Lecture 2.12 Cell Injury, Necrosis & Apoptosis

Question 1

What are the ways that oxygen supply to the cell can be impaired?

Answer 1

Hypoxia, ischaemia, impaired haemoglobin (carbon monoxide)

Question 2

What happens when a hypoxic cell transitions to anaerobic glycolysis?

Answer 2

• pH lowered due to lactic acid production
• Na increased in cell, excess water and cell swelling (Na/K pump fails)
• protein synthesis decreases as ribosomes detach from RER
• Calcium released from mitochondria and SER

Question 3

What characterises irreversible damage?

Answer 3

Severe mitochondrial dysfunction (inability to generate ATP, production of ROD, release or pro-apoptotic proteins) and membrane damage

Question 4

What are free radicals and how do they cause oxidative stress?

Answer 4

Unstable due to one electron in outer orbit, contact other cells and turn them into free radicals, in excess cause oxidative stress by damaging lipid, protein and DNA

Question 5

What are the nuclear changes in cell death?

Answer 5

Karyolysis - breakdown of cells
Pyknosis - cells are tiny
Karyorrhexis - nucleus breaks up into many pieces

Question 6

What are the kinds of necrosis?

Answer 6

• Coagulative: happens in solid organ that has become ischemic, no energy present for cell to breakdown (ghost organ), eventually inflammatory cells break it down (most common necrosis)
• Caseous: cheesy necrotic lesions, specific for TB, no structure or nuclei visible under microscope
• Liquefactive: happens with bacterial infection, neutrophils come to fight bacteria

Question 7

What is the pathway to apoptosis?

Answer 7

Can be activated external by cytotoxic T cells and cytokines or internally by mitochondria releasing pro-apoptotic proteins (caspases) that breakdown cytoskeleton

Question 8

Is there pain associated with apoptosis and is it visible in the blood?

Answer 8

No pain because apoptosis is not inflammatory and it is not detected in the blood because endonuclease remove the sections of the cell and send them to macrophages (no debris)

Question 9

What are the features of autolysis?

Answer 9

Tissues digest themselves slowly over time, increases with heat, looks like necrosis due to structure breakdown but there is no inflammation, and the process is arrested with formalin (fixative)