Exam 2

Question 1

tendon definition

Answer 1

Fibrous cord of connective tissue continuous with the fibers of a muscle, attaching the muscle to bone

Question 2

how are tendon fibers arranged?

Answer 2

Fibers of tendon are arranged in longitudinal rows and secrete collagen

Question 3

collagen

Answer 3

the main supportive protein of connective tissue. Collagen has a limited life, which means that the crimps can only straighten and recoil a certain number of times. Therefore, there is a rapid turnover of collagen within tendons. The production of collagen is a continuous process

Question 4

repair of tendons

Answer 4

Tendons have poor blood supply, and that is why in an event of tendon injury the repair process is very slow.
Repair process for tendons are facilitated by adjacent soft tissue because a tendon cannot repair itself. That is a hindrance when injury happens in the lower legs, where there is not much adjacent tissue to assist in the repair process.

Question 5

repair vs. healing

Answer 5

Repair is different from healing and leaves a scar.
Scar tissue mimics tendon fiber organization, but it cannot be replicated. Therefore, once damaged, a tendon will always be weaker.

Question 6

Ligaments structure

Answer 6

Ligaments are somewhat flexible, but tough and unyielding in consistency. Ligaments differ from tendons in that they do not have a crimp, thus their capacity for extension is limited.

Question 7

function of ligaments

Answer 7

Ligaments help to limit the movement of joints. Ex: lateral and medial collateral ligaments of the fetlock confine the movement to forward and backward only.

Question 8

healing of ligaments

Answer 8

Ligaments have poor blood supply, which makes them slow in healing after injury. But they are rich in sensory nerves, which means they are very sensitive to pain. If a joint is stretched beyond the limitations set by the ligaments, a very painful sprain will occur.

Question 9

collateral ligaments

Answer 9

These ligaments attach bone to bone at a joint, holding the bones in alignment, and they exist on both sides (lateral and medial) of the joints. any identical structure found on both sides of a joint is termed “collateral”

Question 10

fascia

Answer 10

Thick sheets of dense, fibrous connective tissue that are attached to the skeleton, ligaments and tendons in places, and is adherent to many underlying muscles.

Question 11

where is muscle power of the upper limb transmitted to the foot?

Answer 11

via the fetlock joint. There is a substantial change in direction in the angle of the bones at the fetlock, which means that this joint must be extremely stable. fetlock should not move sideways because it carries a large load

Question 12

functions of pastern and coffin joint

Answer 12

accommodate changes of surface in the ground. pastern and coffin joints should move from side to side to preserve the soundness of the limb, although this movement is limited by the collateral ligaments.

Question 13

suspensory ligament

Answer 13

Part of the suspensory apparatus.
It is the longest ligament in the lower leg. It originates distally to the palmar surface of the carpus and runs downward between the 2 splint bones toward the fetlock joint.
It divides into 2 just above the fetlock joint. Each branch attaches to its correspondent sesamoid bone, with some fibers branching forward and blending with the Common Digital Extensor Tendon.

Question 14

main function of suspensory ligament

Answer 14

The main function of the suspensory ligament and apparatus is to support the fetlock joint, preventing it from over-extending downward, which would result in straining the flexor tendons.

Question 15

suspensory apparatus

Answer 15

The conformation of the fetlock is strengthened by the suspensory apparatus (a conjunction of ligaments, tendons and bones).
It holds the proximal sesamoid bones in place and wraps itself around the long pastern bone (1st phalanx) to insert above (dorsal) the pastern joint.
All these ligaments prevent the hinges from being strained.

Question 16

movement process

Answer 16

Bones create angles
• Angles form an apex
• Movement requires force on multiple bones
• Placement of the muscle indicates its function

Question 17

flexion

Answer 17

the angle of the joint is made narrower. Muscles that have the prime function of closing the angle of a joint are called “flexors”.

Question 18

extension

Answer 18

The angle of the joint is widened. Muscles pass over the apex of the joint, and are called “extensors”.

Question 19

adduction

Answer 19

Muscles draw the limb towards the mid- line of the body. Muscles are called “adductors”.

Question 20

abduction

Answer 20

muscles lead the limb away from the mid-line of the body. Muscles are called “abductors”.

