The Spine, Limbs and Locomotion

Question 1

What are intervertebral discs?

Answer 1

They act as tiny shock absorbers and are filled with a jelly like substance called nucleus pulposus, protected by a tough outer shell called annulus fibrosis. They make up 10% of total spine length. The discs allow some movement of the spine but not a lot as rigidity is needed to protect the GIT.

Question 2

Describe the rib cage of the horse

Answer 2

The sternum (breastbone) is the ventral part of the rib cage. There are 8 ‘true’ ribs which connect directly to the sternum and 10 ‘false’ ribs which are connected to the sternum by a piece of cartilage. There may be 17 in arabs.

Question 3

What is the lumbosacral junction?

Answer 3

A hinge joint located between the lumbar and sacral vertebrae. This joint has up to 20 degrees flexion and is most needed in canter and gallop, where the back moves the most out of all the gaits.

Question 4

What is the sacroiliac joint?

Answer 4

A join that attached the sacrum to the ilium (two bones). It is a combination of a synovial and ligamentous joint. It makes use of a lot of ligaments meaning it doesn’t have a lot of movement.

Question 5

What is the axial skeleton?

Answer 5

The bones including the vertebrae, sacrum, coccyx, ribs, and sternum.

Question 6

What are the muscles of the axial skeleton?

Answer 6

The multifidus, the longissimus dorsi, the iliopsoas muscles and the middle gluteals

Question 7

What is the multifidus muscle?

Answer 7

Numerous separate units that each span between 2 and 6 vertebrae and give small postural adjustments.

Question 8

What is the longissimus dorsi?

Answer 8

The longest muscle in the body. The runs the length of the horse’s back from C5 to the sacrum/pelvis. It plays a key role in the extension of the back and allowing the horse to raise its head and neck. It is essential for jumping, turning, kicking and rearing etc.

Question 9

What are the iliopsoas muscles?

Answer 9

These are the main flexors and have the role of strongly supporting lumbar vertebrae. It is important for hip rotation and flexion.

Question 10

What are the middle gluteals?

Answer 10

Make up a large proportion of the horse’s hindquarter. They are used for retraction of the hindlimb. They extend the lumbosacral junction, the sacroiliac joint, the hip join and creates lot of impulsion.

Question 11

What are the ligaments of the axial skeleton?

Answer 11

The superspinous, the interspinous (sits in the gaps of spinal processes and helps to keep the spine straight), vertebral bodies, ventral ligament (stretches when the back hollows), intervertebral discs, spinal cord, dorsal ligament.

Question 12

Define the NUCHAL/SUPERSPINOUS LIGAMENT

Answer 12

The nuchal/supraspinous ligament is the most important one in the horse as it supports the head and neck. It is strong, rope like and has a poor blood supplyThere are two parts: the funicular and lamellar part. AT the wither, it is alled the supraspinous ligament.

Question 13

What is involved in the dorsal chain?

Answer 13

The top line, spine and hip. The splenius, erector spinae group, gluteals and the hamstring group.

Question 14

What does the dorsal chain allow?

Answer 14

They all work together to allow forward movement such as in canter or when jumping (spinal extension).

Question 15

What is involved in the flexor chain?

Answer 15

The horse’s abdominal muscles are needed for support and to maintain posture, as well as support the weight of the rider. Involved is he internal and external abdominal oblique, the transverse abdominals and the rectus abdominals.

Question 16

What does the flexor chain allow?

Answer 16

Spinal flexion.

Question 17

What bones are in the forelimb?

Answer 17

The scapula (shoulder bone), the humerus, radius, third matacarpal, proximal sesamoids, proximal phalanx (P1) and middle phalanx (P2).

Question 18

What muscles are in the forelimb?

Answer 18

They include the cervical portion of the trapezius, the subclavius, common digital extensor and lateral digital extensor.

Question 19

Define PROTRACTION

Answer 19

The first part of movement. It is a forward swinging motion and begins when the foot leaves the ground Once fully protraction, retraction starts. It is initiated by the shoulder and prepares the limb to make contact with the ground. Joints gradually extend.

Question 20

What are the key muscles involved in protraction?

Answer 20

Include the trapezius, supraspinous, common digital extensor and the lateral digital extensor.

Question 21

Define RETRACTION

Answer 21

Retraction starts as soon as the limb hits the ground. It is a backwards swinging motion which uses the gluteals and the hamstrings. When retraction has finished, protraction immediately restarts

Question 22

What are the key muscles involved in retraction?

Answer 22

Include the trapezius, deltoid, intraspinous, superficial digital flexor, deep digital flexor.

Question 23

What is the thoracic sling?

Answer 23

A large trunk of muscles that permits both rotation and sliding movement of the scapula. Uses deep pectoral muscles to transfer the weight off the forelimb and allow front end movement.

Question 24

What superficial muscles are involved in the movement of the scapula?

Answer 24

Include the trapezius, the latissimus dorsi, superficial pectoral.

Question 25

What deep muscles are involved in the movement of the scapula?

Answer 25

Include the rhomboideus and the pectoralis profundus

Question 26

What is the role of the hindlimb?

Answer 26

• to support 40% of the horse’s body weight
• to provide forward impulsion in locomotion
• restrict range and versatility of movement

Question 27

What is the appendicular skeleton?

Answer 27

Consists of the bones that make up the limbs.

Question 28

How many vertebrae are in each part of the spine?

Answer 28

7 in the neck (cervical) 
18 in the chest (thoracic)
6 in the loin (lumbar) 
5 in the pelvic region (sacral) 
18-21 in the tail (coccygeal)