Axilla and Brachial Plexus Flashcards
Axilla
Pyramidal shaped region between arm & chest
Pec. major & minor mm. = Anterior wall
Lat. dorsi, teres major & subscapularis mm. = Posterior wall
Serratus anterior m. = Medial wall
Intertubercular sulcus of humerus = Lateral wall
Skin & Fascia of armpit = base
Axilla boundaries
Pectoralis major & minor mm. = Anterior wall
Lat. dorsi, teres major & subscapularis mm. = Posterior wall
Serratus anterior m. = Medial wall
Intertubercular sulcus of humerus = Lateral wall
Skin & Fascia of armpit = base
Axilla
Muscles in the lateral wall
include the Coracobrachialis (larger and posterior); & anteromedially = short head of Biceps m.; anterolaterally = Long head of Biceps m.
Axilla: Contents
Fat & connective tissue
Axillary v. & lymphatics (outside sheath)
Cutaneous nerves
Axillary sheath – axillary a. & brachial plexus
Axillary nodes
in fat; 5 principle groups:
pectoral nodes (anterior): 3-5 nodes near the lateral thoracic v. & inferior border of the pectoralis minor m. – receiving lymph from ant. thoracic wall and most of breast.
subscapular nodes (posterior): 6-7 nodes along subscapular vessels – receiving lymph from the post. thoracic wall and scapular region
humeral nodes (lateral): 4-6 nodes along lateral axilla and around axillary v. – receiving lymph from UL except for the portion along the cephalic v. which drain into the apical axillary and infraclavicular nodes.
central nodes: 3-4 large nodes deep to pectoralis minor
apical nodes: receive lymph from all the other groups of axillary nodes as well as the proximal cephalic v. nodes; forms the subclavian lymphatic trunk and may be joined by the jugular and bronchomediastinal trunks on the Rt side to form the Rt lymphatic jugular duct OR on the left the subclavian trunk most commonly joins the thoracic duct.
pectoral nodes (anterior)
(anterior): 3-5 nodes near the lateral thoracic v. & inferior border of the pectoralis minor m. – receiving lymph from ant. thoracic wall and most of breast.
subscapular nodes
(posterior): 6-7 nodes along subscapular vessels – receiving lymph from the post. thoracic wall and scapular region
humeral nodes
(lateral): 4-6 nodes along lateral axilla and around axillary v. – receiving lymph from UL except for the portion along the cephalic v. which drain into the apical axillary and infraclavicular nodes.
central nodes
3-4 large nodes deep to pectoralis minor
apical nodes
receive lymph from all the other groups of axillary nodes as well as the proximal cephalic v. nodes; forms the subclavian lymphatic trunk and may be joined by the jugular and bronchomediastinal trunks on the Rt side to for the Rt lymphatic jugular duct OR on the left the subclavian trunk most commonly joins the thoracic duct.
Sensory Innervation of UL
Sensory = cutaneous
Axillary sheath
contains the axillary a., nerves, veins and lymphatics
Location of the sheath is down the medial aspect of the arm
Axillary artery
Arises from the subclavian a. at the lateral border of the 1st rib
gives rise to the brachial a. at the inferior border of the teres major m.
superiorly located branches of the subclavian a.: Suprascapular a. & Dorsal Scapular a. will
anastomose with the more inferiorly found Circumflex scapular arterial branch of the subscapular a from the 3rd part of the Axillary a.
deep transverse cervical branch will
anastomose with the dorsal scapular a.
Axillary Artery: 3 Parts
1st: between 1st rib & pec. minor m.
Gives off Superior thoracic a.
2nd: deep to pec. minor m.
Gives off Thoracoacromial & Lateral Thoracic aa.
3rd: between pec. minor & teres major mm.
Gives off Subscapular, Anterior, & Posterior Circumflex Humeral aa.
