Dictionary

nipple absence See athelia.

nipple, supernumerary An extra nipple. Supernumerary nipples are usually smaller than normal and vestigial (nonfunctional, without accompanying mammary glands). They tend to occur along a roughly curved line that extends from near the armpit, through the center of the normal breast, and down to the lower abdomen. This distribution is very similar to the location…

nitrogen narcosis A condition similar to intoxication with alcohol characterized by euphoria, loss of balance and manual dexterity, disorientation, and impaired reasoning. It can occur in scuba divers below 30 meters (100 feet) who breathe compressed air, because of the high nitrogen content of air. Nitrogen narcosis is reversed as the gas pressure decreases and…

nitrogenous base A molecule that contains nitrogen and has the chemical properties of a base. The nitrogenous bases in DNA are adenine (A), guanine (G), thymine (T), and cytosine (C). The nitrogenous bases in RNA are the same, with one exception: adenine (A), guanine (G), uracil (U), and cytosine (C).

nitroglycerin A medication used to dilate blood vessels and improve blood flow. Nitroglycerin has a rapid effect and is used to treat angina pectoris by increasing blood flow to the heart. Nitroglycerin tablets are taken sublingually (under the tongue). Also known as nitro, NTG.

nitrosourea One of a group of anticancer drugs that can cross the blood–brain barrier.

neuropathy, accessory See accessory neuropathy.

neuropathy, diabetic See diabetic neuropathy.

neuropathy, hypoglossal See hypoglossal neuropathy.

neuropsychologist A psychologist who has completed special training in the neurobiological causes of brain disorders and who specializes in diagnosing and treating these illnesses by using a predominantly medical (as opposed to psychoanalytical) approach.

neurosurgeon A physician who specializes in surgery on the brain and other parts of the nervous system.

neurosyphilis Neurological complications in the third (tertiary) and final phase of syphilis, which involve the central nervous system and can include psychosis, pain, and loss of physical control over a variety of bodily functions. See also syphilis.