Brachial Plexus Flashcards
Brachial plexus
formed by anterior rami of C5 through T1
travels laterally over 1st rib into axilla
roots -> trunks -> divisions -> cords -> terminal nerves
roots
each root recieves a grey ramus communicans from sympathetic trunk
they pass between anterior and middle scalene muscles into posterior triangle
posterior and superior to the subclavian artery
Trunks
roots of C5 and C6 become superior trunk
root of C7 becomes the middle trunk
roots of C8 and T1 become inferior trunk
trunks pass over rib 1 into the axilla
Divisions
each trunk will split into an anterior and posterior division
anterior divisions will supply anterior compartments of the arm and forearm while posterior divisions will supply the posterior compartments
cords
named for relationship to the axillary artery
Lateral cord
medial cord
posterior cord
lateral cord
formed by the anterior divisions of the superior and middle trunks
contains fibers from C5 C6 and C7
lies laterally to the second part of the axillary artery
medial cord
formed by the anterior division of the inferior trunk
contains fibers from C8 and T1
lies medial to the second part of the axillary artery
posterior cord
formed by the union of the posterior divisions of all three trunks
contains fibers from C5 C6 C7 C8 and T1
lies posterior to the second part of the axillary artery
what nerves are formed from the roots of the brachial plexus?
dorsal scapular nerve and long thoracic nerve
dorsal scapular nerve
branches off C5 root
supplies levator scapula (also recieves fibers from C3 and C4), rhomboid major and minor
long thoracic nerve
formed from roots of C5 C6 and C7
supplies the serratus anterior muscle
what nerves branch off the superior trunk of the brachial plexus?
suprascapular nerve, and nerve to the subclavius
suprascapular nerve
fibers from C5 and C6
supplies supraspinatus and infraspinatus
nerve to the subclavius
fibers from C5 and C6
supplies subclavius
what nerves branch off the lateral cord of the brachial plexus?
lateral pectoral nerve, and the two terminal branchs are the musculocutaneous nerve and the median nerve
lateral pectoral nerve
fibers from C5 C6 and C7
supplies pectoralis major (also supplied by medial pectoral nerve)
musculocutaneous nerve
one of the terminal branches of the lateral cord
fibers from C5 C6 and C7
supplies coracobrachialis (nerve pierces coracobrachialis), bicepts brachii, and brachialis
continues between brachialis and bicepts brachii into forearm to become lateral cutaneous nerve of the forearm and supplies skin over the lateral part of the forearm
what are the branches of the medial cord of the brachial plexus?
medial pectoral nerve, medial cutaneous nerve of the arm, medial cutaneous nerve of the forearm, ulnar nerve (one of two terminal branches), and median nerve (also terminal branch for the lateral cord)
medial pectoral nerve
fibers from C8 and T1
supplies pectoralis major and minor
medial cutaneous nerve of the arm
fibers from C8 and T1
supplies skin of medial arm between axilla and elbow
recieves fibers from T2 through communication with intercostobrachial nerve
medial cutaneous nerve of the forearm
fibers from C8 and T1
leaves medial cord just distal of the medial cutaneous nerve of the arm
supplies skin over the bicepts brachii and skin over anterior and medial aspects of forearm to the wrist
ulnar nerve (forearm)
fibers from C8 and T1
travels down forearm between the two heads of the flexor carpi ulnaris
innervates flexor carpi ulnaris and the medial half of the flexor digitorum profundus
ulnar nerve (wrist and hand)
two branches, superficial and deep
superficial - divides into three terminal branches that supply palmar aspect of the little finger and medial half of the ring finger
deep - supplies, abductor digiti minimi, flexor digiti minimi brevis, opponens digiti minimi, abductor pollicis, deep head of the fleor policis brevis, all interossei, and lumbricals 3 and 4
claw hand is a clinical consideration
median nerve (forearm)
both lateral cord and medial cord contribute
fibers from C6 C7 C8 and T1
passes into forearm between the two heads of the pronator teres
supplies - pronator teres, flexor carpi radialis, palmaris longus, flexor digitorum superficialis, and the pronator quadratus
median nerve (wrist and hand)
nerve passes through carpal tunnel and divides into three common palmer digital nerves
supply - lumbricals 1 and 2, abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis
each common palmer digital nerve then splits into two proper palmer digital nerves which are sensory innervation to skin over the lateral three and a half digits.
also supplies periostium, elbow, radiocarpal and midcarpal joints
what are the branches off the posterior cord of the brachial plexus?
superior subscapular nerve thoracodorsal nerve inferior subscapular nerve axillary nerve radial nerve
superior subscapular nerve
fibers from C5 and C6
supplies subscapularis
thoracodorsal nerve
fibers from C6 C7 and C8
travels down posterior axillary wall to supply the latissimus dorsi
inferior subscapular nerve
contains fibers from C5 and C6
supplies subscapularis and teres major
axillary nerve
fibers from C5 and C6
supplies deltoid and teres minor
also gives off sensory branch superior lateral cutaneous nerve of the arm which supplies skin over the lateral shoulder and upper arm
radial nerve (arm and forearm)
fibers from C5 C6 C7 C8 and T1 (sometimes)
supplies all muscles of the posterior arm and forearm