The Brachial Plexus
Composed of ventral rami C5-T1
Provides nerves for all UL mm. except trapezius m. (innervated by CN XI)
8 cervical nn., but only 7 cervical vertebrae
C1-C7 nn. emerge above C1-C7 vertebrae
C8 n. emerges below C7 vertebra
All other spinal nerves emerge below vertebrae of same number
Structure of Brachial plexus
Rami (5): emerge in upper neck Trunks (3): form in lower neck Divisions (6): split off behind clavicle Cords (3): form in axillary region Branches (5): split off in upper arm
Brachial Plexus: Rami
These are the ventral Rami of spinal nerves C5-T1
Brachial Plexus: Trunks
C5 & C6 rami join to form the upper trunk
C7 ramus becomes the middle trunk
C8 and T1 rami join to for the lower trunk
Brachial Plexus: Cords
The divisions recombine into cords (3) where the lateral cord contains the anterior contributions from the upper and middle trunks (thus contributions from C5-C7); the posterior cord combines all the posterior divisions of all the trunks (thus contributions from C5-T1); and the medial cord is derived from the anterior portion of the lower trunk (thus is contains C8 & T1 contributions).
Brachial Plexus: Branches
Read The Darn Cadaver Book
The terminal branches recombine again to give 5 major nerves of the UL. Musculocutaneous C5, C6, & C7 Median C5-T1 Axillary C5 & C6 Radial C5-T1 Ulnar C8 & 1
M” – 3 major branches
Brachial plexus
musculocutaneous n.
median n.
ulnar n
Y - brachial plexus
other 2 major branches (reverse Y)
Radial nerve from posterior cord
and
Axillary n
Musculocutaneous N. (C5-C7)
Formed from lateral cord
Passes thru coracobrachialis m.
Enters biceps brachii & brachialis mm.
‘Major N.’ of the anterior arm
Innervates coracobrachialis, biceps & ½ of brachialis m.
Median N. (C5-T1)
Formed from ½ lateral cord & ½ medial cord
Passes medial to arm mm.
‘Major N.’ of the anterior forearm
Innervates most of the anterior forearm, 3 thenar eminence mm. & 1st 2 lumbricals in hand
Ulnar N. (C8-T1)
Formed from medial cord
Runs behind medial epicondyle
‘Major N.’ of the hand
Innervates most of the mm of the hand, FCU m. & ulnar ½ FDP m. in forearm
Axillary N. (C5-C6)
Formed from posterior cord
Circles behind humerus in quadrangular space
Innervates deltoid & teres minor mm.
Radial N. (C5-T1)
Formed from posterior cord
Passes posterior to humerus in radial groove & within triangular interval
“Major N.” of the posterior arm & forearm
Innervates all mm in both regions + ½ of brachialis m.
Upper plexus includes
branches from C5-C7
Pectoral nn from the
upper and lower trunks
Lower plexus from the
posterior portion of all 3 trunks.
Upper Plexus Nerves
Dorsal scapular n,
Long Thoracic n. (C5-C7)
Suprascapular n. (C5-C6)
Dorsal Scapular n. (C5)
rhomboid & levator scapulae mm.
Long Thoracic n. (C5-C7)
Serratus anterior m.
Suprascapular n. (C5-C6)
supraspinatus & infraspinatus mm.
Pectoral Nerves
Lateral Pectoral n. (C5-C7)
pectoralis major m.
Medial Pectoral n. (C8-T1)
pectoralis major & minor mm.
Lateral Pectoral n. (C5-C7)
pectoralis major m.
Medial Pectoral n. (C8-T1)
pectoralis major & minor mm.
Lower Plexus Nerves
Upper Subscapular n. (C5-C6)
Thoracodorsal n. (C6-C8)
Lower Subscapular n. (C5-C6)
Upper Subscapular n. (C5-C6)
subscapularis m.
Thoracodorsal n. (C6-C8)
latissimus dorsi m.
Lower Subscapular n. (C5-C6)
subscapularis & teres major mm.
Nerve to subclavius m. (C5-C6)
-extra nerves
subclavius m.
Medial brachial cutaneous n. (C8-T1)
extra nerves
sensory to medial arm
Medial antibrachial cutaneous n. (C8-T1)
extra nerves
sensory to medial forearm
