There are thousands of olfactory receptors that sense smell. Olfactory receptor cells are neurons that contain olfactory hairs. Olfactory hairs are long cilia that protrude from nasal epithelium and are continuously bathed by a layer of mucus secreted by underlying glands. The peripheral olfactory organ or organ of smell consists of two parts: an outer, the external nose, which projects from the center of the face; and an internal, the nasal cavity, which is divided by a septum into right and left nasal chambers.

 The respiratory epithelium, a non-neural epithelium found at the most external aspect of the nasal cavity, warms and moistens the inspired air. It also secretes mucus.  Mucus traps and neutralizes potentially harmful particles.  Superficial nasal mucosa allows the olfactory receptor neurons direct access to odorant molecules.

 Hyposmia is the reduced ability to detect odor. It is caused by nasal polyps blocking the nasal cavity. Nasal Polyps are overgrowths of the mucosa, which may obstruct the nasal passageway in the maxillary sinuses.  Anosmia is the complete loss of smell. The depth of the olfactory sulcus is an indicator of congenital anosmia  Anything that interferes with the olfactory process can damage ability to smell: › Injury to the nose and smell nerves from surgery or head trauma. › Exposure to toxic chemicals, such as pesticides or solvents. › Medicines, including antibiotics, anti-depressants, anti-inflammatories, heart medications › Cocaine abuse. › Old age. › Some medical conditions, for example; Alzheimer's disease, Parkinson's disease, multiple sclerosis, nutritional deficiencies, congenital conditions, and hormonal disturbances. › Radiation treatment of head and neck cancers › Nasal polyps