Cellular Adaptations Flashcards
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?
Physiological
Pathological
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
3
- 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
P53
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
Physiological;
- Proliferation of endometrium due to oestrogen
- Increased erythrocyte production by bone marrow due to hypoxia
Pathological;
- 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
Physiological;
- Skeletal muscle in bodybuilders
- Smooth muscle of uterus during pregnancy (Hypertrophy and hyperplasia)
Pathological;
- 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)
Define Aplasia
Give 2 examples
Complete failure of a specific tissue/ organ to develop
OR
Ceased cell proliferation of an organ
- Kidney aplasia
- Thymic aplasia
Define Hypoplasia
Is it the opposite of hyperplasia?
Underdevelopment/ incomplete development of a tissue/ organ at embryonic stage, leading to an inadequate number of cells
No, as it is a congenital condition
Give 4 examples of hypoplasia
- Renal
- Breast
- Heart chambers
- Testicular in Klinefelter’s syndrome
Define Involution
Give 2 examples
Normal programmed organ shrinkage
(Overlaps with atrophy)
- Thymus
- Uterus after childbirth
What is Reconstitution?
Give 2 examples
Define regeneration
Replacement of a lost part of body
- Regrowth of a lizard’s tail
- Growth of antlers
Regeneration: Replacement of cell losses by identical cells to maintain size of tissue/ organ
Define Atresia
Give 4 examples
Congenital imperforation of an opening
- Pulmonary valve
- Anus
- Vagina
- Small bowel
What is Dysplasia
Is it reversible?
What is often a warning of?
Abnormal maturation of cells within a tissue
Potentially reversible
Often pre-cancerous
