Forelimb Nerve, Blood and Lymph Supply

Question 1

what is the nerve supply to the forelimb

Answer 1

most supplied via the brachial plexus –> ventral branches from C6, C7, C8, T1, 2

Question 2

where is the brachial plexus located

Answer 2

in axilla

mult exchange of fibres

emerging nerves supply forelimb muscles

Question 3

what extrinsic muscles does the brachial plexus supply

Answer 3

1. pectoral muscles
2. latissimus dorsi
3. serratus ventralis

(brachiocephalicus and trapezius are not)

Question 4

how does the brachial plexus supply intrinsic muscles

Answer 4

1. subscapular nerve
2. suprascapular nerve
3. musculocutaneous nerve
4. axillary nerve
5. median and ulnar nerve
6. radial nerve

Question 5

what is the funciton of the subscapular nerve

Answer 5

medial shoulder support: subscapularis muscle

Question 6

what is the function of the suprascapular nerve

Answer 6

lateral shoulder support: supraspinatous muscle, infraspinatous muscle

no cutaneous sensation

Question 7

what is the function of the musculocutaneous nerve

Answer 7

flexion of elbow: brachialis muscle, biceps brachii muscle

Question 8

what cutaneous sensation does musculocutaneous nerve

Answer 8

cranial and medial aspect of elbow

medial aspect of antebrachium

Question 9

what does damage of the musculocutaneous nerve cause

Answer 9

loss of elbow flexion (no compensation)

loss of cutaneous sensation

Question 10

what is the function of axillary nerve

Answer 10

dedicated shoulder flexors: deltoideus muscle, teres major muscle

Question 11

what cutaneous sensation does the axillary nerve provide

Answer 11

lateral aspect shoulder and brachium (green)

Question 12

what does damage to the axillary nerve cause

Question 13

what is the function of the median and ulnar nerves

Answer 13

carpal and digital flexors: flexor carpi ulnaris muscle, superficial digital flexor muscle, deep digital flexor muscle

Question 14

what cutaneous sensation does the median and ulnar nerves provide

Answer 14

caudal and palmar aspect of limb (pink)

dorsal aspect 5th digit

Question 15

what does damage of median and ulnar nerves cause

Answer 15

loss of distal limb flexion

no compensation

Question 16

what is the function of the radial nerve

Answer 16

extensors of elbow, carpus, digits

extensor carpi radialis muscle

extensor carpi ulnaris

common digital extensor muscle

Question 17

what cutaneous sensation does the radial nerve

Answer 17

cranial and dorsal aspect limb (purple) (except dorsal aspect 5th digit)

Question 18

what are the routes of the radial nerve

Answer 18

starts in axilla passes caudal to shoulder

passes through triceps muscle (supplies triceps –> elbow extensor)

wraps around humerus (with brachialis muscle)

Question 19

what are the branches of the radial nerve

Answer 19

lateral epicondyle: supplies distal limb extensors

cranial/dorsal aspect limb: runs alongside cephalic vein –> supplies cutaneous sensation

Question 20

what is the most common cause of radial damage

Answer 20

humeral fracture most common cause

Question 21

what occurs if there is proximal damage of the radial nerve

Answer 21

all extensor muscles affected

cannot extend elbow, carpus or digits –> cannot weight bear

Question 22

what occurs if there is distal damage to the radial nerve

Answer 22

cannot extend carpus/digits

triceps supply intact so can extend elbow –> can weight bear if limb extended, can learn to swing leg to compensate

Question 23

what are the problems in distal damage to the radial nerve

Answer 23

sensory losses of cranial and dorsal aspect of limb can lead to trauma to dorsal aspect of paw if drags and also self mutilation

check for sensation using forceps

Question 24

what are the functional effects of complete disruption of the brachial plexus

Answer 24

1. cannot retract/adduct limb
2. cannot extend/flex limb
3. cannot weight bear
4. can protract/abduct limb (brachiocephalicus and trapezius)
5. no cutaneous sensation on limb or lateral thorax to level of 3rd intercostal space

Question 25

what is the equine forelimb nerves that contribute to sensation

Answer 25

different sensory areas proximal to carpus median and ulnar nerves combine to supply distal limb combined with musculocutaneous nerve medial aspect metacarpal area blue: musculocutaneous nerve green: axillary pink: median and ulnar nerves purple: radial

Question 26

what are nerve blocks used for

Answer 26

localize area of lameness desensitize structures check if still lame or has resolved

Question 27

what do the median and ulnar nerve branches distal to carpus

Answer 27

**1. palmar metacarpal nerves (yellow)** - medial and lateral - between MC3 and splint bones - emerge at distal end of splint bones - supply dorsal aspect of digit **2. palmar nerves (blue)** - medial and lateral - between suspensory ligament and SDFT - cross abaxial aspect proximal sesamoids become palmar digital nerves (also blue) --\> dorsal and palmar branches which supply hoof contents

Question 28

what are the equine nerve blocks

Answer 28

1. palmar digital nerve block: palmar digital nerves --\> blocks caudal 1/2 foot 2. abaxial sesamoid nerve block: palmar digital nerves + dorsal branches --\> blocks entire foot 3. palmar metacarpal nerve block: "4 point block" palmar nerves (between suspensory and flexors), palmar metacarpal nerves (distal end splint bones) blocks entire digit

Question 29

what ist he arterial supply to the canine forelimb

Answer 29

oxygenated blood from heart --\> single major vessel changes name with region of forelimb --\> crosses flexor angles of joint 1. subclavian artery: runs around 1st rib --\> axilla 2. axillary artery: runs through axilla 3. brachial artery: runs down brachium various branches **distal limb well supplied**

Question 30

what is the venous drainage of the forelimb

Answer 30

deoxygenated blood back to heart **deep system:** follows arterial supply (vein, artery, nerve often run together) **superficial:** cephalic vein drains into jugular vein/vena cava

Question 31

what are the features of the cephalic vein

Answer 31

access to systemic circulation pressure required to raise vein valves allow blood to pool must release pressure before inject --\> must ensure fluid enters vein and not subcutaneous tissue radial nerve runs alongside cephalic vein

Question 32

what is the forelimb blood supply of the horse

Answer 32

1. brachial artery: medial aspect elbow, palpable pulse 2. medial and lateral digital arteries: abaxial aspect proximal sesamoids, palpable pulse 3. venous drainage is similar to dog, no clinical relevance

Question 33

what is the lymphatic drainage

Answer 33

run from periphery to thoracic duct empties into caudal vena cava node swelling can indicate infeciton if enlarged **prescapular: palpable** **axillary: not palpable**

Question 34

what are the equine distal limb nerves

Answer 34

Question 35

what are the nerves of the equine forelimb

Answer 35