1. Embryological Development and Stem Cells By: Jewel Reuter, LA Virtual School Donald Cronkite, Hope College Attachment #12

2. Two Kinds of Cells During embryological development, cells divide again and again. Eventually, however, cells differentiate. Most differentiated cells do not divide.

3. But if no cells divided… Some cell division is always necessary to Make more blood cells Heal wounds Make a continuous supply of sperm cells

4. So there are stem cells... differentiate Stem cell keeps dividing

5. In early embryos, most cells are stem cells. This membrane of cells attaches the embryo to the mother. Inner cell mass (becomes the embryo) Compared to the more than a trillion cells in an adult, the inner cell mass is scarcely 100 cells. The inner cell mass must give rise to many different cell types. All the inner cell mass is made of stem cells. The blastocyst: A week-old embryo Bgn1

6. Stem cells vary in what they become. Embryonic stem cells: Can become any cell (Inner cell mass of blastocyst) Adult stem cells: Can become a few cell types (Blood-forming, wound- healing, sperm-forming cells) Bgn2

7. Stem cells can be cultured. With the right medium, stem cells can be cultured in dishes. Scientists are learning how to get a stem cell to differentiate into a certain cell type. Bgn3

8. What could we do with stem cells? Many diseases are due to cells that won’t work. Diabetes – cells of the pancreas Parkinson’s disease – cells of the brain The “bubble boy” – cells of the immune system

9. What could we do with stem cells? What if we could replace the cells that won’t work with new ones made from stem cells? Diabetes – cells of the pancreas Parkinson’s disease – cells of the brain The “bubble boy” – cells of the immune system

10. This is the end of this lesson, but not the end of your learning.

11. In early embryos, most cells are stem cells. Trophoblast (becomes part of placenta) Inner cell mass (becomes the embryo) Compared to the more than a trillion cells in an adult, the inner cell mass is scarcely 100 cells. So, the inner cell mass must give rise to many different cell types. All of the inner cell mass is made of stem cells. The blastocyst: A week-old embryo ADV1

12. Stem cells vary in what they become. Totipotent stem cells (the inner cell mass of blastocyst) can become any cell. Pluripotent stem cells can become a few cell types, such as blood-forming, wound- healing, sperm-forming cells. ADV2

13. Stem cells can be cultured. With the right medium, totipotent or pluripotent stem cells can be cultured in dishes. Scientists are learning how to get a stem cell to differentiate into a certain cell type. ADV3