i read somewhere the body replace itself every 7 years. does the brain also do this?
Generally no. Some regeneration and growth of brain (new synapses etc) continue for entire life, but most of the brain cells are the same since early childhood - or we would be unable to retain childhood memories which are saved as deposits of proteins within neurons.
The whole idea is a myth, the reality is that the many different cells in the body are replaced at very different rates, and some like the neurones in the cerebral cortex are not replaced at all in adulthood.
Some examples; sperm cells only last around 3 days, cells lining the colon, 4 days, red blood cells last around 4 months, while white blood cells can live around a year. The rate also changes as we age cells in the heart (cardiomyocytes) are replaced at around 1% a year in young adults but this rate is halved by the age of 70. For most people this means that over half of these cells will never be replaced over their lifespan. It seems that few neurons are replaced over our lifespan though there may be some neurogenesis in very specific areas of the brain like the hippocampus.
@black hole 123 -
The next time you pose a question please consider giving us the source. It is clear that your source was very wrong.
Also consider: when you want to find something in medicine or human biology try a search on NIH. They have wonderful high quality references there, and their general white papers for public consumption are excellent. Prepend "site:NIH" to your google search example:
"site:nih.gov your search term(s) " --- without the quotes, I had to add them to get this to display correctly
Here's a nice source on turnover of cells in the human body: http://book.bionumbers.org/how-quickly-do-different-cells-in-the-body-replace-themselves/
I have a dry patch of skin on my face, my concern is this means a high cell turn overate and is "aging" much faster than the rest of my face!
Just wanted to mention you can append your google search with the site:<url> search modifier. Here's a list of other modifiers for the Google novices: https://moz.com/learn/seo/search-operators
Separate names with a comma.