Stem Cells For Beginners: Where Do They Come From? July 22, 2007Posted by Mrs Weird Scientist in Human Body, Stem Cells, Think About It.
This is the second part of my little series of blog entries that I’m calling Stem Cells For Beginners. You can still read part one, which is called What Are Stem Cells? I started this series because lets face it, stem cells are one complicated subject! They’re going to be talked about a lot more in the weird science blog and you will probably hear about them in the news as well. This series is a primer to give you enough information so that you can read new blog entries with ease and when you hear something on the news, it’ll be easier to follow what’s going on.
In part one, you learned that stem cells have the unique properties of being unspecialized, while still being able to differentiate into specialized cells. You also learned that they can proliferate, which means they multiply into perfect copies of themselves. That still doesn’t answer why there’s so much heated anger and controversy over stem cells. And I’ll tease you a bit by saying that we’re not quite there yet – this blog entry is going to cover where stem cells come from, which you need to understand before we can get into the controversy.
Lets Break It Down
To understand why there’s so much emotion over stem cell use, we have to look at their sources – where they come from. So, grab yourself a glass of milk and a snack and get comfy at your computer for the next five minutes.
Embryonic Stem Cells
You’ve probably heard of an embryo? It’s the period of time from conception to around eight weeks of development. Well right at the beginning of an embryo’s development – just 4 or 5 days after it is created, it’s called a blastocyst. A blastocyst is a tiny little cluster of cells that has an inner cell mass. When you hear about embyronic stem cells, it means the cells are taken from the inner cell mass of the blastocyst. The picture above shows how the stem cells are cultured from the inner cell mass. If you remember from the first blog post in Stem Cells For Beginners, they are undifferentiated. You can see above where these undifferentiated stem cells then differentiate into the three specialized cells above. That was one of the unique things about stem cells.
Fetal Stem Cells
After eight weeks of growth, the embryo is called a fetus. The term fetal stem cells simply means that the stem cells are taken from the fetus.
Adult Stem Cells
You might have already guessed where these come from – adult stem cells are taken from adult tissues. You can see in the picture on the right here some of the places in the body that researchers have found adult stem cells. Researchers are still hoping to identify them in many more adult tissues.
Cord Blood Stem Cells
After a baby is born, its umbilical cord is detached. The umbilical cord and placenta both hold cord blood, which contains a valuable source of stem cells.
Your Knowledge Is Increasing!
So, now you know why stem cells are considered unique and you also know some of their sources – what next? Soon, we’ll see how embryonic, fetal, adult and cord blood stem cells are so different. And if you haven’t already gotten a hint at where the controversy comes in, you’ll definitely get some hints on my next blog post about stem cells. We’re almost up to the very controversial part of stem cell use. And I can tell you, it’s one rocky ride.
Credit: The National Academy of Sciences has kindly allowed the images to be reprinted on the weird science blog. Check out the original link here called Understanding Stem Cells, courtesy of the National Academies Press in Washington, D.C.