BMS271 - Upper Limb Neuro Flashcards
Brachial Plexus
- 5 nerve roots C5, C6, C7, C8, T1
- nerve roots formed by anterior rami of spinal nerves
- 3 trunks, upper, middle and lower
- upper = C5 and C6, middle = C7, lower = C8 and T1
- Trunks divide into anterior and posterior divisions
- anterior = flexors, posterior = extensors
- 3 cords, lateral, posterior and medial
- cords surround axillary artery
- Cords give rise to 5 major nerves
- Roots and trunks = superior to clavicle
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Dorsal scapular nerve (C5)
rhomboid major, rhomboid minor, levator scapulae
Long thoracic nerve (C5, C6, C7)
serratus anterior
Nerve to subclavius (C5, C6)
subclavius
Suprascapular nerve (C5, C6)
supraspinatus, infraspinatus
Lateral pectoral nerve (C5,C6,C7)
pectoralis major, pectoralis minor
Comes from lateral cord
Subscapular nerves (C5,C6)
subscapularis, teres major
Thoracodorsal nerve (C6, C7, C8)
latissimus dorsi
Medial pectoral nerve (C8, T1)
pectoralis major, pectoralis minor
Comes from medial cord
Medial cutaneous nerve of arm (C8, T1)
Medial cutaneous nerve of arm
Medial cutaneous nerve of forearm (C8, T1)
Medial cutaneous nerve of forearm
Myotomes
- Myotome = skeletal muscle tissue innervated by a single pair of spinal nerves
- one myotome may include several muscles (or parts of several muscles)
- one muscle may be part of several myotomes
- Difficult to identify anatomically, but important clinically
hard to differentiate one myotome from the next, but easy to spot functional deficits if one spinal nerve is injured - Muscle groups acting on individual joints may be grouped this way e.g. elbow flexors = C5, C6
Dermatomes
- Dermatome = an area of skin innervated by a pair of spinal nerves
- on the trunk dermatomes are aligned in narrow transverse bands with considerable overlap
- in the limbs the areas of skin are larger
- Two dermatomal maps exist
- one is based on scratch sensitivity tests in patients with herniated IV disks
- the other is based on patients in whom one spinal nerve has been left intact while those above and below are severed
Axillary Nerve
Arises from posterior cord (C5, C6) Passes glenohumeral joint capsule Enters quadrangular space bordered by inferior border of subscapularis teres major long head of triceps brachii surgical neck of the humerus Wraps around surgical neck of humerus Gives off upper lateral brachial cutaneous nerve innervates skin over inferior deltoid and superior triceps Innervates: - glenohumeral joint capsule - deltoid - teres minor - Superior lateral cutaneous nerve of arm: - skin over inferior deltoid and superior triceps
Musculocutaneous Nerve
Arises from lateral cord (C5, C6)
Enters coracobrachialis from axilla
Exits lateral aspect of coracobrachialis and descends between biceps brachii and brachialis
Gives off lateral cutaneous nerve of the forearm
exits from between biceps brachii and brachialis lateral to tendon of biceps brachii
innervates skin over lateral aspect of forearm
Innervates:
- coracobrachialis
- biceps brachii
- brachialis
- humerus
- elbow joint
Lateral cutaneous nerve of the forearm
skin over lateral aspect of forearm