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Anatomy 2 - Equine Stay Apparatus

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drraythe's version from 2015-06-05 22:56

Forelimb (not on quiz)

Question Answer
What does the stay apparatus do? Which limbs are involved? how does the horse weight bear?Enables the horse to stand w/minimal mm effort. both fore and hind limbs are involved, but the forlimb bears more weight (55:45 F:H)
how is body weight transmitted to the forelimb? (What, where, how)via the serratus ventralis m (attaches to facies serrata of scapula). A vertical line (like center of gravity) in mid facies serrata drops CA to the shoulder joint, through the elbow joint, but CR to the distal joints.
because of the way the vertical line of BW falls down the thoracic limb, the limb needs support or what will collapse when?on flexion of the shoulder+elbow, and overextension of the distal joints
Forelimb stay apparatus of the PASTERN? (3)(1) palmar ligaments (2) superficial (straight) sesamoidean ligament prevents over-extension (3) superficial and deep digital flexor mm
forelimb stay apparatus of the FETLOCK? (5)overextension prevented by support from (1) interosseus tendon (2) prox sesamoid bones (3) sesamoiden ligaments. The (4) digital flexor tendons and the (5) accessory ligament (one for DDF AND SDF) also play a role
forelimb stay apparatus of the CARPUS? (2)(1) the flat nature of the dorsal parts of the articular surfaces of the radiocarpal (antebrachiocarpal) and mid-carpal joints, and (2) the PALMAR CARPAL LIG (holding composite bones together) prevent overextension
What is the maximum extension of the carpus? 180*
forelimb stay apparatus of the elbow? (how is it fixed? what prevents collapse?(3) )fixed by the BW at the joint, acting through the radius distalward. Collapse is prevented by (1) TONIC ACTIVITY of the TRICEPS BRACHII M (2) collateral ligaments (eccentric b/c CA to axis of rotation of the joint, tensed in normal standing postition and must be stretched to permit flexion) and (3) flexor mm (SDF, FCU, Ulnaris lateralis) are CA to axis of rotation of the joint, so tensed in normal standing. The joint is also close-packed
at the elbow, what nerve damage can cause collapse of the limb?radial n. paralysis will cause collapse (prevent tonic activity of triceps)
what prevents the collapse of the shoulder joint? (3) What prevents flexion of the shoulder? (2) Collapse is prevented by (1) highly tendinous biceps, (2) extensor carpi radialis, and the (3) tendinous lacertus fibrosis which unites both of these mm. Flexion is PREVENTED by (1) tensed biceps, as its distal attachment (radius) and that of the (2) extensor carpi radialis (metacarpal bone) are fixed by the BW
list the 13 components of the stay apparatus of the forelimb(1) serratus ventralis m (2) biceps brachii m (internal tendon) (3) lacertus fibrosus (4)**lateral collateral lig of the cubital joint (5) extensor carpi radialis m (6) common digital extensor m tendon (7) extensor slips of interosseus m (8) interosseus m (9) DDF tendon (10) accessory lig of DDF (11) SDF tendon (12) accessory lig of SDF (13) straight and oblique sesamoidean lig.
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Hindlimb

Question Answer
where does BW rest in the hindlimb? describe the vertical line (like center of gravity) of the BW on the hindlimb.BW rests on head of the femur. vertical line drops down from head CA to the stifle but CR to the distal joints.
because of the way the vertical line of BW falls down the hindlimb, the limb needs support or what will collapse when?the limb would collapse on flexion of the stifle+hock, and overextension of the distal joints
where are the structures/mechanism of the stay apparatus of the hindlimb similar to the forelimb?below to hock
which ligaments are weak/not present in the hindlimb?accessory ligament (DDF) maybe be weak or absent in the hindlimb. the accessory lig of the SDF is NOT present in the hindlimb
what makes up for the fact the accessory ligs are/may not be present?the attachment of the SDF to the point of the hock
What is a critical component of the stay apparatus of the hindlimb?the stifle-lock/"patellar-lock"
What is the reciprocal apparatus? what does it help with? how does it work?unique to the hindlimb! it is a huge addition to, and support for, the stifle-lock. When the stifle is in lock (ie: extended) the hock is AUTOMATICALLY extended. the tension in the SUPERFICIAL FLEXOR TENDON is high, and this helps support the PASTERN joint also
what is going on when you see a horse resting one back leg on the tip of its hoof?the horse shifts weight from one limb to the other, and while the limb bearing the BW is in lock, the other rests on the hoof tip "toe"
list the 9 components of the stay apparatus in the hindlimb(1) patellar locking system (2) reciprocal apparatus (3) long digital extensor m. tendon (4) extensor slips of interosseus m (5) interosseus m (6) DDF tendon (7) accessory lig of DDF (if present) (8) SDF tendon (9) straight and oblique sesamoidean lig
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Nerve-blocking

