Exam 3: Brachial Plexus

Question 1

Brachial Plexus

Answer 1

• formed by union of ant. (ventral) rami of C5,6,7,8 &T1 spinal nerves
• begins in neck & extends into axilla
• carries n. fibers from motor neurons & sensory ANS (sympathetic) neurons

Question 2

Sections of Brachial Plexus (5)

Answer 2

• roots (5): C5-T1
• trunks (3): sup, mid, inf
• divisions (6): each trunk divides into ant. & post.
• cords (3): lat, med, post
• terminal branches (5)

Question 3

Relationship: BP & Surrounding Structures

Answer 3

• scalene m.: BP root travels between ant. & mid. scalene (1st & 2nd rib)
  
  • when scalene muscle gets too big it can compress
• clavicle- travels under
• axillary a.- wraps around
• axilla- send many branches

Question 4

Roots

Answer 4

• ventral rami of C5-8 & T1
• Gives off 3 nerves:
  
  • dorsal scapular n. (C5)- innervates rhomboids & occasionally levator scapulae
  • phrenic (C3,4,5)- innervate diaphragm
  • long thoracic n.- innervate serrates ant. & travels between ant & mid scalene m

Question 5

Trunks

Answer 5

*superior- from union of C5 & 6 roots
-2 nerves:
~n. to subclavius (C5). innervates subclavius
~suprascapular n. (C4,5,6). innervates supraspinatus, infraspinatus & glenoid joine
*middle- continuation of C7 root
*inferior- from union of C8 & T1

Question 6

Divisions

Answer 6

• formed from trunks (split ant/post)
• no branches
• ant. division n. mainly innervate muscles in ant region of upper limb (flexor m.)
• post division n mainly innervate muscles in post region of upper limb (extensor m.)

Question 7

Lateral Cord

Answer 7

*formed from union of ant. division of superior & medial trunks
-carry fibers from C5,6,7
-1 branch: lateral pectoral n. (C5,6,7). innervates pec major & minor
*formed from continuation of ant division of inf trunk
-carries fibers from C8 & T1
-3 branches:
~med. pectoral n. (C8, T1): innervates pec major & minor
~med. cutaneus n. of arm (C8, T1): supplies skin on med. side of arm & sup part of forearm
~med cutaneus n. of forearm (C8, T1): supplies skin on med. side of forearm

Question 8

Medial Cord

Answer 8

*formed from continuation of ant division of inf trunk
-carries fibers from C8 & T1
-3 branches:
~med. pectoral n. (C8, T1): innervates pec major & minor
~med. cutaneus n. of arm (C8, T1): supplies skin on med. side of arm & sup part of forearm
~med cutaneus n. of forearm (C8, T1): supplies skin on med. side of forearm

Question 9

Posterior Cord

Answer 9

*formed by post divisions of 3 trunks
-3 branches
~upper scapular n. (C5,6)- innervates subscapularis
~thoracodorsal n. (C6,7)- supplies latissimus dorsi
~lower subscapularis n. (C6,7)- supplies t. major & inf part of subscapularis

Question 10

Terminal Branches

Answer 10

• axillary- post. cord
• musculocutaneous- lat. cord
• median- lat. & med. cord: forearm innervation
• radial- post cord
• ulnar- med. cord

Question 11

Prefixed BP

Answer 11

plexus formed from C4-8

Question 12

Postfixed BP

Answer 12

• formed from C6-T12

* inf. trunk may be compressed by 1st rib, producing neurovascular symptoms in upper limb

Question 13

Erbs Palsy

Answer 13

• superior (C5,6)
• cause: excessive separation of head & neck such as falling on shoulder
  
  • excessive stretching during baby delivery
• appearance: waiters tip- injured limb hangs by side of med rot
  
  • loss of sensation on lat. aspect of upper limb
• muscle paralyss- deltoid, biceps, brachialis, & brachioradialis

Question 14

Backpackers Palsy

Answer 14

• microinjury of sup trunk of BP due to carrying heavy backpack
• results in sensory deficits in distribution of musculocutaneousn. & radial n.
• may also produce spasms

Question 15

Acute BP nueritis

Answer 15

• neurological disorder (unknown cause)
• involves sup. trunk
• onset w/ sever pain around shoulder

Question 16

Compression of Cords

Answer 16

• caused by hyperabduction of arm
• pain down arm.
• numbness/tingling

Question 17

Inf Injury (C8-T1)

Answer 17

• sudden pull of arm sup.

- short m. of hand affected (claw hand)