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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
- G2/M
- 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

CDK inhibitors

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

- Oncogenes
- 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?

- Hyperplasia
- Hypertrophy
- Atrophy
- Metalasia


How can Hyperplasia lead to Dysplasia?

If stimulus is not removed


Define Hyperplasia

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


Define Hypertrophy

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


Define Atrophy

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
- Aging
- Pressure
- X rays
- Occlusion of a secretory duct
- Toxic agents/ drugs
- Immunological mechanisms


Define Metaplasia

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


Identify 3 examples of Metaplasia

- Myeloid metaplasia (Splenic tissue-> Bone marrow)

- Smoking->> Bronchial pseudostratified epithelium->stratified squamous

- Barret’s oesophagus (Stratified squamous in oesophagus-> Gastic/ intestinal epithelium due to persistent acid reflux)