Anatomy: Nerves and Muscles Flashcards
Long thoracic nerve innervates
serratus anterior –> holds scapula to thorax
Damage to long thoracic nerve
winged scapula
Suprascapular nerve
infraspinatus –> external rotation
supraspinatus –> abducts arm
Lateral pectoral nerve
pectoralis major –> flexion, adduction, and medial rotation
Upper subscapular nerve
subscapularis –> internal rotation
Thoracodorsal nerve
latissimus dorsi –> extension, adduction, transverse extension, flexion from an extended position and internal rotation
Lower subscapular nerve
teres major –> medial rotation and adduction
Musculocutaneous nerve
biceps, coracobrachialis, and brachialis –> major flexors of arm
Axillary nerve
deltoid –> abduction
teres minor –> lateral rotation of the humerus
Radial nerve
triceps and extensors –> extend forearm
Medial nerve
pronators and thenar muscles –> pronate the arm
Ulnar nerve
flexor carpi ulnaris, interosseus, hypothenar –> flex and adduct the hand
Major function of muscles innervated by radial nerve
extend forearm, wrist, and fingers
Sensation provided by radial nerve
posterior arm, dorsal side of hand
Muscles innervated by radial nerve
BEST - brachioradialis, extensors, supinator, triceps brachii
Key pathologic finding with radial nerve injury
wrist drop
Pathology that occurs with compression of radial nerve against spiral groove of the humerus
Saturday night palsy –> wrist drop, difficulty straightening fingers, numbness on the back of the hand and posterior arm
What nerve is damaged with fracture to the shaft of the humerus?
radial nerve
What muscles are innervated by the ulnar nerve?
hypothenar muscles –> control hand and 5th digit
3rd and 4th lumbricals –> flex at MCP and extend at IP joints
Interosseous –> abducts and adducts digits
Adductor pollicis –> adducts thumb
What areas are provided with sensation by the ulnar nerve?
5th digit and half of 4th digit
medial side of palm and dorsal hand
What does damage to the proximal ulnar nerve cause? (i.e. fracture of medial epicondyle)
loss of flexion of the wrist and digits
-looks like pt is make the OK sign with digits 1-3
What does damage to the distal ulnar nerve cause? (i.e. fractured hook of hamate)
Ulnar claw - MCP joint hyperextension and IP joint flexion at 4th and 5th digits
What deficits can be seen with ulnar nerve injury?
loss of sensation to half of 4th digit and 5th digit, weak abduction and adduction of digits, hypothenar wasting
What is the major function of the muscles innervated by the median nerve?
flexion and pronation
What muscles are innervated by the median nerve?
pronator teres and pronator quadratus –> pronate hand
flexor carpi radialis and palmaris longus –> flex forearm
flexor digitorum superficialis and lateral half of flexor digitorum profundus –> flex wrist and digits
flexor pollicis longus –> flexes thumb
1st and 2nd lumbricals –> flex MCP joints and extend IP joints
What sensation is provided by the median nerve?
lateral palm and first 3 1/2 digits
What pathology is seen with median nerve injury at the elbow?
Ape hand - loss of thumb abduction
What pathology is seen with median nerve injury above the elbow?
Hand of benediction - loss of flexion of the 2nd and 3rd digits
What pathology is seen with entrapment of the median nerve under the flexor retinaculum?
Carpal tunnel syndrome - numbness of the first 3 1/2 digits
-can also be damaged with suicide attempt by slitting wrists
What muscles are innervated the musculocutaneous nerve?
coracobrachialis, biceps, and brachialis –> flex and supinate forearm
What sensation is provided by the musculocutaneous nerve?
sensation to the lateral side of the forearm
What pathology is seen with damage to the musculocutaneous nerve?
decreased flexion and supination of forearm
What muscles are innervated by the axillary nerve?
deltoid –> abducts shoulder
long head of triceps –> extends forearm
teres minor –> externally rotates arm
What sensation is provided by the axillary nerve?
lateral shoulder
What pathology can be seen with injury of the axillary nerve?
loss of abduction + weak flexion, extension and rotation of shoulder
loss of sensation to lateral shoulder
What types of injury are associated with damage to the axillary nerve?
dislocation of the shoulder
fracture of the surgical neck of the humerus
What artery runs with the axillary nerve and can be damaged with fracture of the surgical neck of the humerus?
posterior circumflex artery
What muscle is innervated by the long thoracic nerve?
