Brachial Plexus & More
Describe the radial nerve
-C5-T1 -located on the posterior cord (posterior divisions of superior, middle, and inferior trunks) -course: winds around the spiral groove of humerus, passes through ACF into forearm then divides into two terminal branches (superficial and deep/posterior interosseous) -motor innervation: posterior compartment of the arm (triceps brachii) and posterior compartment of forearm (wrist extensors, finger extensors, brachioradialis, and supinator) -injuries: fracture of proximal humerus, humeral shaft, or proximal radius. -results of injuries (motor): weak elbow extension, absent triceps reflex, weak wrist extension, weak finger MCPJ extension, absent supinator reflex. -deformity: wasting of triceps and posterior compartment of arm, wrist drop on attempted wrist extension.
Describe the arrangement of carpal bones
-8 bones -2 rows -4 bones per row
What are the boundaries of the axilla?
-Apex -Base -4 walls (medial, lateral, posterior, anterior)
What muscles are innervated by the musculocutaneous nerve?
-BBC (biceps brachii, brachialis, and coracobrachialis muscles)
What are the major contents of the axilla?
-Brachial plexus -Axillary blood vessels -Axillary lymph nodes
Describe the axillary nerve
-C5-C6 -located on the posterior cord (posterior division of superior trunk) -course: passes beneath shoulder joint into posterior compartment of arm and wraps around surgical neck of humerus. Goes through the quadrangular space. -motor innervation includes: deltoid and teres minor muscles -sensory innervation includes: sergeant's patch over lower deltoid. -sensory loss: numb sergeants patch. -motor loss: very weak motor abduction from 15-90 degrees, weak shoulder flexion, weak shoulder extension, weak shoulder external rotation.
Describe the musculocutanous neve
-C5-C8 -located on the lateral cord (anterior divisions of superior and middle trunks) -action: flexes at elbow, supination of forearm -course: pierces corachobrachialis and passes down anterior compartment of arm beneath biceps muscle, then becomes lateral cutaneous of forearm. -motor innervation includes the anterior compartment of arm: biceps brachii, brachialis, coracobrachialis (BBC) -sensory innervation includes lateral forearm -results of injuries includes sensory loss to the lateral forearm, weak elbow flexion, weak forearm supination, absent biceps reflex.
Describe the median nerve
-C5-T1 -located on the lateral (lateral root from anterior divisions of superior and middle trunks) and medial cords (medial root from anterior division of inferior trunk) -course: runs down arm with brachial artery, passes through ACF (antecubital fossa) into forearm then divides into three terminal branches: anterior interosseous, deep, and superficial/palmer cutaneous. -motor innervation includes: all muscles of the anterior compartment of forearm EXCEPT flexor carpi ulnaris and medial two parts of flexor digitorum profundus. This includes the wrist flexors, finger flexors, and pronator teres + quadratus. -Also includes the "LOAF" muscles of the hands: L - lateral two lumbircals O - opponens pollicis A - abductor pollicis brevis F - flexor pollicis brevis -Sensory innervation includes: thenar eminence, lateral 2/3 palm of hand, palmar aspect lateral 3.5 fingers, distal doral aspect of lateral 3.5 fingers. -Injuries include: supracondylar fracture of humerus, stab wounds to ACF/forearm/wrist, or wrist lacerations in deliberate self harm, and compression at carpal tunnel in wrist. -Can cause flattening of the thenar eminence, often referred to as the ape hand. -sensory loss: numb thenar eminence and numb median distribution of hand. -motor deficit: weak forearm prontatoin, weak wrist flexion, weak wrist abduction, weak finger flexion, flexion of ring and little finger DIPJs persevered, weak grip strength and opposition.
Describe the ulnar nerve
-C8-T1 -located in the medial cord (anterior division of inferior trunk) -course: runs down arm with brachial artery, passes behind medial epicondyle into forearm, then travels down anterior compartment with ulnar artery to enter palm of hand via Guyon's canal. -motor innervation: two muscles of anterior compartment of forearm (flexor carpi ulnaris and medial two parts of flexor digitorum profundus). HILA muscles of hand H- hypothenar eminence I - interossei L - lumbricals (medial two) A - adductor pollicis -sensory innervation: hypothenar eminence, medial 1/3 palm of hand, palmer aspect medial 1.5 fingers, whole dorsal aspect of medial 1.5 fingers, medial 1/3 dorsum of hand. -common injuries: supracondylar fracture of humerus, medial epicondylar fracture or injury, stab wounds to forearm/wrist, compression at cubital tunnel in elbow or Guyons' canal in wrist. -sensory loss: numb hypthenar eminence and numb ulnar distribution of hand. -motor deficits: weak wrist flexion, weak wrist adduction, weak flexion of ring and little finger MCPJs and DIPJs and weak extension at their IPJs. Weak finger abduction, adduction, and opposition. -Deformity: wasting of hypothenar eminence and intrinsic muscles of hand. Claw hand at attempted finger extension.
