Senile plaques are extracellular deposits of amyloid in the gray matter of the brain.
Comment:
Senile plaques can be found in human and animal brains. From an age of 60 years (10%) to an age of 80 years (60%) the proportion of people with plaques increases approximately linearly. A small number of plaques can be due to the physiological process of aging. Women are slightly more likely to have plaques than males. The plaques occur commonly in the amygdoid nucleus and the sulci of the cortex of brain. The deposits are associated with degenerative neural structures and an abundance of microglia and astrocytes. Large numbers of senile plaques and neurofibrillary tangles are characteristic features of Alzheimers disease, and some of the abnormal neurites in senile plaques are composed primarily of paired helical filaments, a component of neurofibrillary tangles. In Alzheimer's disease they are primarily composed of amyloid beta peptides. These polypeptides tend to aggregate and are believed to be neurotoxic.