Cellular Injury and Adaptation

Question 1

Characteristics of reversible cell injury

Answer 1

1. Decreased synthesis of ATP by oxidative phosphorylation
2. Decreased function of Na+K+ ATPase membrane pumps, cellular swelling and swelling of the endoplasmic reticulum (ER)
3. The switch to anaerobic glycolysis results in depletion of cytoplasmic glycogen, increased lactic acid production, and decreased intracellular pH
4. Decreased protein synthesis leads to detachment of ribosomes from the rough ER
5. Plasma-membrane blebs and myelin figures may be seen

Question 2

Characteristics of irreversible cell injury

Answer 2

1. Severe membrane damage plays a critical role in irreversible injury, allows a massive influx of calcium into the cell, and allows efflux of intracellular enzymes and proteins into the circulation
2. Marked mitochondrial dysfunction produces mitochondrial swelling, large densities seen within the mitochondrial matrix, irreparable damage of the oxidative phosphorylation pathway, and an inability to produce ATP
3. Rupture of the lysosomes causes release of lysosomal digestive enzymes into the cytosol and activation of acid hydrolases followed by autolysis
4. Nuclear changes can include pyknosis, karyorrhexis, karyolysis

Question 3

Characteristics of coagulative necrosis

Answer 3

1. The most common form of necrosis, is most often due to ischemic injury.
2. It is caused by the denaturing of proteins within the cytoplasm.
3. Microscopic examination shows loss of the nucleus but preservation of cellular shape.
4. Coagulative necrosis is common in most organs

Question 4

Characteristics of liquefaction necrosis

Answer 4

1. Results from cellular destruction by hydrolytic enzymes, leading autolysis and heterolysis.
2. Liquefaction necrosis occurs in abscesses, brain infarcts, and pancreatic necrosis

Question 5

Characteristics caseous necrosis

Answer 5

1. Combination of coagulation and liquefaction necrosis
2. The gross appearance is soft, friable, and cheese-like.
3. Caseous necrosis is characteristic of granulomatous diseases, including tuberculosis

Question 6

Characteristics of fat necrosis

Answer 6

1. Caused by the action of lipases on adipocytes and is characteristic of acute pancreatitis
2. Fat necrosis has chalky white appearance

Question 7

Characteristics fibrinoid necrosis

Answer 7

1. Form of necrotic tissue connective tissue that histologically resembles fibrin.
2. On microscopic examination fibrionoid necrosis has an eosinophilic (pink) homogenous appearance.
3. Due to acute immunologic injury and vascular hypertensive damage

Question 8

Characteristics of gangrenous necrosis

Answer 8

1. Gross term used to describe dead tissue

2. Common sites of involvement include lower limbs, gallbladder, GI tract and testes,

Question 9

What are the two types of gangrenous necrosis?

Answer 9

Dry gangrene and wet gangrene

Question 10

Characteristics of dry gangrene

Answer 10

Coagulative necrosis

Question 11

Characteristics of wet gangrene

Answer 11

Liquefactive necrosis

Question 12

What protein inhibits apoptosis?

Answer 12

bcl-2

Question 13

How does bcl-2 inhibit apoptosis?

Answer 13

bcl-2 prevents the release of cytochrome c from mitochondria and binds pro-apoptotis protease activating factor (Apaf-1)

Question 14

What protein stimulates apoptosis?

Answer 14

p53

Question 15

What are the adaptive responses to injury?

Answer 15

Atrophy, Hyperplasia, Hypertrophy, Metaplasia and Dysplasia

Question 16

What is atrophy?

Answer 16

Decrease in cell/organ size and functional ability.

Question 17

What are the different causes of atrophy?

Answer 17

Decreased workload
Ischemia
Lack of hormonal or neural stimulation
Malnutrition
Aging

Question 18

What is hypertrophy?

Answer 18

Increase in cell size and functional ability

Question 19

What are the causes of hypertrophy?

Answer 19

1. Increased mechanical demand can be physiologic

2. Increased endocrine stimulation

Question 20

What is hyperplasia?

Answer 20

Increase in the number of cells in a tissue or organ

Question 21

What is metaplasia?

Answer 21

Reversible change of one fully differentiated cell type to another

Question 22

What is lipofuscin?

Answer 22

Wear-and-tear pigment that is seen as perinuclear yellow-brown pigment

Question 23

What is melanin?

Answer 23

Black-brown pigment derived from tyrosine found in melanocytes and substantia nigra

Question 24

What is hemosiderin?

Answer 24

Golden yellow-brown granular pigment found in areas of hemorrhage of bruises. Systemic iron overload can lead to hemosiderosis (increase in total body iron stores without tissue injury) of hemochromatosis (increase in total body iron stores with tissue injury).

Prussian blue stains can identify the iron in the hemosiderin

Question 25

What are the two types of calcification?

Answer 25

Dystrophic calcification and metastatic calcification

Question 26

What is dystrophic calcification?

Answer 26

Precipitation of calcium phosphate in dying or necrotic tissues.

Normal calcium deposited in dead tissue

Question 27

What is metastatic calcification?

Answer 27

Precipitation of calcium phosphatein normal tissue due to hypercalcemia

High serum calcium gets deposited into normal tissues

Question 28

What is dysplasia?

Answer 28

1. Disordered cell growth
2. Potential precursor to cancer if the irritant is not removed
3. Sometimes reversible if the irritant is removed