Smell receptors. Comparison between a scanning election micrograph (SEM left) and transmission electron micrograph (TEM right) of the olfactory epithelium.The nerve cell (green) is found in the nasal epithelium. The swollen part of the cell is the olfactory vesicle. Protruding from it are small hairs (cilia). These are the smell receptors. The information from these receptors is passed to the olfactory bulb in the brain where it is processed. In order for a substance to be smelled it must be a gas, and water and lipid soluble. There are over a million olfactory receptor cells in a human nose, all located in a small area at the back of the nasal cavity. In the SEM the surface structure of the specimen is visible. Magnification SEM X 3000 TEM X 5000 when printed @ 10cm high. For a series of comparisons between SEMs and TEMs see images C047/7006 to C047/7034.