Overview
This lecture covers the types of stem cells, their abilities (self-renewal and potency), and ranks them from most to least powerful based on their capacity to differentiate.
Stem Cell Basics
- Stem cells are original cells that generate all other cells in the body.
- They have two main properties: self-renewal (ability to make more of themselves) and potency (range of cell types they can become).
Types of Stem Cells Ranked by Potency
Totipotent Stem Cells
- Totipotent cells can become any cell in the body and placenta.
- Example: Zygote (fertilized egg) is totipotent and forms all tissues and placenta.
Pluripotent Stem Cells
- Pluripotent cells can become almost any cell (≈200 types) except placenta.
- Example: Inner cell mass of blastocyst develops into the three germ layers (ectoderm, mesoderm, endoderm).
Multipotent Stem Cells
- Multipotent cells can form multiple, but limited, cell types within a specific lineage.
- Example: Hematopoietic stem cells form all blood cell types; mesenchymal stem cells form bone, cartilage, fat, and muscle.
Oligopotent Stem Cells
- Oligopotent cells can produce a few closely related cell types.
- Example: Lymphoblasts create specific immune cells (B cells, T cells, NK cells); myeloblasts form types of granulocytes (neutrophils, basophils, eosinophils).
Unipotent Stem Cells
- Unipotent cells can only produce one specific cell type but can self-renew.
- Example: Germline stem cells produce sperm; basal cells produce lung cells; epidermal stem cells produce skin cells.
Key Terms & Definitions
- Stem Cell — Cell with the ability to self-renew and differentiate into specialized cell types.
- Self-renewal — The process by which stem cells divide and produce more stem cells.
- Potency — A stem cell’s ability to differentiate into different cell types.
- Totipotent — Can generate all cell types including placenta.
- Pluripotent — Can generate almost any cell type, excluding placenta.
- Multipotent — Can generate multiple cell types within a specific family.
- Oligopotent — Can generate only a few related cell types.
- Unipotent — Can generate only one cell type.
Action Items / Next Steps
- Review the types and properties of stem cells.
- Memorize examples for each potency level.
- Study the three germ layers and their derivatives.