Atherosclerosis, Apoptosis, Cell Definitions, Cancer Pathology Flashcards
Definition of atherosclerosis?
formation of fibrolipid plaques in the intima of systemic arteries
When do plaques develop?
teens - fatty streaks
30s-50s - established plaques
40s-80s - complications of plaques
What is plaque composed of?
central lipid core and cap of fibrous tissue. Inflammatory cells such as lymphocytes reside in cap
Where does plaque tend to form?
arterieal branching points
What leads to plaque formation?
chronic or episodic exposure of arterial wall due to endothelial cells being easily damaged
How is plaque formed? (4 steps)
- damaged endothelial cells are more permeable and have increased adhesion - allows lipids and inflammatory cells to accumulate
- macrophages and lymphocytes accumulate - macrophages undergo apoptosis and leak lipids
- growth factors secreted by platelets and endothelium stimulate smooth muscle cells which form fibrous cap
- haemorrhage results from rupture of vessels within plaque - this causes expansion
What are common risk factors for atherosclerosis?
hypercholesterolaemia, hyperlipidaemia, hypertension, smoking, diabetes, male gender, increasing age
Why is smoking a risk factor for atherosclerosis?
increases blood pressure and damages endothelial wall due to free radicals, nicotine and CO
What are some complications of atherosclerosis?
- lumen narrowing due to stenosis
- atherothrombotic occlusion
- embolism and ruptured abdominal aorta
- cerebral/myocardial infarction
- peripheral vascular disease
- gangrene
Definition of apoptosis?
programmed cell death
Why is apoptosis needed?
for development and cell turnover
What disease can a lack of apoptosis cause?
cancer - mutation of p53 gene
What disease can too much apoptosis cause?
HIV - kills antibodies (CD4 helper cells) so no defense
What is apoptosis normally triggered by?
DNA damage, eg. single/double strand break, base alteration, or cross-linkage
Does apoptosis require energy?
Yes - energy dependent mechanism
What are some inhibitors of apoptosis?
growth factors, extracellular matrix, sex steroids
What are some inducers of apoptosis?
growth factor withdrawal, loss of matrix, glucocorticoids, free radicals, ionising radiation
What does the intrinsic apoptosis mechanism use?
Bcl2 (induces) and Bax (inhibits) ratio determine cell’s susceptibility to apoptotic stimuli and whether a cell expands tissues or dies
What does the p53 protein do in apoptosis?
induces cell cycle arrest and initiates dividing of cells. however if damage is difficult to repair then p53 can induce apoptosis
What is the extrinsic mechanism of apoptosis?
specific mechanism by ligand-binding at death receptors on the cell surface
What receptors are used in extrinsic apoptosis?
tumour necrosis factor receptors (TNFR), eg. TNFR1 and Fas
What does ligand binding promote in extrinsic apoptosis?
clustering of receptor molecules and initiation of signal –> transduction cascade activates caspases
What are caspases?
cell death enzymes
Which pathway do intrinsic and extrinsic apoptosis both lead to?
Cytotoxic/Common/Execution
What produces active caspases in sytotoxic apoptosis?
activation of intiator caspases cleaves pro-caspases
What do active caspases cause the degradation of?
cytoskeletal framework and nuclear proteins
What is the last stage of cytotoxic apoptosis?
dead cells fragment into small membrane-bound apoptotic bodies - this triggers inflammatory response
Definition of necrosis?
death of most or all cells in organ tissue due to disease, injury, or failure of blood supply
How does necrosis induce inflammation and repair?
rupture of plasma membrane spills cell contents and some of these are immunostimulatory
What are some examples of necrosis?
infarction, pancreatitis, frostbite, toxic venom, avascular necrosis of bone (eg. femur)
What is caseous necrosis?
soft cheese appearance due to tuberculosis
Definition of Hypertrophy?
Increase in size of an organ due to increase in size of constituent cells
Where does hypertrophy occur?
In organs where cells cannot divide eg. skeletal muscle in bodybuilders and athletes
Definition of Hyperplasia?
Increase in size of an organ due to increase in number of constituent cells
Where does hyperplasia occur?
In organs where cells can divide, eg. benign prostatic hyperplasia, endometrial hyperplasia
What is mixed hypertrophy/hyperplasia?
Increase in size of an organ due to both the size and number of constituent cells increasing
Where does mixed hypertrophy/hyperplasia occur?
In organs where cells can divide eg. smooth muscle cells of uterus in pregnancy
Definition of atrophy?
Decrease in size of an organ due to decrease in size or number of constituent cells
Examples of atrophy?
Alzheimier’s dementia, quadriceps muscle following knee injury
How does atrophy occur?
Naturally by apoptosis, eg. regression of wolfian or mullerian ducts
What is atrophy often a result of?
decreased function, loss of innervation, lack of nutrition
Definition of metaplasia?
Change in cell differentiation from one fully differentiated type to another
What is metaplasia usually caused by?
Consistent change in environment of epithelial surface
Three examples of metaplasia?
- Smoking: bronchial epithelium from ciliated respiratory –> squamous
- Barrett’s Oesophagus: squamous epithelium –> glandular
- Puberty: uterine cervix from columnar –> squamous
Definition of dysplasia?
Imprecise term for morphological changes that are seen in cells in development of cancer
How is dysplasia classified?
Spectrum from mild to sever, carcinoma in situ, and invasive cancer
Example of dysplasia?
Bronchial epithelium in smokers: metaplasia from ciliated to squamous, then dysplasia in squamous
What is ageing?
Cells in the body divide continuously during life (eg. skin and gut lining) or stop dividing shortly after birth (eg. neurones)
What is the Hayflick limit?
limit to how many times a human cell can divide
Why do skin cells divide less in older people?
Telomere (non-coding) region becomes too short after repeated cell division
Why can’t chromosomes divide in ageing people?
Telomere length too short to engage with DNA polymerase
Is telomere length maternally or paternally inherited?
Paternally
How can ageing be accelerated?
Due to mutations in the cell membrane proteins which make cell division impossible
What are non-dividing cells?
Cells that can’t replace themselves by dividing so they die once they have accumulared a certain amount of damage
What factors cause damage to cells and contribute to ageing? (7)
- cross-linking of DNA or proteins
- damage to mitochondrial DNA, loss of DNA repair mechanism
- loss of calcium controls, peroxidation of membranes
- free radical generation
- time-dependent activation of death genes
- telomere shortening
- accumulation of toxic by-products
Definition of prolonging life?
Anything that reduces damage to cells can reduce defects of ageing
What are methods for delaying ageing?
local measures for specific parts of the body, eg. sun protection to reduce UV cross-linking of proteins in the dermis
How is skin affected by ageing?
Wrinkling (dermal elastosis) caused by UV-B light causing cross-linking of proteins, especially collagen