Anatomy and Function of the Spine.
The equine spine is made up of the vertebra, which are uncompressible, and intervertebral disks, which are slightly compressible. These disks allow for some movement along the length of the spine. In between each vertebra is a pair of facet joints, one of each side. These joints allow for some very limited movement. The vertebra themselves have a bony projection on the top, known as the dorsal spinous process and from the sides, called transverse processes. Ligament and muscles attach to these areas.
Image credit: https://commons.wikimedia.org/wiki/File:Vertebra_Superior_View-en.svg
The spine can be divided into 5 distinct sections:
- Cervical Spine – made up of 7 vertebrae in the neck.
The first cervical vertebrae or C1 is known as the Atlas and the second or C2 is the axis. The atlas has slightly wider transverse processes, known as the wing of atlas.
- Thoracic Spine – made up of 18 vertebrae that form the withers and the ribcage is suspended from. There is one vertebra for each pair of ribs.
- The lumbar spine – made up of 6 vertebrae – This is a very vulnerable area of the spine as its main function is to absorb the shock from the propulsion of the hind limb.
- The sacrum – made up of 5 vertebrae that fuse at around 4-5 years old to make one structure. Sometimes the first vertebrae of the coccygeal is also fused to the back of the sacrum.
- The coccygeal vertebrae – this can be anywhere between 15-24 vertebrae and these form the tail. The vertebrae decrease in size as you move further down the tail.
Image credit: https://en.wikipedia.org/wiki/File:Horse_anatomy.svg
The equine spine is more rigid in comparison to that of a dog or a cat. There is very little lateral movement except in the cervical spine. A horse will pivot on its hind legs and that coupled with the abduction and adduction of the limbs and swing of the thoracic girdle, that enables a horse to turn quickly. Lateral (sideways) flexion of the spine is limited.
The horse anatomically wasn’t designed to move in circles or take very tight turns. The wild horse grazes and moves in a forwards motion, the flight instinct is to run in a straight line at high speed. The horse wouldn’t attempt to outfox a predator by taking a tight turn. As mentioned before, a cat, whether it be a lion or something smaller has more flexibility in both their spine and fascial system to be able to turn much quicker than a horse.
Therefore when we’re training horses, we need to consider their anatomy before asking them to physically perform movements they’re not capable of. Horse’s can learn to bend, but you need to create length and space in the spine by stretching and strengthening the ligaments and muscles.
Come back next week for part 2, where we’ll look at spinal pathologies.