Alveoli: The plural of alveolus. The alveoli are tiny air sacs within the lungs where the exchange of oxygen and carbon dioxide takes place.
- Alzheimer disease, early-onset familial
Alzheimer disease, early-onset familial: Alzheimer disease that runs in families and strikes at an unusually early age (with its onset under the age of 60). About 7% of early-onset cases of Alzheimer’s are familial and are inherited in an autosomal dominant manner with high penetrance. Mutations in three different genes — the amyloid precursor protein […]
- Alzheimer's disease
Alzheimer’s disease: A progressive degenerative disease of the brain that leads to dementia. On a cellular level, Alzheimer’s disease is characterized by the finding of unusual helical protein filaments in nerve cells of the brain. These twisted filaments are called neurofibrillary tangles. In the brain, Alzheimer’s disease involves degeneration of the cortical regions, especially the […]
Amalgam: In dentistry, an alloy of mercury, silver, tin, etc. used in dental restorations.
Amastia: A rare condition wherein the normal growth of the breast or nipple does not occur. Unilateral amastia (just on one side) is often associated with absence of the pectoral muscles. Bilateral amastia (with absence of both breasts) is associated in 40% of cases with multiple congenital anomalies (birth defects) involving other parts of the […]
Amathophobia: An abnormal and persistent fear of dust. Sufferers experience anxiety even though they realize dust poses no threat. From the Greek “amathos” (sand) and “phobos” (fear).