Week 3: Equine Thoracic Limb, Passive Stay and Fibrous Support

Question 1

Functions of the fibrous support mechanism (stay apparatus) (2)

Answer 1

• Reduce the energy expelled to stand (rest/sleep while standing)
• Make movement efficient (groups of muscles and tendons/ligaments work in synchronyand create a motion )

Question 2

What allows horses to doze while standing up, using minimal muscular activity (locks joint and limbs to prevent collapse)

Answer 2

Stay apparatus

Question 3

Is it normal for horses to lay down and rest?

Answer 3

Yes

Question 4

Approximately ___% of the weight is on what

Answer 4

thoracic limbs

Question 5

Clinical relevance of weight distribution

Answer 5

60% of lameness is due to thoracic limb problems

Question 6

Pastern Joint

Answer 6

Proximal interphalangeal joint

Question 7

Coffin Joint

Answer 7

Distal interphalangeal joint

Question 8

Carpus (knee)

Answer 8

Radiocarpal joint (antebrachiocarpal joint) + midcarpal joint + carpometacarpal joint

Question 9

Fetlock

Answer 9

Metacarpophalangeal

Question 10

If left unsupported, what would happen to the jointed bony column of the thoracic limb?

Answer 10

• Flexion of elbow joint
• Marked flexion of shoulder joint
• Flexion (buckling forwards) of carpus
• Marked hypertension/dorsiflexion of the fetlock and pastern

Results in collapse under the weight of the animal

Question 11

Normal standing horse is in a constant state of

Answer 11

hypertension

Question 12

Just as seen in the dog, the body weight is transferred to the _______ and _______ which then exert a downward force onto the thoracic limb

Answer 12

Pectoral muscles and serratus ventralis

Question 13

The tendon of the ____ prevents the should from flexing

Answer 13

biceps brachii

Question 14

Tendon of the biceps brachii origin engages on the

Answer 14

intermediate tubercle

Question 15

Tension on the bicep is also transmitted to the extensor carpi radialis via the

Answer 15

lacertus fibrosus

Question 16

Molding of the biceps brachii tendon to the intermediate tubercle of the humerus, it causes

Answer 16

the shoulder joint to lock

Question 17

When bicep tendon is locked on intermediate tubercle

Answer 17

the shoulder doesn’t flex

Question 18

When the shoulder is fixed, the weight rests on a nearly

Answer 18

vertical radius

Question 19

Triceps muscle remains ____ during standing phase

Answer 19

flaccid

Question 20

Carpus cannot flex unless the ECR is

Answer 20

flaccid

Question 21

Two parts of stabilization of the carpus

Answer 21

• Tension on biceps brachii

- Strong palmar carpal ligment prevents hyperextension

Question 22

Tension on tendons of the SDF and DDF are checked by

Answer 22

the accessory ligaments of these tendons

Question 23

Downwards force on the fetlock engages

Answer 23

the suspensory apparatus (interosseus ligament)

Question 24

The extensor branches of the interosseus counteract flexion of

Answer 24

the coffin joint

Question 25

Tension of the DDF tendon tends to flex the coffin joint, which

Answer 25

causes the toe of the hoof to dig into the ground

Question 26

What counteracts the hyperextension of the fetlock joint

Answer 26

Distal sesoidean ligaments

Question 27

What muscle in the horse gives the shoulder a nice, rounded appearance?

Answer 27

Subclavius

Question 28

What forms the ventral border of the jugular groove in the horse?

Answer 28

sternomandibularis

Question 29

“Popped” splints

Answer 29

• Damage to the interosseous ligament between MT/MC II and III or between III VI
• Carpal bone II rets entirely on the medial splint bone; carpal bone IV rests on both metacarpals III and IV
• Medial II is more frequently affected