MSK Session 1: pectoral region and axilla Flashcards
Which bones constitute the pectoral girdle?
Clavicle and scapula
State the borders of the axilla, a pyramidal area
Apex: lateral border of 1st rib, superior border of scapula and posterior border of clavicle
Lateral wall: intertubecular groove of humerus
Medial wall: serratus anterior and thoracic wall
Anterior wall: pectoralis major, pectoralis minor, subclavius
Posterior wall: subscapularis, teres major and lattisimus dorsi
How may structures leave the axilla?
- Into upper limb (main way. Inferiorally and laterally)
- Quadrangular space: gap in posterior wall allowing access to posterior arm and shoulder
- Clavipectoral triangle: opening in anterior wall
State the contents of the axilla
Axillary artery (medial and posterior parts)
Axillary vein
Brachial plexus
Muscles: biceps brachii and coracobrachialis tendons
Axillary lymph nodes
Origin of pectoralis major
Clavicular head-clavicle
Sternocostal head-sternum and ribs
Insertion of pec major
Intertubecular groove of humerus
Innervation and roots of pec major
Lateral (C5-C7) and medial (C8-T1) pectoral nerves
Action of pec major
ADducts and medially rotates humerus at shoulder
Draws scapula inferiorly and anteriorly
Clavicular head flexes humerus
Sternocostal head extends humerus
Where is pec minor in relation to pec major?
Posterior. Triangular shape compared to pec major fan
Origin of pec minor
Anterior surfaces of ribs 3-5
Insertion of pec minor
Coracoid process
Innervation and roots of pec minor
Medial pectoral nerve (C8, T1)
Action of pec minor
Depresses shoulder Stabilises scapula (pulls inferiorly and anteriorly against thoracic wall)
Where is serratus anterior located?
More laterally in chest, forms medial axillary wall. Several strips. Deep to subscapularis
Origin of serratus anterior
External surfaces of ribs 1-8
Insertion of serratus anterior
Anterior surface of medial border of scapula
Innervation and roots of serratus anterior
Long thoracic nerve (C5, C6, C7)
Action of serratus anterior
Rotates scapula over 90 degrees
Holds scapula against thoracic wall
Describe what happens in winging of the scapula
Damage to long thoracic nerve due to trauma, repetitive strain or inflammation, causing paralysis of serratus anterior. Can happen after axillary lymph node clearance surgery
Medial border of scapula moves away from thoracic wall
When affected limb is moved/pushed with, scapula not held against rib cage so moves away and protrudes out the back
Where in the brachial plexus does the dorsal scapular nerve arise?
Root C5
From where do the suprascapular and subclavian nerves arise?
Superior trunk, roots C5 and C6
From where does the lateral pectoral nerve arise?
Superior trunk, anterior division, lateral cord, roots C5-C7
What are the sections of the brachial plexus, from roots to branches?
Roots: paired spinal nerves (left and right) leave spinal cord at each vertebral level
Trunks: the 5 roots come together to form a superior, middle and inferior trunk
Divisions: divide into 3 anterior, 3 posterior divisions that leave the neck and pass into the axilla
Cords: within the axilla. Lateral, posterior and media in relation to the axillary artery
Branches: peripheral nerves
Which nerves come from the posterior cord and what are their contributing nerve roots?
Thoracodorsal-C6,7&8
Superior subscapular-C5,6,7
Inferior subscapular-C5,6,7
From where does medial pectoral nerve arise and roots?
Medial cord. Roots C8, T1
Where do the medial cutaneous nerves of the arm and forearm originate from?
Medial cord, roots C8 & T1
What does the ‘M’ in dissection of brachial plexus represent?
Middle is median, lateral side is musculocutaneous, medial side is ulnar
What is the order of the peripheral nerves that come off the brachial plexus, from lateral to medial?
Musculocutaneous, axillary (posterior), median, radial (posterior), ulnar
Function and roots of musculocutaneous nerves
Motor: innervates anterior arm muscles
Sensory: lateral cutaneous branch of forearm which innervates lateral half of anteriro forearm and small portion of posterior forearm
Roots: C5, C6, C7
Injury to musculocutaneous nerve
Uncommon but possible if stab wound to axilla
Paralyses muscles of anterior arm:
-weakens shoulder flexion (some movement by pec major)
-weakens elbow flexion (brachioradialis can perform)
-weakens supination (supinator muscle can perform)
-loss of sensation over lateral forearm
Functions and roots of axillary nerve
Wraps around humeral head.
