What is alzheimer's disease caused by?

Like all types of dementia, Alzheimer's is caused by brain cell death. It is a neurodegenerative disease, which means there is progressive brain cell death that happens over a course of time. The total brain size shrinks with Alzheimer's - the tissue has progressively fewer nerve cells and connections.

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The fetus at this stage is curled up, almost doubled over, so remember to consider this as you draw the fetus the correct length