Passive Stay Apparatus

Question 1

How do large animals oppose gravity without expending lots of energy?

Answer 1

fibrous support mechanism (stay apparatus)

Question 2

What are the functions of the stay apparatus?

Answer 2

1. Reduce the energy required to stand (rest while standing), minimal muscular activity
2. Make movement efficient (groups of muscles and tendons/ligaments works in synchrony to create motion and conserve energy)

Question 3

What percentage of lameness happens to the thoracic limb and why?

Answer 3

60% because 60% of the animals weight is on the thoracic limb

Question 4

What joint is called the “knee” in horses?

Answer 4

carpus, radiocarpal joint+middle carpal joint+carpometacarpal joint

Question 5

What is called the pastern joint in horses?

Answer 5

proximal interphalangeal joint

Question 6

What is called the fetlock joint in horses?

Answer 6

metacarpophalangeal joint

Question 7

What is called the coffin joint in horses?

Answer 7

distal interphalangeal joint

Question 8

What joint in the horse is in a constant state of hyperextension when standing?

Answer 8

fetlock joint

Question 9

How is body weight transferred from the head and neck to the thoracic limb in the horse?

Answer 9

Same as the dog- pectoral muscles and serratus ventralis

Question 10

What stabilizes the shoulder joint in the stay apparatus and how?

Answer 10

The tendon of biceps brachii prevents the shoulder from flexing; tendon of origin of the biceps brachii puts pressure on the intermediate tubercle of the humerus locking it in place

Question 11

What stabilizes the elbow joint in the stay apparatus and how?

Answer 11

Since the shoulder joint is locked, forces of the humerus rest on the nearly vertical radius (crooked post)

No forces acting on the elbow to flex or extend if balanced

Question 12

What is necessary to maintain balance in regards to the elbow joint in the stay apparatus?

Answer 12

Small corrections to keep body weight balanced on radius

Question 13

How are the triceps used in the stay apparatus?

Answer 13

They remain flaccid

Question 14

What stabilizes the carpus in the stay apparatus and how?

Answer 14

The tension on the biceps brachii is transmitted to the extensor carpi radialis via lacertus fibrous

The strong palmar carpal ligament also prevents the hyperextension of this joint

Question 15

Where is the palmar carpal ligament and what does it do?

Answer 15

At the dorsal border of the carpal canal; extends from the distal radius to the proximal metacarpus III

stops hyperextension of carpus

Question 16

How do we take the tension of SDF and DDF?

Answer 16

Accessory ligaments! proximal and distal check ligaments counteract downward force from fetlock joint

Question 17

In summary, what needs to happen to stabilize the fetlock, pastern, and coffin joints and how it is accomplished?

Answer 17

stop hypertension of these joints; suspensory apparatus along with proximal and distal check ligaments

Question 18

What are the components of the suspensory apparatus?

Answer 18

interosseus, proximal sesamoids, sesamoidean ligaments

Question 19

How does the suspensory apparatus work?

Answer 19

downward force of the fetlock joint stretches the suspensory ligament (interosseus ligment) which inserts on the proximal sesamoid bones counteracting hyperextension of the fetlock

Question 20

What joins the tendon of the common digital extensor?

Answer 20

the extensor branches of interosseous

Question 21

What is the role of the distal sesamoidean ligaments in the stay apparatus? Where do they attach and originate?

Answer 21

Counteract hyperextension of the fetlock joint; all originate from proximal sesamoid bones and have distal attachments to the proximal phalanx

Question 22

How are the SDF and DDF engaged during hyperextension of the fetlock?

Answer 22

Allows for storage of potential energy, fetlock “springs” back to normal state of extension quickly

Question 23

What are the posture differences between digitigrade, unguligrade, and plantigrade?

Answer 23

digitigrade- walks/bears weight on digits
unguligrade- walks/bears weight on distal phalanx
plantigrade- walks/bears weight on the digits, metatarsals, and plantar tarsus

Question 24

Which bones of the carpus are fused in the dog vs. the horse vs. the ox?

Answer 24

dog- radial and intermediate carpal bones are fused
horse- distal carpal I and II are fused
ox- distal carpal II and III are fused

Question 25

Which metacarpal bones are weight-bearing in the horse and the ox?

Answer 25

horse-metacarpal III

ox- metacarpal III and IV which are fused

Question 26

Which metacarpal bones are the medial and lateral splint bones in the horse?

Answer 26

metacarpals II and IV

Question 27

In what species are the radius and ulna fused?

Answer 27

equine and bovine

bovine ulna runs full length of the radius, equine ulna runs 1/2 length of the radius