Cell Response to Injury: Ultra-structural Changes Flashcards Preview

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Flashcards in Cell Response to Injury: Ultra-structural Changes Deck (32):
1

what causes cell injury?

Results from disruption of structure and function of sub-cellular components

2

what are the consequences of cell injury?

damage to cellular components

3

where is the damage seen?

• Mitochondria
• Plasma membrane
• Lysosomes
• Nucleus

4

what can damage the mitochondria?

Hypoxia, hypoglycaemia & toxins

5

how are mitochondria damaged?

• Development of vacuoles
• Cristae become damaged

6

what does a decrease in oxidative phosphorylation lead to?

Reduced levels of ATP

7

what is reduced ATP level known as?

low amplitude swelling

8

can low amplitude swelling be reversed?

yes

9

what are the effects of reduced ATP?

• Reduced activity of Na pump which leads to changes in Na+ and K+ concentration
• Net influx of H2O across plasma membrane which leads to swelling
• Failure of intracellular Ca2+ homeostasis

10

Why is Ca2+ concentration in cytosol low?

Ca2+ activates cytosolic enzymes

11

Which enzymes keep calcium levels in check?

ATP dependent enzymes

12

What does a reduction in cellular ATP lead to in terms of calcium levels?

It leads to increase intracellular calcium

13

what does intracellular calcium increase lead to?

Activation of:
• Phospholipases
• Endonucleases
• Proteases

14

how is plasma membrane damage caused?

The damaged mitochondria lead to reduced ATP which leads to reduced activity of the Na pump and a net influx of H2O into the cell, which causes cellular swelling and the formation of blebs

15

what does the disruption of membrane lead to?

the leakage of enzymes

16

what does leakage of enzymes lead to?

Activation of acid hydrolases:
• RNAases
• DNAases
• Proteases

Enzymatic digestion/irreversible damage

17

If acid hydrolases are activated which pathway of cell death will occur?

Necrosis

18

how is the endoplasmic reticulum damaged?

• Vacuolation and swelling seen early in injury
• Prolonged injury leads to detachment of ribosomes

19

what does ribosome detachment result in?

Decreased protein synthesis

20

how can the nucleus be damaged?

• Invagination of nuclear membrane
• Chromatin clumping
• Distinct nuclear changes

21

what are the features of necrosis?

• Loss of membrane integrity/enzymatic destruction
• Leakage of cellular constituents
• Inflammatory response
• Necrotic cell changes reflect key processes

22

Why do cells that have undergone necrosis stain pink with H&E?

• Demonstrate denatured and coagulation of protein
• Loss of cytoplasmic RNA

23

What are the features of cells that lose definition?

• Loss of organelles
• Enzyme digestion: phospholipases and proteases
• Replacement of dead cells: myelin figures and calcium deposition

24

what is Pkynosis?

nuclear shrinkage

25

what is Karyorrhexis?

nuclear fragmentation

26

what is Karyolysis?

nuclear disintegration

27

what are the distinct nuclear changes?

pkynosis, kerhyorrhexis, Karyolysis

28

what can be seen in a normal cell (stages of necrosis)?

distinct nucleus and nucleolus

cytoplasm:pale pink/purple due to cellular RNA in rough endoplasmic reticulum

29

what are the features of an early necrotic cell (stages of necrosis)?

cytoplasm shrinks and increase in eosinophilia (pink staining) - loss of ribosomes

nucleus shrinks and basophilic (purple) cessation DNA transcription

30

what happens to the cell as necrosis occurs?

after early necrotic cell features:-
the cell remains small and eosinophilic and the cell membrane breakdown results in irregular shape and karyorrhexis occurs

finally the cell is partly denatured mass protein and the cytoplasm is eosinophilic and the nucleus completely dissolves

31

what are the features of apoptosis?

• Programmed cell death – induced by a tightly regulated suicide programme
• Deletion of individual cells
• No inflammatory response

32

what do apoptotic cell changes involve?

• Cells shrink – dense cytoplasm, more tightly packed organelles
• Chromatin condensation – aggregation chromatin under nuclear membrane; fragmentation of nucleus
• Formation of blebs and apoptotic bodies – extensive surface blebbing leads to fragmentation
• Phagocytosis of apoptotic bodies by macrophages