embryo stem cells
- forms all cell types (pluripotent)
- grow continuously
- great potential
- abundant
adult stem cells
- tissue specific
- form some cell types (multipotent)
- limited life span in culture
- limited numbers
The SC Stem Cell Transient-Amplifying (TA) Cell Concept
All stem cells undergo asymmetric cell division to generate daughter cells that retain the stem cell phenotype, and daughter transient-amplifying cells that proliferate and differentiate to replenish the cells that are lost to the environment after terminal differentiation.
rate of stem cell cycle
Stem cells are generally slow-cycling in vivo, but they have a high proliferative potential and proliferate at times of tissue expansion such as during fetal development and wound healing.
What are the two most important features of epithelial stem cells?
- unlimited capacity for self-renewal
- slow-cycling nature
benefits of slow cycling
- avoid cell damage or potential mutation
- conserve proliferative potential
- minimize DNA replication errors
Steps of stem cell division
- one daughter cell remains a SC stem cell
- the other becomes a TA cell
- TA cells divide several cycles and become post-mitotic
- Terminal differentiation occurs (keratinocytes for SC)
Which 3 sites do the stem cells of the epidermis exist?
- interfollicular epidermis
- bulge region of outer root sheath of hair follicle
- the sebaceous gland
Which layer does the development and growth of the keratinocytes start?
the basal cell layer
epidermal skin cells
- responsible for everyday regeneration of the different layers of the epidermis
- found in basal layer of epidermis
hair follicle stem cells
- ensure constant renewal of the hair follicles
- regenerate epidermis and sebaceous glands if tissues are damaged
- found throughout the hair follicles
melanocyte stem cells
- responsible for regeneration of melanocytes
- not certain where the stem cells are found in humans
cell nucleus contains ….
all information required to make a new tissue or organ
