Horse Anatomy Explained: Parts That Make Up the Horse

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Talitha vanNiekerk

Talitha fell in with all things horses when she bought a horse in her late twenties. Her desire to train her horse using only humane methods took her on the journey of a lifetime. She's managed a public stable yard with over 80 horses in her care. Sharing her passion online is second nature, and she loves to combine her love for horses and writing together on The Horse and Stable!

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Every year, I have a kids camp where I teach children about horses, what makes up the different parts of the horse, and what contributes to making up a whole horse. Children and many parents who attend are stunned by just how complex a horse is.

When explaining a horse’s anatomy, it should be clear that horses have several advanced body mechanisms, each contributing to the horse’s successful survival and existence.  Horses are made of outer or external parts such as the ears, skin, and tail, while they also have internal systems that handle their digestion, breathing, and excretion. Whenever something goes wrong with any one of these systems, it can be devastating for the horse’s health. 

Horses on the Outside

Let’s start with what you see when you approach a horse. In simple layman’s terms, a horse is a four-legged herbivore or grass-eating mammal with a flowing mane and tail, and it can move at fast speeds by running in any of the four main gaits trot, canter, gallop, and lope.

Horses nurse their young, and they are built to run fast to avoid being caught and eaten by predators. When you first see a horse, it seems impossible that they can stand (never mind run) on those skinny legs, but boy, do they run! A fine coat of furry hair covers their body, which usually lies in one direction (which is why they can be brushed). 

Along the neck is a mane of longer hair that forms the horse’s flowing mane. At the opposite end of the trunk, above the anus, is the horse’s long tail, which can reach the ground. The tail and mane’s purpose is to swat at flies when the horse flicks their tail or shakes its mane. 

Most of the horse’s body is broad and barrel-shaped. This is where the horse’s heart, lungs, and internal organs are located. A leg at each barrel corner supports the horse’s massive weight effortlessly.  But let’s look at each part of this body in detail.

The Horse’s Head

Horses have unique head shapes. For many years, horse people have believed that certainly shaped heads indicate the horse’s temperament. Indeed, a broad forehead does seem to show more space for a larger brain and better-thinking skills. Close-set eyes are linked to being flighty and even aggressive behavior. 

The Eyes

In the horse’s head, we find two eyes on the head’s lateral sides. This allows the horse to have a clear field of vision; however, the horse has two blind spots—right behind it and right in front of it (within proximity). Having an interrupted field of vision is also why many horses spook so quickly when they “suddenly” see something on the ground before them.

The horse’s eyes retract slightly into the skull when depressed, and the horse can also roll their eyes backward while blinking. With the ability to gently move their eyes, a horse can avoid minor scrapes and scratches that would have left them blinded if they couldn’t protect their eyes more. 

Covering your horse’s face and eyes with a good quality fly mask is essential to help prevent eye infections and damage from insect bites and sun damage.  The Horse Fly Mask Super Comfort Horse Fly Mask is highly rated for fly protection. With nifty ear attachments, this fly mask will help keep flies from your horse’s eyes and eliminate head-shaking behavior.

This fly mask is available in 22 colors and four sizes to choose from. At $12.92, the Horse fly mask is ideal for protecting your fur baby’s eyes. 

The Ears

Horses have prominent ears; the higher the breeding in some breeds, the closer the ears will sit together. Some horses are so finely bred that their ears face each other or curve inward. The horse’s ears are mobile and can flex laterally and to the front and back.

A horse’s ears are their primary source of information.  When their ears are perked forward, a horse is listening. If the ears are flattened backward, the horse is annoyed and about to lash out. Floppy “donkey” ears mean the horse is relaxed.

The Mouth

The mouth comprises several parts, including the prehensile lips, which are designed to help the horse forage on short grasses. Incisor teeth line the horse’s jaws in the front and molars in the back. These allow for grabbing grass and chewing it in a slightly side-to-side grinding motion. 

The jaws have a space between the incisors and the molars where the bit fits when the horse is ridden. Once the foal’s baby teeth erupt, the adult teeth follow in stages until the horse has a full adult and permanent set of teeth at the age of four to five. These teeth require maintenance by a qualified dentist. 

Teeth should be floated and balanced once every six months when the horse is younger than 10 years old and once a year after age 10.