Question 21

knee: carpus

Answer 21

Joint between Radius, carpus and metacarpus,Although it is referred to as the “knee”, this joint actually corresponds to the human wrist joint. The degree of flexion that allows horses to tuck up their forelegs over an obstacle or lay down is achieved with a double tier of hinges

Question 22

functions of the knee

Answer 22

it flexes so limb can be lifted from the ground. It also stabilizes the entire forelimb while the body is propelled forward

Question 23

shoulder joint

Answer 23

a horizontal ball and socket, the ball being formed by the head of the humerus. The socket is the glenoid cavity of the scapula.
The shoulder joint is unique because it has no ligaments of its own.
The muscles determine and limit the extent of movement and double-up as ligaments.
The shoulder joint can be a vulnerable source of pain.

Question 24

pelvic griddle function

Answer 24

It protects the internal organs, forming a solid housing so that the soft inner organs are not crushed by the power of muscles. Tolerates different levels of movement. Propels the body onwards and upwards.

Question 25

broad sacrotubule ligament function

Answer 25

form a tent that separates the deep muscles and sciatic nerve on the outside of the pelvic griddle from the inner organs.

Question 26

suspensory apparatus function

Answer 26

Its function is to support the fetlock joint during the weight- bearing phase of the stride.
Uneven loading of the limb during weight bearing, uneven ground and poor foot balance or rider balance are the main contributing causes for suspensory apparatus injuries.

Question 27

components of the suspensory apparatus

Answer 27

Suspensory ligament
•2 proximal sesamoid bones •Intersesamoidean ligament •Distal sesamoidean ligament •Collateral sesamoidean ligament •Superficial digital flexor tendon •Deep digital flexor tendon

Question 28

stay apparatus function

Answer 28

Enables the horse to stand for long periods of time with minimal fatigue.
Consists of muscles, ligaments and tendons that stabilize all the joints of the forelimb and the lower joints (the fetlock and pastern) of the hind limb.
Minimal muscular activity is needed to hold tension on these ligaments and tendons, which in turn prevent flexion of the joints and collapsing of the leg.

Question 29

components of the stay apparatus

Answer 29

Suspensory ligament
•2 proximal sesamoid bones •Intersesamoidean ligament •Distal sesamoidean ligament •Collateral sesamoidean ligament •Superficial digital flexor tendon •Deep digital flexor tendon
Suspensory apparatus: supports the fetlock and prevents it from collapsing and falling to the ground
•Common digital extensor tendon
•Radial check ligament to the superficial digital flexor tendon •Carpal check ligament to the suspensory ligament
•Radial carpal extensor muscle •Ventral serrate muscle
•Triceps muscle
•Superficial digital flexor muscle •Deep digital flexor muscle

Question 30

hind leg locking mechanism function

Answer 30

The patella rests 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 the horse is moving and the quadriceps muscle is operational, the patella enables the passage of the muscle over the ridges of the trochlea.
However, when the horse is resting, the patella is a labor-saving device. By raising one hip, the horse can cause the quadriceps muscle to lift the patella into a position above the medial trochleal ridge. This locks the hinge and, in conjunction with the reciprocal apparatus to the hock, fixes the limb so that it becomes self-supporting. The other hind leg can rest on its toe. The system is unlocked by the contraction of quadriceps femoris and biceps femoris.

Question 31

upward fixation of the patella

Answer 31

Seen mostly in young, immature horses and ponies, with Shetlands especially prone.
Causes:
Straight hindlimb conformation: typical of many ponies; the patella is already riding high in the trochlea, so the slightest bad step can allow inadvertent fixation
Poor muscle tone: typical of young, immature horses; a loose, flabby quadriceps allows the patella to bounce around in the trochlea
Poor condition: leading to weak muscles
Hereditary factors: the inheritable nature of straight hindlimb conformation Trauma to the stifle: leading to loss of muscle tone and condition.

Question 32

treatment of upward fixation of the patella

Answer 32

Establishing a conditioning program to increase level of fitness and strength of muscle tone.
Injecting irritants (“blistering”), such as an iodine-based product, into and around the middle and medial patellar ligaments to thicken and shorten them. The results are unpredictable and there are possibly disastrous complications should synovial sheath structures be involved.
Corrective shoeing with raised heels may help by limiting the degree of extension of the stifle joint.
Surgical treatments include:
•Medial patellar ligament desmotomy: cutting the medial patellar ligament. This disrupts the patellar locking mechanism.
•Medial patellar ligament splitting: multiple incisions into the ligament, resulting in localized thickening and increased stability.
Hormonal therapy: Estrogen increases the strength of the ligament. Administered weekly until horse shows no sign of patellar fixation.


