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ASC 310 Exam 2

Terms in this set (33)

Functions of skeletal muscle
1. Support skeleton
2. Move skeleton
3. Maintain joint stability, preventing excessive movement
4. Produce heat by shivering
Smooth Muscle
unstriated and involuntary

controlled by the autonomic nervous system

in digestive and reproductive system
Cardiac Muscle
Also involuntary, specialized muscle found only in the heart
Skeletal or striated muscle
attached to skeleton, move the skeleton, under voluntary control
Type 1 fibers (red endurance muscle)
Slow-twitch fibers: high amount of myoglobin, store more oxygen. Less susceptible to fatigue, better adapted for continual contraction. Dark red color.

Best for endurance

1 motor neuron per 20-30muscle fibers, small motor unit, less powerful contraction
Type II Fiber (white sprint muscle)
Type IIA: high oxidative fast-twitch fibers: in between aerobic/anaerobic. High amount of myoglobin.
Best for race horses

Type IIX: low oxidative fast twitch fibers: low aerobic, high glycolytic capacity, less mitochondria, less myoglobin, rapidly fatigued. Pale, white muscle.
Best for Sprinters, QH, jumpers
1 motor neuron, per 2,000 muscle fibers, very powerful contraction when stimulated.
Lactic acid
Lactate is released into the blood stream during exercise

Released faster at a trot, then walking or standing.

Essential for acceleration, speed and explosive efforts
Muscle belly
Contains a blend of 3 muscle fiber types, depending on gender, breed, training.

Can be changed and adapted
Supraspinatus
When contracted the apex of the shoulder joint opens, scapula moves forward

When relaxed the shoulder joint remains closed

Aids in stability: same with infraspinatus

Prevents adduction of the leg: same with infraspinatus
Deltoid
Thick muscle, aids in movement

When contracted scapula moves backward, apex of the shoulder joint opens in the front
Biceps Brachii
Acts on shoulder and elbow joint

2 joints, attaches at scapula and radius

Extends shoulder, flexes elbow
Brachialis
Fits in the musculospiral groove
Extensor carpi radialis
Flexes elbow slightly
Extends carpus/knee
Triceps brachii
3 attachments, all convene on olecranon

Shoulder flexes

Elbow extends
Flexor Carpii radialis, Flexor carpi ulnaris and Lateral ulna
Backside of forelimb

Attaches to metacarpal

Flexes carpal joint
Common and Lateral digital extensor muscle and tendon
Responsible for movement during swing phase
Manica flexoria
Flexes the joint of the foot and the carpus
Extensor Retinaculum
Bundles the tendons and keeps them from sliding side to side
What causes suspensory apparatus injuries
Uneven loading of the limb during weight bearing, uneven ground and poor foot balance or rider balance
Stay Apparatus
Enables the horse to stand for long periods of time with min fatigue

It stabilizes all the joints of the forelimb and the lower joints of the hindlimb

Prevents flexion of the joints and collapsing of the leg
Muscles, tendons and ligaments form the stay apparatus are
Suspensory ligament, proximal sesamoid bones, intersesamoidean ligaments, collateral sesamoidean ligament, superficial digital flexor tendon, deep digital flexor tendon
Check ligaments
These allow the deep digital flexor tendon to be a ligament as well, connecting bone to bone, but majority also connects muscle to bone

2 check ligaments per leg
Femuro-tibial-patellar joint
Patella sits on top of trochlea
Hind leg locking mechanism
The patella sits in the groove of the trochlea and is located underneath the end of the quadriceps femoris muscle. It slides between the trochlea ridges in response to the muscle's movement.

When horse is moving the patella allows quadriceps to pass over the ridges of the trochlea

The patella is a labor saving device by raising one hip, the quad muscles lift the patella into position above the medial trochlea ridge. This locks the hinge along with the reciprocal apparatus to the hock.
The hind leg lock mechanism is unlocked by what?
The contraction of the quadriceps femoris and biceps femoris.
Stifle
Lateral collateral ligament, lateral femuropatellar ligament, lateral patellar ligament, middle patellar ligament and the medial patellar ligament make up the stifle

When the patella moves the stifle tightens allowing stabilization
Reciprocal apparatus
Locks leg in place using apparatus by shifting hip joint
What is the cause of the hind leg locking mechanism not working?
Upward fixation of the patella-seen mostly in young horses and ponies

Causes
1: straight hindlimb conformation
2: poor muscle tone
3: poor condition
4: hereditary features
5: Trauma to the stifle
Reciprocal apparatus
Movement of the hindlimb
The hock cannot move without the stifle
The calcaneus works as a lever
Two fundamental structures of the reciprocal apparatus
1: the Peroneus tertius, a tendon that originates at the stifle joint just infront of the condyle of the femur. Goes down the front of the leg and splits into multiple sections.

2: The superficial digital flexor muscle: it orginates in the intercondylar fossa, attaches to the calcaneus and becomes the superficial digital flexor tendon
If the stifle extends
the superficial digital flexor extends the hock
If the stifle flexes
The peroneus teritus closes the angle of the hock and the hock flexes
Gastrocnemius muscle
Attaches at the rear of the femur above the condyles

Gives rise to the achilles' tendon which inserts on the calcaneus

Extends the hock joint, but it is very limited because of the peroneus tertius
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