norovirus One of a group of viruses that cause the “stomach flu,” or gastroenteritis. The term norovirus was approved as the official name for this group of viruses. Several other names have been used for noroviruses, including Norwalk-like viruses, caliciviruses (because they belong to the virus family Caliciviridae), and small round structured viruses. The virus…
North Asian tick-borne rickettsiosis See rickettsiosis, North Asian tick-borne.
Norwalk virus The prototype virus of the genus Norovirus. See norovirus.
nose The external midline projection from the face. The purpose of the nose is to warm, clean, and humidify the air that a person breathes. In addition, it helps a person to smell and taste. The nose is divided into two passageways by a partition called the septum. Opening to these passageways are the nostrils….
nose, runny The production of extra mucus by the nose. Rhinorrhea is the medical term for this common problem. The nose makes extra mucus whenever something that is in the nose, such as pollen or dust, needs to be removed. Mucus formation is also part of the histamine reaction to allergies and of the body’s…
nose job See rhinoplasty.
nose picking Using the finger to remove debris from within the nose. Compulsive nose picking, known medically as rhinotillexomania, is common among children.
nitrous oxide A gas that can cause general anesthesia and that should be administered with other anesthetic agents. Nitrous oxide is not used alone today because the concentration of nitrous oxide needed to produce anesthesia is close to the concentration that seriously lowers the blood oxygen level, creating a hazardous hypoxic state. Nitrous oxide is…
nits Lice eggs. Nits are hard to see, and they are often confused with dandruff or hair-spray droplets. Nits firmly attach to the hair shaft with a glue-like substance. They are oval and range in color from yellow to white. Nits take about a week to hatch. All nits must be removed to prevent reinfestation…
NK cell Natural killer cell.
NMR Nuclear magnetic resonance, an imaging technique that does not use radiation, but instead employs large magnetic forces to produce detailed images of body tissues.
nocardiosis Infection with Nocardia, filamentous bacteria found in soil worldwide. Infection tends to strike the lungs, brain, and skin, particularly in people with an impaired immune system. The inhalation of Nocardia spores usually initiates nocardiosis in the lung. The skin form of nocardiosis is contracted through soil contamination of wounds. There is no evidence for…