Roots: C5&C6
Motor: innervates teres minor and deltoid
Sensory: upper lateral brachial cutaneous nerve
Injury to axillary nerve
By damage to shoulder or proximal humerus
Motor effects: paralysis of deltoid and teres minir, so ABduction is prevented. Long term results in atrophy of deltoid
Sensory effects: loss of sensation over regimental badge area, paraesthesia over distribution of axillary nerve
Functions and roots of median nerve
Roots: C5-T1
Motor: innervates anterior forearm muscles (Except FCU and medial half of FDP), thenar muscles and lateral two lumbricals in hand
Sensory: palmar cutaneous branch innnervates lateral palm, digital cutaneous branch innervates lateral 3.5 fingers palmar surface
What is carpal tunnel syndrome?
Compression of the median nerve. Causes weakness and atrophy of the thenar muscles, numbnress, tingling and pain radiating to the forearm.
Tests: tapping nerve to elicit pain (Tinels sign), holding wrist in flexion for 1 min to elicit numbness or pain (Phalen’s manoeuvre)
TreatmentL splint in dorsiflexion overnight, coricosteroid injections, surgical release
Lesions to median nerve at elbow
Due to humeral fracture. Causes lack of sensation, paralysis of muscles it usually innervates therefore forearm supinated, weak flexion, thumb flexion inhibited
Lesions to median nerve at wrist (proximal to flexor retinaculum)
Thenar muscles paralysed, oppostion of thumb and flexion of 2nd and 3rd digits paralysed
Functions and roots of radial nerve
Roots: C5-T1
Motor: innervates posterior arm and forearm
Sensory: posterior arm and forearm, posterior lateral hand
How can the radial nerve be injured?
Dislocation of humerus, excess pressure onaxilla, radial groove damage through humeral shaft fracture
Give some effects of damage to radial nerve
Paralysed posterior arm and forearm muscles so can’t extend forearm
Wrist drop
Loss of sensation in lateral and posterior arm, posterior forearm and dorsal surface of lateral 3.5 fingers
Describe damage to the deep branch of the radial nerve
Due to fractured radial head or a posterior dislocation of the radius at the elbbow
No sensory effects as deep branch is motor
No wrist drop as extensor carpi radialis not affected, but other post forearm muscles affected
Describe what happens when superficial radial nerve is damaged
From stabbing or laceration of the forearm.
No motor effects as is snesory
Sensory loss over dorsal aspect of the lateral 3.5 digits and their palm area
Functions and roots of ulnar nerve
Roots: C8&T1
Motor: innervates hand muscles (except thenars and the lateral 2 lumbricals), FCU, medial half of FDP
Sensory: anterior and posterior surfaces of the medial 1.5 fingers and associated palm
How may the ulnar nerve be damaged and what would be the effects?
Damage at elbow: fracture of medial epicondyle. All sensory branches affectted causing loss of sensation. Patient cannot grasp paper placed between fingers
Damage at wrist: due to laacerations. Motor and sensory effects, can’t grip paper, long term may develop ulnar claw
What is Erb’s Palsy?
Damage to the C5&C6 roots due to an ecess increased angle between neck and shoulder
Which nerves are affected in Erbs palsy?
Musculocutaneous, axillary, suprascapular, subclavian
What muscles are paralysed in Erbs palsy?
Supraspinatous, infraspinatous, subclavius, biceps brachii, brachialis, coracobrachialis, deltoid, teres minor
Which actions can be affected in Erbs palsy?
Flexion and abduction of shoulder, lateral rotation of arm, supination of forearm.
Loss of sensation on lateral arm
What is waiters tip?
Limb hangs limply and medially rotated. Due to unopposed action of pec major (can’t abduct so adducted permanently). Can be sa result of Erbs palsy
Briefly describe the lymph nodes of the axilla
Lateral, central, posterior, pectoral and apical
Pectoral nodes receive the majority of breast lymph drainage
What is the clinical relevance of the axillary lymph nodes?
Lymph node enlargement: infection of upper limb or pectoral region or breast, or first place for breast cancer mets
Lymphoedema: accumulated lymph in subcutaneous tissue leads to painful swelling of the upper limb. Can occur after lymph node removal due to interruption of lymph drainage
Describe the main artery system in the axilla
Lateral border of 1st rub, subclavian artery becomes axillary
Axillary artery: passes beneath pec minor, at teres major becomes the brachial artery
Describe the main veins in the axilla and arm
Axillary vein: most superficial
Tribituaries:
-cephalic: from dorsal venous network of hand, ascends antero-lateral aspect of upper limb, at shoulder passes between deltoid and pec major to enter axillaa through clavipectoral area–>joins axillary vein
-basilic: from dorsal venous network of hand, ascends medially, at teres major moves deep and forms axillary vein
-median cubital vein: at elbow, cephalic and basilic veins connect
