Olfactory epithelium. Computer illustration of a section through the olfactory epithelium of a rat (Rattus sp.). The olfactory epithelium is the specialised layer of tissue that lines the inside of the nasal cavity and is involved in smell. The olfactory bulb, situated in the forebrain (prosencephalon), contains many olfactory receptor cells (pink) that project into the epithelial lining of the nasal cavity. Receptors embedded in the membrane of the receptor cells pick up smell information from molecules inhaled through the nose. This information is transmitted to the olfactory bulb and sent as a nerve impulse to the brain. Seen here are: bipolar olfactory neurons (sensor cells, pink), sustentacular cells (blue), a microvillar cell (yellow) and basal cells (green).