6 - The Stay Apparatus In Horses Flashcards
What enables the horse both fore- and hindlimbs to be on its feet for long periods with a minimum of muscular effort.
PASSIVE STAY-APPARATUS
The effort of the intrinsic limb muscles of horses is greatly reduced by the non-tiring tendons and ligaments of the ?, which stabilizes the joints in a position suitable for the support of the body.
stay-apparatus
In most joints _____________ means preventing them from flexing
stabilization
Joints in the standing horse, however, are extended and overextended, respectively; their stabilization requires them not to overextend further so as to prevent the fetlock from sinking to the ground
Pastern and fetlock joints
The fleshy attachment (synsarcosis) of the forelimb to the trunk is not part of the stay-apparatus, though what muscle serves as the principal weight-bearing connection is heavily interlaced with non-tiring tendinous tissue?
serratus ventralis
Though no collateral ligaments are present, the movements in what joint are restricted largely to flexion and extension in the sagittal plane by the subscapularis medially and the infraspinatus and (to a lesser degree) the supraspinatus laterally?
shoulder joint
The principal stabilizer of the shoulder joint in the standing horse is ? that pressing against the cranial (extensor) surface of the joint. The way the tendon caps the intermediate tubercle of the intertubercular groove suggests a partial locking of the joint.
biceps tendon
collapsing (flexing) of the shoulder joint is further prevented by the y what tendon ? that anchors the muscle to the most proximal part of the radius and, via the lacertus fibrosus and extensor carpi radialis, to a similar point on the large metacarpal bone.
internal tendon of the biceps
Principally stabilized (i. e., prevented from flexing) by tension in a group of ? that arise on the medial and lateral epicondyles of the humerus and contain much fibrous tissue. (Stabilization of the Elbow Joint)
carpal and digital flexors
Eccentrically placed what ligaments in elbow joint inhibit flexion to a lesser degree?
collateral ligaments
The principal extensor of the elbow joint, the ?, seems inactive by its flabbiness in the quietly standing horse, although some believe that its tonus alone would prevent collapse of this key joint.
triceps
What joint is stabilized (prevented from flexing) by the (dorsal) “pressure” of the extensor carpi radialis tendon?
carpal joint
The carpal joint is stabilized (prevented from flexing) by the (dorsal) “pressure” of what tendon?
extensor carpi radialis tendon.
What muscles ending on the accessory carpal and being tensed by the weight of the trunk via scapula, fixed shoulder joint, and humerus, “pulls” on the flexor surface of the carpal joint in an attempt to keep the joint extended.
flexor carpi ulnaris and ulnaris lateralis
What ligaments attaching on the palmar surface of radius and large metacarpal bone above and below the carpus tend to supply a similar “pull”, again by the weight of the animal, but in the opposite direction—distally. Some ascribe a similar potential to the interosseus
accessory ligaments of the supficial and deep digital flexors
What joint needs to be stabilized by being prevented from further overextending, i. e., sinking toward the ground. This is accomplished by three elements: the suspensory apparatus associated with the interosseus, and the supf. and deep digital flexor tendons. These attach to the palmar surface of the limb skeleton proximal and distal to the joint and are tensed when the weight of the horse overextends the joint.
fetlock joint
suspensory apparatus consists of three parts:
- interosseus, 2. proximal sesamoid bones, and 3. sesamoidean ligaments.
What arises from the carpus and a The intense sarise rond the es. one droni ese of the laser branchepal bone around the proximal phalanx to the common extensor tendon.)
interosseus
What bones articulate with the distal end of the large metacarpal bone to reduce friction between the suspensory apparatus and the palmar surface of the fetlock joint.
proximal sesamoid bones
What ligaments tie the proximal sesamoid bones to the cannon bone and proximal phalanx?
Collateral ligaments
What ligaments unites the proximal sesamoid bones and forms a smooth bearing surface for the digital flexor tendons?
palmar ligament
What joint is prevented from overextension by four pastern ligament that connect the two bones that form the joint on the palmar surface?
pastern joint
The pastern joint is prevented from overextension by what ligament? that connect the two bones that form the joint on the palmar surface.
four pastern ligament
What joint actually flexes when the fetlock sinks under weight and can be disregarded in the consideration of the stay apparatus?
coffin joint
When horses stand quietly for extended periods they support the hindquarters with only?
one hindlimb
An important part of the passive stay-apparatus is the so-called ? that links the actions of stifle and hock joints.
reciprocal mechanism
An important part of the passive stay-apparatus is the so-called reciprocal mechanismthat links the actions of stifle and hock joints. This is accomplished by the ?, both crossing the joint spaces of the two joints.
tendinous peroneus tertius muscle and the nearly tendinous supf. digital flexor muscle
What muscle arises (by a common tendon with the long digital extensor) from the lateral condyle of the femur and, passing cranial to the tibia, ends by complex attachments on certain tarsal bones and the proximal end of the large metatarsal bone.
peroneus tertius
What muscle lies caudal to the tibia and connects the caudal surface of the femur with the calcanean tuber?
supf. digital flexor
By being able to lock the stifle, the horse converts the jointed column of its hindlimb into?
weight-bearing pillar
Patellar Locking Mechanism
• By being able to lock the stifle, the horse converts the jointed column of its hindlimb into a weight-bearing pillar.
• This is accomplished by the?
very asymmetrical femoral trochlea, the patella, and two of the three patellar ligaments
The medial ridge of the trochlea is larger than the lateral and is prolonged proximally to form a rounded?
tubercle
What ligament connects to the medial border of the patella via the patellar fibrocartilage?
medial patellar ligament
The medial patellar ligament connects to the medial border of the patella via the patellar fibrocartilage, while what ligament attaches directly on the patellar apex?
intermediate patellar ligament
When the horse is standing squarely on both hindlimbs the patella rests at the proximal end of the ?, without the loop fully embracing the tubercle.
trochlea
When the horse rests one hindlimb on the toe of the hoof, the patella in the supporting limb rotates medially about what degrees?
15 degrees
When the horse rests one hindlimb on the toe of the hoof, the patella in the supporting limb rotates medially (about 15 degrees) and the ? slide farther caudally on the tubercle, fully locking the stifle.
fibrocartilage and medial patellar ligament
What joints are supported as in the forelimb by the interosseus and the supf. and deep flexor tendons?
fetlock and phalangeal joints
What arises proximal to the fetlock, attaches on the proximal sesamoid bones in the hind limb?
tendinous interosseous
The tendinous interosseous arises proximal to the fetlock, attaches on the proximal sesamoid bones, and is functionally continued by the ? that attach on the plantar surface of the proximal two phalanges.
distal sesamoidean ligaments
What tendons also attach proximal and distal phalanx to the fetlock in the hind limb and lend further support?
The supf. and deep flexor tendons
What ligament of the hind limb is much thinner and may be absent compared on the fore limbs?
accessory (check) ligament of the deep flexor
What tendon has no accessory ligament, but this is compensated for in the hindlimb by its firm attachment on the calcanean tuber: its attachment proximal and distal to the fetlock joint still helps to prevent overextension in this joint when the limb is supporting weight
supf. digital flexor tendon
