Lecture 15: Posture and Passive stay apparatus

Question 1

explain the passive stay apparatus

Answer 1

combines the force of gravity w/ properties of the skeleton, tendons and ligaments to maintain balance during standing, while reducing muscular effort to a minimal level

Question 2

what are the 3 components of the passive stay apparatus?

Answer 2

1. suspensory apparatus
2. check apparatus
3. stay apparatus

Question 3

what is the suspensory apparatus composed of

Answer 3

interosseous ligament (yellow)
distal sesamoidean ligaments (purple)

Question 4

the suspensory ligament is the ________ muscle

Answer 4

TENDINOUS interosseous muscle

Question 5

what prevents the hyperextension of the manus and pes

Answer 5

suspensory apparatus

Question 6

what ligaments extend the suspensory apparatus to the pastern

Answer 6

distal sesamoidean ligaments

Question 7

what is the check apparatus composed of

Answer 7

flexor digitorum profundus
- connects via a check ligament to the metapodial in both limbs

flexor digitorum superficialis
- connects via a check ligament to the metacarpal forelimb

Question 8

what muscles comprise the stay apparatus in the thoracic limb

Answer 8

• serratus ventralis (silly villains)
• biceps brachii (bike bravely)
• extensor carpi radialis (every cold road)
• lacterus fibrosus (lactating freely)

Question 9

what muscles comprise the stay apparatus in the pelvic limb

Answer 9

• peronius tertius
• flexor digitorum superficialis + fibrous band of gastrocnemius

Question 10

how does locked patella occur

Answer 10

• medial patellar ligament remains hooked over the medial trochlear ridge of the femur

Question 11

what is a temporary vs persistent locked patella

Answer 11

temporary lock = may be released by startling the horse into sudden movement

persistent lock = startling horse does not release the stifle, may require sectioning of the medial patellar ligament

Question 12

clinical sign of ruptured peroneus tertius

Answer 12

the ability to extend the hock while flexing the stifle

Question 13

what is the reciprocal mechanism?

Answer 13

(passive stay apparatus in hindlimb)
peroneus tertius + flexor digitorum superfilcialis

• ensures that when the femur swings one way the distal limb will swing the opposite way
• also ensures that when the patella and stifle are locked, the hock is immobile too