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Stem Cells

Human Biology (Year 11) - Cellular Reproduction

Ben Whitten

What are stem cells?

  • Stem cells are immature cells that can make other blood cells that mature and function as needed. These cells are used in procedures such as bone marrow transplants.

  • Stem cells are unspecialised cells. They have not developed into cells that perform a specific function.

  • Human development starts with just one cell – the fertilized egg. This cell divides to produce 2 ‘daughter cells'. These daughters divide, and their daughters divide again, and so on. There are a great many steps needed to form an adult body or even a baby. Along the way, lots of different types of cells must be made.

    Stem cells are different from other cells of the body because stem cells can both:

    • 1) Self‐renew: Make copies of themselves and;

    • 2) Differentiate: Make other types of cells – specialized cells of the body.

  • ‘Specialized’ or ‘differentiated’ cells play particular roles in the body, e.g., blood, nerve, and muscle cells. Specialized cells cannot divide to make copies of themselves. This makes stem cells very important. The body needs stem cells to replace specialized cells that die, are damaged or get used up.

Stem Cell Self-Renewal

  • If stem cells don’t copy themselves, you would quickly run out.

  • Must maintain a pool of stem cells to use throughout your life.

Stem Cell Differentiation

  • Specialised cells are used up, damaged or die.

  • Cannot divide or make copies of themselves therefore requires replacing for normal functioning of your body.

  • To make specialised cells with specialised functions e.g. from fertilized egg to embryo.

Types of Stem Cells

  • Embryonic Stem Cells: Found in the blastocyst, a very early stage embryo; contains 50-100 cells

  • Tissue Stem Cells: Also referred to as adult stem cells; found in tissues of the body in fetus, baby, child or adult

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