How long take toreplanall the skin in a human body?
Answers
This is a broad based question. I shall confine my a answer to a few key points that strike my mind:
Dermal tissues (skin) are replaced quickly and as a matter of routine. A patch of skin replaces in about 25 days.
It takes about 5 months for a nail to grow/replace from bottom to top .
Liver cells regenerate very fast. liver is the only complex organ that can "grow". The liver will return to a normal size in one to two weeks following the removal of greater than 50% of the liver by mass.
Nerve cells get TERMINALLY differentiated in a mature brain and are NOT replaced.
Similarly the rod and cone cells in the retina of eye may not be replaced.
Unlike liver, cells of most of human/animal organs are terminally differentiated. For example if thumb is cut from the base the natural repair that follows never results in replacement of the thumb.
In human females egg cells (number of eggs) is preformed towards the onset of puberty. These are simply discharged one by one during the menstrual cycle till the on set of menopause.
In human males sperm cells are rapidly produces from puberty onwards till old age when these may be limited by some clinical conditions.
That process is easy to see if you watch babies' limbs grow and their bodies get bigger. It's also obvious when our toenails grow or healthy skin emerges after a burn peels away.
But less obvious systems of regrowth and rebirth in the body continue through adulthood. Dead skin cells constantly rise to the surface of our body, get sloughed off, then are replaced by new stem cells.
Some areas of the body take a long time to refresh themselves - for example, our fat-storage cells shift roughly once per decade, while we get fresh liver cells about once every 300 days.
Of course, your body doesn't simply throw away an entire liver's worth of cells on day 300 and create a brand new set on 301. Instead, it's more of an organic cycle, since liver cells continue to divide and regenerate long after they're mature.
Not every body part regenerates or changes, though. While the body's hairs are in a near constant state of growth, parts of the human brain and head pretty much finish developing at birth (like the lens of the eye that's helping you read this).
Eventually, the tips of our DNA begin to fray as years of wear and tear take their toll on the body - part of the natural aging process.
Here are just a few of the myriad ways that your body regenerates, regrows, and starts anew all the time.
