Axillary and Brachial plexus Flashcards
What is the axilla?
Region under the armpit which is an important anatomical point for structures that control the upper limb.
What does the axilla contain?
Axillary artery
Axillary vein
Axillary lymph nodes
Brachial plexus
Muscles:
Biceps brachii
Coracobrachialis muscle
What are the relations to the apex of the axilla?
Border of 1st rib, clavicle, coracoid process and superior border of scapula.
What are the relations to the anterior of the axilla?
Pectoralis major and pectoralis minor muscles and subclavius muscle.
What are the relations to the medial border of the axilla?
Ribs, intercostal muscles and serratus anterior.
What are the relations to the lateral border of the axilla?
Intertubular groove of humerus.
What are the relations to the posterior border of the axilla?
Lattisimus dorsi, teres major and subcapsularis muscle.
What are the axillary lymph nodes?
Drain the breast and upper limb and consist of 5 groups:
Apical/infraclavicular
Anterior/pectoral
Central
Lateral
Posterior/subcapsular
What axillary lymph node is most clinically relevant?
Axillary lymph node drains into the
R: Subclavian duct
L: Thoracic duct
Cancers of the breast which spread here can metastasise easily.
What is the direction of drainage in the axillary lymph nodes?
They drain into the central lymph node or apical lymph node. Central drains into the apical lymph node.
What is the brachial plexus?
Group of nerves innervating the upper limb which arise from C5,C6, C7, C8 and T1. It is located between the anterior and posterior scalene muscles.
Which nerve comes off C5?
Dorsal scapulae nerve which innervates the rhombdoid major, rhombdoid minor and levator scapulae.
Which nerve arises from C5, C6 and C7?
Long thoracic nerve which innervates the serratus anterior
What are the components of the brachial plexus?
C5 and C6 form the upper trunk
C7 forms the middle trunk
C8 and T1 forms the lower trunk
Which nerves arise from the upper trunk?
Suprascapular nerve
Subclavius nerve
What is the supracapsular nerve?
Innervates the supraspinatous muscle and infraspinatous muscle and shoulder joint.
What is the subclavius nerve?
Innervates the subclavius muscle to depress the clavicle.
What are the cords of the brachial plexus?
Lateral cord
Posterior cord
Medial cord
What is the lateral cord?
Formed of the anterior divisions of the upper and middle trunk (C5-C7)
What is the posterior cord?
Formed of the posterior divisions of all 3 trunks. (C5-T1)
What is the medial cord?
Formed of the anterior division of the lower trunk. (C8-T1)
Which nerve comes off the lateral cord?
Lateral pectoralis nerve supplying the pectoralis major muscle.
What forms the musculocutaneous nerve?
Lateral cord
-> Anterior division of upper and middle trunk (C5-C7)
What is the function of the musculocutaneous nerve?
Sensation of the lateral forearm
Innervation of elbow flexor muscles: Coracobrachialis, brachialis and biceps brachii
Which nerve comes off the posterior cord?
Upper Subscapular nerve
Thoracodorsal nerve
Lower subscapular nerve
What is the upper subcapsular nerve?
Innervates subcapsularis muscle for internal rotation at shoulder joint
Works with lower subcapsular nerve to innervate the teres major.
-> Branch of posterior cord
What is the thoracodorsal nerve?
Innervates the lattisimus dorsifor medial rotation, extension and adduction of shoulder.
-> Branch of posterior cord
What is the lower subcapsular nerve?
Innervates the teres major and subscapularis along with the upper subcapsular nerve.
-> Branch of posterior cord
What forms the axillary nerve?
Posterior cord
-> posterior division of all 3 trunks (C5-T1)
What is the function of the axillary nerve?
Motor function is innervation of deltoid muscle and teres minor
Cutaneous sensation to lateral and posterior surface of deltoid muscle
What forms the radial nerve?
Posterior cord
-> posterior division of all 3 trunks (C5-T1)
What is the cutaneous function of the radial nerve?
Dorsum of hand from thumb, parts of digit 2 and 3
Sensation to the posterior and lateral forearm
What is the motor function of the radial nerve?
Tricep muscle, extensor muscles of forearm and superficial cutaneous branch to the thumb and index finger.
What forms the median nerve?
