A: Axilla, Brachial plexus, posterior triangle Flashcards
What is the base of axilla made of?
Skin going from arm to chest wall
What is apex of axilla made of?
1st rib, clavicle in front + superior edge of subscapularis behind
What is anterior wall of axilla made of?
Pectoralis minor + pectoralis major
What is posterior wall of axilla made of?
Subscapularis, latissimus dorsi + teres major
What are the gateways through posterior wall?
Quadrangular space, triangular interval, triangular space
Medial wall of axilla made of?
Serratus anterior + intercostal space
Lateral wall of axilla made of?
Upper end of humerus, biceps brachii, coracobrachialis.
Axillary sheath contains:
axillary artery, axillary vein and cords of brachial plexus.
Brachial plexus is made of:
Anterior rami of C5-T1
Components of brachial plexus:
Roots, trunks, divisions, cords, branches.
What spinal nerve is responsible for abduction?
C5
What spinal nerve is responsible for flexion of digits?
C8
What spinal nerve is responsible for adduction and abduction of digits?
T1
What spinal nerve is responsible for flexion of elbow
C6,C7
What spinal nerve is responsible for extension of elbow
C6,7,8
Anterior boundary for posterior triangle of neck
Posterior of sternocleidomastoid
Posterior boundary for posterior triangle of neck
Anterior of trapezius
Inferior boundary for posterior triangle of neck
Middle 1/3 of clavicle
Apex of posterior triangle of neck
Where trapezius and SCM meet on occipital bone
Roof of posterior triangle of neck
Cervical fascia
Floor of posterior triangle of neck
Splenius capitis, levator sculpae, posterior scalene, middle scalene, anterior scalene.
How is the posterior triangle divided?
By omohyoid muscle
What cord forms musculocutaneous nerve?
lateral
What cord forms median nerve
lateral + medial
What cord forms radial nerve?
posterior
What cord forms ulnar nerve?
medial
What structures mark the beginning and the end of the axillary artery
begins = lateral border of 1st rib
ends = inferior border of teres major.
Pectoral lymph node
Receives lymph from anterior thoracic wall + breast
Subscapular lymph node
Receives lymph from upper quadrant of back
Infraclavicular lymph node
Receives lymph from lymphatics accompanying cephalic vein
Central lymph node
Receives lymph from anterior, posterior + lateral groups
Apical lymph node
Receives lymph from all other groups of axillary LN + lymphatics accompanying cephalic vein
Humeral lymph node
Receives all lymph from upper limb.
Sternocleidomastoid
- Sternal head: manubrium of sternum. Clavicular head: medial 1/3 of clavicle
- Mastoid process of skull
- Rotate neck to face superiorly to opposite side, tilt neck laterally, flex neck
- Accessory nerve
Posterior scalene
- Cervical vertebrae
- 2nd rib
- Raises 2nd rib
- Cervical nerves
Middle scalene
- Cervical vertebrae
- 1st rib
- Raises 1st rib
- Cervical nerves
Anterior scalene
- Cervical vertebrae
- 1st rib
- Raises 1st rib
- Cervical nerves
Omohyoid
- superior border of scapula near suprascapular notch
- Hyoid bone
- Depresses + steadies hyoid bone
- Cervical nerves
Axillary sheath
Encloses axillary artery, vein + brachial plexus
External jugular vein
Drains scalp + face.
Starts at angle of mandible and crosses superficial SCM.
Descends to inferior of posterior triangle and terminates in subclavian vein
Subclavian vein
Drains upper limb
Passes through inferior part of posterior triangle
Lies anterior to anterior scalene muscle.
Joins internal jugular vein to form brachiocephalic vein.
Subclavian artery
Passes through inferior part of posterior triangle
Lies posterior to anterior scalene
Passes over 1st rib, so if there is a haemorrhage from UL, you can press on first rib to block artery and control bleeding.
Accessory nerve
Passes deep (supplies) SCM, crosses posterior triangle + supplies trapezius muscle.
Enters posterior triangle along posterior border of SCM, passes postero-inferiorly through posterior triangle within roof.
