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MABS Medical Anatomy > Brachial and Lumbosacral Plexi > Flashcards

Brachial and Lumbosacral Plexi Flashcards

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USMLE® Step 1 flashcards
1
Q

what is the brachial plexus?

A

formed by intercommunications among the ventral rami of C5 through T1

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2
Q

describe the course of the brachial plexus?

A

from the vertebral column to the axilla

  • deep to clavicle but superficial to ribs 1 and 2
  • transverses between scalenes
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3
Q

what is the axillary sheath?

A

contains initial portion of axially vessels + brachial plexus

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4
Q

what is the motor function of the brachial plexus?

A

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

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5
Q

what is the sensory function of the brachial plexus?

A

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

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6
Q

what is the result of the brachial plexus?

A

results in peripheral nerves being composed of multiple spinal roots

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7
Q

how is the organization of the brachial plexus organized?

A

roots, trunks, divisions, cords, branches

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8
Q

what are the roots of the brachial plexus?

A

anterior rami of the C5-T1

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9
Q

how are the trunks of the brachial plexus formed?

A

merging of roots

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10
Q

what comprises the trunk of the brachial plexus?

A

superior trunk
middle trunk
inferior trunk

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11
Q

what forms the superior trunk of the brachial plexus?

A

formed by the combination of C5 and C6 roots

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12
Q

what is the middle trunk of the brachial plexus?

A

a continuation of C7

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13
Q

what forms the inferior trunk of the brachial plexus?

A

formed by the combination of C8 and T1 roots

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14
Q

what are the divisions of the brachial plexus?

A

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

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15
Q

how are the cords of the brachial plexus?

A

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

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16
Q

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

A

terminate in five major nerves of the upper extremity

radial nerve
axillary nerve
median nerve
musculocutaneous nerve
ulnar nerve
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17
Q

what are the roots and innervations of the radial nerve?

A

(1) roots = C5 – T1

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

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18
Q

what are the roots and innervations of axillary nerve?

A

(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)

19
Q

what are the roots and innervations of median nerve?

A

(1) roots = C5 – T1

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

20
Q

what are the roots and innervations of musculocutaneous nerve?

A

(1) roots = C5, C6, C7

(2) innervates anterior compartment of arm

21
Q

what are the roots and innervations of ulnar nerve

A

(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

22
Q

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

A

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

23
Q

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

A

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

24
Q

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

A

within axillary sheath

25
Q

what are the common injuries to the brachial plexus?

A

Erb-Duchene palsy

Klumpke’s palsy

26
Q

what is Erb-Duchene palsy?

A

injury to superior roots (C5 and C6)

27
Q

how does Erb-Duchene palsy happen?

A

A. due to trauma that widely separates neck and shoulder&raquo_space; being thrown on shoulder/neck or excessive stretching during delivery

B. results in “waiter’s tip” position of affected extremity

28
Q

what is Klumpke’s palsy?

A

injury to inferior roots (C8-T1)

29
Q

how does Klumpke’s palsy occur?

A

A. due to pulling trauma of abducted arm&raquo_space; grasping hold during a free fall or excessive stretching during birth

B. results in claw hand

30
Q

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

A

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

31
Q

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

A

supernumerary rib that articulates with C7 (slide 13)&raquo_space; usually asymptomatic

32
Q

what is the significance of the cervical rib?

A

A. can compress C8 and T1 spinal nerves or inferior trunk of brachial plexus&raquo_space; typically produces tingling sensation along medial aspect of forearm

B. can also compress subclavian artery&raquo_space; ischemic muscle pain in upper limb

33
Q

what is the lumbosacral plexus?

A

formed by intercommunications among the ventral rami of L2-S4

34
Q

what are the portions of the lumbosacral plexus?

A

superior and inferior

35
Q

what is the superior portion of the lumbosacral plexus?

A

located within abdominal cavity&raquo_space; gives rise to 2 major nerves

36
Q

what two nerves does the lumbosacral plexus give rise too?

A

A. obturator nerve

B. femoral nerve

37
Q

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

A

A. obturator nerve – innervates adductor compartment of thigh

B. femoral nerve – innervates flexors of hip and extensors of knee

38
Q

what is the inferior portion of the lumbosacral plexus?

A

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

39
Q

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

A

pudendal nerve
tibial nerve
common peronial nerve

40
Q

describe the pudendal nerve of the lumbosacral plexus?

A

main nerve of the peritoneum

41
Q

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

A

division of the sciatic nerve

42
Q

describe the innervations of the tibial nerve?

A

i. muscles of posterior thigh and posterior leg

ii. sensory innervation to postero-lateral leg and sole of foot

43
Q

describe the innervations of the common peronial nerve?

A

i. muscles of lateral and anterior leg

ii. sensory innervation to lateral leg and superior surface of foot

MABS Medical Anatomy (35 decks)

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