Unit 18: Stem Cells Flashcards
(41 cards)
what is totipotency?
ability to form a fully formed, complex, multicellular organism
what are the requirements to be a tissue?
- mechanical strength (connective tissues)
- delivery of oxygen and nutrients and removal of waste (blood vessels)
- electrical signaling (nerve cells)
- disposal of dead and damaged cells (macrophages, lymphocytes)
which cells originate outside the tissue and then invade it during development?
nerve cell axons, endothelial cells, schwann cells
which cells originate outside the tissue and then invade it continuously?
macrophages, other blood cells
what are the 3 factors contributing to tissue stability?
- cell communication
- selective cell adhesion
- cell memory
what is cell memory?
when cell preserve their distinct identity and pass it onto their progeny
what is selective cell adhesion?
homophilic binding and other selective attachments keeping cells in their proper place
how long does it take for intestinal cells to renew?
3-6 days
how long does it take fornerve cells to renew?
trick question they NEVER do
what do osteoclasts do?
slowly eat away old bone matrix
what do osteoblasts do?
deposit new bone matrix
how long does it take blood cells to be removed from bone marrow?
120 days
how long does it take for skin to be renewed?
2 months
what makes a cell terminally differentiated? give some examples.
unable to divide themselves.
red blood cells, epidermal cells in upper layers of skin, cells in gut epithelium
where do replacement cells come from for terminally differentiated cells?
proliferating precursor cells which come from undifferentiated stem cells
how can stem cells be identified if they are difficult to spot in tissues?
specific molecular markers
how do stem cells differentiate into the appropriate cell type?
- express specific transcription regulators
- developmentally restricted
describe how cell replacement occurs in the lining of the small intestine?
we have stem cells at the bottom of crypts which give rise to precursor cells.
the precursor cells move upward in the epithelial sheet and then differentiate into absorptive/secretory cells
differentiated cells die when they get to the top of villi
what are crypts?
epithelial tissue that descend down into underlying connective tissue
describe cell replacement in the stratified epithelium epidermis?
- the stem cells and precursor cells are attached to the basal lamina
- differentiating cells travel outward from site of origin, perpendicular to cell sheet
- terminally differentiated/dead cells are shed from kin surface
what is hematopoiesis?
the process of forming many possible types of blood cells and platelets from one hematopoietic stem cell
where are hematopoietic stem cells found?
bone marrow
describe how Wnt proteins stimulate cell proliferation in intestine.
- the signal molecule promoting proliferation is located in the crypt
- crypt cells secrete proteins that prevent Wnt pathways outside the cell from being stimulated
when Wnt active, we get cell proliferation
how do stem cells repair lost and damaged tissues?
proliferate indefinitely and produce progeny that differentiate
continuously renew normal tissues