Brachial Plexus

Question 1

Brachial plexus

Answer 1

formed by anterior rami of C5 through T1
travels laterally over 1st rib into axilla
roots -> trunks -> divisions -> cords -> terminal nerves

Question 2

roots

Answer 2

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

Question 3

Trunks

Answer 3

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

Question 4

Divisions

Answer 4

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

Question 5

cords

Answer 5

named for relationship to the axillary artery
Lateral cord
medial cord
posterior cord

Question 6

lateral cord

Answer 6

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

Question 7

medial cord

Answer 7

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

Question 8

posterior cord

Answer 8

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

Question 9

what nerves are formed from the roots of the brachial plexus?

Answer 9

dorsal scapular nerve and long thoracic nerve

Question 10

dorsal scapular nerve

Answer 10

branches off C5 root

supplies levator scapula (also recieves fibers from C3 and C4), rhomboid major and minor

Question 11

long thoracic nerve

Answer 11

formed from roots of C5 C6 and C7

supplies the serratus anterior muscle

Question 12

what nerves branch off the superior trunk of the brachial plexus?

Answer 12

suprascapular nerve, and nerve to the subclavius

Question 13

suprascapular nerve

Answer 13

fibers from C5 and C6

supplies supraspinatus and infraspinatus

Question 14

nerve to the subclavius

Answer 14

fibers from C5 and C6

supplies subclavius

Question 15

what nerves branch off the lateral cord of the brachial plexus?

Answer 15

lateral pectoral nerve, and the two terminal branchs are the musculocutaneous nerve and the median nerve

Question 16

lateral pectoral nerve

Answer 16

fibers from C5 C6 and C7

supplies pectoralis major (also supplied by medial pectoral nerve)

Question 17

musculocutaneous nerve

Answer 17

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

Question 18

what are the branches of the medial cord of the brachial plexus?

Answer 18

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)

Question 19

medial pectoral nerve

Answer 19

fibers from C8 and T1

supplies pectoralis major and minor

Question 20

medial cutaneous nerve of the arm

Answer 20

fibers from C8 and T1
supplies skin of medial arm between axilla and elbow
recieves fibers from T2 through communication with intercostobrachial nerve

Question 21

medial cutaneous nerve of the forearm

Answer 21

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

Question 22

ulnar nerve (forearm)

Answer 22

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

Question 23

ulnar nerve (wrist and hand)

Answer 23

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

Question 24

median nerve (forearm)

Answer 24

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

Question 25

median nerve (wrist and hand)

Answer 25

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

Question 26

what are the branches off the posterior cord of the brachial plexus?

Answer 26

superior subscapular nerve
thoracodorsal nerve
inferior subscapular nerve
axillary nerve
radial nerve

Question 27

superior subscapular nerve

Answer 27

fibers from C5 and C6

supplies subscapularis

Question 28

thoracodorsal nerve

Answer 28

fibers from C6 C7 and C8

travels down posterior axillary wall to supply the latissimus dorsi

Question 29

inferior subscapular nerve

Answer 29

contains fibers from C5 and C6

supplies subscapularis and teres major

Question 30

axillary nerve

Answer 30

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

Question 31

radial nerve (arm and forearm)

Answer 31

fibers from C5 C6 C7 C8 and T1 (sometimes)

supplies all muscles of the posterior arm and forearm