Joining of the lateral cord and median cord (C5 -T1)
What is the cutaneous function of the median nerve?
Sensation to ventral surface of hand of thumb, digit 2, 3 and 1/2 of digit 4
What is the motor function of the median nerve?
Radial side of flexor digitorum profundus
Muscles of thenar eminence
Radial side flexors of hand and forearm
What nerve comes off the median cord?
Medial pectoral nerve
Medial brachial cutaneous nerve
Medial antebrachial cutaneous nerve
What is the medial pectoral nerve?
Innervates pectoralis major and pectoralis minor
-> Branch of median cord
What is the medial brachial nerve?
Cutaneous innervation to the medial side of the arm
-> Branch of median cord
What is the medial antebrachial cutaneous nerve?
Cutaneous innervation to the medial side of the forearm.
-> Branch of median cord
What forms the ulnar nerve?
Median cord
-> Anterior division of lower trunk (C8 and T1)
What is the cutaneous function of the ulnar nerve?
Hand dorsum digit 4 and 5
Hand ventral 1/2 of digit 4 and digit 5
What is the motor function of the ulnar nerve?
Ulnar side of flexor digitorum profundus
Palmar and dorsal interosseus muscles
Provides innervation to majority of muscles of the hand such as Hypothenar eminence
->THENAR EMINENCE IS EXECEPTION
What is a claw hand?
Flexed fingers of hand that are unable to straighten, commonly due to ulnar nerve lesion.
Partial claw hand: ulnar nerve
Complete claw hand: ulnar and median nerve lesion
What is the consequence of a radial nerve lesion?
Weakness of extensor muscles of forearm
Loss of sensation in dorsum of hand web between thumb and digit 2
What is the consequence of a ulnar nerve lesion?
Partial claw hand affecting digit 4 and 5 due to paralysis of intrinsic muscles of hand
Atrophy of hypothenar eminence
What is the consequence of a median nerve lesion?
Atrophy of thenar eminence and flexor forearm muscles
Sensory loss in digit 2 and 3 and half of palm
What happens in upper brachial plexus injury?
Head and neck are moved away from the shoulder violently which damages C5 and C6, causing Erb’s palsy with arm and shoulder paralysis. The hand is rotated backwards.
-> can occur in childbirth
What happens in lower brachial plexus injury?
Injury to C8 and T1 due to excessive abduction, typically during birth which affects lower myotomes and dermatomes with muscles of forearm and hand
-> Horner syndrome can occur due to T1 being affected
What is Horner syndrome?
Lesion in the sympathetic nerve which results in:
Ptosis (drooping of eyelid), mioisis (constricted pupil) and anhydrosis (no sweating)
What does C5 myotome innervate?
Deltoid muscle
What does the C6 myotome innervate?
Biceps.
What does the C7 myotome innervate?
Triceps
What does the C8 myotome in nervate?
Hand muscled
What does the T1 myotome innervate?
Finger muscles
Which nerve root in the brachial plexus is important for shoulder abduction?
C5
Which nerve root in the brachial plexus is important for shoulder adduction?
C6, C7, C8
Which nerve root in the brachial plexus is important for elbow flexion?
C5 and C6
Which nerve root in the brachial plexus is important for elbow extension
C7 and C8
Which nerve root in the brachial plexus is important for forearm pronation?
C6 controls forearm pronation and supination.
Which nerve root in the brachial plexus is important for wrist movements?
C6 and C7.
Which myotome for wrist flexion?
C7
Which myotome for wrist extension
C6
Which nerve root in the brachial plexus is important for finger and thumb movement?
C8 control the flexion and extension of fingers and thumb
Which nerve root in the brachial plexus is important for finger abduction?
T1 controls finger abduction.
Where is the brachial plexus located?
Between the anterior and middle scalene muscle, close to the axiliary artery. The cords are named based on their relation to the auxiliary artery
Loss of sensation over upper right lateral arm
Axillary nerve damage over regimental badge area.
Winging of scapula
Damage to long thoracic nerve which innervates the serratus anterior.
Innovation to lateral forearm
Musculouutaneous nerve.
What is the role of the anterior divisions of the brachial plexus?
Innervates the flexor muscles.
What is the role of the posterior division of the brachial plexus?
Innervates the extensor muscles.
