A Horse’s Body Characteristics & Functions
The physical characteristics of horses have evolved over thousands of years. Horses evolved as social herbivores, grazing on poor fibrous material while moving frequently. Horses were domesticated over thousands of years, used initially as a food source. Horses have been domesticated for almost as long. These animals are now used primarily for recreation, companionship, breeding, sport and competition, and to some extent, meat production. Horses are also still used in agricultural settings, for tasks that include riding, driving and pulling. These varied uses have resulted in the development of a number of horse breeds that display a wide variation in size, conformation and coat colour.
Horses are prey animals. This means that horses:
- Tend to herd together for safety and mutual comfort.
- Will take flight in response to perceived danger or threats.
Anatomy refers to the form and structure of organisms. In comparison, physiology is the study of the functions of the body and its parts.
Physiology looks at body systems, organs, tissues and cells.
The parts of a horse’s anatomy are also known as the points of the horse. Many body parts have the same name as human body parts, but have different functions.
In Canada, equines are considered livestock, even though they are primarily raised and used for recreation, breeding, work and competition. Horse owners and caregivers have a responsibility to know and understand a horse’s anatomy and physiology, regardless of why or how they use horses. A horse’s anatomy includes its skeletal system, muscles, the brain and nervous system, all internal organs and the hair and skin.
KNOW A HORSE’S BODY CHARACTERISTICS
Traditionally, a horse’s size is measured in “hands” at the withers, which is the highest part of the backbone and is located between the neck and back. One hand equals about 10 cm or 4 inches. Horses have hair coats in a range of colours, such as black, brown, grey, white and tan, and a long mane and tail. They grow a heavier winter coat in the fall and shed it in the spring.
A horse’s head is formed by the cranium, which encloses the brain, the bones of the forehead and face, and the muzzle, which consists of the nose, lips and the lower jaw, or mandible. Horses have powerful teeth and jaws and their teeth grow continuously as the surfaces wear down. A horse’s head is held up by its long, flexible neck.
The horse has unique eyes – they are both monocular and binocular vision. Monocular means that the horse can see objects with one eye. As a result, the brain usually gets two images simultaneously. With binocular vision, the horse can focus with both eyes and the brain receives only one signal. The horse has primarily monocular vision with a small binocular field at the front, meaning, horses can observe the ground directly in front of them with both eyes. People only have binocular vision and see with both eyes at the same time.
The structure of a horse’s skeletal system and the angles at which its bones connect determines the horse’s physical capacity and athletic potential. Joints and ligaments allow the horse to move smoothly. The horse’s body has a wide chest, which protects internal organs like the lungs and heart, and a muscular back. The tail helps with temperature regulation to swish away biting insects. The position and movement of the tail is also used for communication purposes.
The skeleton gives the horse its physical structure.
The specialized structures of the horse’s legs make it a fast and efficient runner.
What is commonly perceived as the horse’s knee is actually the equivalent of a person’s wrist, and the leg from the fetlock down is actually a highly elongated foot. The tip of its “toe” is protected by the tough hoof and the sole helps absorb the impact of the foot against the ground. Many of the joints in the horse’s leg are like hinges that allow forward and backward motion. This type of joint requires fewer muscles than a ball-and socket joint that can rotate in any direction. Therefore, the horse has long, light legs that allow a lengthy stride with a minimal expenditure of energy.
A horse has the same requirements for water, energy, protein, vitamins and minerals as do all animals, but differs in the type and function of its digestive system. The horse is a non-ruminant. Non-ruminants (humans, pigs and dogs) digest carbohydrates, protein and fat by enzymatic action. Ruminants (cattle, sheep and deer) use bacteria in the fore stomachs to digest fibre by fermentation and use enzymatic digestion in the small intestines.
The horse’s foregut includes the mouth, esophagus, stomach and small intestine. The hindgut includes the cecum, large colon, small colon and rectum. A horse’s stomach can hold only about 8 to 15 litres. The food passes through the stomach into the small intestine and then to the cecum, large intestine and colon, called the hindgut. The process of fermentation, which allows horses to break down cellulose, takes place in the hindgut of the horse. This system allows the horse to digest simple carbohydrate sources such as starch from grain in the foregut. Fibrous sources such as oat hulls, soy hulls, beet pulp, hay and pasture grass are digested in the hindgut. The small intestine is where the nutrients from carbohydrates are absorbed. Nutrients from fibre in the diet are absorbed in the hindgut.
LINK: Go to Think Like a Horse to explore many different photographs, illustrations and drawings – some of them interactive – on horse anatomy. How do these photographs, illustrations and drawings help to expand your understanding of horse anatomy?
The relationship between the structure and function of a horse’s body can help you better understand, care for and responsibly manage a horse.
The poll is the highest point on a horse’s head and is found between the ears.
The crest is the top line of the neck. Withers are the prominent “bony” ridge near the base of the mane where the neck meets the back. A horse’s height is measured at its withers.
The back stretches from the withers to the loin and includes part of the horse’s spinal column.
The loin is a short, muscled area that joins the back to the croup.
The croup is the area at the top of the rump and in front of the tail. It extends from the highest part of the hip to the tail.
The point of the hip is the bony point that lies just forward and below the croup.
The horse’s tail helps provide the horse with balance.
The tailhead is the base of the horse’s tail. The tail has many small vertebrae in it, called the dock.
The thigh is a large muscled area below the croup. It is in front of the buttock and behind the stifle joint.
The flank is the area between the belly and the hindquarters.
The stifle is a joint, similar to a person’s knee joint, at the front of the thigh in the flank area. It is the point where the horse’s hind leg meets the body. It is the largest joint in the horse’s body and stabilizes the leg when the horse is moving.
The gaskin is a muscled area of the hind leg. It is above the hock and below the stifle.