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