Leaves deep to anterior border of trapezius.
How to test function of accessory nerve?
Ask patient to shrug shoulder while pushing their shoulder down with your hand. Test for weakness of SCM + trapezius.
Injury to upper lesion of brachial plexus
C5+C6
UL hangs limply
UL medially rotated at shoulder due to unopposed action of pectoralis major
Elbow extended + forearm pronated due to loss of action of biceps + brachialis
Loss of sensation to lateral side of arm
Injury to lower lesion of brachial plexus
C8, T1
All small muscles of hand affected
Loss of sensation along medial side of arm
Injury to accessory nerve
Drooping of shoulder + inability to lift arm above shoulder
SCM and trapezius lost nerve supply.
Name the nerve(s) and vessel(s) which lie anterior and posterior to anterior scalene muscle
Anterior: Subclavian vein, phrenic nerve (lies immediately posterior to the vein)
Posterior: Roots of brachial plexus, subclavian artery
Erb-Duchenne palsy
Waiters tip position
Injury to C5-6
UL hangs limply
UL medially rotated at shoulder due to unopposed action of pectoralis major
Elbow extended + forearm pronated due to loss of action of biceps + brachialis
Loss of sensation to lateral side of arm
Klumpke palsy
Injured C8-T1
Small muscles of hand affected (claw hand deformity)
Loss of sensation across medial side of arm
Where is the accessory nerve vulnerable to injury?
As it crosses posterior triangle - within roof (i.e. investing layer of deep cervical fascia) - susceptible to injury due to its superficial location
You can see the sternocleidomastoid muscle contracting on your patient while he is resting in bed. Why is this significant?
Physical sign of respiratory distress - used for deep inspiration.
What is the location of the subclavian artery and vein relative to the anterior scalene muscle?
Subclavian artery: posterior to anterior scalene muscle
Subclavian vein: anterior to anterior scalene muscle
What forms the inferior boundary of the posterior triangle
Middle third of clavicle, between attachments of trapezius and sternocleidomastoid
Profunda brachii artery + where can it be injured
Branch of brachial artery that accompanies radial nerve in spiral groove. Can be injured from fracture of midshaft of humerus.
Where does the cephalic vein terminate
Drains into axillary vein in deltopectoral groove
Brachial artery division
Divides at apex of cubital fossa into ulnar + radial artery.
Which roots supply bicepts tendon reflex?
c6
Which roots supply triceps tendon reflex
C7
Where can the pulse of brachial artery be found?
- Mid arm - against medial side of humerus
- Cubital fossa: medial to biceps tendon
Which nerve is closely related to basilic vein
Medial cutaneous nerve of forearm
Course of basilic vein
It drains medial aspect of dorsal venous arch.
It ascends the medial side of forearm and arm.
In mid-arm region, it pierces deep fascia of the arm and joins with veins accompanying the brachial artery to form axillary vein
Course of cephalic vein
Drains lateral aspect of dorsal venous arch.
Ascends anterolateral border of forearm and arm, enters delto-pectoral groove and pierces clavi-pectoral fascia and empties into axillary vein.
When can long thoracic nerve be damaged
mastectomy
Damage to thoracic wall when UL is abducted.
Fracture of midshaft of humerus can damage profunda brachii artery - why?
Lies in spiral groove close to bone
Where can brachial artery pulse be palpated?
Mid arm - against medial side of humerus
Cubital fossa: medial to biceps tendon
Which artery is most likely injured in supracondylar fracture of the humerus? What is the consequence for the patient?
Brachial artery
Ischaemia (lack of blood supply) of forearm muscles →
ischaemic contracture (uncontrolled flexion of hand)
In which direction is dislocation most likely to occur in axilla?
Inferior direction dislocation most common.
Coracoacromial arch & rotator cuff support joint superiorly, anteriorly & posteriorly. Inferiorly, it is not supported.
Where is the axillary nerve liable to injury?
Dislocation (inferior) of shoulder joint
Fracture of surgical neck of humerus
Quadrangular space syndrome
