A 90-Year-Old Man Died in a Nursing Home

A 90-year-old man died in a nursing home. During the past 10 years, he was unable to care for himself and was mentally incoherent. He had no memory and could not hold a conversation. He was unaware of his surroundings. At autopsy, the brain showed signs of Alzheimer disease, and there were neurons containing numerous neurofibrillary tangles. These cytoplasmic structures are formed from which component of the neurons?

A) Nucleus
B) Rough endoplasmic reticulum
C) Smooth endoplasmic reticulum
D) Mitochondria
E) Cytoskeleton