Exam 1 (Lecture 4) - Necrosis

Question 1

What are the types of necrosis?

Answer 1

1) Coagulative
2) Liquefactive (lytic)
3) Caseous
4) Gangrenous (wet vs. dry)
5) Enzymatic

Question 2

What is apoptosis and how is it controlled?

Answer 2

Programmed cell death; controlled by nucleus.

Many pathologic and physiologic triggers.

Question 3

Describe the extrinsic pathway of apoptosis.

Answer 3

1) The “death” ligand binds to “death” ligand receptor on a normal cell.

2) Second messenger system activates procapase 8

3) Procapase 8 activates effector capases (3,6,7, and 12)

4) Initiation of apoptosis

Question 4

Describe the intrinsic pathway of apoptosis.

Answer 4

1) Damage to cytocavitary system or irreversible damage to DNA

2) Apoptosome formation and activation and activation of procapase 9

3) Procapase 9 activates effector capases (3,6,and 7)

4) Initiation of apoptosis

Question 5

What are useful functions of apoptosis?

Answer 5

1) Digit formation (during embryologic development)

2) Cell infection (viral)

3) Neoplastic (DNA damage)

4) Immune system (cells that recognize self)

5) Normal involution (shrinkage) (thymus/uterus)

6) Old/senescent cells

Question 6

Necrosis vs. Apoptosis

Answer 6

Necrosis: Fragments released into extracellular space (inflammation IS present)

Apoptosis: Fragments are membrane-bound (inflammation IS NOT present)

Question 7

What happens to cells during necrosis?

Answer 7

1) Cell size: Enlarged (swelling)

2) Nucleus: pyknosis (shinkage), karyorrhexis (exploded nucleus), or karyolysis (faded nucleus)

3) Plasma membrane: disrupted

4) Cellular contents: enzymatic digestion (may leak out of cell)

5) Adjacent inflammation (frequent)

6) Physiologic or Pathologic role: Usually pathologic (culmination of reversible cell injury)

Question 8

What happens to cells during apoptosis?

Answer 8

1) Cell size: Reduced (shrinkage)

2) Nucleus: Fragmentation into neuclosome-size fragments

3) Plasma membrane: Intact (altered structure, especially orientation of lipids)

4) Cellular contents: Intact (may be released in apoptotic bodies)

5) NO adjacent inflammation

6) Physiologic or Pathologic role: Usually physiologic (means of eliminating unwanted cells); MAY be pathologic after some forms of cell injury (especially DNA damage)

Question 9

What are the causes of free radical injury to cells?

Answer 9

1) Inflammation
2) Radiation
3) Oxygen toxicity
4) Chemicals
5) Reperfusion injury

Question 10

What are some examples of antioxidants?

Answer 10

1) SOD
2) Vitamin C
3) Glutathione peroxidase
4) Ferritin
5) Ceruloplasmin

Question 11

What are the histologic hallmarks of necrosis?

Answer 11

1) Pyknosis (nuclear condensation with shrinkage and intense basophilia)

2) Karyorrhexis (nuclear fragmentation)

3) Karyolysis (nuclear dissolution or loss)

4) Hypereosinophilic cytoplasm (intensely pink cytoplasm); due to denaturation of proteins, loss of ribosomes

5) Later, the dead cell may have cytoplasmic pallor

6) Become swollen, rounded, and detached from the basement membrane/neighboring cells

Question 12

What are the characteristics of coagulative necrosis?

Answer 12

1) Blood supply has been cut off

2) Loss of differential staining, but retention of cellular structures (can still make out individual cells)

3) Nuclear change: pyknotic

4) Cytoplasm: hypereosinophilic (homogenous)

5) Causes: hypoxia, cell membrane injury, toxins

6) Tissues affected: liver, kidney, muscle, neurons

Question 13

What are the characteristics of caseous necrosis?

Answer 13

1) Cells and tissues are unidentifiable

2) Coagulum of debris (more chronic cases); “onion layers” look to lesion

3) Causes: TB granuloma, Mycobacteria sp. and Rhodococcus equi

4) Tissues affected: any site possible (abscesses), lymph nodes, deep skin wounds

Question 14

What are the characteristics of liquefactive necrosis?

Answer 14

1) Cells and tissues are unidentifiable

2) Cavitation or focal loss of structure (liquid debris and fluid)

3) Causes: hypoxia, bacteria

4) Tissues affected: CNS (enzymatic destruction, high lipid content); Abscess (early) (neutrophils, hydrolytic enzymes)

Question 15

What are the characteristics of gangrenous necrosis?

Answer 15

1) Coagulative necrosis + saprophytic bacteria (ischemia or local irritant)

2) Wet Gangrene: Good blood supply; +/- bacteria

3) Dry Gangrene: Is the result of decreased vascular perfusion!! Affects distal extremity (udders/distal ends of appendages); mummification, usually lacks bacteria; dry/leathery appearance

Question 16

What are the characteristic of enzymatic necrosis of fat (fat necrosis)?

Answer 16

1) Necrosis of adipose tissue

2) Occurs mainly in peripancreatic adipose tissue (attributed to release of lipases from necrotic pancreatic acinar cells)

3) Grossly appears as chalky-white nodular deposits (the result of saponification = soap formation)

Question 17

Erosion vs. Ulceration

Answer 17

Erosion: Necrosis in epithelial surfaces (epidermis or corneal epithelium), or epithelial linings (mucosal epithelium); causes exfoliation or sloughing of dead cells, resulting in erosion of epithelium

Ulceration: Full-thickness necrosis (through mucosa, submucosa, etc)