Dictionary

node, Heberden’s See Heberden’s node.

node, AV See atrioventricular node.

node, atrioventricular See atrioventricular node.

node A knot, a collection of tissue. For example, a lymph node is a collection of lymphoid tissue. See also nodule.

nocturnal enuresis See bedwetting.

nocturnal amblyopia See nyctanopia.

nocturia Excessive urinating at night. Nocturia can be normal and more common with aging. Nocturia can also be a sign of an underlying condition, such as diabetes or urinary infection.

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…

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.

NK cell Natural killer cell.

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…

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…