Where is the ulnar nerve located?
-arises from the medial cord of brachial plexus; -runs down medial aspect of the arm, pierces the medial intermuscular septum at the middle of the arm, and descends together with the superior ulnar collateral branch of the brachial artery. -descends behind the medial epicondyle in a groove or tunnel (cubital tunnel) - ulnar nerve can be readily palpated and most commonly injured. -enter the forearm - passing between the two heads of the flexor capri ulnaris and descends between the flexor carpi ulnaris and flexor digitorum profundus muscles. -enter the hand superficially - flexor retinaculum and lateral to the pisiform bone - vulnerable to damafe from cuts or stab sounds. -terminates by dividing into superficial and deep branches at the root of the hypothenar eminence.
What which muscles are innervated by the palmar digital branches?
-cutaneous innervation of the skin of the little finger and the medial side of the ring finger.
What're the two branches coming off of the radial nerve?
-deep branch -superficial branch
What muscles do the axillary nerves innervate?
-deltoid and teres minor
Where is the superficial branch of the radial nerve?
-descends from the forearm deep to the brachioradialis muscle and then passes dorsally around the radium under the tendon of the brachioradialis.
What 3 muscles do the anterior interossesous innervate?
-flexor digitorum profundus -flexor pollicus longus -pronator quadratus
What is the carpal tunnel?
-formed by the flexor retinaculum anteriorly and the carpal bone posteriorly. -transmits the median nerve and the tendons of the flexor pollicis longus, flexor digitorum profundus, and flexor digitorum superficialis muscles.
What are the boundaries of the lateral wall of the axilla?
-intertubercular groove of the humerus -
What're the two branches from the lateral cord?
-lateral pectoral nerve (c5-C7) -musculocutaneous nerve (c5-C7)
What muscles are innervated by the dorsal scapular nerve?
-levator scapulae -rhomboid major and minor
What're the 3 branches from the medial cord?
-medial pectoral nerve -medial arm cutaneous nerve -medial forearm cutaneous nerve -ulnar nerve
What muscles do the superficial branch innervate?
-motor innervation for the palmaris brevis -sensory innervation for the palmar and dorsal surfaces of the medial 1/3 of the hand, including the hypothenar eminence.
What muscle does the lateral pectoral nerve innervate?
-pectoralis major muscle -pectoralis minor muscle
What are some examples of injury to the posterior cord?
-pressure of the crosspiece of a crutch resulting in crutch palsy -results in the loss in function of the extensor of the arm, forearm, and hand and produces wrist drop.
What movement and body part will be affected in a "waiter tips hand" injury
-results from a loss of abduction, flexion, and lateral rotation of the arm.
What is the location of the supscapular nerve?
-runs laterally across the posterior cervical triangle -passes under the superior transverse scapular ligament.
What're the two branches of the ulnar nerve?
-superficial branch -deep branch
What're the 2 branches from the upper trunk?
-suprascapular nerve (C5-C6) -Nerve to subclavius (C5)
What muscles are innervated by the suprascapular nerve?
-supraspinatus muscle -infraspinatus muscle
What are the boundaries of the medial wall of the axilla?
-upper ribs and intercostal msucles -serratus anterior muscles
What are the (5) branches from the posterior cord?
-upper subscapular nerve -lower subscapular nerve -thoracodorsal nerve -axillary nerve -radial nerve
What are the 3 thenar eminence muscles?
1) Abductor Pollicis Brevis 2) Flexor Pollicis Brevis
What are the 4 palmar compartments of the hand?
1) Thenar 2) Hypothenar 3) Central (midpalmar) 4) Interosseous/adductor
What're the 2 compartments of the antebrachium?
1. Anterior compartment 2. Posterior compartment
What're the 6 major contents on the cubital fossa?
1. Radial nerve 2. Tendon of the biceps muscles 3. Terminal bifurcation of the brachial artery 4. Formation of the radial artery 5. Formation of the ulnar artery 5. Median nerve
How to remember the number of superficial, intermediate, and deep nerves in the anterior compartment of forearm
4-1=3 -4 muscles in the superficial area -1 muscles in the intermediate area -3 muscles in the deep area of the anterior compartment of the forearm.
What are the deep layers of the posterior compartment of the forearm?
Abductor pollicis longus, extensor pollicis brevis, extensor indicis, supinator
Where is the long thoracic nerve located?