The length can also tell the horse’s age of a line (called Galvayne’s groove), which shows up at the age of 10. The line is halfway down the tooth by 15 years and has fully grown down the length of the tooth by 20 years. By 25 years, the groove has disappeared halfway, and by the age of 30, the groove will be gone entirely again. 

The Horse’s Neck

The horse’s head balances on the top vertebrae of the spinal column with many thick muscles structuring the rest of the neck. The neck is required for balancing the rest of the horse’s body, and if the neck is poorly developed, the horse will lack the strength to carry weight on its back. 

The neck dimensions will influence whether the horse is suited to a particular sport, such as jumping or endurance. The neck is also responsible for the horse’s ability to run at speed around obstacles or change direction. The horse’s speed and direction can be controlled when the neck is bent. 

Training the horse to develop the correct musculature on its neck is essential to help build a strong horse. Working the horse long and low lets the neck muscles naturally develop on the upper side of the neck and form a natural arch.  The confirmation of the neck, where it attaches to the trunk, and how it balances the head will all determine the horse’s capabilities. 

One flaw of the horse’s neck is that the length makes it impossible for the horse to vomit if they have indigestion. Therefore, horses can’t throw up if they have eaten too much or eaten something that upsets their digestion (like dogs can). They will suffer from choking if they overeat or colic if they have eaten the wrong food and suffer from digestive issues. 

To build a good neck or topline, it is beneficial to lunge your horse in the round pen with side reins such as these Camelot German Rubber Ring Side Horse Reins, which have the elasticity to give and take contact when lunging the horse. The side reins encourage the horse to lower its head, lift its stomach muscles and raise its back, all of which create a stronger and more elastic neck. 

Horse’s Barrel or Central Body

The neck and legs connect to the horse’s core, which is barrel-shaped from muscles around the spine and ribcage, ending at the horse’s hips. The barrel is where the saddle fits, where the rider sits, and where the internal organs, such as the digestive tract, lungs, heart, kidneys, and bladder, are located.

Riders mount from the left or “near side,” while the right side is called the “far side” or “off side.” The top of the neck joins the trunk at the withers, the highest point of the barrel. The bottom of the neck joins the barrel at the breastbone, forming the neck V at the center of the horse’s chest. 

The Withers and Chest

The horses wither is important as many core muscles attach here. If the wither is too high, the horse will be difficult to fit a saddle too, and if the withers are too low or fleshy, the saddle will slide over the horse’s barrel. Medium withers with strong shoulders are a good combination for conformation and saddling. 

Likewise, if the horse’s chest is too narrow, there will be issues with the horse’s lungs, yet a large chest could lead to issues with the horse’s movement. Medium depth chest musculature is ideal for stamina, movement, and good breathing.

To ensure your saddle fits correctly, especially over the shoulders and withers, a vest in a saddle fit gauge. Or you can use the services of a professional saddle fitter. Saddle systems like the Easy Change Gullet System Gauge can help you determine what size gullet your saddle requires. This system is ideal for English saddles, which often come with an interchangeable gullet system. 

The Barrel

The sides of the barrel are created by the horse’s ribcage, with the spinal column’s vertebrae at the top of the horse’s back. The last vertebrae of the spinal column make a thick fleshy extension known as the dock from which the tail hair grows.

If the spinal column is too long in comparison to the hips and shoulders, the horse is known as being long-backed. These types of backs are often weak, and if the horse’s muscles don’t develop fully, they may form a sway back, where the back hangs. A swayback can experience issues with the pressure that can be painful when fitted with a saddle or ridden. 

Short-backed horses where the barrel is more compacted are more robust, but these horses may struggle with fitting a saddle, as no saddle should extend past the last rib of the ribcage. The horse’s soft, slightly hollowed areas on either side of the barrel after the trunk are called the flanks. These areas are where you will find the horse’s internal organs, such as the kidneys, digestive tract, and liver. 

A horse in good condition will have a nice covered barrel, where the ribs can be felt but not seen. The flanks are almost completely filled (but not bulging out), and the hips have a nice curve before moving into powerful hindquarters.

