How many stem cells does an adult have?

Question

How many stem cells does an adult have?

Answer 1

Number can not be ascertained. Adult stem cells come only from umbilical cord and bone marrow.

Answer 2

The number of stem cells that an adult has can depend on a few different factors, and no one really knows an exact number.

Although there are stem cells (pluripotent in nature) in a fetus's/ newborn's umbilical cord, an adult will not have stem cells around his or her belly button. Once a newborn's umbilical cord is severed and clamped, the cells in the cord start to die. These cells will certainly not be proliferative in an adult.

The longer your bones are (the taller you are), generally the more stem cells you will have, as most stem cells in the body reside in bone marrow.

Also, as you grow older, the number of actively dividing stem cells that you have goes down. These are the stem cells that are really of importance. Since the classification of "adult" starts at 18, there can be a big difference between an 18 yr old adult and an 80 yr old adult in this area.

In the adult brain, stem cells reside in the subventricular zone (SVZ) and the subgranular layer (SGL). In response to brain damage, such as a stroke or traumatic brain injury, stem cells in this area can become more proliferative, and move toward the injured area of the brain. If you have recently injured your brain, you will have an increase of stem cells in the brain.

There is also current speculation as to the possible presence of stem cells in the adult spinal cord.

Answer 3

trillions?