Forelimb Nerve, Blood and Lymph Supply Flashcards
what is the nerve supply to the forelimb
most supplied via the brachial plexus –> ventral branches from C6, C7, C8, T1, 2
where is the brachial plexus located
in axilla
mult exchange of fibres
emerging nerves supply forelimb muscles
what extrinsic muscles does the brachial plexus supply
- pectoral muscles
- latissimus dorsi
- serratus ventralis
(brachiocephalicus and trapezius are not)
how does the brachial plexus supply intrinsic muscles
- subscapular nerve
- suprascapular nerve
- musculocutaneous nerve
- axillary nerve
- median and ulnar nerve
- radial nerve
what is the funciton of the subscapular nerve
medial shoulder support: subscapularis muscle
what is the function of the suprascapular nerve
lateral shoulder support: supraspinatous muscle, infraspinatous muscle
no cutaneous sensation
what is the function of the musculocutaneous nerve
flexion of elbow: brachialis muscle, biceps brachii muscle
what cutaneous sensation does musculocutaneous nerve
cranial and medial aspect of elbow
medial aspect of antebrachium
what does damage of the musculocutaneous nerve cause
loss of elbow flexion (no compensation)
loss of cutaneous sensation
what is the function of axillary nerve
dedicated shoulder flexors: deltoideus muscle, teres major muscle
what cutaneous sensation does the axillary nerve provide
lateral aspect shoulder and brachium (green)
what does damage to the axillary nerve cause
what is the function of the median and ulnar nerves
carpal and digital flexors: flexor carpi ulnaris muscle, superficial digital flexor muscle, deep digital flexor muscle
what cutaneous sensation does the median and ulnar nerves provide
caudal and palmar aspect of limb (pink)
dorsal aspect 5th digit
what does damage of median and ulnar nerves cause
loss of distal limb flexion
no compensation
what is the function of the radial nerve
extensors of elbow, carpus, digits
extensor carpi radialis muscle
extensor carpi ulnaris
common digital extensor muscle
what cutaneous sensation does the radial nerve
cranial and dorsal aspect limb (purple) (except dorsal aspect 5th digit)
what are the routes of the radial nerve
starts in axilla passes caudal to shoulder
passes through triceps muscle (supplies triceps –> elbow extensor)
wraps around humerus (with brachialis muscle)
what are the branches of the radial nerve
lateral epicondyle: supplies distal limb extensors
cranial/dorsal aspect limb: runs alongside cephalic vein –> supplies cutaneous sensation
what is the most common cause of radial damage
humeral fracture most common cause
what occurs if there is proximal damage of the radial nerve
all extensor muscles affected
cannot extend elbow, carpus or digits –> cannot weight bear
what occurs if there is distal damage to the radial nerve
cannot extend carpus/digits
triceps supply intact so can extend elbow –> can weight bear if limb extended, can learn to swing leg to compensate
what are the problems in distal damage to the radial nerve
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
what are the functional effects of complete disruption of the brachial plexus
- cannot retract/adduct limb
- cannot extend/flex limb
- cannot weight bear
- can protract/abduct limb (brachiocephalicus and trapezius)
- no cutaneous sensation on limb or lateral thorax to level of 3rd intercostal space
what is the equine forelimb nerves that contribute to sensation
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
what are nerve blocks used for
localize area of lameness
desensitize structures
check if still lame or has resolved
what do the median and ulnar nerve branches distal to carpus
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
what are the equine nerve blocks
- palmar digital nerve block: palmar digital nerves –> blocks caudal 1/2 foot
- abaxial sesamoid nerve block: palmar digital nerves + dorsal branches –> blocks entire foot
- palmar metacarpal nerve block: “4 point block” palmar nerves (between suspensory and flexors), palmar metacarpal nerves (distal end splint bones) blocks entire digit
what ist he arterial supply to the canine forelimb
oxygenated blood from heart –> single major vessel changes name with region of forelimb –> crosses flexor angles of joint
- subclavian artery: runs around 1st rib –> axilla
- axillary artery: runs through axilla
- brachial artery: runs down brachium
various branches
distal limb well supplied
what is the venous drainage of the forelimb
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
what are the features of the cephalic vein
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
what is the forelimb blood supply of the horse
- brachial artery: medial aspect elbow, palpable pulse
- medial and lateral digital arteries: abaxial aspect proximal sesamoids, palpable pulse
- venous drainage is similar to dog, no clinical relevance
what is the lymphatic drainage
run from periphery to thoracic duct
empties into caudal vena cava
node swelling can indicate infeciton if enlarged
prescapular: palpable
axillary: not palpable
what are the equine distal limb nerves
what are the nerves of the equine forelimb
