In our new ten part sequence, we will take look at the equine anatomy. This is meant to be an informative series for horsemen of all levels. Let’s start by comparing horses to humans.
The evolution of the horse from a tiny, four-toed animal, perhaps no more than one foot tall, to the variety of equines in existence today, is one of the wonders of nature. During that process of change, the horse evolved over many thousands of years from an animal that predators hunted for food to an animal that became a servant and friend for mankind.
Today’s horses are designed to do one of two things–pull a load with their shoulders or carry riders on their backs. The type of horses utilized for these respective tasks varies a good deal; one is large and ponderous and the other is lighter-boned with less muscle mass. Even within these two types, there are significant differences. For example, the conformation of a roping or cutting horse is different from that of the American Saddlebred. Yet there is a basic sameness to anatomy.
Comparisons of humans to horses logically can start with the anatomy. We stand upright; horses stand prone on their four limbs. What we call our knees are the stifles of horses, and our heels or ankles are horses’ hocks. Our foot is their cannon bone, and from the fetlocks to the ground are our fingers and toes. Our fingernail is their hoof, and our nail growth generates from the cuticle, their hoof from the coronary band. The hoof is the weight-bearing structure so susceptible to laminitis (founder). Humans don’t founder, although a diabetic’s loss of blood supply to the legs has some comparable pathology.
The forelimb is complex in the horse, with the head and neck being a crane-like structure that causes 60% of a horse’s body weight distribution to the forelimbs. Therefore, impact is greatest on the front legs (except when pushing off from behind).
What we really call the horse’s knee is our wrist. From our wrist to the first knuckle is their single cannon bone, with the splints along the side being remnants of our other palm bones. Again, each finger is analogous to the horse’s single fetlock and hoof. Our hands and feet are well endowed with muscle. Contrary, the forelimbs and hind limbs of the horse are essentially devoid of muscle below their so-called knees and hocks, with the tendons and ligaments being a “spring loading” system of recoil that adds to their efficiency of movement.
Because we stand upright and they are prone, this creates the forelimb concussion issue for the horse, but also loads the spring.
Horses don’t have clavicles (collarbones), so the front limbs are held to the body by soft tissue alone (muscle, tendons, and fibrous sheets of fascia).
Internally, the horse has lungs similar to ours, but a gastrointestinal tract that is more complicated. Humans are omnivores (eating both meat and plant material), while the horse is a herbivore (grass eater or grazing species). The horse stomach is relatively small (3-5 gallons) compared to the overall size of the animal, and it has a muscular valve from the esophagus to the stomach that prevents vomiting. If the valve is not stimulated, the horse can passively reflux up to the oral cavity. Humans can vomit, and sometimes learn to vomit at will.
The stomach of the horse is divided into two sections, a glandular and a non-glandular (squamous) section, separated by a demarcation called the margo plicatus. Humans have a uniform stomach similar to that of pigs; in fact a pig gastrointestinal tract is often used as a research model for human research. All these species get gastric ulcers, principally from stress and confinement.
The horse is obviously different from humans. The horse to human bond grows perpetually both physically and emotionally by understanding and education. The instinctive behaviors of a horse include flight and claustrophobia (while humans have panic attacks!). Domestication of the horse is evidence that the horse might be more malleable than many humans.