This is the second in a series of four videos that goes over how to memorize the dermatomes, or the area of skin supplied by nerves from a single spinal root. The last video already covered the cervical nerves, so in this video, I will cover the sensory distributions of the cranial nerves. Cranial nerves are twelve pairs of nerves that originate directly from the brain, instead of the spinal cord, passing through certain foramina in the skull.
Using two classic mnemonics, I will go over the twelve cranial nerves before focusing on only the ones with sensory distributions. First, the names of the cranial nerves can be remembered from the first letters of the following phrase. “Oh, oh, oh, to touch and feel very good velvet. Such heaven!” These letters represent the olfactory, optic, oculomotor, trochlear, trigeminal, abducens, facial, vestibulocochlear, glossopharyngeal, vagus, accessory, and hypoglossal nerves. The next mnemonic covers the function of the nerve in the same manner as before. “Some say money matters, but my brother says big brains matter more.” S stands for sensory, m stands for motor, and b stands for both. As it turns out, the cranial nerves with a purely sensory function are actually considered special sensory. The olfactory nerve conducts olfaction (smell), the optic nerve conducts optics (sight), and the vestibulocochlear nerve conducts hearing and equilibrium. In this video we will only cover the nerves with distributed sensory functions mapped to an area – so those four marked with a B.
The fifth cranial nerve, trigeminal, is named as such because it has three (tri) sensory distribution areas corresponding to the three main sensory branches known as V1, V2, and V3. These branches exit from three separate foramina, the superior orbital fissure, the foramen rotundum, and the foramen ovale. I like to remember these foramina by the phrase “to and FRO” . . . The areas that the nerves cover are called the ophthalmic area, the maxillary area, and the mandibular area. Importantly, the ophthalmic area includes the superior nasal mucosa and the conjunctiva and cornea of the eye. The maxillary area includes the nostrils, the nasolabial folds, inferior nasal mucosa, the palate, superior teeth and gums, and roof of the pharynx (which is the superior part of the throat), and importantly the maxillary, ethmoid, and sphenoid sinuses. The mandibular area includes the inferior teeth, gums, and anterior tongue and importantly EXcludes the angle of the jaw which is supplied instead by C2/C3.
The ear has a variety of innervations that is difficult to pin down exactly. For most students, it is sufficient to know that V3 contributes anteriorly, C2/C3 contributes posteriorly, and that VII and X contribute in the middle. There will be a link to the exact distribution in the description box below for those who are curious.

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The tongue has an interesting mixture of innervation. To draw the tongue accurately, simply draw a large oval with an inverted ‘v’ near the top. The ‘v’ corresponds to the terminal sulcus, and the tip of the ‘v’ corresponds to the foramen cecum. Just below the ‘v’ draw a bunch of circles to represent the circumvallate papillae. Above the V draw a bunch more circles with dots in them to represent the lingual tonsils. Good, now let me show you how the four cranial nerves we discussed at the beginning map to our drawing. V and VII cover the anterior part of the tongue. V contains only the simple touch and pain sensation (known as visceral afferent), while VII contains the special taste sensation. IX overlaps a bit just anterior the the circumvallate papillae, but covers almost all of the rest of the tongue with both visceral afferent and special sensation (taste). X gives off a branch known as the internal laryngeal to cover this small area with both visceral afferent and special sensory.

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