intro Flashcards
what are stem cells?
cells that can self renewal to make new stem cells or can differentiate into other cell types
How long do these cell types last?
- intestine
- brain
- blood
Intestine cells last for a few days, have high stem cell levels and a high cancer risk.
Brain cells are permanent have very few stem cells and a very low cancer risk
Blood cells last a few weeks and are in between
What are the types of stem cells in regards to the cell type/where they come from?
Germinal stem cells come from the zygote and are totipotent
Embryonal stem cells come from the embryo and are pluripotent
Somatic stem cells come from foetal and adult tissue and are multipotent or unipotent
Give some examples of adult stem cells, where they are and what they differentiate into
Neural stem cells are in the brain and differentiate into neurons and supporting glial cells
Haematopoetic stem cells are in the bone marrow and differentiate into myeloid and lymphoid progenitors and blood cells
Follicular stem cells are found in the hair follicles and make epidermal cells
How do stem cells control self renewal
By divisional asymmetry or environmental asymmetry
What is divisional asymmetry?
Two daughter cells. One inherits a signal for self renewal to stay a stem cell. The other inherits a signal to differentiate. This results in a 50/50 ratio of self renewal and differentiation meaning that stem cells like this cannot be regenerated when lost as they can only maintain their numbers
What is environmental asymmetry?
Both daughter cells are identical. One may receive signals for self renewal and the other for differentiation. Around 50/50 split but two daughter cells can have the same fate.
Clinical applications of tissue engineering examples
Airway replacement by taking airway ECM and making it acellular then seeding it with stem cells to create a new airway
Urethra replacement has also been achieved this way but using artificial scaffolds rather then acellular ECM from the patient
