In the following chapters we consider cranial nerves in groups concerned with their functions. These are, in no particular order, ingestion and chewing, cutaneous sensation, swallowing and speaking, autonomic function, taste and smell, and sight, hearing and balance.

The ingestion of food is dependent on opening the mouth. This is a function of the mandibular division of the trigeminal (Vc) and facial (VII) nerves: the mandibular opens the jaw and the facial parts the lips. The facial, mandibular and hypoglossal (XII) nerves are involved in taking the food into the mouth and closing the lips. Chewing is served by the same three nerves: in simple language, the facial nerve keeps the lips closed, the mandibular nerve moves the mandible for its mastication, and both facial and hypoglossal nerves maintain the food between the teeth. Also, the trigeminal senses its position and consistency, and regulates the force of contraction of the muscles, and both trigeminal and facial nerves are responsible for taste perception from the mouth. The trigeminal nerve also has another important function: the cutaneous sensation of the face and anterior scalp. It is, except for a small area of skin in the external ear, the only nerve concerned with this. So, the trigeminal, facial and hypoglossal nerves will be considered first.

After we eat and chew, we swallow. The motor components of swallowing are mainly the responsibility of the vagus (X) and glossopharyngeal (IX) nerves, with the hypoglossal (XII) nerve also initially involved.