Brachial Plexus and Pectoral Flashcards
3 main transition zones in upper limb
axilla- armpit
cubital fossa- depression anterior to elbow
carpal tunnel- flexor tendons and median nerve gateway to wrist
fn of clavicle
moveable strut allowing scapula to move
helps transmit shock from upper limb to axial skeleton
most common fracture
clavicle- usually through middle third of bone
shoulder falls lower than other side, pts hold and support arm
subclavian muscle
lays under clavicle, protects brachial plexus and other structures under clavicle
SC joint
synovial joint b/w clavicle and manubrium- only articulation b/w upper limb and axial skeleton
very strong articulation w/ rare dislocation, but have around 60 degree ROM
SC dislocaitons
can be an emergency, heart and trachea lie behind the joint
SC ligaments
anterior and posterior SC ligaments
interclavicular ligement along superior aspect of both joints
intra articular fiborcartilagenous disc acts as shock absorber (helps w/ FOOSH)
AC joint
synovial joint b/w acromion and clavicle, surrounded by loose fibrous capsule
AC ligaments
AC ligament- superior strength to capsue
coracoclavicular ligaments (trapezoid and conoid ligaments)- provides main strength
coracoacromial ligament- arch, bw/ coracoid and acromion processes
contrast 3 degrees of AC injuries
first- stretch or minor tear of AC ligament, still intact
second- subluxation, not totally separate
third- both AC and coracoclavicular ligaments torn, shoulder separation (essentially similar to broken clavicle)
insertion of pec major
lateral lip of intertubercular sulcus or bicipital groove
fn of pec major
internal rotation and adduction and flexor of arm
innervation of pec major
medial and lateral pec nerves
pec minor
inserts coracoid process
stabilizes scapula against thoracic wall
innervated by medial pec nerve
pec minor “bridge”
arches over axillary artery, axillary vein, brachial plexus
axillary artery progression
from subclavian as passes first rib, then 3 parts by pec minor as axillary, then brachial artery as passes lateral to teres major
2 key branches of axillary
subscapular- largest branch, anastamoses around scapula
anterior and posteriorr humeral circumflex- vascularize humerus and surrounding msucles
key role of suprascapular artery
can provide collateral circulation if axillary artery is thrombosed
5 segments of brachial plexus
roots trunks divisions cords branches
BP roots
formed by ventral rami of C5 thru T1
formation of BP trunks
C5 and C6 form superior trunk
C7 is middle trunk
C8 and T1 form inferior trunk
formation of BP divisions
each trunk forms anterior and posterior divisions
anterior forms nerves that innervate anterior compartments, posterior form posterior nerves
formation of BP cords
anterior divisions of superior and middle trunk form lateral cord
anterior division of inferior trunk is medial cord
posterior of all three form posterior cord
formation of BP terminal branches
lateral cord rise to musculocutaneous and lateral root of median nerve
posteriror cord gives rise to radial and axillary nerves
medial cord gives rise to ulnar nerve and medial root of median nerve
innervation of 5 terminal branches of BP
musculocutaneous- flexors of arm
ulnar- intrinsic muscles of hand and some forearm flexors
axillary- deltoid and teres minor
radial- extensors of arm and forearm
median- most forearm flexors and thenar (thumb) muscles
spinal nerve origins for each BP terminal branch
musculocutaneous- C5,6,7
axillary- C5,6
radial- C5,6,7,8, T1
median- C5,6,7,8 T1
ulnar- C8, T1 (sometimes C7)
muscles that BP and subclavian must pass thru
anterior and middle scalene, prevertebral fascia surrounds these muscles
axillary sheath
extension of prevertebral fascia extending laterally, surrounds BP and axillary artery
names of BP cords depend on
location relative to axillary artery- ie lateral cord is lateral to axillary artery
exception to BP innervation in upper limb
intercostobrachial nerve- lateral cutaneous sensory nerve, branch of T2 intercostal nerve
supplies region of skin along medial aspect of arm
not affected by BP nerve block
components of BP below clavicle
cords and terminal branches, everything else is cranial
sensory info from dermatomes to spinal cord enter..
via dorsal root, cell bodies in DRG
site of dormancy of VZV
DRG of certain spinal nerves, reactivate along dermatomes, usually unilateral
key dermatomes for MSK
C5- tip of shoulder C6- thumb C7- middle finger C8- little finger T1- medial arm
8 branches of BP
long thoracic dorsal scapular suprascapular upper subscapular middle subscapular lower subscapular medial and lateral pectoral medial cutaneous nerves (arm and forearm)
long thoracic
from C5,7
serratus anterior
dorsal scapular
C5, rhomboids and levator scapula
suprascapular
C5,6
supra and infraspinatus
upper subscapular
C5,6
subscapularis
middle subscapular
C6,7,8
latissimus dorsi
lower subscapular
C5,6
teres major and subscapularis
medial and lateral pectoral
medial C8, T1
lateral C5,6,7
pectoral muscles
medial cutaneous nerves of arm and forearm
C8, T1
sensation to medial arm and forearm