C5-C7; descends behind the brachial plexus and runs on the external surface of the serratus anterior muscles.
Where is the dorsal scapular nerve located?
C5; reaches the posterior cervical triangle and descends deep to the levator scap and rhomboids
What type of interossei muscles are responsible for abducting the digits?
Dorsal (remember DAB)
T/F the lumbricals are only innervated by the median nerve?
False - the lumbricals have dual motor innervation Median nerve supplies the lateral two lumbricals that goes to digits 2-3 Deep branch of ulnar nerve supplies the two medial lumbricals that run out to digit 4-5
What're the 4 superficial muscles of the anterior forearm?
Flexor carpi ulnaris, parlmaris longus (if present), flexor carpi radialis, and prontator teres muscles pass, fail, pass, fail
Where is the anterior interosseous nerve located?
In the cubital fossa. descends on the interosseous membrane between the flexor digitorum profundus and the flexor pollicis longus.
Carpal tunnel syndrome is caused by compression what what nerve?
Median nerve
What're the 3 motor nerves in the antebrachium?
Median, ulnar, and radial
What type of innervation does the deep ulnar nerve have on the hand?
Motor innervation
What type of interossei muscles are responsible for adducting the digits?
Palmar (remember PAD)
Describe the brachial plexus
The brachial plexus is a network of nerves formed by branches of spinal nerve segments C5-T1 -Trunks: superior, middle, inferior -Divisions: anterior, posterior -Cords: lateral, posterior, medial -Terminal branches: Musculocutanous, Axillary, Median, Radial, Ulnar.
What is the course of the radial nerve?
The radial nerve enters the forearm *anterior the the lateral epicondyle* and divides into *superficial and deep* branches. The *superficial branch* provides *purely somatic sensory innervation to the radial half of the dorsal hand*, and the *deep branch* innervates the *extensor compartment muscles in the forearm*. After passing through the *supinator canal*, the deep branch continues to the wrist to becomes the *posterior interosseous nerve*, which innervates muscles involved in *finger and thumb extension*
How many interossei muscles are there? How many dorsal? How many palmer?
There are 7 interossei muscles dorsal - 4 palmar - 3
T/F Injury of the lower trunk will be expressed largely through the ulnar nerve.
True
T/F the musculocutaneous never has a narrow zone of cutaneous territory along the lateral aspect of the forearm (beyond the elbow).
True
T/F the radial nerve is the largest branch of the brachial plexus?
True
What is the "major nerve" of the hand?
Ulnar nerve (deep ulnar nerve)
What is the cubitcal fossa?
a triangular intermuscular space anterior to the elbow. It's a transition zone between the arm and the forearm.
What are the main actions of the interossei muscles?
abduct/adduct digits #2-5
What're the branches of the median nerve?
anterior interosseous nerve, recurrent branch (thenar muscles), terminates by dividing into three common palmar digits nerves.
What are three terminal branches of the median nerve?
anterior interosseous, deep and superficial/palmer cutaneous.
The posterior cord is connected to the:
axillary and radial nerve
What're the 3 superficial muscles of the anterior arm?
biceps brachii, corachobrachalis, and brachialis (BBC)
What muscles are responsible for flexion or extension?
brachialis, biceps brachii, brachioradialis, and triceps
What're the superficial layers of the posterior compartment of the forearm?
brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensory digitorum, extersor digiti minimi, extensory carpi ulnaris
What is a common injury to the ulnar nerve?
claw hand which can be from a fracture of the medial epicondyle.
The median nerve terminates by dividing into three______
common palmar digital nerves
What is the course of the median nerve?
courses between the humeral and ulnar heads of the pronator teres muscle and then runs between the flexor digitorum superficialis and the flexor digitorum profundus before entering the wrist and hand within the carpal tunnel.
What type of innervation does the superficial ulnar nerve have on the hand?
cutaneous innervation
What type of innervation does the superficial branch of the radial nerve supply?
cutaneous innervation of the radial (back) side of hand.
What makes up the cords of the brachial plexus?
divisions lateral cords: anterior divisions of the superior and middle trunks posterior cords: posterior divisions of the superior, middle, and inferior trunks medial cords: anterior divisions of the inferior trunks
What nerve comes from the C5 ventral rami?
dorsal scapular nerve
What're the two branches from the roots?
dorsal scapular nerve long thoracic nerve
What motions do the anterior compartment of the antebrachium consist of?
extension and supination -some flexion of the elbow. what particular muscle does this?
What muscle does the posterior interosseous nerve innervate?
extensor muscles of the forearm
What is the action of the flexor digitorum superficialis muscle?
flex the fingers
What are the main actions of the lumbricals?
flex the metacarpophalangeal (MP) joint and extends interphalangeal (IP) joints.
