The horse’s neck is a continuation of the spine with vertebrae and a continuation of tubes for the passage of food, air, water and blood. The head has the ear, mouth and eyes as well as an area where movement of the body is controlled. The neck is very mobile and can move to the left and right as well as up and down. It is important for horses to have a neck that is proportional to their size. An equine neck that is too short or long makes the body appear to be out of balance, making it difficult to carry weight and creating a clumsy horse.
The head is a complex structure, made up of bones, joints, muscles and ligaments. It controls the movement of the horse’s head, jaw and ears. The eyes and ears provide sensory input from the outside world, funneling sound into action potentials in the brain. These are then interpreted and understood by the horse. The ears also help in determining direction and velocity of the horse’s movement.
Like other animals, the neck of the horse consists of 7 cervical (neck) vertebrae and the first thoracic vertebrae where the rib cage begins. The first cervical vertebrae is the atlas and together with the occiput creates an up and down motion of the neck. The second cervical vertebrae is called the axis and together with the atlas creates rotation of the neck. The remaining cervical vertebrae have rudimentary spinous processes on the sixth and seventh cervical vertebrae, which allows for more rotation of these regions.
There are many muscles that are essential to movement of the head and neck, including those which lift and those which lower it. Muscles above the line of the neck are called epaxial muscles and those below are called hypaxial muscles. The two most important muscles to understand when it comes to lifting and lowering the head are the multifidus and the longissimus dorsi.
The upper jaw of the horse has a number of teeth including the incisors and premolars. There are also permanent molars which form the “bar” of the mouth. There are no deciduous canines in the equine upper jaw, though small, vestigial canines may be seen on a skull.
The upper neck is connected to the lower neck by the jugular vein and the internal carotid artery. There are also several other arteries and veins in the occipital region of the horse’s skull. The nasoincisive notch can be found in the facial tuberosity of the skull and is where the infraorbital canal passes through the skull. The infraorbital nerve (CN V Trigeminal) exits the infraorbital canal through the infraorbital foramen. Rostral to this notch is the palpable nasoincisive cleft between the incisive and nasal bones on the rostrum of the skull. There is a nasoccipital foramen in the rostral surface of the skull just in front of this nasoincisive slit. The nasoincisive foramen is a good point to start finding other structures in the rostrum of the skull.