Cell death

Question 1

types of cell death

Answer 1

oncosis

necrosis

apoptosis

Question 2

oncosis

Answer 2

cell death with swelling, the spectrum of changes that occur in injured cells prior to death

Question 3

necrosis

Answer 3

in a living organism, the morphological changes that occur after a cell has been dead for some time e.g. 12-24h

Question 4

apoptosis

Answer 4

Cell death with shrinkage, induced by a regulated intracellular program where a cell activates enzymes that degrade it’s own nuclear DNA and proteins

Question 5

types of necrosis

Answer 5

coagulative (main)

liquefactive (main)

caseous

fat necrosis

Question 6

coagulative necrosis occurs in

Answer 6

ischaemia in solid organs

Question 7

liquefactive necrosis occurs in

Answer 7

ischaemia in loose tissue

*presence of many neutrophils*

Question 8

coagualtive necorsis due to

Answer 8

protein denaturation dominates over release of active proteases

Question 9

liquefactive necrosis due to

Answer 9

enzyme release dominated over protein denaturation

Question 11

what do cells that have undergone coagulative necrosis look like

Answer 11

cellular architecture is somewhat preserved-ghost outline

Question 12

liquefactive necrosis lead to

Answer 12

liquefaction of tissue

• cell architecture lost

Question 13

caseous necrosis is a distinctive form of

Answer 13

coagulative necrosis

• amphorous (structureless debris)
• tissue maintains a cheese-like appearance.

Question 14

where does caseous necrosis occur

Answer 14

mainly in the lungs

• particularly associated with infection e.g. TB

Question 15

fat necrosis

Answer 15

• Destruction in the adipose tissue
• Present in people with pancreatitis and in breast tissue after trauma

Question 16

infarction

Answer 16

necrosis caused by reduction in arterial blood flow

• Can result in gangrene

Question 17

gangrene

Answer 17

necrosis visible to the naked eye

• An appearance of necrosis

Question 18

dry gangrene

Answer 18

necrosis modified by exposure to air (coagulative)

Question 19

wet gangrene

Answer 19

necrosis modified by infection (liquefactive)

Question 20

gas gangrene

Answer 20

Wet gangrene where the infection is with anaerobic bacteria that produce gas

Question 21

what is an infarct

Answer 21

an area of necrotic tissue which is the result of loss of arterial blood supply

• An area ischaemic necrosis

Question 22

apoptosis is

Answer 22

Cell death with shrinkage, induced by a regulated intracellular program where a cell activates enzymes that degrade it’s own nuclear DNA and proteins

Characteristic microscopic appearance

Question 23

what does apoptosis look like

Answer 23

• Characteristic microscopic appearance
• Characteristic DNA breakdown
• Non-random, internucleosomal cleavage of DNA (in oncosis, DNA is chopped into pieces of random length)

Question 25

apoptosis is the …. and …. force to mitosis

Answer 25

equal and opposite

Question 26

characteristics of apoptosis

Answer 26

• Active process
• Single cell process
• Enzymes activated that degrade nuclear DNA and protein
• Membrane integrity is maintained
• lysosomal enzymes not involved
• Quick
• Pathological or physiological

Question 27

1) Physiological apoptosis

Answer 27

1. In order to maintain a steady state
2. Hormone-controlled involution
3. Embryogenesis
   e. g. sculpting a hand during development

Question 28

2) pathological apoptosis

Answer 28

• Cytotoxic T cell killing of virus-infected or neoplastic cells
• When cells are damaged, particularly with damaged DNA
• Graft versus host disease

Question 29

How does apoptosis occur?

Answer 29

1. Initiation
   
   • Triggered by either intrinsic or extrinsic pathways
     
     • Results in activation of caspases (enzymes which control and mediate apoptosis. Cause cleave of DNA and proteins of the cytoskeleton)
2. Execution
3. Degradation and phagocytosis
   
   • Both pathways cause the cells to shrink and break into apoptotic bodies, which express proteins on their surface
   • Now recognised by phagocytes or neighbouring cells
   • Finally degradation takes place within the phagocytes/neighbour

Question 30

intrinsic pathway

Answer 30

• Initial signal comes from within the cell
• Triggers:
  
  • Irreparable DNA damage
  • Withdrawal of growth factors or hormones
• P53 protein is activated and this results in the outer mitochondrial membrane becoming leaky
• Cytochrome C is released from mitochondria and activates caspases

Question 31

Extrinsic

Answer 31

• Initiated by extracellular signals
  
  • Triggers:
    
    • Cells that are a danger e.g. tumour cells, virus-infected
  • One of the signals is TNFalpha
    
    • Secreted by T-killer cells
    • Binds to cell membrane receptor (death receptor)
    • Results in activation of caspases

Question 32

Apoptosis versus oncosis/necrosis

Answer 32

Question 33

Ends of chromosomes are called telomeres, with every replication the telomere

Answer 33

is shortened.

When the telomeres reach a critical length, the cell can no longer divide

Question 34

germ cells, stem cells and many cancer cells can produce

Answer 34

telemerase increasing the cells ability to replicates

Question 35

Cell immortality

Answer 35

• As cells age they accumulate damage to cellular constituents and DNA
• After a certain number of divisions they reach replicative senescence - related to the length of chromosomes (telomeres)