What motions do the anterior compartment of the antebracium consist of?
flexion and pronation
Which muscles of the anterior compartment of the forearm are not innervated by the median nerve?
flexor carpi ulnaris muscle - innervated by the ulnar nerve. medial part of the flexor digitorum profundus - innervated by the ulnar nerve laternal part of the flexor digitorum profundus - innervated by the anterior interosseous branch of the median nerve
What muscles are innervated by the anterior antebrachial interosseous nerve?
flexor digitorum profundus (lateral part), flexor pollicis longus, pronator quadratus muscle.
What is the one intermediate layer of the anterior compartment of the forearm?
flexor digitorum superficialis
What are the 3 deep layers of the anterior compartment of the forearm?
flexor pollicus longus, flexor digitorum profundus, pronator quadratus.
What muscles are responsible for pronation of the forearm?
forearm muscles - pronator tere, pronator quadratus, and flexor carpi radialis.
What are the distal carpal bones?
hamate, capitate, trapezoid, trapezium Here comes the thumb!
What muscles fo the deep branch of the ulnar nerve innervate?
hypothenar muscles, the medial two lumbircals, all of the interossei, the adductor pollicis, and usually the deep head of the flexor pollicis brevis.
Where is the median nerve located?
lateral and medial cord. runs down the arm with brachial artery, passes through antecubital fossa into forearm then divides into three terminal branches.
The axillary nerve gives rise to the_____
lateral brachial cutaneous nerve.
What muscles do the thoracodorsal nerves innervate?
latissmus dorsi; runs next to the thoracoartery
What nerve lies within the carpal tunnel?
median nerve
What is the "minor nerve" of the hand?
median nerve - supplies the 3 little muscles within the thenar compartments of the hand + first 2 lumbarcal muscles within the central compartment of the hand.
What 3 nerves are responsible for forearm, wrist, and hand innervation?
median nerve, ulnar nerve, and radial nerve.
Where is the musculocutaneous nerve?
most lateral formed by the lateral cord
What nerve innervates the superior muscles of the anterior compartment of the arm?
musculocutaneous
The lateral cord is connected to the:
musculocutaneous and median nerve
The superficial branch of the ulnar nerve terminates in the ______ by dividing into _______
palm; three palmar digital branches.
What do the common palmar digital nerves then divide to?
palmar digital branches.
Where is the axillary nerve located?
posterior cord - passes beneath shoulder joint into posterior compartment of arm and wraps around surgical neck of humerus.
Where is the radial nerve located?
posterior cord - wind around spiral groove of humerus, passes though antecubital fossa into forearm then divides into two terminal branches (superficial and deep/posterior interosseous)
What nerve innervates the deep muscles of the posterior compartment of the forearm?
radial nerve
What nerve innervates the superficial layer of the posterior compartment of the forearm?
radial nerve
What muscular branch are given off at the carpal tunnel in the median nerve?
recurrent branch
What are the proximal carpal bones?
scaphoid, lunate, triquetrum, pisiform So long there pinky!
What muscles do the upper subscapular nerve innervate?
subscapularis muscle
What muscles do the lower subscapular nerve innervate?
subscapularis muscles and teres major
What're the 3 border of the cubital fossa?
superior border - imaginary line between the epicondyles, medial border - pronator teres, lateral border - brachioradialis.
What muscle is responsible for supination of the arm?
supinator and biceps brachii.
The deep branch enters the ______
supinator muscles
What muscles does the deep branch innervate?
the extensor carpi radiallis brevis and supinator muscles
The median nerve comes from which two cords?
the lateral and medial cords.
What is the branch from the medial and lateral cords?
the median nerve
What is the axilla?
the passageway from the root of the neck and the thorax to the upper limb -the "armpit"
What emerges from the supinator?
the posterior interosseous nerve
What muscle is innervated by the long thoracic nerve?
the serratus anterior muscles.
Where does the suprascapular artery pass?
the suprascapular artery passes above/over the ligament.
What muscles do the recurrent branch of the median nerve innervate?
the thenar muscles.
What is the cubital fossa?
triangular depression anterior to elbow joint, a transition zone between the arm and the forearm.
The medial cord is connected to the:
ulnar and median nerve
What are the arteries outside the carpal tunnel?
ulnar and radial artery
Which nerve will be damaged by a fracture of the medial epicondlye?
ulnar nerve
Which nerve innervates the interossei muscles?
ulnar nerve - deep branch
What are the nerves located outside the carpal tunnel?
ulnar nerve and superficial branch of radial nerve