1 How do we go from one cell to many? • Cell division to create more cells. • Differentiation: process by which cells becomes specialized into cell types so that they can carry out special functions. • Controlled by a number of interacting factors in the embryo, many of which are still not well understood.
2 embryology – study of developing embryo egg and sperm zygote cleavage morula blastula gastrula
3 Cells involved in embryonic development The fertilized egg cell and the cells that results from the first few divisions in embryonic development are called totipotent. Totipotent is a cell that can develop into any cell of the body. They can even become cells that surround the embryo. After about 4 days, the embryo forms a hollow ball, called a blastocyst, where cells are already beginning to specialize. The outer cells of the blastocyst form tissues that attach the embryo to the uterine lining, while the inner mass are cells that will form the embryo itself. The inner mass cells are said to be pluripotent because they can form all the body’s cell type but cannot form tissues surrounding the embryo.
4 Stem Cells • Unspecialized cells from which differentiated cells develop • Why are stem cells important? Because of their potential to develop into other cell types, stem cells are the subject of intense interest by researchers. • Source of Stem Cells: • Embryonic – pluripotent cells from inner mass of blastula • Adult – multipotent because they can differentiate into several cell types but not all cell types • - bone marrow stem cells can produce • several different kinds of cells
6 totipotent pluripotent multipotent
8 Potential Benefits of Stem Cell Research Cells get damaged. Examples: heart attack, stroke, spinal cord and brain injuries Stem cells offer the potential benefit of using undifferentiated cells to repair or replace badly damaged cells and tissues. Ex. Reverse damage of a heart attack
9 Ethical Issues Most techniques of harvesting embryonic stem cells cause the destruction of an embryo or a terminated fetus. Groups seeking to protect the rights of embryos oppose stem cell research as unethical. Other groups support stem cell research as essential for saving human lives and argue that would be unethical to restrict research. Human embryonic stem cell research is controversial because the arguments for and against it involve ethical issues about life and death.