Axilla and the brachial plexus Flashcards
what is the axilla?
- an anatomical region (armpit) under the shoulder joint** where the arm connects to the shoulder **
- it contains a lot of neurovascular structures including the brachial plexus, the axillary artery and vein and lymph nodes
what are the major contents of the axilla?
- axillary artery
- axillary vein
- brachial plexus
- nodes
- adipose tissue
what is the anterior border of the axilla?
- pectoralis major muscle
- pectoralis minor muscle
- subclavius muscle
what is the posterior border of the axilla?
- subscapularis
- teres major
- latissimus dorsi
- scapula
what is the medial border of the axilla?
- ribs
- serratus anterior
what is the lateral border of the axilla?
the humerus
where does the pectoralis major muscle originate and insert onto?
- O: 3 places - sternal part of clavicle, the sternum and costal cartilages 1-7, and the rectus sheath
- I: humerus - lateral to the bicipital groove (crista tuberculi majoris)
what are the main actions of the pectoralis major muscle?
- arm adduction
- arm internal rotation
- arm flexion
- elevates the rib cage during inspiration
what nerve supplies the pec major muscle?
- pectoral nerves from the brachial plexus
what are the ‘3 portions’ of the pec major muscle?
- clavicular
- abdominal
- sterno costal
where does the pectoralis minor originate and insert?
- O: ribs 3-5
- I: on the coracoid process of the scapula
what are the actions of the pectoralis minor muscle?
* depression - pulls the scapula anteriorly
* also involved in** elevation of the rib cage** during inspiration
where does the subclavious muscle originate and insert onto?
- O: sternal end of rib 1 and costal cartilage
- I: lower aspect of the clavicle
what nerve supplies the pectoralis minor muscle?
pectoral nerves from the brachial plexus
what is the main action of the subclavius muscle?
- stabilisation of the clavicle during movements of the shoulder girdle
what nerve supplies the subclavius muscle?
- subclavius nerve from the brachial plexus
where does the subscapularis originate and insert onto?
- O: subscapular fossa of the scapula
- I: lesser tubercle of the humerus
what is the main function / action of the subscapularis muscle?
- medial rotation of the arm
what nerve supplies the subscapularis muscle?
the subscapular nerves from the brachial plexus
where does the latissimus dorsi originate and insert onto?
- O: (4 parts) vertebral: spinous processes T7-T12, iliac part - posterior third of crest of ilium, **scapula part: inferior angle of scapula, costal part**: 0 10-12 ribs
- I: intertubucular sulcus/ groove between pec major and teres major (lady between 2 majors)
what nerve supplies the latissimus dorsi?
- thoraco-dorsal nerve from the brachial plexus
what are the main actions of the latissimus dorsi muscle?
- arm adduction
- elevation of the trunk - think of hands on bar
- arm internal rotation
- arm extension
- depression of the scapula
where does the** teres major** originate and insert onto?
- O: lateral margin and inferior angle of the scapula
- I: intertubular groove
what is the origin and insertion of the serratus anterior?
- O : ribs 1-2 (superior), ribs 2-4 (middle) and ribs 5-9 (inferior)
- I: superior part - superior angle of scapula, middle part - medial margin of scapula, inferior part - lower angle of scapula
what are the actions of the serratus anterior on the shoulder girdle?
- keeps scapula close to throacic cage
- superior part elevates the scapula
- middle part depresses the scapula
- inferior part depresses and rotates the scapula
what are the actions of the serratus anterior on the thorax?
- elevates the thoracic cage - for inspiration
what nerve supplies the serratus anterior muscle?
- long thoracic nerve from the brachial plexus
what are the medial, middle and lateral branches of the axillary artery?
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- medial - sup thoracic
- middle - thoracoacromial and lateral thoracic
- lateral - subscapular, anterior circumflex humeral artery and posterior circumflex humeral artery
what is the brachial plexus?
network of nerves originating in the neck region, passes through the axilla where it then supplies many peripheral nerves to the upper limb
what are the roots of the brachial plexus?
C5
C6
C7
C8
T1
what do the roots of the branchial plexus unite to form?
trunks
* superior (C5 + C6)
* Middle (C7)
* Inferior (C8 + T1)
as the trunks reach the posterior aspect of the middle third of the clavicle, what do they divide into?
- each of the trunks divide into an anterior and posterior division - which gives rise to 6 divisions which then pass inferiorly behind the clavicle to enter the axilla
instead of the divisions giving rise to branches, what do they do instead?
they merge to form cords - lateral cord (anterior div of superior and medial trunk), medial cord (anterior divisions from inferior trunk) and posterior cord (posterior divisions from all 3 trunks)
what do the lateral and medial cords supply?
the anterior flexor compartment of the forearm
what does the posterior cord supply?
innervates the muscles of posterior (extensor) compartment of the forearm
what braches do the trunks of the brachial plexus give off?
- long thoracic nerve (C5-C7)
- dorsal scapular nerve (C5)
- phrenic nerve (C5)
- subclavius nerve (C5-C6)
what nerves arise from the lateral cord?
remember: 2L 1M
- Lateral pectoral nerve
- Lateral root of the Median Nerve
- Musculocutaneous nerve
what nerves does the medial cord give off?
remember : 4M, 1U
- Medial pectoral nerve
- Medial cuteanous nerve of arm
- Medial cuteanous nerve of forearm
- Medial root of the median nerve
- Ulnar nerve
what nerves arise from the posterior cord of the branchial plexus?
remember STARS
- Upper** S**ubscapular nerve
- Thoracodorsal nerve
- Axillary nerve
- Radial nerve
- Lower Scapular nerve
what are the 5 groups of axillary lymph nodes?
- anterior (pectoral)
- posterior (subscapular)
- lateral (humeral)
- central
- apical
what is erbs palsy?
- occurs when there is injury to the brachial plexus - specifically the upper brachial plexus
- can happen due to hyperextension and or lateral extension of the neck or can happen at birth when baby coming out
what are the clinical signs and symptoms of erb’s palsy?
- waiters tip deformity - due to loss of lateral rotators of the shoulders, arm flexors and hand extensor muscles
- the arm cannot be raised from the side - all power for flexion of the elbow and supination of the hand is lost
what is klumpke’s palsy?
- neuropathy of the lower brachial plexus that may have resulted from difficulted delivery of baby
what is a classic symptom of klumpke’s palsy?
- ‘claw hand’
