OB P2-Epithelial Cell Biology and the Cell Cycle. Flashcards
What is the defintion of epithelium?
Tissue of closely packed cells that forms a surface or lines a cavity or tube
what does epithelium line?
the inside surfaces of fluid or air filled tubes and spaces inside the body
when is epithelium protective?
In skin
When is epithelium secretory?
In the lining of gut
When is epithelium joined together?
desmosomes
What drives proliferation of epithelial cells?
basal lamina
How are epithelial cells classified?
- depends on the number of layers
- depends on shape of cells
what are the 2 types of one layer epithelial cells?
- simple
- multi layered nuclei
what is the name for two or more layers of epithelium?
stratified
Name the type of multi layered nuclei.
pseudostratified
What are the 3 shapes of cells?
- Flattened scale like - squamous
- Cells are cubes - cuboidal
- cells are columns - columnar
Name the 3 types of oral mucosa.
- Masticatory
- lining
- specialised
Where is masticatory oral mucosa found?
gingival and hard palate- keratinising
Where is lining oral mucosa found?
floor of mouth, buccal regions and oesophagus- non keratinising
Where is specialised oral mucosa found?
the dorsum of the tongue- both.
what are the functions of oral mucosa epithelium?
- Protection of underlying tissue
- The different epithelium form lipid based permeability barriers.
- Protect from fluid loss
- Protect from ingress of potentially harmful environmental agents
What is the definition of cell proliferation?
An increase in the number of cells; as a result of cell growth and cell division
What is the cell cycle?
A cell reproduces by performing an orderly sequence of events in which it duplicates its contents and then divides in two
What are the phases of the cell cycle?
M (mitosis + cytokinesis)
G1
S (DNA replication)
G2
What controls the cell cycle?
- Timer
- Events in correct order
- Event takes place only once per cycle
- On/Off switch trigger events in a complete and irreversible fashion
- Robustness
- Adaptability
Name cell cycle controllers.
Family of protein kinases:
Cyclin dependent kinases (Cdks)
How do cyclin dependent kinsases control the cell cycle?
- Activity rises and falls.
- Cyclical changes in phosphorylation- intracellular proteins
- Initiate and control major events of cell cycle- DNA replication, mitosis and cytokinesis
What are Cdk’s controlled by?
cyclins
what do Cdk need cyclins for?
protein kinase activity
What do cyclins undergo during the cell cycle?
cycle of synthesis
What are the 4 classes of cyclins?
G1/S-cyclins bind at end G1- commit cell to DNA replication
S-cyclins bind Cdks during S phase initiate DNA replication
M-cyclins promote events of mitosis
G1- cyclins promote passage through restriction point
What are keys point to remember about cyclins?
- Points to remember:
- Cyclin does not simply activate the Cdk but directs it.
- Different proteins phosphorylated.
- Accessibility
What is involved in proliferation control?
- Receptors
- Signalling
- Extracellular matrix
- Phosphorylation
What is the definition of growth factor?
Polypeptides that control animal cell growth and differentiation. Usually produced near where they act. Can be stored and released by ECM
What is the definition of transcription factor?
a protein that regulates the activity of RNA polymerase
What cells make up the cell proliferation unit?
progenitor cells in the basal cell layer
how do dividing cells appear ?
in clusters
what are the two populations (in proliferations)?
- Two populations one slow dividing but always retain proliferative potential.
- Faster dividing but limited number of divisions
What are problems with proliferation (Stem cells)?
- Cyclin D1- no stopping G1/S
- P53 in leukoplakia
- VEGF and Akt
