Forearm and Hand Flashcards
The posterior compartment consists of what major movements?
Extension and supination
Muscles of the posterior compartment are innervated by what nerve?
Radial Nerve
What are the superficial muscles of the posterior forearm?
Bracheoradialis, Extensor Carpi radialis longus, Extensor carpi radialis brevis, Extensor digitorum, Extensor digiti minimi, Extensor carpi ulnaris
Which posterior superficial forearm muscles are attached by a common extensor tendon to lateral epicondyle
Extensor carpi radialis brevis, Extensor digitorum, Extensor digiti minimi, Extensor carpi ulnaris
What is the function of the extensor retinaculum?
Holds tendons in place which prevents bowstringing during hyperextension
Identify this muscle: (posterior view)
Brachioradilais
Identify this muscle: (anterior view)
Brachioradialis
The brachioradialis forms of
lateral border of cubital fossa
Action of brachioradialis muscle
FLEXES forearm at elbow (exception muscle of posterior compartment). aka “handshake muscle”
Does not act on wrist joint
The brachioradialis is innervated by
Radial nerve (C5, C6, C7)
Identify the muscle: (posterior view)
Extensor Carpi Radialis Brevis
Action of the Extensor Carpi Radialis Brevis
- Extend and abduct wrist
- Indispensible when clenching fist (longus)
- Act with extensor carpi ulnaris to steady wrist during tight flexion of medial four digits
The Extensor Carpi Radialis Brevis is innervated by
Radial nerve (C7, C8)
Identify the muscle: (posterior view)
Extensor Carpi Radialis Longus
Action of the extensor carpi radialis longus
- Extend and abduct wrist
- Indispensible when clenching fist (longus)
- Act with extensor carpi ulnaris to steady wrist during tight flexion of medial four digits
The extensor carpi radialis longus is innervated by
Radial nerve (C6, C7)
The extensor carpi radialis longus and brevis tendons are crossed by what muscles
Deep muscles (abductor pollicis longus & extensor pollicis brevis)
Identify the muscle: (posterior view)
Extensor digitorum
Action of the extensor digitorum muscle
Principal extensor of the medial four digits at MCP
•Can help extend phalanges at IP joints via tendinous extensor expansions
The extensor digitorum muscle is innervated by
Radial nerve (C7, C8)
The extensor digitorum muscle splits into how many tendons at the extensor retinaculum?
4
How are the extensor digitorum tendons linked together?
Linked together by intertendinous connections
What is the function of intertendinous connections of the extensor digitorum tendons?
Restricts independent actions of fingers (especially ring finger); therefore, no digit can remain fully flexed as the other ones are fully extended
Identify the structure
Intertendinous connections of extensor digitorum
Distally, extensor digtorum tendons form over digits
extensor expansions “hood”
Identify the muscle: (posterior view)
Extensor digiti minimi
The belly of the extensor digiti minimi blends in with what muscle?
extensor digitorum
Does the tendon of the extensor digiti minimi run in the same compartment of the digitorum muscle?
No, number 5 in picture is extensor digiti minimi tendon and number 4 is the extensor digitorum muscle
Action of the extensor digiti minimi?
Extends proximal phalanx of 5th digit at MCP joint & assists with extension of it’s IP joints
The extensor digiti minimi is innervated by what nerve?
Radial nerve (C7, C8)
What is this structure?
extensor tendon
Identify the muscle: (posterior view)
Extensor carpi ulnaris
Action of the extensor carpi ulnaris
Extends and adducts hand at wrist joint when acting alone
Extends hand when acting with extensor carpi radialis
adducts hand when acting with flexor carpi ulnaris
indispensible when clenching fist
The extensor carpi ulanirs is innervated by what nerve?
Radial (C7, C8); because posterior compartment
What are the deep muscles of the posterior forearm?
- Abductor pollicis longus
- Extensor pollicis brevis
- Extensor pollicis longus
- Extensor indicis
- Supinator
What are the Outcropping muscles (muscles lie deep, but their tendons emerge superficially)
- Abductor pollicis longus
- Extensor pollicis brevis
- Extensor pollicis longus
Identify the muscle: (posterior view)
Abductor pollicis longus
Describe the abductor pollicis longus muscle
Emerges at wrist superficially (covers tendons of extensor carpi radialis muscles)
Forms lateral side of snuff box
Action of the abductor pollicis longus
Abducts and extends thumb at carpometacarpal joint
The abductor pollicis longus is innervated by
Radial nerve (C7, C8)
Identify the muscle: (posterior view)
Extensor pollicis brevis
Describe the extensor pollicis brevis
Emerges at wrist superifically (covers tendons of extensor carpi radialis muscles)
Lies on lateral side of snuff box
Action of the extensor pollicis brevis
Extends proximal phalanx of thumb at metacarpophalangeal joint and helps extend distal phalanx
innervation of extensor pollicis brevis
Radial nerve (C7, C8)
Identify the muscle: (posterior view)
Extensor Pollicis Longus
Describe the extensor pollicis longus muscle
Forms medial side of snuff box
Action of the extensor pollicis longus muscle
Extends distal phalanx of thumb at IP joint, and, in continued action, extends the metacarpophalangeal and interphalangeal joints
Also, adducts extended thumb & rotates laterally
Innervation of extensor pollicis longus muscle
Radial nerve (C7, C8)
The anatomical snuff box borders consists of what muscles?
- Extensor pollicis longus (medial)
- Extensor pollicis brevis (middle-ish)
- Abductor pollicis longus (lateral)
Identify the muscle: (posterior view)
Extensor Indicis
Action of the Extensor Indicis muscle
Confers independence to index finger. Therefore, extensor indicis can act alone OR act with extensor digitorum to extend index finger at PIP (“pointing”)
Innervation of the Extensor Indicis muscle
Radial nerve (C7, C8)