Introduction to Equine Functional Anatomy
Many apparent anomalies of anatomy can be explained if we remember that the horse has evolved from a small animal no bigger than a dog. The first animals were small and simple, having developed in water, and needing no complex structure to survive. As the animals became bigger they evolved supporting structures such as skeletons and specific organs, and gradually moved onto land.
The early animals had a simple skeleton with a head, a backbone, and four limbs. The limbs were attached to the spine with a front and back pair. Each limb then had a basic structure of one bone attached to the trunk (humerus/femur), then two bones (radius and ulna/tibia and fibula), then multiple bones of the wrist and ankle, ending in five digits.
Evolution has caused different animals to develop in different ways. The dog has maintained the basic bone anatomy (although one digit is often rudimentary), but has a specialised carnivorous intestinal tract. The pig has a standard intestinal tract able to digest a wide variety of food, but the limbs have developed to give greater speed by lengthening the distal limb, and standing on only two toes in each foot. The horse has developed a specialised intestinal tract to digest grass and grains. Its main protection is to run away from danger, and so the limbs have been highly modified, using only one digit on each limb, but elongating this to the extreme to give maximum leverage and increase its speed when running.
If this evolution from one basic type to achieve several special ends is borne in mind, then anatomy starts to make more sense. For example, the horse's splint bones are really not necessary to the mechanical functioning of the limbs, but are left over from the second and fourth digits that are gradually being lost with continued development of the equine limb.
A basic knowledge of how the organs and tissues work is essential if we are to understand how to work and manage horses to obtain their best performance.
Anatomical Directions
When describing anatomy we need to be able to use a standard set of directions that we all understand.
Caudal - towards the tail
Cranial - towards the skull
Dorsal - towards the back or top surface (think of the dorsal fin on a fish)
Ventral - towards the under surface (belly)
Rostral - toward the nose (relates to the head)
Palmar - in the lower front limbs toward the back surface when standing
Plantar - the back of the lower hind limb
Proximal - toward the point of attachment to the body
Distal - away from the point of attachment to the body
Lateral - towards the outside of the body
Medial - towards the mid-line of the body
Points of the Horse
Knowing the points of the horse can prove valuable when trying to convey an issue to your vet or animal chiropractor and vice versa when you are listening to their findings and being able to understand any terminology.