Figure 1.

Anatomy and histology of the nasal cavity, epithelium, and transport pathway to the CNS. (A) Drugs administered to the nasal cavity cross the epithelium in either the superior olfactory region (OR) and move along the olfactory nerve (left arrow) to the olfactory bulb (OB), or the lateral respiratory regions (RR) and the trigeminal nerve (right arrow) to the pons. (B) From the lamina propria (LP), drugs are transported to the CNS along the olfactory sensory neuron (OSN, left arrow) p through the cribriform place (CP). A similar process occurs along the trigeminal nerve. Drugs can also be lost to systemic absorption via lymphatics (LV) or vasculature (BV). The anterior vestibular region (VR) is minimally involved in the intranasal route to the brain.