May23 M3-Brachial Plexus and Axilla Flashcards
armpit 3 borders (what muscles form the axilla)
- anterior: pectoralis major m.
- posterior: latissimus dorsi m. and subscapularis m.
- medial: serratus anterior m. (+ ribs)
3 pathways in upper limb
- axilla (neck to upper extremities)
- cubital fossa (arm to forearm)
- carpal tunnel (forearm to hand)
problems involving invasion of the axilla pathway (2 examples)
- tumor of lung (like pancoast tumor)
- thoracic outlet syndrome (compression of structures passing between rib1 and clavicle)
where the neurovascular bundle crosses the axilla
medially in axilla (medial border)
big arteries (is the same continuous one) to the upper extremity are what
- brachiocephalic trunk (out of arch of aorta)
- splits in carotid and subclavian a. (subclavian to the UL)
- subclavian a. becomes axillary a. after crosses rib 1
- axillary a. becomes brachial a. after it passes teres major
2 branches of the brachial a. we have to know
- humeral circumflex a. (goes around the neck of humerus)
2. deep brachial a. (goes deep to posterior arm)
axillary pulse taken how
put finger in axilla and push towards the arm
brachial pulse is taken how
in arm region, posterior to the biceps brachii m.
how do we keep the blood supply to our arm all the time (even though the subclavian, axillary, brachial a. can get compressed when we lift our arm)
anastomoses present (small routes joining subclavian and axillary to brachial a., other than the main artery)
- useful in case of ligature or compression*
- concept applies to upper and lower limbs a lot*
veins to know in armpit region and where they run
- subclavian vein -> axillary vein (after rib 1) -> basilic vein (after teres major) runs deep, on side of brachial a.
- cephalic vein runs laterally, superficially
- brachial veins (are small, deep veins) run on side of brachial a. and on side of humeral circumflex a.
lymphatics in the armpit region clinical relevance
lymph nodes surrounding the basilic-axillary vein
-may see nodule there if metastatic breast tumor
plexus definition
mingling of nerves that share info and then separate and go off
brachial plexus levels of spinal cord involved + innervates what part of the body
C5,6,7,8 + T1
(C5-T1)
-innervates upper extremities
diff stages of a plexus where spinal nerves share content
(initially, each level gives an anterior ramus)
- ramus called roots
- trunks (from some roots fusing or continuation of root)
- divisions (from trunks dividing or coninuation of trunk)
- cords (from divisions fusing or continuing)
- terminal branches (nerves)
mnemonic to remember parts of a plexus
really thirsty? drink cold beer.
Roots, trunks, divisions, cords, terminal branches (nerves. terminal branches = nerves)
how many cords and how many terminal branches in the brachial plexus
- 3 cords
- 5 terminal branches (3 come from 2 cords, last 2 come from the last cord)
where do terminal branches branch off the plexus
around axillary artery
3 cords surrounding the axillary artery and their spinal levels (names mean position relatively to the axillary a.)
- lateral cord (C5,C6,C7) (anterior arm and forearm)
- medial cord (C8, T1) (anterior arm and forearm)
- posterior cord (C5 to T1) (posterior arm and forearm)
terminal branch that is the continuation of the lateral cord and spinal levels in it
musculo-cutaneous nerve (C5,C6,C7)
terminal branch that is the continuation of the medial cord + spinal levels in it
ulnar nerve (C8, T1)
terminal branch coming off both the lateral and medial cords + levels)
median nerve (C5 to T1). both medial and lateral cord give a branch going on top of axillary artery and these 2 fuse to form the median n.
what do the spinal levels in a nerve tell us about it in the brachial plexus
- more proximal spinal levels = more proximal innervation (arm only)
- more distal = distal inn only (forearm, hand)
- all spinal levels = inn in all the upper extremity
name of the concept of how a nerve’s spinal levels content tells us where the nerve goes
gradient of the brachial plexus
clinical significance of the gradient of the brachial plexus
- general weakness in arm muscles, around shoulder = proximal injury (C5-C7)
- general weakness in forearm, hand, distally = distal lesion (C8-T1)
what region and compartment does the musculocutaneous n. innervate
anterior compartment of the arm (remember lat cord is to anterior upper extremity)