HORSE- SPECIES ADAPTATIONS Flashcards
Describe the strategies used to optimise speed
-Increase stride length
-increase stride rate
However these are anatgonistic so a compromise is required - increasing the rate, reduces the length
How are horses adapted to increase its stride length
- Mediolaterally flattened thorax with the scapula positioned laterally
- Scapula and shoulder joint free to move- no clavical
- Ulna becomes vestigial- fuses with radius
- Elongation of the distal bones
How is the horse adapted to increase its stride rate
- concentration of musculature proximally
- reduction to a single digit (lost other digits as extra unnecessary weight )
- brachium is relatively short and highly muscular- light tendons act as levers
Describe the structure, function and adaptations of the equine forelimb
- carry more static body weight (allows hind limbs to minimise wasteful vertical energy)
- shorter ad straighter than hindlimbs (no bone articulation to the skeleton so effectively act as suspension
- broader more rounded hoof
- forelimbs act as suspension and absorb energy (energy storage- tendons)
Describe how tendons are able to conserve energy
- tendons are able to store kinetic energy
- potential energy is stored in stretched tendons, which is converted back to kinetic energy
Describe the structure, function and adaptations of the equine hindlimb
-forward impulsion of the horse (direct bone articulations- between the femur and pelvis, pelvis and sacral spine)
-reciprocal apparatus allows simultaneous extension of the hip, stifle and hock
-narrower and more pointed hoof (more traction and friction on ground )
No lost energy by extra movement of bones
Explain the function of the passive stay apparatus of the equine hindlimb
-minimal energy whilst standing still
On leg straight, other with toe on floor
Stifle and hock positioned at acute angles
Locks in position without muscles
Explain the anatomy of the passive stay apparatus of the equine hindlimb
- uses 3 ligaments (medial,middle and lateral
- moves patella over the femur (locks )
- femur cannot move- active process to contract quadriceps to move patella
- medial patella ligament locks-up and medial
How does the passive stay apparatus unlock
Quadriceps contract to release, down into gliding position between trochlear ridges
What does the suspensory apparatus in horses do
Maintains the fetlock in a position of mild hyper-extension
What anatomy is involved in the suspensory apparatus in horses
The suspensory ligament (interosseus muscle ) which originates in the proximal metacarpal/tarsal region.
Runs deep to the DDFT and SDFT to the proximal sesamoid bones and then continues in a series of distal sesamoidean
What does it mean when you say stride length is antagonistic to stride rate
It can increase one only by decreasing the other
Define inertia in terms of locomotion
inertia is the force needed to move a limb (determined by mass x radial distance^2)
How does increasing limb length affect inertia force
Inertia= mass x radial distance^2
If you increase limb length, you increase stride length- so you increase inertia. You limit stride rate
Can increased stride length easily be achieved through flexion and extension in back of horses
No, horses are not as flexible as carnivores
How does the scapula of the horse allow for speed
Slides forward and back to allow for longer extension of leg and longer strides
Explain how the relative lengths of the forelimbs and hindlimbs help the horse to run faster
Forelimbs are shorter and straighter than hind so they can translate horizontal velocity provided by hind limbs whilst minimising wasteful vertical energy. Conserves energy.
How does the variation in shape of hoof between fore- and hind-limb of a horse help running?
Broader more rounded hoof to help with landing in forelimb.Narrow hind hoof can grip more to help generate more energy
How are the bones arranged in the limbs to conserve energy?
In hindlimb there is direct bone articulations:
•Femur and pelvis
•Pelvis and sacral spine. So fewer space to lose energy.
In forelimb:
No bone articulation to the skeleton so effectively act as suspension
What is the main use of the thoracic and hindlimbs?
Thoracic (Forelimb) - Carry static body weight. Needed for converting the kinetic energy of downward movement into the potential energy of stretched muscles & ligaments, which rebound to generate upward movement.
Hindlimb - provide impulsion and passive stay
What is the reciprocal apparatus?
Allows simultaneous extension of the hip, stifle and hock, extensor muscle which is proximal can move distal limb
- Cranially the proneus tertius tendon and caudally the superficial digital flexor tendon constitute two fibrous cords that mechanically link stifle and hock joints.
The fibrous cords (reciprocal apparatus) keep the two joints synchronized even during conditions of neuromuscular fatigue. Also allows coordination of limbs.
Give another name for the suspensory ligament
Interosseous muscle
Where does the interosseous muscle originate and insert?
Proximal metacarpal/tarsal region.Runs to the proximal sesamoid bones and then continues in a series of distal sesamoidean
How does the interosseous muscle help with the passive stay apparatus?
Maintains the fetlock in a position of mild hyper-extension
What muscles assist with the passive stay of the forelimb?
- Serratus ventralis forms a suspensory sling but must be counter-balanced. Therefore the shoulder is also maintained in extension by
- Supraspinatus muscle
- Co-operative antagonism of the biceps, which has extensive inelastic tendinous components, with reciprocal contraction of the triceps
Explain how ligaments in the forelimb assist with the stay apparatus.
- “Superior check ligament” (ALSDFT) is the ligamentous attachment of the radial head•Distal tendonous insertion onto proximal and distal phalanges to the pastern region prevents extension of the carpus and fetlock
- “Inferior check ligament” (ALDDFT) joins the tendon in the mid metacarpus•Distal tendonous insertion of DDFT onto distal phalanx prevents extension of all joints distal to the fetlock
What are the superior and inferior check ligaments from?
Accessory ligaments to the superficial and deep digital flexor tendons respectably
What prevents the buckling of the stifle in the stay apparatus?
Lacertus fibrosus, running through extensor carpi radialis prevents carpal flexion
Can the horse be bred to be faster anymore?
No, reached maximum physiological adaptation.
What physiological adaptations does the horse have to help with speed?
•Cardiovascular system-Adaptations are almost more to making it function at sedentary levels (rest)
•Respiratory system - Coupled with stride rate
How does the structure of the hips affect movement.
Hips in large herbivores:
• Much more supportive.
• Asymmetric femoral head.
• Femoral neck is more compact and vertical.
• Limited Rand of Motion.
