Stay Apparatus Flashcards
What two species have the stay apparatus and in which is more developed?
Horse and rmt; more developed in the horse
What does the stay apparatus allow for?
Allows animal to stand for long periods of time without wasting a lot of energy (can even sleep standing up)
What is the nuchal ligament useful for?
Helps to elevate the head
What are the abdominal muscles useful for?
Aponeurotic insertions allow passive support of abdominal viscera
What % of weight is carried by the thoracic limb and what is it used for?
60%; steering and shock absorption
What % of weight is carried by the pelvic limb and what is it used for?
40%; motor
What are the 9 components of the stay apparatus of the thoracic limb?
- Biceps brachii tendon
- Lacertus fibrosus
- Extensor carpi radialis tendon
- Common digital extensor tendon
- Serratus ventralis m.
- Triceps brachii m.
- Superficial digital flexor tendon (proximal check ligament)
- Deep digital flexor tendon (distal check ligament)
- Suspensory apparatus (fetlock stabilization in both limbs)
What is the origin and insertion of the biceps brachii m.?
O: supraglenoid tubercle
I (deep): radius
I (superficial): lacertus fibrosus –> MC 3
What is the origin and insertion of the superficial digital flexor?
O: medial epicondyle of humerus
I: distal P1 and proximal P2
What does the proximal check ligament join?
tendon of the SDF
What is the origin and insertion of the deep digital flexor m.?
O: medial epicondyle of humerus
I: P3
What does the distal check ligament join?
tendon of the DDF
Where does the proximal check ligament originate?
proximal radius
Where does the distal check ligament originate?
fascia overlying the carpal region
Where do the check ligaments insert in relation to the flexor muscles?
In bt the muscle bellies and the insertion of the flexor mm.
What 3 things make up the suspensory apparatus?
suspensory ligament, proximal sesamoids, distal sesamoidean ligaments
What is the origin and insertion of the suspensory ligament?
O: proximal part of cannon
I: proximal sesamoids
What are the 2 extensor branches given off by the suspensory ligament and what do they join with?
Medial and lateral; join with the tendon of the common digital extensor (thoracic) or long digital extensor (pelvic)
What are the distal sesamoidean ligaments present in the horse?
Short, cruciate, oblique, straight
What is the origin and insertion of the short and cruciate sesamoidean ligaments?
O: proximal sesamoids
I: proximal P1
What is the origin and insertion of the oblique sesamoidean ligament?
O: proximal sesamoids
I: bony ridge on P1
What is the origin and insertion of the superficial part of the straight sesamoidean ligament?
O: proximal sesamoids
I: proximal P2
What is the origin and insertion of the deep part of the straight sesamoidean ligament?
O: proximal sesamoids
I: bony ridge on P1
What does the suspensory ligament in a standing horse feel like?
bone
What structures fix the proximal sesamoids into location?
Distal sesamoidean ligaments
What occurs at the fetlock when the animal bears weight?
extension
When an animal bears weight, in what direction do the proximal sesamoids move?
downward
When an animal bears weight, what happens to the tension in the suspensory ligament?
it increases, also causing more extension
What happens to the fetlock during weight bearing when enough tension is built?
Any further extension at the fetlock stops
How many degrees of articular surface are present at the fetlock?
220
What 2 muscle tendons pass over the fetlock to help aid in stabilization?
SDF and DDF
What does the pastern joint want to do when the limb is under weight and what limits this movement?
Wants to extend; is limited by the extensor branches of the suspensory ligament which stabilize it
What does the coffin joint want to do when the limb is under weight and what limits this movement?
Wants to flex; is limited by tension within extensor branches which help to extend the joint
What is the role of the check ligaments in shock absorption as the limb strikes the ground?
They push shock back into the bone to help absorb it
When a horse is at a gallop, what position is the fetlock mainly in?
extended
What muscle inserts on the medial aspect of the scapula that helps to fix it on the proximal aspect?
serratus ventralis
As the limb comes under weight, what does the shoulder want to do and what type of traction results?
Wants to flex; results in cranial traction due to the supraglenoid tibercle pulling up on the biceps brachii
As the limb comes under weight, what does the elbow want to do, what type of traction results, and how is this movement stabilized?
Wants to flex; results in cranial traction that is stabilized by the tendon of origin of the biceps that helps apply cranial pressure
What type of traction does the lacertus fibrosus apply at the carpal region and what prevents this?
dorsal traction; prevented by the joint construction (digital flexors pull carpal region caudally)
What are the 6 components of the stay apparatus of the pelvic limb?
- Patellar lock
- Reciprocal apparatus
- Long digital extensor tendon
- Superficial digital flexor tendon
- Deep digital flexor tendon (check ligament, but not always present)
- Suspensory apparatus
What are the 3 parts of the patellar ligament?
medial, intermediate, lateral
What two patellar ligaments have the largest space in bt them?
intermediate and medial parts
What two things in the stifle work together to pull the patella dorsal to the medial ridge of the femoral trochlea?
Large space bt medial and intermediate parts of the patellar ligament + asymmetry of the medial ridge of femoral trochlea
(Makes a loop and locks the patella in place)
What does the femur act as during the patellar lock?
crowbar
What do the patella and ligaments act as during the patellar lock?
nail
How does the femur act as a crowbar during the patellar lock?
The horse extends the stifle with some muscular activity in the quads that pulls the patella dorsal to the medial ridge, & the femur rocks back on the locked patella
Which limb carries the body weight: limb WITH locked patella or limb WITHOUT locked patella?
limb WITH locked patella (unlocked limb is resting, tow barely touches the ground)
What 2 muscles make up the reciprocal apparatus?
peroneus tertius and superficial digital flexor
What is the origin and insertion of the peroneus tertius?
O: extensor fossa of femur
I: 3rd MT, 4th tarsal bone, calcaneus
What is the origin and insertion of the SDF in regards to the reciprocal apparatus?
O: supracondylar fossa
I: tuber calcanei
What is the relationship bt the stifle and the hock in regards to movement?
If one flexes, the other flexes; if one extends, the other extends
What causes the hock to flex when the stifle flexes?
Stifle pulls on peroneus teritus insertion at the hock
What causes the hock to extend when the stifle extends?
Stifle pulls hock bc of SDF insertion on tuber calcanei
How can the peroneus tertius rupture?
When the stifle is flexed but the hock is extended
When is it common doe the peroneus tertius to rupture?
Barrel racing with tight turns, or horse gets its shoe stuck in a halter and yanks to free its leg
What happens to the entire limb if the patella is locked?
it becomes fixed
