Horse Skull Anatomy
The horse’s front limbs have long, straight bones, enabling it to make big strides as it runs. Its hind limbs are short, allowing it to turn quickly. Its head is large, designed to allow the animal to easily see food it eats. The eyes are set back on the skull, another adaptation for grazing.
There are 34 small and large bones in the horse’s skull. Its most notable features are its horns and its complete bony orbit (the circle around the eye that contains all of the surrounding muscles and nerves).
The horse skull is the largest of all mammals, with more than double the volume of humans. The largest single bone is the sphenoid bone, which forms the top of the skull. There are two other large bones that join the sphenoid to the rest of the skull: the palatine and vomer.
Between these three bones sits a cavity that houses the brain. A horse’s brain is much larger than a human’s.
The skull has a number of other interesting features. For example, the frontal bone has a tubular projection at its proximal end that extends toward the eye, called the cornual process. This horn-like structure, along with a pair of jugular veins and the facial nerve, carry motor innervation to muscles that move the eyebrows and upper lids. The jugular veins also carry blood to the brain.
Another feature of the equine head is the nasal septum, a cartilaginous structure that splits the nasal cavity into two. In addition, there are bilateral sets of thin-walled, bony ridges in the nasal cavity, called conchae. Each concha has a dorsal, middle, and ventral meatus. The nasolacrimal sac, the lacrimal canal, and the nasolacrimal duct are all part of the nasolacrimal apparatus.
A horse’s forelimbs are divided into the stylopod (humerus and radius) and zeugopod (carpals, metacarpals, and phalanges). The distal autopod segments of equids have experienced more variation throughout equid evolution than the proximal stylopod and zeugopod components.