Passive Stay

Question 1

What are the components of the passive stay apparatus?

Answer 1

Forelimb: susponsory apparatus, biceps brachii and lacertus fibrosis

Hindlimb: patellar sling, reciprocal mechanism, and suspensory apparatus

Question 2

Explain how the biceps brachii and lacertus fibrosis work in the passive stay apparatus

Answer 2

Biceps brachii on the cranial side prevents the shoulder from falling into flexion. lacertus fibrosis connects biceps brachii to extensor capri radialis to continue down the leg, preventing flexion.

Question 3

Explain how the suspensory apparatus works for both the forelimb and hindlimb

Answer 3

the interosseus, superficial and deep digital flexor tendons all prevent hyperextension of the fetlock joint. Since they are all tendonous, no energy is exerted by the horse. It creates tension and pulls the digit caudally to counteract the ground force.

Question 4

How does serratus ventralis aid in the passive stay apparatus?

Answer 4

it has tendonized sections to make it easier to support the trunk

Question 5

Explain how the patella sling woks

Answer 5

the medial femoral chondyle is larger than the lateral one, and the patellar ligament is split into 3. The medial patella ligament is able to hook over the medial chondyle of the femur to lock the stifle joint. The horse does this by engaing the quadriceps muscles.

Question 6

Explain the reciporal mechanism

Answer 6

proneus tercius on the cranial side and the common calcaneal tendon on the caudal side work together to ensure the hock joint moves with the stifle joint. they cannot move independently of each other, so when the stifle becomes locked, so does the hock