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Questions and Answers
Which muscle is responsible for adducting the thumb?
Which nerve supplies the thenar eminence muscles?
Which muscle is responsible for flexing the metacarpophalangeal joint of the thumb?
Which muscle is responsible for abducting the little finger?
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Which muscle is responsible for opposing the little finger?
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Which muscle is responsible for flexing the little finger?
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Which structure does the flexor retinaculum attach to?
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Which nerve supplies the cutaneous innervation of the nail bed?
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Which muscle is responsible for pulling the 5th metacarpal forward, cupping the palm?
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What is the effect on the thumb muscles if there is a fracture at the base of the 1st metacarpal bone?
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Study Notes
Anatomy of the Hand Muscles
- Thenar eminence skin supplied by the superficial branch of the radial nerve
- Group of small muscles includes:
- Palmaris brevis
- Lumbrical muscles (4)
- Interossei muscles (3 palmar, 4 dorsal)
Palmaris Brevis
- Origin: Flexor retinaculum, palmar aponeurosis
- Insertion: Skin of the palm
- Nerve Supply: Superficial branch of the ulnar nerve
- Action: Corrugates skin to enhance grip
Lumbricals
-
Origin:
- 1st and 2nd from the flexor digitorum profundus (lateral side of index and middle tendon)
- 3rd and 4th from adjacent sides (middle, ring, little fingers)
- Insertion: Extensor expansion
-
Nerve Supply:
- 1st and 2nd lumbricals by the median nerve
- 3rd and 4th lumbricals by the deep branch of the ulnar nerve
-
Action:
- Flexion of metacarpophalangeal joints (MPJ)
- Extension of interphalangeal joints (IPJ)
Interossei Muscles
- Origin: Between the metacarpal bones
- Nerve Supply: Deep branch of the ulnar nerve
-
Action:
- Palmar interossei: Adduction of fingers towards the third finger
- Dorsal interossei: Abduction of fingers away from the third finger
- Both types assist with flexing MPJ and extending IPJ
Carpal Tunnel Syndrome (CTS)
- Caused by:
- Edema of flexor tendons
- Fractures or dislocations of carpal bones
- Fibrosis/thickening of the flexor retinaculum
- Symptoms: Severe burning pain and numbness along median nerve distribution
- Motor Affection: Paralysis of thenar muscles and first/second lumbricals
- Sensory Affection: No sensory loss due to palmar cutaneous branch passing superficial to the flexor retinaculum
- Management: Decompressing the tunnel via a longitudinal incision through the flexor retinaculum
Anatomical Snuff Box
- Triangular skin depression on the lateral side of the wrist visible when the thumb is abducted and extended
-
Boundaries:
- Laterally: Abductor pollicis longus (AbPL) and extensor pollicis brevis (EPB)
- Medially: Extensor pollicis longus (EPL)
- Floor: Scaphoid bone
- Clinical Importance: Site to palpate the pulse of the radial artery
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Description
Test your knowledge on the muscles and nerve supply of the hand, including details on muscles such as Palmaris brevis, lumbrical muscles, interossei muscles, and more. Learn about the origin, insertion, nerve supply, and actions of these important hand muscles.