Question 33

reciprocal apparatus

Answer 33

the hock cannot move without the stifle.

Question 34

fundamental structures of the reciprocal apparatus

Answer 34

peroneus tertius and superficial digital flexor muscle,The fetlock joint is also connected to the mechanism. It automatically adopts the correct position for whatever the stifle and hock are about to do.

Question 35

peroneus tertius

Answer 35

a tendon that originates at the stifle joint just in front of the condyle of the femur. At the opposite end, it divides into three and inserts: 1/ on the inside of the cannon bone; 2/ on the central and third tarsal bones, and at the top of the cannon bone; and, 3/ after passing under the trochlea of the talus, on the fourth tarsal bone.

Question 36

superficial digital flexor muscle

Answer 36

It originates in the intercondylar fossa (between the two condyles at the back of the femur). It attaches to the calcaneus (point of the hock), and becomes the superficial digital flexor tendon. This inserts at the back of the 2nd phalanx.

Question 37

quadricep femoris muscle

Answer 37

pulls the patella in the groove between the trochlea of the femur. extends the stifle joint. and automatically engages the reciprocal apparatus

Question 38

gastrocnemius muscle

Answer 38

attaches at the rear of the femur above the condyles and surround the origin of the superficial digital flexor muscle.
The gastrocnemius muscle gives rise to the Achilles’ tendon, which inserts on the calcaneus tuberosity.
The gastrocnemius muscle extends the hock joint. However, because of the peroneus tertius, this extension is limited and always influenced by the position of the pelvis.

Question 39

brachiocephalicus

Answer 39

forms the upper portion of the jugular groove.in horses that are not encouraged to stretch their necks during training, this muscle becomes hard and unyielding

Question 40

serratus ventralis

Answer 40

constitutes the most important element of suspension in the horse’s natural forehand movement. It originates at the top of the underside of the scapula. From here it diverges into ‘serrated’ insertions along the first nine ribs and fan-like insertions at the transverse processes of the neck vertebrae.ustom-made to elasticize the stride as the horse’s limbs hit the ground. It is similar in effect to a trampoline. However, the action of the thoracic serratus ventralis muscle is combined with the latissimus dorsi and teres major muscles to draw the leg back and flex the shoulder, providing a springboard from which to launch the stride into the next phase.
If the serratus ventralis muscles are bruised by the pressure of the girth straps, or the neck is fixed by the rider’s hands (or draw reins) the whole system becomes useless. The horse’s chest cavity is then shaken with every stride.

Question 41

areas of tension and soreness when the suspension is used incorrectly

Answer 41

The rear border of the scapula where the latissimus dorsi, trapezius, and teres major muscles intersect. This place is directly under the tree of the saddle.

2. In the brachiocephalicus muscle, in front of the shoulder joint or at the base of the neck just above the jugular groove.
3. In front of the withers, where the trapezius and rhomboideus muscles overlap.
4. In the brachiocephalicus muscle, between the wing of the atlas and the jaw line.
5. In the sternomandibularis muscle below the line of the jaw.

Question 42

psoas muscles

Answer 42

As the horse pushes off with the hind limb, the psoas muscles stabilize and round the lumbar spine. Then the back muscles extend the spine and raise the head and neck. This lifts the forehand off the ground. This is the natural mechanism, and not necessarily what happens in all the maneuvers when the horse is ridden.

Question 43

bowstring effect

Answer 43

Although the abdominal muscles do not produce locomotion, they make a vital contribution to the stability of the spinal column. spine represents a bow and the line of the abdomen the bowstring both need to be in traction before the body can be effectively supported during movement.

Question 44

type 1 fibers

Answer 44

Slow-twitch fibers: high amount of myoglobin, thus store more oxygen. These fibers are less susceptible to fatigue, and are better adapted for continual contraction. Dark red in color because of the myoglobin: called red muscle.
Type of work/horse that benefit from these fibers: Endurance, Arabians.
1 motor neuron per 20-30 muscle fibers􏰀small motor unit, less powerful contractions.