Older horses often struggle with weight maintenance, so adequate supplementary feeding is required. A supplementary feed additive such as Manna Pro Weight Accelerator for Senior Horses can help address weight loss issues. Correct nutrition will help an older horse keep or gain weight. 

The Horse’s Limbs

Horses have two front legs and two back legs, and these legs each end on the hoof, which is made of hardened nail growth. Horses carry their total weight on a small percentage of their actual body weight, and their hooves take up a small surface area compared to their overall size. Each horse leg has 20 bones in it. From larger bones like the tibia and smaller bones like the navicular bone in the hoof, the legs are complex structures that provide strength and stability to the horse’s body. 

The horse’s ability to move depends on the front legs bending backward to reach forward in the stride, while its back legs bend forward, pushing the body off the furthest back position. Since the horse’s legs and hooves do all the work to move it forward, stop, turn, and keep it upright, these areas usually sustain the most injuries. 

The Front Legs

Knowing if a horse has good legs can help you choose a horse that will be more secure on its hooves and suffer fewer injuries from incorrect movement. Breeders assess a horse based on the following concepts:

Correct leg placement

When a horse has correct placement, they have “a leg in each corner” of its barrel. Their front hooves will be slightly toward the middle of their chest, giving the legs a slightly bowed appearance as the muscles will show a good tone on the forearms. The back legs will be well-positioned, without the hocks (back knees) bending over each other or being too far apart. 

Base wide vs. base narrow

The base is the bottom of the horse’s chest. When the horse is base-wide, its legs seem to move apart from the corners of its chest, creating the appearance that they are standing with splayed legs. 

Base narrow legs give the horse the appearance that their legs (or knees) point toward each other, narrowing the gap between the front legs to less than the bottom of the chest. Base narrow horses tend to kick themselves when moving. 

Horse’s Limbs

A horse is considered bow-legged if its legs curve outward from the knee, creating a bowed appearance. These horses also tend to kick themselves when moving.

The horse’s weight will be carried to the inside of its hooves, leaving excess pressure to stretch the outside ligaments and tendons. Horses with this condition often wear away their inside hoof more easily, and they have a flaring of the nail to the outside as the hoof wall stretches. 

Toes out and pigeon-toed hooves

Both these types of conformation affect the legs, and horses can be either toed-out, where their hooves rotate slightly, so their toes face outward, or they can be pigeon-toed. When a horse is pigeon-toed, they tend to be more trippy as their toes face inward. 

Knock-kneed legs

When horses have knees that point in, while their hooves point out, you have a typical cartoon-style horse with knock knees. Since the legs aren’t straight, the horse has weakened legs and can’t carry much weight. Corrective shoeing can improve this conformation, but the flaw will never be eliminated. 

The Back Legs

When a line is drawn from either side of the horse’s tail to the ground (roughly where the middle of each of the horse’s butt cheeks would be), the horse’s hind legs should run in the path of those lines. Legs placed on the outsides of the lines are considered wide-legged, while legs inside the line are considered narrow. The horse is in good conformation if the line runs through the leg. 

Narrow legs

When the legs are narrow at the ankles, the horse may hit themselves with each stride. Using a product like Woof Wear Sport Brushing Boot may help prevent serious injury, but there is nothing that can be done to remove the issue entirely. Brushing boots help protect the horse’s legs by wrapping the area where the legs brush in padded layers. Instead of the horse hitting themselves, they impact the boots instead. 

Cow hocked legs

If the horse has their hocks or knees turned toward each other, they are said to be cow hocked. A horse with this conformation issue will be weaker and unable to engage its back legs correctly. 

In addition to horses’ legs needing to meet a particular conformation from the front and back, their legs must be shaped at the correct angle from the side. Legs that slant too much, have disproportions between the lower and upper legs, and are poorly shaped can mean a horse has concussion problems when running. 

The Horse’s Hooves

Horses have four hooves that carry their weight over rough terrain and at speed. While we can only see the outer surface of the hoof, hooves have a delicate internal structure that can easily become damaged and suffer injuries related to equestrian sports. 

The outer shell of the hoof or the hoof capsule covers and protects the sensitive tissue of the hoof itself. The shell ends on the hoof wall or nail, which is what the horse walks on. This nail is what makes contact with the ground, so your horse is not walking on four solid “feet” but instead on four crescent-shaped nails. 

