The Trigeminal nerve is composed of a large sensory portion (portio major) and a smaller motor portion (portio minor). Its sensory fibers are carried from the greatest part of the face, mucosa of the nasal cavity and paranasal sinuses, as well as from the oral mucosa and teeth. Its motor fibers innervate the muscles of mastication and floor of the mouth. It has three well developed main branches- Ophthalmic, Maxillary, and Mandibular.
The Ophthalmic nerve divides into Lacrimal, Frontal, and Nasociliary nerves. The frontal nerve carries sensation from the skin of the foehead and upper eyelid via the Supraorbital and Supratrochlear branches. The nasociliary carries sensation from the frontal sinus, ethmoid air cells, and the and the anterior part of the nasal cavity via the Anterior Ethmoidal, Lateral Nasal, and Infratrochlear branches.