Question 45

type IIA

Answer 45

High-oxidative fast-twitch fibers: is in between the other 2 types of fiber in terms of aerobic/anaerobic capacity. Has a high amount of myoglobin, which enables the use of large amounts of oxygen. Type of work/horse that benefit from these fibers: Racing horses.

Question 46

type IIX

Answer 46

Low-oxidative Fast-twitch fibers: low aerobic capacity, high glycolytic capacity, less mitochondria, less myoglobin, rapidly fatigued. Pale in color, called white muscle. Type of work/horse that benefit from these fibers: Sprinters, QH, during the jump. 1 motor neuron per 2,000 muscle fibers􏰀very powerful contractions when stimulated.

Question 47

Lactic Acid

Answer 47

When the anaerobic pathways are used during exercise, the result is the production of lactic acid (or lactate) within the muscle fiber. This lactate then reaches the blood.
The rate of lactate removal from blood depends on the level of activity taken during the recovery period following an exercise bout.
Lactate is removed from the blood faster at trot > walk > standing.
Lactic acid is very important to muscle. If muscle could not produce any lactic acid, exercise would be limited to low and moderate intensities only. Lactic acid production is essential for acceleration, speed and explosive efforts.
Muscle soreness immediately after the exercise bout is caused in part by lactate. Delayed Onset Muscle Soreness (24-48 hrs after exercise) is a result of tissue damage and subsequent inflammation, and has nothing to do with lactic acid.

Question 48

what type of muscle does a muscle belly contain?

Answer 48

a blend of the 3 types of fiber, the proportion varying according to the muscle’s use. The blend depends on gender, breed and training.
The blend can be changed and adapted somewhat with exercise, such as a horse training for one type of discipline or another.
During exercise all the types of fiber are used, with Type I being recruited first, followed by Type IIA and IIX.

Question 49

fascia of the hind limb

Answer 49

n the hind limb, the structure of the fascia plays a very important role in movement. The fascia of the hind limb consists of several layers. The superficial layer encloses the whole musculature. The deeper layers wrap around individual muscles.
However, the fascia has fibrous attachments to bone surfaces and ligaments, and, most importantly, serves as a place of insertion for the powerful muscles of the hindquarters.
Unlike those of the upper forelimb, many muscles of the upper hind limb do not attach directly to the bones. They use the fascia.
The result is that the muscles pull on the fascia and the fascia pulls on the joint.

Question 50

semitendinosus muscle function

Answer 50

The semitendinosus muscle has two origins, at the sacrum and first tail vertebrae, and at the ischiatic tuberosity. The insertions of this muscle are on the inside of the leg. The semitendinosus muscle inserts partly on the tibia and partly in the fascia.
In the stance phase, the semitendinosus muscle extends the hip, stifle and hock joints, thereby pushing the body forwards. In the swing phase, this muscle
flexes the stifle.
Any ridden movement that requires the horse to push the body forwards, relies on the power of the biceps femoris and semitendinosus, but also on the strength and elasticity of the fascia.

Question 51

semimembranosus muscle function

Answer 51

The semimembranosus muscle inserts on the inside of the thigh (it is an adductor).
Its action supports that of the biceps femoris and semitendinosus muscles, extending the hip and stifle joints and pushing the body forward in the stance phase of the stride.
However, the muscle forms a direct connection between the point of buttocks (ischiatic tuberosity) and the tibia. Therefore, when the foot is off the ground this muscle flexes the stifle and pulls the tibia backward.

Question 52

psoas minor and iliopsoas muscles function

Answer 52

The psoas minor and iliopsoas muscles are responsible for lowering the pelvis and bracing the spine when the hind limb muscles push the body forward.
The horse’s natural response to the weight of the saddle and rider is to tense these muscles. This prevents him from stepping under with the hind legs. If, in the course of daily riding, these muscles do not soften and become supple, the horse will never engage his hindquarters correctly.
The consequence of this lack of engagement is that structures in the mid-back and stifle bear the brunt of the power produced by the hind limb muscles, becoming damaged in the process.
Warming-up exercises can be useful to “unlock” these muscles.