Cell Injury, Adaptation and Death (Lecture 23)

Question 1

Homeostasis

Answer 1

cells maintain their intracellular environment within a narrow range of physiological parameters

Question 2

Adaptation

Answer 2

as a cell encounters physiological stress or pathological stimuli, they can undergo adaptation, achieving a new steady state and preserving viability

Question 3

Hypertrophy

Answer 3

an increase in the size of cells resulting in increase in the size of the organ. NO INCREASE IN CELL NUMBER

only occurs in cells that are incapable of dividing: striated muscle cells in both skeletal muscle and the heart

caused by increase workload (physiologic) or hypertension (pathologic)

Question 4

Hyperplasia

Answer 4

Increase in the number of cells (not cell size)

Examples:
proliferation of the female mammary epithelium during puberty

proliferation of connective tissue cells during wound healing

regeneration of a partially resected liver by the remaining hepatocytes (physiologic)

excessive hormonal or growth factor stimulation (pathological)

may become malignant

Question 5

Atrophy

Answer 5

shrinkage of cell size of the cell by loss of cell substance. No decrease in cell number!

Caused by: decreased workload, loss of innervation, reduced blood supply, inadequate nutrition, aging

Decreased cell size is caused by: increased protein degradation or reduced protein synthesis

Question 6

Metaplasia

Answer 6

reversible change in which one adult cell type is replaced by another adult cell type

response to chronic irritation and inflammation

Examples:
A. ciliated columnar epithelial cells of the trachea and bronchi help clear foreign materials and mucous
B. In smokers they may be replaced with squamous epithelial cells, which are more rugged, leads to coughing
C. Barrett’s esophagus

precursor of malignancy

Question 7

Dysplasia

Answer 7

deranged cell growth of a specific tissue that results in cells that vary in size, number, shape, and organization

associated with chronic irritation and inflammation

occurs in metaplastic squamous epithelium in respiratory tract and uterine cervix

precursor of cancer

Question 8

Cell injury

Answer 8

occurs when cells are stressed to the point they are unable to adapt

Question 9

Eight causes of cell injury

Answer 9

1. oxygen deprivation
2. chemical agents
3. infectious agents
4. immunological reactions
5. genetic defects
6. physical agents
7. nutritional imbalances
8. aging

Question 10

Oxygen deprivation

Answer 10

hypoxia: oxygen deficiency
ischemia: loss of oxygenated blood supply to tissues

Question 11

Chemical agents

Answer 11

poisons, air pollutants, CO, asbestos

Question 12

Infectious agents

Answer 12

viruses, bacteria, fungi, parasites

Question 13

Immunological reactions

Answer 13

autoimmune diseases

Question 14

Genetic defects

Answer 14

sickle cell anemia, familial hypercholesterolemia

Question 15

Physical agents

Answer 15

trauma, heat, cold, electric shock

Question 16

Nutritional imbalances

Answer 16

diabetes, atherosclerosis

Question 17

Aging

Answer 17

accumulation of damage by ROS, loss of telomerase function

Question 18

Characteristics of reversible injury

Answer 18

Cellular swelling: result of failure of energy-dependent ion pumps in the plasma membrane, leading to an inability to maintain ionic and fluid homeostasis

Fatty change: occurs in hypoxic injury and various forms of toxic or metabolic injury, occurs mainly in cells involved in metabolism such as hepatocytes and myocardial cells

Question 19

Characteristics of irreversible injury

Answer 19

Inability to reverse mitochondrial dysfunction (lack of oxidative phosphorylation and ATP generation)

membrane dysfunction

Question 20

Ischemia in myocardial cells

Answer 20

Noncontractile after 1-2 minutes

Cell death occurs after 20-30 minutes

Appear dead by electron microscopy at 2-3 hours

Appear dead by light microscopy at 6-12 hours