Cranial nerves and facial muscles: Dental assisting

The cranial nerves and facial muscles play an integral role in the function of the head and neck. These nerves are needed for sensation, facial expression, and important functions like speech, chewing, and swallowing. As a dental assistant, understanding these important structures promotes patient comfort and safe, effective care.

Now, there are 12 pairs of cranial nerves. Each pair has specific motor or sensory functions.
CRANIAL NERVE I, the olfactory nerve, is responsible for the sense of smell and has a role in taste by helping to process the distinct flavors of food.
CRANIAL NERVE II, the optic nerve, is responsible for vision;

while CRANIAL NERVE III, the oculomotor nerve; CRANIAL NERVE IV, the trochlear nerve; and CRANIAL NERVE VI, the abducens nerve, work together to control eye movements.

CRANIAL NERVE V, the trigeminal nerve, provides sensory information for the face and mouth, and motor control for the muscles of mastication, which are the muscles for chewing.

CRANIAL NERVE VII, the facial nerve, provides motor function for the muscles of facial expression, and taste sensation for the anterior two-thirds of the tongue.

CRANIAL NERVE VIII, the vestibulocochlear nerve, is responsible for hearing and balance.

CRANIAL NERVE IX, the glossopharyngeal nerve, provides sensation around the ears, and controls the function of the parotid salivary gland.

The vagus nerve, or CRANIAL NERVE X, moves the soft palate, along with the pharynx and larynx, and connects the brain to the heart, lungs, and digestive tract.

CRANIAL NERVE XI, the accessory nerve, is responsible for movement of the neck muscles, pharynx, and the soft palate.

And finally, CRANIAL NERVE XII, the hypoglossal nerve, controls tongue movement.

Okay, let’s take a closer look at two cranial nerves that are especially important to dentistry: the trigeminal nerve and the facial nerve.

First, let’s focus on the trigeminal nerve, which has three branches: the ophthalmic, maxillary, and the mandibular.

The first branch is the ophthalmic branch, which only has sensory functions. It supplies areas like the forehead, upper eyelids, and the eye. Although it’s not a major focus in dentistry, it’s involved in an important reflex called the blink reflex, which causes involuntary blinking when the eye senses a foreign body like a pesky grain of sand getting in your eye.

The second branch is the maxillary branch, which is a sensory nerve that supplies areas like the upper lip, upper teeth, maxillary gingiva, and soft palate, and the skin of the cheek, and nose.

Lastly, the third branch is the mandibular branch, which has both sensory and motor functions. It supplies sensory information to the lower lip, lower teeth, mandibular gingiva, and tongue;

as well as motor function to the muscles of mastication.

Next, let’s switch gears and review the functions of the facial nerve. As far as motor function goes, important roles include control of the muscles of facial expression and involvement in the production of tears and saliva.

Additionally, it provides taste sensation from the anterior two-thirds of the tongue.

These two nerves allow you to enjoy wonderful things, like your favorite foods, the kiss of your partner, or a summer breeze on your face, as well as less pleasant things, like a toothache or a dentist drilling into your teeth.

Alright, let’s switch gears and look at the facial muscles.

The muscles of facial expression are innervated by the facial nerve, and control expressions.