Brachial and Lumbosacral Plexi

Question 1

what is the brachial plexus?

Answer 1

formed by intercommunications among the ventral rami of C5 through T1

Question 2

describe the course of the brachial plexus?

Answer 2

from the vertebral column to the axilla

• deep to clavicle but superficial to ribs 1 and 2
• transverses between scalenes

Question 3

what is the axillary sheath?

Answer 3

contains initial portion of axially vessels + brachial plexus

Question 4

what is the motor function of the brachial plexus?

Answer 4

provides motor function to all muscles of the upper limb with the exception of the trapezius and levator scapula

Question 5

what is the sensory function of the brachial plexus?

Answer 5

supplies all sensory input from upper limb with exception of axilla and mid sagittal dorsal skin

Question 6

what is the result of the brachial plexus?

Answer 6

results in peripheral nerves being composed of multiple spinal roots

Question 7

how is the organization of the brachial plexus organized?

Answer 7

roots, trunks, divisions, cords, branches

Question 8

what are the roots of the brachial plexus?

Answer 8

anterior rami of the C5-T1

Question 9

how are the trunks of the brachial plexus formed?

Answer 9

merging of roots

Question 10

what comprises the trunk of the brachial plexus?

Answer 10

superior trunk
middle trunk
inferior trunk

Question 11

what forms the superior trunk of the brachial plexus?

Answer 11

formed by the combination of C5 and C6 roots

Question 12

what is the middle trunk of the brachial plexus?

Answer 12

a continuation of C7

Question 13

what forms the inferior trunk of the brachial plexus?

Answer 13

formed by the combination of C8 and T1 roots

Question 14

what are the divisions of the brachial plexus?

Answer 14

each of the trunks bifurcates&raquo_space; named according to whether they are anterior or posterior to axillary artery

Question 15

how are the cords of the brachial plexus?

Answer 15

formed by merging of 2 or 3 divisions&raquo_space; named in relation to the axillary artery (lateral cord, posterior cord and medial cord)

Question 16

where do the branches terminate and what are the branches of the brachial plexus?

Answer 16

terminate in five major nerves of the upper extremity

radial nerve
axillary nerve
median nerve
musculocutaneous nerve
ulnar nerve

Question 17

what are the roots and innervations of the radial nerve?

Answer 17

(1) roots = C5 – T1

(2) innervates the triceps brachii and the extensor muscles in the posterior compartment of the forearm

Question 18

what are the roots and innervations of axillary nerve?

Answer 18

(1) roots = C5 and C6
(2) innervates the deltoid, teres minor and the long head of the triceps brachii (anatomical variation from person to person)

Question 19

what are the roots and innervations of median nerve?

Answer 19

(1) roots = C5 – T1

(2) innervates most of the flexor muscles in the forearm, the thenar muscles, and the two lateral lumbrical muscles

Question 20

what are the roots and innervations of musculocutaneous nerve?

Answer 20

(1) roots = C5, C6, C7

(2) innervates anterior compartment of arm

Question 21

what are the roots and innervations of ulnar nerve

Answer 21

(1) roots = C8 and T1
(2) innervates the muscles of the hand (apart from the thenar muscles and two lateral lumbricals) + 1.5 anteromedial forearm muscles

Question 22

many anatomical variations of the brachial plexus exist, what is the prefixed brachial plexus?

Answer 22

C4 input to brachial plexus, often with lessened input from T1

Question 23

many anatomical variations of the brachial plexus exist, what is the postfixed brachial plexus?

Answer 23

T2 input to brachial plexus, often with diminished input from C5

Question 24

where can anesthesia be applied to allow for surgical procedures on the upper extremity without use of general anesthetic?

Answer 24

within axillary sheath

Question 25

what are the common injuries to the brachial plexus?

Answer 25

Erb-Duchene palsy | Klumpke’s palsy

Question 26

what is Erb-Duchene palsy?

Answer 26

injury to superior roots (C5 and C6)

Question 27

how does Erb-Duchene palsy happen?

Answer 27

A. due to trauma that widely separates neck and shoulder >> being thrown on shoulder/neck or excessive stretching during delivery B. results in “waiter’s tip” position of affected extremity

Question 28

what is Klumpke's palsy?

Answer 28

injury to inferior roots (C8-T1)

Question 29

how does Klumpke's palsy occur?

Answer 29

A. due to pulling trauma of abducted arm >> grasping hold during a free fall or excessive stretching during birth B. results in claw hand

Question 30

what is another injury that can happen to the brachial plexus?

Answer 30

wounds to posterior triangle of neck or axilla can damage other components of brachial plexus, and each damaged component has characteristic symptoms

Question 31

in terms of clinical applications, a cervical rib can be noted, what is this?

Answer 31

supernumerary rib that articulates with C7 (slide 13) >> usually asymptomatic

Question 32

what is the significance of the cervical rib?

Answer 32

A. can compress C8 and T1 spinal nerves or inferior trunk of brachial plexus >> typically produces tingling sensation along medial aspect of forearm B. can also compress subclavian artery >> ischemic muscle pain in upper limb

Question 33

what is the lumbosacral plexus?

Answer 33

formed by intercommunications among the ventral rami of L2-S4

Question 34

what are the portions of the lumbosacral plexus?

Answer 34

superior and inferior

Question 35

what is the superior portion of the lumbosacral plexus?

Answer 35

located within abdominal cavity >> gives rise to 2 major nerves

Question 36

what two nerves does the lumbosacral plexus give rise too?

Answer 36

A. obturator nerve | B. femoral nerve

Question 37

so we know the lumbosacral plexus gives rise to the obturator and femoral nerve, what can we note about the obturator and femoral nerve?

Answer 37

A. obturator nerve – innervates adductor compartment of thigh B. femoral nerve – innervates flexors of hip and extensors of knee

Question 38

what is the inferior portion of the lumbosacral plexus?

Answer 38

located on posterolateral wall of lesser pelvis and in close association with anterior surface of piriformis >> most branches exit though the greater sciatic foramen

Question 39

what are the three major nerves of the inferior portion of the lumbosacral plexus?

Answer 39

pudendal nerve tibial nerve common peronial nerve

Question 40

describe the pudendal nerve of the lumbosacral plexus?

Answer 40

main nerve of the peritoneum

Question 41

the tibial nerve and the common peronial nerve of the inferior portion of the lumbosacral plexus are part of which division?

Answer 41

division of the sciatic nerve

Question 42

describe the innervations of the tibial nerve?

Answer 42

i. muscles of posterior thigh and posterior leg | ii. sensory innervation to postero-lateral leg and sole of foot

Question 43

describe the innervations of the common peronial nerve?

Answer 43

i. muscles of lateral and anterior leg | ii. sensory innervation to lateral leg and superior surface of foot