Serratus anterior –> holds scapula to the thorax
What pathology is associated with damage to the long thoracic nerve?
winged scapula
-due to blow to the neck or shoulder or after radical mastectomy
What deficit is seen with damage to the upper trunk of the brachial plexus?
Erb palsy (Waiter’s tip) - arm hangs by side, is medially rotated, arm extended and pronated
What types of injury cause Erb palsy?
infants - lateral traction on neck during delivery, adults - trauma
What nerves are damaged with injury to the upper trunk?
suprascapular - infraspinatus, supraspinatus
musculocutaneous - biceps brachii
axillary - deltoid
-roots C5 and C6
What deficits are seen with damage to the lower trunk of the brachial plexus?
Klupke’s palsy - total claw hand
- lumbricals can’t flex MCP joints and can’t extend DIP and PIP joints
- lose sensation to inner hand, inner forearm
What types of injury cause Klumpke’s palsy?
infants - upward force on arm during delivery, adults - grabbing onto a tree branch to break fall
What nerves are damaged in Klumpke’s palsy?
C8-T1 roots
-primarily damage to ulnar nerve
What is thoracic outlet syndrome?
compression of lower trunk and subclavian vessels –> results in same presentation as Klumpke’s palsy + ischemia/pain/edema due to vascular compression
What types of injury cause thoracic outlet syndrome?
pancoast tumor, cervical rib fracture
What motor function does the femoral nerve innervate?
hip flexors - psoas, iliacus, pectineus, sartorius
knee extensors
What sensation does the femoral nerve provide?
anterior thigh, medial lower leg
What nerve is injured in a pelvic fracture?
femoral nerve
What nerve is injured in an anterior hip dislocation?
obturator nerve
What motor innervation does the obturator nerve supply?
hip adduction (main function) knee flexion
What sensation does the obturator nerve supply?
medial thigh
What motor innervation does the superior gluteal nerve supply?
hip abduction, medial rotation
NO SENSATION
What nerve is damaged if a patient is showing Trendelenburg gait?
superior gluteal nerve - tilt pelvis to contralateral side of injury
What nerve is commonly damaged in polio?
superior gluteal nerve
What nerve is injured with a posterior hip dislocation?
superior gluteal nerve or inferior gluteal nerve
What nerve innervates the gluteus maximus to cause hip extension and lateral rotation?
inferior gluteal nerve
What nerve is injured in a hip replacement?
inferior gluteal nerve
What nerve is injured if a pt can’t stand up or walk up stairs?
inferior gluteal nerve
What is the motor innervation of the sciatic nerve?
hip extension and knee flexion
What sensation is provided by sciatic nerve?
posterior thigh and gluteal regions, entire lower leg except medial aspect
What pathologies can lead to damage of the sciatic nerve?
intervertebral disc herniation, spinal stenosis, spondylolisthesis
What motor innervation is provided by the tibial nerve?
plantar flexion, unlocks knee, toe flexion
What sensation is provided by the tibial nerve?
sole of the foot, back of the calf
What nerve is damaged with knee injuries?
tibial nerve
What nerve is damaged with lateral knee trauma?
deep fibular nerve (deep peroneal nerve)
What does damage to the deep fibular nerve cause?
foot drop
What motor innervation is provided by the deep fibular nerve?
foot eversion, foot dorsiflexion
What sensation is provided by the deep fibular nerve?
webbing of the first and second digits
What pathologies are associated with injury to the common fibular nerve?
foot drop, fracture of the neck of fibula, habitual leg crossing, chronic compression
What sensation is provided by the common fibular nerve?
lateral lower leg, dorsal side of foot (top of foot)
What motor innervation is provided by the common fibular nerve?
peroneus longus, peroneus brevis, short head of the biceps femoris
