Passive Stay Apparatus Flashcards
How do large animals oppose gravity without expending lots of energy?
fibrous support mechanism (stay apparatus)
What are the functions of the stay apparatus?
- Reduce the energy required to stand (rest while standing), minimal muscular activity
- Make movement efficient (groups of muscles and tendons/ligaments works in synchrony to create motion and conserve energy)
What percentage of lameness happens to the thoracic limb and why?
60% because 60% of the animals weight is on the thoracic limb
What joint is called the “knee” in horses?
carpus, radiocarpal joint+middle carpal joint+carpometacarpal joint
What is called the pastern joint in horses?
proximal interphalangeal joint
What is called the fetlock joint in horses?
metacarpophalangeal joint
What is called the coffin joint in horses?
distal interphalangeal joint
What joint in the horse is in a constant state of hyperextension when standing?
fetlock joint
How is body weight transferred from the head and neck to the thoracic limb in the horse?
Same as the dog- pectoral muscles and serratus ventralis
What stabilizes the shoulder joint in the stay apparatus and how?
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
What stabilizes the elbow joint in the stay apparatus and how?
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
What is necessary to maintain balance in regards to the elbow joint in the stay apparatus?
Small corrections to keep body weight balanced on radius
How are the triceps used in the stay apparatus?
They remain flaccid
What stabilizes the carpus in the stay apparatus and how?
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
Where is the palmar carpal ligament and what does it do?
At the dorsal border of the carpal canal; extends from the distal radius to the proximal metacarpus III
stops hyperextension of carpus
How do we take the tension of SDF and DDF?
Accessory ligaments! proximal and distal check ligaments counteract downward force from fetlock joint
In summary, what needs to happen to stabilize the fetlock, pastern, and coffin joints and how it is accomplished?
stop hypertension of these joints; suspensory apparatus along with proximal and distal check ligaments
What are the components of the suspensory apparatus?
interosseus, proximal sesamoids, sesamoidean ligaments
How does the suspensory apparatus work?
downward force of the fetlock joint stretches the suspensory ligament (interosseus ligment) which inserts on the proximal sesamoid bones counteracting hyperextension of the fetlock
What joins the tendon of the common digital extensor?
the extensor branches of interosseous
What is the role of the distal sesamoidean ligaments in the stay apparatus? Where do they attach and originate?
Counteract hyperextension of the fetlock joint; all originate from proximal sesamoid bones and have distal attachments to the proximal phalanx
How are the SDF and DDF engaged during hyperextension of the fetlock?
Allows for storage of potential energy, fetlock “springs” back to normal state of extension quickly
What are the posture differences between digitigrade, unguligrade, and plantigrade?
digitigrade- walks/bears weight on digits
unguligrade- walks/bears weight on distal phalanx
plantigrade- walks/bears weight on the digits, metatarsals, and plantar tarsus
Which bones of the carpus are fused in the dog vs. the horse vs. the ox?
dog- radial and intermediate carpal bones are fused
horse- distal carpal I and II are fused
ox- distal carpal II and III are fused
Which metacarpal bones are weight-bearing in the horse and the ox?
horse-metacarpal III
ox- metacarpal III and IV which are fused
Which metacarpal bones are the medial and lateral splint bones in the horse?
metacarpals II and IV
In what species are the radius and ulna fused?
equine and bovine
bovine ulna runs full length of the radius, equine ulna runs 1/2 length of the radius
