Flashcards in Cellular Adaptations Deck (37)
What 3 things affect cell population
Rate of cell proliferation
Rate of cell differentiation
Rate of deal death by apoptosis
What are 2 types of causes of cell proliferation
How are they related?
Excessive physiological can become pathological
In regards to the cell cycle , what are 2 ways increased tissue growth occurs?
- Shortening of cell cycle
- Conversion of quiescent cells to proliferating cells
How many key checkpoints are there in the cell cycle?
What are they? Which is the most critical?
Out of the 3, which is most commonly altered in cancer cells
- G1/ S
- Restriction Point (Towards end of G1), Most critical
In cancer, Restriction point
Compare the G1/ S and G2/ M checkpoints
G1/ S: Checks for DNA damage before replication
G2/ M: Checks for DNA damage after replication
What happens the the majority of cells that pass the Restriction point of cell cycle?
What happens if the checkpoint is activated?
Most will complete the cell cycle
If the checkpoint is activated, protein p53 arrests the cell cycle and triggers DNA repair mechanisms OR apoptosis
Which protein is called the guardian of the genome
What proteins and enzymes control the cell cycle?
How are they linked?
Cyclins and Cyclin Dependent Kinases (CDKs)
CDKs become activated by binding to cyclins
How do ACTIVATED CDKs control the cell cycle?
Drive cell cycle by phosphorylation of proteins, that are needed for cell cycle to progress to next stage
What molecules regulate the activity of Cyclin-CDK complexes?
How do growth factors affect Cyclins and CDKs
Growth factors either;
- Stimulate cyclin production
- Inhibit CDK Inhibitor production
What is the role of Retinoblastoma Protein?
Which cyclin/ CDK complex affects it and how?
- Prevents DNA Replication
- Inactivated by phosphorylation by Cyclin D/ CDK 4 complex
Name 3 molecules that stimulate cell proliferation
Name 2 that inhibit cell proliferation
- Cyclins/ CDK complex
- Growth factors
- CDK inhibitors
- Tumour suppressor genes
Define Cellular Adaptation
The reversible state between normal under stressed cell and injured over stressed cell
What are 4 ways cells can adapt?
How can Hyperplasia lead to Dysplasia?
If stimulus is not removed
In which 2 tissue types can it occur?
What are 2 types of reasons it can occur?
What can occur if cells divide repeatedly?
Increase in tissue/ organ size due to Increased Cell Numbers
- In labile and stable tissues
- Increased functional demand/ hormonal stimulation
Repeated cell division exposes cell to risk of mutation and neoplasia
Give 2 physiological and 2 pathological examples of Hyperplasia
- Proliferation of endometrium due to oestrogen
- Increased erythrocyte production by bone marrow due to hypoxia
- Epidermal thickening in Eczema/ Psoriasis
- Enlargement of thyroid gland in response to iodine deficiency
In which 3 tissue types can it occur?
What are 2 types of reasons it can occur?
How is the workload of the cell affected?
Increase in tissue/ organ size to increase in cell size
Labile, stable but especially permanent tissues
- Increased functional demand
- Increased hormonal stimulation
Workload is shared by more structural components
How are Hypertrophy and hyperplasia linked in labile and stable tissues
In labile and stable tissues, Hypertrophy usually occurs with hyperplasia
Give 2 physiological and 3 pathological examples of Hypertrophy
- Skeletal muscle in bodybuilders
- Smooth muscle of uterus during pregnancy (Hypertrophy and hyperplasia)
- Cardiac muscle hypertrophy
- Smooth muscle hypertrophy due to intestinal stenosis
- Prostate gland enlargement-> Urethra obstruction-> Bladder smooth muscle hypertrophy
What is Compensatory Hypertrophy?
Give an example
Increase in size of an organ/ tissue when needed to do additional work or to perform the work of a destroyed tissue/ paired organ
If one kidney is removed/ damaged
What happens to cells/ organs when the stimulus causing hypertrophy/ hyperplasia disappears
Returns to normal size
Shrinkage of a tissue/ organ due to increase in size and/ or number of cells to a size at which survival is possible
What is tissue atrophy usually a result of?
Is it reversible?
Usually a combo of cellular atrophy and apoptosis
Reversible up to a point
Other than cells, what can undergo atrophy?
How is atrophy best treated?
ECM can also undergo atrophy
Best treated by removal of the cause
Give 2 physiological examples of atrophy
- Ovarian atrophy in post menopausal women
- Decrease in size of uterus after child birth
Give 12 pathological causes of atrophy
- Reduced functional demand/ workload
- Loss of innervation
- Inadequate blood supply
- Inadequate nutrition
- Loss of endocrine stimuli
- Persistent injury
- X rays
- Occlusion of a secretory duct
- Toxic agents/ drugs
- Immunological mechanisms
Why does it happen?
Reversible change of one differentiated cell type to another
(In labile and stable tissues)
Adaptive substitution of cells that are sensitive to stress by cell types that are able to better withstand the adverse environment
What 2 things can metaplasia lead to?
When can metaplasia not happen
Can lead to dysplasia and cancer
No metaplasia across germ layers