1.3 Cell Death

Question 1

What is the hallmark of cell death?

Answer 1

Loss of the nucleus

Question 2

What are the 3 major processes in the loss of a nucleus?

Answer 2

Pyknosis: nuclear condensation
Karyorrhexis: nuclear fragmentation
Karyolysis: nuclear dissolution

Question 3

How is necrosis different from apoptosis?

Answer 3

Necrosis is never physiologic and is caused by irreversible cell damage that causes death of large groups of cells and is followed by inflammation

Apoptosis is programmed and controlled cell death that often only involves a few cells and it does not cause inflammation

Question 4

Coagulative necrosis

Answer 4

Necrotic tissue remains firm; cell structure and organ structure are preserved by coagulation of proteins, but the nucleus disappears

Characteristic of ischemic infarction in any tissue except the brain (liquefactive), often wedge shaped and pale

Red infarction arises if blood re-enters a loosely organized tissue like in pulmonary or testicular infarction

Question 5

Liquefactive necrosis

Answer 5

Necrotic tissue becomes liquefied–enzymatic lysis of cells and protein leads to liquefaction

Characteristic of:
brain infarction–proteolytic enzymes from microglial cells liquefy the brain
Abscess–proteolytic enzymes from neutrophils
Pancreatitis–proteolytic enzymes from pancreas

Question 6

Gangrenous necrosis

Answer 6

Coagulative necrosis that resembles mummified tissue

Characteristic of ischemia of lower limb and GI tract

If infection is superimposed, then liquefactive necrosis ensues changing it from dry gangrene to wet gangrene

Question 7

Caseous necrosis

Answer 7

Soft and friable necrotic tissue with cottage cheese-like appearance, think liquefactive with stuff mixed in like TB or fungal stuff

Characteristic of granulomatous inflammation from TB or fungal

Question 8

Fat necrosis

Answer 8

Necrotic adipose tissue with chalky white appearance from Ca depostition

Characteristic of trauma to fat and pancreatitis-mediated damage to peripancreatic fat

Fatty acids released by trauma or lipase join with Ca via saponification–a type of dystrophic calcification where Ca deposits on dead tissue

Question 9

Differentiate dystrophic and metastatic calcification

Answer 9

Dystrophic is deposition of Ca on dead tissues in the setting of normal Ca and Phosphate levels

Metastatic occurs with high levels of Ca and phosphate leading to deposition in normal tissues, does not equal cancer

Question 10

Fibrinoid necrosis

Answer 10

Necrotic damage to blood vessel wall
Leaking of proteins including fibrin into the wall results in pink staining of the wall
Characteristic of malignant HTN and vasculitis

Question 11

Brief description of apoptosis

Answer 11

ATP-dependent, genetically programmed cell death involving single cells or small groups and causing no inflammation

Question 12

Examples of apoptosis in the body

Answer 12

Endometrial shedding during menstruation
Removal of cells during emryogenesis
CD8 T-Cell mediated killing of virally infected cells

Question 13

Morphology of apoptotic cells

Answer 13

Dying cell shrinks causing cytoplasm to become more eosinophilic
Nucleus condenses and fragments in an organized manner
Apoptotic bodies fall from the cell and are cleaned up by macrophages

Question 14

What molecule mediates apoptosis and what does it do?

Answer 14

Caspases

Activates proteases that break down the cytoskeleton and endonucleases that break down DNA

Question 15

Name the pathways that can activate caspases and signal apoptosis

Answer 15

Intrinsic mitochondrial pathway
Extrinsic receptor-ligand pathway
Cytotoxic CD8 T-cell mediated pathway

Question 16

Describe the Intrinsic pathway to apoptosis

Answer 16

Cellular injury, DNA damage, or decreased hormonal stimulation leads to inactivation of Bcl2 which stabilizes the mitochondrial membrane keeping Cytochrome C in the mitochondria
Leads to release of Cyt C and activation of caspases

Question 17

Describe the extrinsic pathway to apoptosis

Answer 17

Extrinsic receptor-ligand pathway
FAS ligand binds FAS death receptor (CD95) on the target cell activating caspases
Example is negative selection of thymocytes in the thymus
Also TNF binding to TNF receptor

Question 18

Cytotoxic T-cell mediated apoptosis pathwya

Answer 18

Perforins from T-cell creates pores in the membrane of target cell
Granzyme from T-cell enters pores and activates caspases
Killing of virally infected cells is example