Question Answer
explain the "step wise" method of nerve blocking in horses (in what direction? what 5 steps?)you start distally, move proximally. You (1) perform perineural n block (2) was for anesthetic to act (3) test its effectiveness (4) let the horse walk (5) interpret this
where is the site of injection for a distal palmar/plantar digital nerve block? (around P2) (3 options)(1) along the M and L edges of the flexor tendons. (2) At the level of the pastern joint/ just above the collateral cartilages of the distal phalanx. (3) Can also be done just prox. to the previous site
what is the site of injection for a prox. palmar/plantar digital n block?on abaxial sides just below the prox. sesamoid bones
in a palmar/plantar digital nerve anesthesia, which nn are blocked?M and L palmar/plantar proper digital nn
in a palmar/plantar digital nerve anesthesia, which structures are desensitized? (7)(1) navicular bone+bursa (2) digital cusion (3) palmar/ plantar aspect of the sole and frog (4) palmar/plantar aspect of the coffin bone (5) palmar/plantar aspect of the pastern and coffin joint (6) distal sessamoidean ligaments (PDB) (7) distal superficial and deep digital flexor tendons
look at picture of distal and proximal palmar/plantar digital blocksseriously this packet
Where is the site of injection in a ring (field) block? (2) how much anesthetic do you inject?(1) perform distal palmar/plantar digital nerve anesthesia and redirect needle to the dorsal aspect of the digit, OR (2) on both sides of the common/long digital extensor tendon at the same level. inject 3-5ml of anesthetic solution
which nerves are blocked in a ring (field) block?the palmar/plantar proper digital nerves and--- (forelimb) dorsal branches of palmar/plantar proper digital nerves (hindlimb) dorsal branches of palmar/plantar proper digital nerves AND lateral and medial dorsal digital nn
what are the structures desensitized in a ring (field) block?complete analgesia of the foot distal to the site of injection (all structures desensitized in the palmar/plantar digital nerve block)
where is the site of injection for the LOW four point block? (3)(1) at the level of the buttons (2) needle inserted deeper to achieve anesthesia of the lateral and medial metacarpal/tarsal nerves (3) at the same level superficially on both sides of the flexor tendons to access palmar/plantar nn
site of injection for a HIGH four point block? (2)(1) at level of junction between head and shaft of the splint bones on their AXIAL sides and deep injection (2) at the same level on both sides of the flexor tendons to access palmar/plantar nn
nerves blocked by low/high 4-point blocks? (2 sets)(1) L and M palmar/plantar nn (2) L and M palmar/plantar metacarpal/tarsal nn
if you inject anesthetic on the dorsal surface of the manus/pes, where do you inject?on both sides of the comon/long digital extensor tendon at the same level of palmar/plantar injections
on a dorsal surface of manus/pes injection, which nerves are blocked in which limbs?(hindlimb) L and M dorsal metatarsal nn (forelimb) medial cutaneous antebrachial and dorsal branch of the ulnar nn
structures desensitized by four point (high and low) and dorsal manus/pes injections?part of the manus/pes below the site of injection. (high 4 point) almost entire manus/pes. Includes the fetlock joint. also deep structures of the metacarus/tarsus region. Interosseus m.
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