces away from the center of the middle finger Actions: ABduct fingers II-IV at MCP joints Flex fingers II-IV at MCP joints Extend fingers II-IV at PIP and DIP joints Course notes are created for exclusive use at WCCMT Victoria.  Bipennate fibers of Unipennate fibers of dorsal interossei palmar interossei DAB PAD Course notes are created for exclusive use at WCCMT Victoria.  Carpal Tunnel Transverse carpal ligament is part of the flexor retinaculum, and forms the roof of the tunnel. Lateral border is the scaphoid and trapezium. Medial border is the hamate and pisiform. Contains: median nerve 9 tendons of: flexor pollicis longus (1) flexor digitorum profundus (4) flexor digitorum superficialis (4) Course notes are created for exclusive use at WCCMT Victoria.  Tunnel of Guyon (Ulnar Tunnel) Fibro-osseous tunnel for ulnar nerve and ulnar artery Passes between hook of hamate and pisiform Roof made up of palmar carpal ligament and palmaris brevis Floor is transverse carpal ligament Compression here is much less common than carpal tunnel syndrome Course notes are created for exclusive use at WCCMT Victoria.  See it Feel it Say it Do it ❖ What is the function of the: Teach it ❖ Lumbricals manus ❖ Palmar interossei ❖ Dorsal interossei manus ❖ What forms the roof of the carpal tunnel? ❖ How many tendons run through the carpal tunnel? ❖ Can you name them? Course notes are created for exclusive use at WCCMT Victoria.  Arches of the Hand 3 Arches: Transverse Carpal Transverse Metacarpal @MCP joints Longitudinal Centered in 2nd and 3rd metacarpals Assist in grasping objects Course notes are created for exclusive use at WCCMT Victoria.  LESSON OBJECTIVES ❑Describe movements of the thumb and fingers ❑List the intrinsic muscles of the hand and their relative location ❑Discuss the Origin, Insertion, and Actions of the muscles ❑What is the extensor expansion? ❑Describe the anatomy and contents of the carpal tunnel Course notes are created for exclusive use at WCCMT Victoria.