Cell Death Flashcards
What is necrosis ?
The death of tissues following bioenergetic failure and loss of plasma membrane integrity.
Induces inflammation and repair.
What is apoptosis ?
Usually involves DNA fragmentation.
Apoptosis is an active process.
State some features of necrosis
Pathological process
Affects cell groups
Cell membrane integrity is lost
Cell swelling and lysis
Inflammatory response
Dead cells are phagocytosed by inflammatory cells
Abnormal ion homeostasis
State some features of apoptosis
Physiological or Pathological induced
Affects single cells
Cell membrane integrity is maintained
Cell shrinkage and fragmentation
NO inflammatory response
Dead cells are phagocytosed by neighbouring cells
Energy-dependent fragmentation of DNA
State some features of reversible cell injury
REVERSIBLE
Increased intracellular volume
Mitochondrial swelling and calcification
What is key to the homeostasis of a cell ?
The mitochondria
Function of the mitochondria
They oxidise things, as oxygen is dangerous to the cell.
This process produces free radicals (e.g. hydrogen peroxide), due to burning glucose.
Free radical
Any species with an unpaired electron.
Goes to things that like an electron, for example DNA, RNA, membranes. This can cause damage to any of these.
What happens if metabolism (respiration) is not properly controlled ?
You can risk further damage to the cell.
Function of mitochondria in reversible injury
The mitochondria is important to generate energy, to maintain the cells homeostasis, to keep water out.
Also because the mitochondria can be a potent source of molecules e.g. SOD, which can cause secondary damage.
Describe lethal injury
Reversible injury
Not able to restore e.g. membrane pumps to keep water and sodium out
Mitochondria may release oxygen free radicals, causing further damage.
Not enough energy produced.
Cell dies via necrosis.
Causes of necrosis
Ischaemia
Metabolic
Trauma
Coagulative necrosis
Commonest type
Firm, pale area with ghost outlines in microscopy
Colliquative necrosis
Seen in the brain
Dead area is liquefied
Caseous necrosis
Seen in tuberculosis
Pale yellow semi-solid material
Gangrene necrosis
Necrosis with putrefaction
Follows vascular occlusion or certain infections and is black.
Fibrinoid necrosis
Microscopic feature in arterioles in malignant hypertension
Fat necrosis
May follow trauma and cause a mass
OR
May follow pancreatitis visible as multiple white spots.
Key feature of necrosis
Evokes an inflammatory response
Loss of energy
Why don’t you get inflammation in apoptosis ?
As cell membrane integrity is maintained. No cell contents are spilled.
Fragments are phagocytosed and quickly sucked up by adjacent cells.
Give some examples of apoptosis
Embryology - lumen of tubules e.g. oesophagus
Inflammation - resolution and death of neutrophils
How to end inflammation ?
Acute inflammation can be controlled by neutrophils.
Neutrophils have a limited lifespan, they only stay around for <20hrs and then die.
So after 20hrs there is no inflammation, unless you recruit new cells.
How do neutrophils die ?
Apoptosis
What does clearance of apoptotic cells require ?
Clearance of apoptotic cells by macrophages requires reorganisation of phosphatidylserine.
