Upper forelimb

Question 1

compare attachment of fore and hind limbs to the body and reasons for the differences

Answer 1

• strong attachment of the hindquarters to the vertebrae via sacro-iliac joint but no bony attachment of the forelimb to axial skeleton
• allows for mobile scapula (increased stride length) and shock absorption (due to muscular attachment)

Question 2

differentiate between extrinsic and intrinsic muscles and give examples

Answer 2

• extrinsic muscles attach limb to body: serratus ventralis, deep pectoral, latissimus dorsi, brachiocephalicus
• intrinsic (attachments only within limb): brachialis, biceps brachii, shoulder muscles, extensor carpi radialis

Question 3

what is main weight bearing forelimb extrinsic muscle and how does horse reduce gravitational stress on it

Answer 3

• serratus ventralis

- forelimb stay apparatus that fixes the shoulder and carpal joints

Question 4

3 common nerve damage syndromes of upper forelimb

Answer 4

• sweeny: damage to suprascapular nerve associated with collar (supplies infra and supraspinatus mm)
• radial nerve paralysis: supplies all intrinsic extensors (distal part vulnerable to damage)
• brachial plexus paralysis: from lateral recumbency

Question 5

what is structure and function of lacertus fibrosis

Answer 5

• long tendon of the biceps: connects central tendon of biceps to extensor carpi radialis
• continuous tendon extending from metacarpus to scapula: fixes shoulder and carpal joints with little or no effect on elbow joint

Question 6

compare hind and forelimb stay apparatus structure and function

Answer 6

• hind: stifle/patella lock mechanism, superficial digital flexor, suspensory apparatus (locks 1 leg at a time)
• fire: biceps tendon, lacertus fibrosus, extensor carpi radialis, suspensory apparatus (both legs fixed at same time)

Question 7

compare radius and ulnar fusion in various domestic species

Answer 7

• pig: fibrous fusion of radius and ulna
• cow: bony fusion of radius and ulna
• horse: bony fusion; distal part of ulna absorbed within radius

Question 8

how is bone maturity for racing determined in the horse

Answer 8

radiology of distal radial physis

Question 9

what is significance of absence of clavicle in quadrupeds

Answer 9

allows the shoulder not to be fixed, allowing for a much more mobile scapula to increase stride length and therefore speed

Question 10

what muscles cause advancement and retraction of entire forelimb

Answer 10

• advancement by brachiocephalicus

- retraction by deep pectoral (ascending) and latissimus muscles

Question 11

what are principal inputs and outputs of brachial plexus

Answer 11

• inputs: numbered nerves C5-8, T1-2

- outputs: named nerves (suprascapular, thoracodorsal, subscapular, axillary, median, ulnar, radial, musculocutaneous)

Question 12

differentiate between flexor and extensor epicondyles of humerus

Answer 12

• flexor: medial epicondyle (origin of antebrachial flexor muscles)
• extensor: lateral epicondyle (origin of antebrachial extensor muscles)

Question 13

what is the chestnut and what is it homologous to

Answer 13

• thickening of skin with no hair on it

- remnant of carpal/tarsal pad

Question 14

compare fore and hind limb chestnuts

Answer 14

located higher in the forelimb (above carpus) than in the hind limb (below hock)