Histology of Alzheimer's Disease



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Chapter 3 : Histology of Alzheimer's disease

Topics covered in this snack-sized chapter:



Alzheimer's and the Brain arrow_upward


  • Microscopic changes in the brain begin long before the first signs of memory loss.
  • The brain has 100 billion nerve cells (neurons).
  • Each nerve cell connects with many others to form communication networks.
  • Groups of nerve cells have special jobs. Some are involved in thinking, learning and remembering. Others help us see, hear and smell.
  • To do their work, brain cells operate like tiny factories.
  • They receive supplies, generate energy, construct equipment and get rid of waste.
  • Cells also process and store information and communicate with other cells.
  • Keeping everything running requires coordination as well as large amounts of fuel and oxygen.
  • Scientists believe Alzheimer's disease prevents parts of a cell's factory from running well.
  • They are not sure where the trouble starts. But just like a real factory, backups and breakdowns in one system cause problems in other areas.
  • As damage spreads, cells lose their ability to do their jobs and, eventually die, causing irreversible changes in the brain.
  • The cross-section on the left represents a normal brain and the one on the right represents a brain with Alzheimer's disease.
  • In Alzheimer's disease, there is an overall shrinkage of brain tissue.
  • The grooves or furrows in the brain, called sulci (plural of sulcus), are noticeably widened and there is shrinkage of the gyri (plural of gyrus), the well-developed folds of the brain's outer layer.
  • In addition, the ventricles, or chambers within the brain that contain cerebrospinal fluid, are noticeably enlarged.
  • In the early stages of Alzheimer's disease, short-term memory begins to fade when the cells in the hippocampus, which is part of the limbic system, degenerate.
  • The ability to perform routine tasks also declines.
  • As Alzheimer's disease spreads through the cerebral cortex (the outer layer of the brain), judgment declines, emotional outbursts and language is impaired.
  • As the disease progresses, more nerve cells die, leading to changes in behavior, such as wandering and agitation.
  • In the final stages of the disease, people may lose the ability to recognize faces and communicate; they normally cannot control bodily functions and require constant care.
  • On average, the disease lasts for 8 to 10 years, but individuals with Alzheimer's can live for up to 20 years.

  • Alzheimer's Changes the Whole Brain arrow_upward


  • Alzheimer's disease leads to nerve cell death and tissue loss throughout the brain.
  • Over time, the brain shrinks dramatically, affecting nearly all its functions.
  • Here is another view of how massive cell loss changes the whole brain in advanced Alzheimer's disease.
  • This shows a crosswise "slice" through the middle of the brain between the ears.
  • The cortex shrivels up, damaging areas involved in thinking, planning and remembering.
  • Shrinkage is especially severe in the hippocampus, an area of the cortex that plays a key role in formation of new memories.
  • Ventricles (fluid-filled spaces within the brain) grow larger.


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