WK 1- CELL INJURY AND DEATH

Question 1

What are the 4 types of physiological adaptations and what are their cellular characteristics

Answer 1

Hypertrophy (cell increases in size), metaplasia (change in cell type), atrophy (cell shrinkage), hyperplasia (increase in cell number)

Question 2

What are the 5 types of necrosis

Answer 2

Gangrenous, Liquefactive, Caseous, Coagulative and Fat

Question 3

What is gangrenous necrosis- characterstics

Answer 3

• occurs when a limb loses blood supply and dies
• skin will be black and the underlying tissue will be at varying stages of necrosis
• initially starts as coagulative necrosis due to blood loss, but if bacterial infection also occurs it will become liquefactive necrosis (wet gangrene)

Question 4

What is caseous necrosis- characteristics

Answer 4

• occurs due to complex peptido–glycolipids present in the cell wall of tubercle bacilli (TB)
• has a cheesy white granular appearance where there is no histological architecture preserved

Question 5

What is liquefactive necrosis

Answer 5

• characteristic of bacterial or fungal infections
• can occur in nervous tissue (brain)
• infection causes release of lysosomes that completely digest the cell
• causes a circumscribed lesion containing pus and fluid of necrotic tissue

Question 6

What is coagulative necrosis

Answer 6

• characteristic of infarcts
• can occur in any tissue but the brain
• appears as a pale segment surrounded by well vascularised tissue
• histologically, cells contain no nuclei with very little structural damage

Question 7

What is fat necrosis

Answer 7

• occurs due to acute pancreatitis
• affects the tissue and mesentery of the pancreas
• occurs due to injury to the pancreas causing a release of lipases that split the triglyceride esters contained within the fat cells→ these released FFA combine with calcium to form chalky/white nodules characteristic of fat necrosis

Question 8

What are the two pathways of apoptosis

Answer 8

Mitochondrial (intrinsic) and Death receptor (extrinsic)

Question 9

How is the mitochondrial apoptotic pathway triggered and how does it cause apoptosis

Answer 9

• Damage to DNA, misfolded proteins or deprivation of growth factors causes sensors on the mitochondrial membrane to be switched on
• > these sensors are part of the Bcl2 family (this regulates permeability of mitochondrial membrane)-> activation of BH3 causes activation of Bax and Bak-> these dimerize and insert into mitochondrial membrane and allow cytochrome C to escape and activate caspase 9-> caspase 9 is an initiator caspase that will activate executioner caspases-> these cause the breakdown of the cytoskeleton and breakdown of cell

Question 10

How is the death receptor pathway triggered and how does it cause apoptosis

Answer 10

• acts via receptors on the cell membrane (TNF, Fas)
• When a FasL binds to Fas it will cause activation of the adaptor proteins-> these activate caspase 8 and 9-> these activate executioner caspases that cause the breakdown of the cytoskeleton and breakdown of cell

Question 11

Is apoptosis pathological or physiological

Answer 11

Mainly physiological but can be dysregulated and pathological in disorders such as cancer, autoimmune disorders, neurodegenerative disorders and viral infections

Question 12

What are 3 physiological roles of apoptosis

Answer 12

1. Programmed destruction of cells during embryogenesis
2. Involution of hormone-dependent tissues upon hormone deprivation such as endometrial cell breakdown during menstruation
3. Cell loss in proliferating cell populations such as intestinal crypt epithelia

Question 13

What nuclear changes occur in apoptosis

Answer 13

FRAGMENTATION INTO NUCLEOSOME, KARYORRHEXIS, PYKNOSIS

Question 14

What nuclear changes occur in necrosis

Answer 14

SHRINKAGE, DISSOLUTION AND FRAGMENTATION (pyknosis, karyohexxis and karyolysis)