Axilla is the area that lies underneath the glenohumeral joint. It is significant because it contains the axillary artery and the neurovascular bundle known as brachial plexus.
- Pyramid shaped (with apex & 5 other borders)
- Apex (axillary inlet) – lateral border of 1st rib, superior border of scapula & posterior border of clavicle
- Lateral wall – intertubercular groove of humerus
- Medial wall – serratus anterior & thoracic wall
- Anterior wall – pectoralis major, pectoralis minor & subclavius muscles
- Posterior wall – subscapularis, teres major, latissimus dorsi
- Has anterior, middle and posterior parts
- Origin – scapula & clavicle
- Insertion – deltoid tuberosity on lateral surface of humerus
- Innervation – axillary nerve (C5-C6)
- anterior fibres – flexion & medial rotation
- middle fibres – major ABDuctor of arm (15-90 degrees with the help of supraspinatus)
- posterior fibres – extension & lateral rotation
- Origin – dorsal surface of inferior angle of scapula
- Insertion – medial lip of intertubercular groove of humerus
- Innervation – lower subscapular nerve (C5-C6)
- Action – extension, ADDuction & medial rotation of arm
- Become axillary artery from subclavian artery when it emerges from beneath the clavicle & crosses the 1st rib.
- Continues as brachial artery once reaches inferior border of teres major muscle.
- Provides blood to all shoulder muscles
Two good mnemonic I use are “Rugby Teams Drink Cold Beer” – to remember the roots, trunks, divisions, cords and branches!
Another good mnemonic is “Most Alcoholics Must Really Urinate” – to remember the order of the nerve branches
- Musculocutaneous nerve
- Supplies anterior flexor compartment of arm
- Injury = inability to flex elbow
- Axillary nerve
- Behind surgical neck of humerus
- Supplies deltoid & teres minor
- Injury = usually surgical neck fracture, loss of ABDuction of shoulder from 15-90 degrees
- Median nerve
- Anterior to the elbow, runs between two heads of the pronator teres
- Supplies lateral flexors of the wrist, 2 lateral lumbricals & thenar eminence (via recurrent branch)
- Injury = usually carpal tunnel syndrome, supracondylar fractur or lunate dislocation; common signs are resulting in “hand of benediction”, thenar eminence atrophy
- Runs in radial groove in posterior humerus
- Supplies triceps, brachioradialis & extensors of the wrist
- Injury = fracture to body of humerus, Saturday night palsy, resulting in “wrist drop”
- Posterior to medial epicondyle, superficial to flexor retinaculum
- Supplies medial flexors of wrist, 3rd & 4th lumbricals, interosseous muscles, hypothenar eminence
- Injury = medial epicondyle fracture or fracture of hook of hamate; results in inability to ABD/ADDuct fingers, hypothenar atrophy or “ulnar claw hand”
This video is a great quick resource that summarises everything.
Although this is a paediatric EM resource, I find this is still helpful to use in adults & an easy way to remember!
- C5/C6 injury
- Usually resulting from trauma or traumatic birth
- Limb handing by the side, medially rotated with pronated forearm
- Usually pancoast tumour, traumatic birth
- Radial, ulnar and median nerves affected – all fingers clawed, loss of all lumbricals
- Teach Me Anatomy (teachmeanatomy.info)