Cellular adaptations Flashcards
What controls cell proliferation
Proto-oncogenes and tumour suppressor genes
Chemical mediators/ signals from the micro environment
Signalling molecules
Restriction point checpoint
Most critical
Majority of cels that will pas this pint will complete the cell cycle
Also known as p53
How does p53 work
DNA Damage
Increase in activated p53 leads to induction of apoptosis an increase in p21
Increase in p21 leads to the prevention of phosphorylation of cyclin
This causes cell cycle arrest as CDK inhibitors are activated
DNA repair is allowed then
How do growth factors work
Stimulating the producition of cyclins and shutting off the production of cycling dependent kinase inhibitors
How does increased growth of a tissue occur
Shortening the cell cycle
Conversion of quiescent cells to proliferating cells by making them enter the cell cycle
G1/S checkpoint
is the cell big enough
is environment favorable
is DNA damaged
G2/M checkpoint
Checks for DNA damage after DNA replication
What are cyclin and CDKs
Proteins that tightly regulate progression through the cell cycle
How do CDKs get activated
By binding to cyclins
How do CDKs drive the cell cycle
Phosphorylation of proteins
What is hyperplasia
Increase in tissue or organ size due to increased cell numbers
Reversible
Why does hyperplasia occur
A response to increased functional demand and/or external stimulation
Can only occur in labels and stable cell populations
Examples of physiological hyperplasia
Increased bone marrow production of erythrocytes in response to hypoxia
Pathological hyperplasia examples
Epidermal thickening of chronic eczema or psoriasis
Hypertrophy
Increase in tissue or organ size without an increase in cell numbers
When does hypertrophy occur
In permanent tissues as they have little or replicative potential
In response to increased functional demand
Examples of physiological hypertrophy
Skeletal muscle hypertrophy
Smooth muscle hypertrophy of uterus in pregnancy
Examples of pathological hypertrophy
Ventricular cardiac muscle in response to hypertension or valvular disease
What is atrophy
Shrinkage of a issue or organ due to an acquired decrease in size or number of cells
What can cause atrophy
A decrease in supply of growth factors and or nutrients
Reversible
Examples of physiological atrophy
Ovarian atrophy in post menopausal; women
Pathological atrophy examples
Reduced functional demand- muscle atrophy after disease due to immobilisation
Loss of innervation- wasted striated muscle within the hand after nerve damage
Inadequate blood supply- thinning of skin on legs with peripheral vascular disease
Metaplasia
Reversible replacement of one adult differentiated cel type by another of a different type in the same germ layer
Aplasia
Complete failure of a specific tissue or organ to develop
Embryonic developmental disorder
Examples of aplasia
Bone marrow in aplastic anaemia
Thymic aplasia which results in infections and auto-immune disorders
Hypoplasia
The congenital underdevelopment or incomplete development of a tissue or organ. There are an inadequate number of cells within the tissue. Embryonic developmental disorder
Examples of hypoplasia
Renal hypoplasia
Breast hypoplasia
Testicular hypoplasia
Atresia
The congenial imperforation of an opening
Reconstitution
This is different to regeneration
Replacement of a lost part of the body rather than a small group of cells
Involution
Normal programmed shrinkage of an organ
- uterus after childbirth
- thymus in early life
- temporary foetal organs
Dysplasia
The abnormal maturation of cells within a tissue
Potential reversible but is often pre-cancerous
