FIGURE 2.

(A) Skull structure presenting major components of nose and brain involved in drug transport to the brain, (B) structural components of nasal mucosa, (C) the various pathways (highlighted in different colors; yellow, red, and green) for the delivery of drugs into the brain through intranasal route. Yellow arrows present the major direct pathway involving the olfactory nerve, red arrows present the pathway primarily involving the germinal nerve route, and green arrows illustrate the minor pathway involving blood–brain barrier (BBB) following the systemic absorption of the drug molecules through respiratory epithelium. BBB, blood–brain barrier; CSF, cerebrospinal fluid.