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)
Identify the muscle: (posterior view)

Supinator
Action of the supinator muscle
Prime mover for slow, unopposed supination esp. when forearm extended (rotates radius)
Does not act on wrist joint
Innervation of supinator muscle
Radial nreve (C5, C6)
Identify the nerve

Deep branch of radial nerve (motor) passes between muscle
Sensory innervation of pink area what nerve?

Radial nerve
Sensory innervation of purple area what nerve?

Medial Cutaneous nerve of forearm directly arises from medial cord
Sensory innervation of green area what nerve?

Lateral cutaneous nerve from Musculocutaneous nerve
Intrinsic muscles of the hand consist of what four groups?
- Thenar muscles
- Adductor pollicis
- Hypothenar muscles
- Short muscles of hand
Identify the muscle group

Thenar muscles
The thenar muscle group consists of what muscles?
Abductor pollicis brevis, flexor pollici brevis, opponens pollicis
Identify the muscle

Abductor pollicis brevis
Action of abductor pollicis brevis
abducts thumb at carpometacarpal joint & assist in opposition
most lateral muscle
Innervation of abductor pollicis brevis
Median nerve (C8, T1)
Identify the muscle

Flexor pollicis brevis
Action of Flexor pollicis brevis
Flexes thumb at carpometacarpal & MCP joints & aids in opposition
most medial
Innervation of flexor pollicis brevis
Median nerve (C8, T1)
Identify the muscle

opponens pollicis
Action of the opponens pollicis
Opposes thumb which is most important movement
located deep
Innervation of the opponens pollicis
Median nerve (C8, T1)
Identify the muscle

Flexor pollicis brevis
Identify the muscle

Adductor pollicis
Describe the adductor pollicis
Lies deep, Fan-shaped
Action of adductor pollicis
Adducts thumb (moves thumb to palm of hand); therefore, gives power to grip
Adductor pollicis innervated by
Ulnar nerve (C8, T1)
Identify the muscle group

Hypothenar muscles
The hypothenar muscles are all innervated by what nerve?
ulnar nerve (C8, T1)
The thenar muscles are all innervated by what nerve?
median nerve (C8, T1)
Identify the muscle

abductor digiti minimi
Action of abductor digiti minimi muscle
Abducts 5th digit
Abductor digiti minimi are innervated by
ulnar nerve (C8, T1)
Identify the muscle

Flexor digiti minimi (brevis)
Action of flexor digiti minimi (brevis)
Flexes proximal phalanx of 5th digit at MCP joint
Innervation of flexor digiti minimi (brevis)
ulnar nerve (C8, T1)
Identify the muscle

opponens digiti minimi
action of opponens digiti minimi
Draws 5th metacarpal bone anteriorly & rotates it laterally → deepening hollow of palm & bringing 5th digit into opposition with thumb
innervation of opponens digiti minimi
ulnar nerve (C8, T1)
Identify the muscle group

Short muscles of the hand: Lumbricals
The lumbricals consist of (describe muscles)
4 slender muscles that resemble worms (“lumbricus”= earthworm)
Lumbricals attach to
Tendons of Flexor digitorum profundus
Lateral sides of extensor expansions, so it will extend the phalanges

action of lumbricals
Flex digits at MCP joints & extends the IP joint
Innervation of lumbricals?
Median (1st & 2nd) nerve –C8, T1
ulnar (3rd & 4th) nerve – C8, T1
Identify the muscle group (anterior view)

3 palmar interosseous muscles
Action of palmar interosseous muscles
Adducts digits PAD (palmar adduct
Innervation of palmar interosseous muscles
Ulnar nerve (C8, T1)
Identify the muscle group (posterior view)

4 dorsal interosseous muscles
action of dorsal interosseous muscles
Abducts digits DAB (dorsal abduct)
Dorsal interosseous muscles are innervated by
Ulnar nerve (C8, T1)
Blue area indicates what sensory nerve?

Ulnar nerve
Yellow area indicates what sensory nerve?

Median
Pink area indicates what sensory nerve?

radial nerve
What nerve is commonly injured where nerve passes posterior to medial epicondyle?
ulnar nerve
Claw hand is an indication of injury to what nerve?
Ulnar nerve
Describe claw hand
Ulnar nerve may be injured with fracture to medial epicondyle of humerus
unable to flex 4th and 5th digits at DIP
difficulty with extending phalanges fully
MCP joints hyperextended
Pressure on the hook of hamate compresses what nerve?
Where is sensation lost?
Ulnar; sensory loss over medial half of hand and weak hand muscles
Handle bar neuropathy (extended hand against bike handle over long period of time)
Identify the muscle

Pronator teres
Pronator teres innervated by
median nerve (C6, C7)
Action of pronator teres
pronator of forearm and flexor of elbow joint
Identify the muscle

flexor carpi radialis
Flexor carpi radialis innervated by
median nerve (C6, C7)
Action of flexor carpi radialis
Flexion and adduction of wrist
Alone flexes and adducts so wrist moves anterolaterally
Identify the muscle

Flexor carpi ulnaris
Innervation of flexor carpi ulnaris
ulnar nerve (C7, C8)
Action of flexor carpi ulnaris
Alone flexes & adducts wrist simulataneously
Flexes wrist with flexor carpi radialis
adducts wrist with flexor extensor carpi ulnaris
Identify the muscle

Palmaris longus
Innervation of palmaris longus
median nerve (C7, C8)
Identify the muscle

Flexor digitorum superficialis
Identify the muscle

Flexor digitorum superficialis
Innervation of flexor digitorum superficialis
Median nerve (C7, C8, T1)
Action of flexor digitorum superficialis
Flexes middle phalanges of medial four digits at proximal interphalangeal joint (PIP)
Also, in cont. action, flexes proximal phalanges at MCP joints and wrist joint
Identify the muscle

Flexor digtorum profundus
Action of flexor digitorum profundus
Only muscle that can flex DIP joints of digits
Flexes distal phalanges of medial four digits after flexor digitorum superficialis has flexed their middle phalanges “curls fingers”
assists with flexion of hand- “making fist”
Innervation of flexor digitorum profundus
Lateral part (digits 2 & 3) median nerve (C8, T1)
Medial part (digits 4 & 5) ulnar nerve (C8, T1)
Identify the muscle

Flexor pollicis longus
Action of flexor pollicis longus
flexes the distal phalanx of 1st digit (thumb) at IP joint
Innervation of flexor pollicis longus
median nerve (C8, T1)
Identify the muscle

Pronator quadratus
Action of pronator quadratus
Pronates forearm
Initiates pronation; assisted by pronator teres when more speed or power needed
Innervation of pronator quadratus
median nerve (C8, T1)