Cell Ageing and Death Flashcards
What are the two pathways of irreversible cell death?
Necrosis
Apoptosis
What is necrosis?
Death of cells with loss of membrane integrity and enzymatic destruction of cellular constituents. Require NO ENERGY
Always PATHOLOGICAL
How does necrosis stimulate an inflammatory response?
Cellular constituents leak into surrounding tissues and circulation.
Inflammatory response to these constituents and initiation of repair process
What is dystrophic calcification?
Calcium deposition into dead cells. Used to identify necrosis
What is the most common necrosis?
Coagulative Necrosis
How does coagulative necrosis occur?
Cells are consumed by various enzymatic processes and cells but the CELL OUTLINE is preserved (no nucleus can be seen)
Give an example of when coagulative necrosis would occur
Often in cardiac muscle after myocardial infarction (can be follow by restitution - scar formation and fibrosis - so no hole forms)
What is liquefactive necrosis?
Necrosis leaves no cell structure remaining leading to PUS formation
Example of where liquefactive necrosis can occur?
When cells die in brain a hole appears (no healing or scarring occurs)
Associated with localised bacterial/fungal infections
What is caseous necrosis?
Cheesy appearing necrosis due to granulomatous inflammation
Amorphous (no clear form) white centre to granulomas (epithelial cells and histiocytes) associated with chronic inflammation
When does caseous necrosis occur?
In TB
What is apoptosis?
Programmed cell death in response to a range of stimuli
Requires energy as the death is controlled
Can be PHYSIOLOGICAL/PATHOLGICAL
How does apoptosis occur?
Cells undergo shrinkage, with condensation/fragmentation of nuclear chromatin.
Cells are PACKAGED before being destroyed, resulting in “spotty” debris
Example of physiological apoptosis and what happens when this fails
Formation of fingers (apoptosis of cells between fingers)
Removal of self-reactive lymphocytes (antibodies constantly changing, so inevitably, some will attach to lymphocyte itself) - if this fails, autoimmune disease results
Inducing cancer cell death
Hormonal-dependent involution (endometrial lining proliferates during menstruation and these cells undergo apoptosis)
When does pathological apoptosis occur?
In response to injury by: Radiation (inc. UV light) Chemotherapy Viral infection, like Hepatitis Cancers Graft vs Host disease (rejection of transplanted tissue)
