Cell Injury, Degeneration And Death

Question 1

Describe the outcomes of cellular injury to cell processes

Answer 1

• disrupted aerobic respiration/ATP synthesis in mitochondria (oxidative stress)
• damaged cell membrane causes disrupted ion concentration (increased Ca2+)
• enzymes and ribosomes affected causing disruption to protein synthesis and architecture
• damage to the nucleus causes damaged DNA and disrupted DNA maintenance

Question 2

Describe cellular features of reversible cell injury

Answer 2

• cloudy swelling: osmotic disturbance, loss of energy-dependent Na pump resulting in Na influx and build up of intracellular metabolites
• cytoplasmic blebs, disrupted microvilli, swollen mitochondria
• fatty change: accumulation of lipid vacuoles in cytoplasm caused by disruption of fatty acid metabolism

Question 3

Describe features of necrosis and the process

Answer 3

• uncontrolled cell death
• injury from external stimuli which is always pathological
• elicits an inflammatory response
• cell contents leaks from breakdown of cell membrane (lysis) which can affect surrounding environment
• histological swelling, vacuolation and disruption of membranes and its organelles (mitochondria, lysosomes and ER)

Question 4

Describe the nuclear changes that can take place in necrosis

Answer 4

• karyolysis: nuclear fading due to chromatin dissolution due to actions of DNAases and RNAases
• pyknosis: nuclear shrinkage due to condensation of DNA into shrunken basophilic mass
• karyorrhexis: nuclear fragmentation where pyknotic nuclei membrane has ruptured

Question 5

Describe the morphological sub-types of necrosis with examples

Answer 5

• coagulative (firm, tissue outline retained): can be haemorrhagic (blockage of venous drainage) or gangrenous (larger area)
• colliquitive (tissue turns to liquid losing its structure) eg. Abscesses
• caseous (combination of coagulative and colliquitive): cheese-like appearance eg. TB
• fat: due to action of lipases on fatty tissue

Question 6

Describe features of apoptosis

Answer 6

• usually physiological eg. Deletion of cell populations in embryogenesis
• can be pathological eg. Cytotoxic T-lymphocytes in viral infection
• controlled cell death (requires energy and has distinct pathways involved)
• cell contents do not leak due to cell membrane remaining intact
• no inflammatory response but can be caused by immunological mechanisms

Question 7

Describe the process of apoptosis

Answer 7

• cell shrinks, condensing chromatin and packaging up nucleus
• membranes all remain intact
• cytoplasmic blebs form and break off forming apoptotic bodies
• bodies are phagocytosed by macrophages

Question 8

Describe amyloid formation

Answer 8

• localised/systemic accumulation of protein aggregates outside of cells
• formation of beta pleated sheets from abnormal folding of protein fibrils
• 2 types: AL (immunoglobulin light chain - B cell neoplasms) and AA (serum amyloid associated protein - prolonged chronic inflammation)
• viewed through electron microscopy
• can be stained by Congo red: pink or apple green under polarised light

Question 9

Describe the different types of pathological calcification

Answer 9

• dystrophic: deposition in abnormal tissue with normal serum calcium levels
• metastatic: deposition in normal living tissue with raised serum calcium (commonly connective tissue of blood vessels) - can impair function