Farriers trim these nails to prevent them from breaking unevenly and maintain the correct angle at which the horse’s hooves meet the ground. When these angles are off, the horse’s legs, shoulder, hips, and spine will suffer an increased concussion, leading to long-term damage. 

Some horses are prone to poor hoof growth, making them susceptible to hoof diseases and breakage, leading to health risks. These horses require dietary supplementation to ensure their hooves grow more naturally and with the required thickness to support their weight. 

A supplement like Farrier’s Formula Double Strength is reinforced with omega acids, lipids, vitamins, minerals, and amino acids that help promote hoof growth. With correct supplementations, cracks grow out faster, infection risks are reduced, microbial infections are neutralized, and horses with laminitis recover much faster.  

Inside the hoof, there are delicate bones such as the coffin bone, the navicular bone, and delicate bursae (oily pouches) that work together to give the horse flexion and movement over uneven terrain. To maintain these joints, the horse needs to have a balanced diet that contains all the essential nutrients to help produce the fluids and fibers of the joints. 

Horseshoes can be fitted to limit some compressive pressures from working on hard ground or if the horse is prone to sensitivity in their hooves. Horseshoes help limit the amount of concussion and irregular wear that could negatively affect the horse’s hooves and overall health.

Horses on the Inside

The horse is already an incredibly complex animal on the outside and much more on the inside. The horse inside has many organs and systems that help the animal live, thrive, and reproduce. Like other mammals, horses have digestive, respiratory, and reproductive systems that work together to ensure the horse is healthy and sound. 

The Horse’s Respiratory System

Horses have large lungs that occupy most of their chest cavity space. The horse’s lungs are not the only part of the respiratory system. The nose, trachea, sinuses, larynx and pharynx, and diaphragm are all part of the complex system that allows horses to breathe and smell. 

Interestingly, the horse can’t breathe through their mouth. Horses can only inhale through their nostrils. You won’t see tired horses panting like other mammals such as dogs. 

The Horse’s Circulatory System 

Horses have a complex circulatory system. Being such large animals, their blood flow has a long distance to cover. Part of this system is the heart, weighing 8.5 pounds, a network of blood vessels and blood. Horses have an average of 55 gallons of blood in their circulatory system. 

With so much blood, it’s no wonder that horses look like they’re bleeding out when they have an injury. Their powerful heart manages to move all that blood in a closed circulation from the frogs in their hooves (the lowest living tissue of the horse’s body) up to the rest of their body (with the ears being the highest point). 

The Horse’s Digestive System

Horses are meant to graze, which requires an advanced system to digest the nutrients of grasses and other plant fibers fully. Unlike humans with relatively short digestive tracts, horses have a long track averaging over a hundred feet.

This length is required to help process and ferment the proteins and starches contained in roughage. The horse’s digestive process requires specialized enzymes that can help ferment the fibers of grass, roots, and other plant matter.

The fermentation process allows horses to absorb the total nutritional value of their food. The different parts of the digestive system and their corresponding lengths are:

• Esophagus: 4-5 feet
• Stomach: 5 gallons capacity 
• Small intestine: 50-70 feet
• Cecum: 4 feet
• Colon, small colon, and rectum: 24 feet

The Horse’s Reproductive System

Mares have two mammary glands below their belly; their reproductive organs are located internally, with the vagina below the anus.

The highly flexible vulva can stretch to accommodate the birth of a large foal, returning to normal size within a few minutes to an hour after birth.  Mares conceive the unborn fetus that will become a foal at birth. The mare’s hormonal balance controls her ability to mate, gestate the embryo, and begin the lactation cycle that will trigger the birthing or foaling process. 

Stallions have external sex organs, with their penis located inside a sheath that hangs externally to the body between their back legs. The testes are located here, though the horse can retract these into their body when it’s cold or the horse is in pain.

The penis extends or drops when the stallion urinates or when they mate.  A stallion is needed to impregnate the mare. Impregnation occurs during a mating session between the mare and stallion. Mares are said to produce offspring of different genders each season they reproduce, though this is not always true.

Some mares will only give birth to female offspring, while others will only have males or colts. The genetic contribution of the stallion and mare will determine the gender of the foal. 

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