[?/??Receptor binding 
produces depolarization of the gustatory cells, stimulating the 
sensory nerve fibers that send information to the brain for 
processing.Taste buds detect at least five broad categories of tastants: 
sodium ions (salty); hydrogen ions from acids (sour); sugars 
and related compounds (sweet); alkaloids and certain toxins (bitter); and amino acids such as glutamate and aspartate 
(umami; Jap.?] Dr/Samaher Mohammed ?: The lamina propria of the olfactory epithelium possesses 
large serous glands, the olfactory glands (of Bowman), which 
produce a constant flow of fluid surrounding the olfactory cilia 
and facilitating the access of new odoriferous substance
[?/???] Dr/Samaher Mohammed ?: Olfactory Epithelium
The olfactory chemoreceptors for the sense of smell are located 
in the olfactory epithelium, a specialized region of the 
mucous membrane covering the superior conchae at the roof 
of the nasal cavity.They are not restricted to papillae and are also widely 
scattered elsewhere on the dorsal and lateral surfaces of the 
tongue, where they are also continuously flushed by numerous 
minor salivary glands.The 
apical (luminal) pole of each olfactory cell is its dendrite 
end and has a knoblike swelling with about a dozen basal 
bodies, from which long cilia project into the overlying 
aqueous layer.Supporting cells are columnar, with narrow bases 
and broad, cylindrical apexes containing the nuclei and 
extending microvilli into the fluid layer.The 
paranasal sinuses communicate with the nasal cavities through 
small openings; mucus produced there is moved into the nasal 
passages by the activity of the ciliated epithelial cells.?] Dr/Samaher Mohammed ?: Paranasal Sinuses
The paranasal sinuses are bilateral cavities in the frontal, maxillary, ethmoid, and sphenoid bones of the skull (Figure 17-1).Approximately 250 taste buds are present on the lateral surface of each vallate papilla, with many others present 
on fungiform and foliate (but not the keratinized filiform) 
papillae.?] Dr/Samaher Mohammed ?: Taste buds are ovoid structures within the stratified 
epithelium on the tongue's surface, which sample the general 
chemical composition of ingested material (Figures 15-4 and 
15-5).Salt and sour tastes are produced by ion channels and the other three taste categories are 
mediated by G-protein-coupled receptors.Olfactory neurons are bipolar neurons present 
throughout this epithelium.?:?????:???:??[??/???:??