02/16a Cell Injury I - Adaptation, Injury, and Necrosis

Question 1

What is the cellular adaption to increased metabolic demand?

Answer 1

Hyperplasia or hypertrophy

Question 2

What is the cellular adaptation to decreased stimulation or nutrients?

Answer 2

Atrophy

Question 3

What is the cellular adaptation to chronic irritation

Answer 3

Metaplasia

Question 4

What is a cellular adaption? When does it happen?

Answer 4

Reversible change that occurs in response to stress

Question 5

What happens to a cell if it become irreversibly injured?

Answer 5

Undergoes necrosis or apoptosis

Question 6

What is hypertrophy?

Answer 6

Increase in the SIZE of cells which results in increased size of the organ
Can be physiological or pathological

Question 7

What are two examples of physiologic hypertrophy?

Answer 7

Increased workload on skeletal and cardiac muscle in athletes
Hormone induction in the pregnant uterus

Question 8

What is hyperplasia?

Answer 8

Increase in the NUMBER of cells which results in increased size of the organ
Can be physiological or pathological

Question 9

What are two causes of physiological hyperplasia, with examples?

Answer 9

Hormonal - female breast during puberty and pregnancy

Compensatory - renal hyperplasia after unilateral nephrectomy, erythroid hyperplasia of bone marrow in mountain climbers

Question 10

What are two causes of pathological hyperplasia, with examples?

Answer 10

Excessive hormone stimulation - endometrial hyperplasia during menopause, prostatic hyperplasia
Viral infections - papilloma virus warts on the skin

Question 11

What is atrophy?

Answer 11

Reduction in size of an organ due to a decrease in cell size AND number

Question 12

What are seven causes of atrophy? Give examples of each

Answer 12

Decreased workload (disuse) - limbs that have been immobilized in casts
Loss of innervation (denervation) - loss of muscle tone in patients with spinal injuries and paralysis
Diminished blood supply (ischemia) - smaller legs in patients with severe peripheral atherosclerosis
Inadequate nutrition - marasmus (inadequate protein), cachexia (cancer)
Loss of endocrine stimulation - uterus and ovaries after menopause
Aging - old people shrink!
Pressure - enlarging benign tumor encroaching on surrounding structures

Question 13

What are four mechanisms of atrophy?

Answer 13

1) Decreased protein synthesis
2) Increased protein degradation
3) Ubiquitin-proteasome pathway - degrades proteins
4) Autophagic vacuoles with lipofuscin granules

Question 14

What is metaplasia? When does it occur?

Answer 14

Reversible change in which one differentiated cell type is replaced by another cell type
Usually occurs in response to stress or chronic irritation

Question 15

What are three causes and examples of metaplasia?

Answer 15

Tobacco smoke –> squamous metaplasia in the respiratory tract
Gastric acid reflux –> gastric metaplasia of the distal esophagus, which can lead to Barrett’s esophagus and cancer
Repeated skeletal muscle injury with hemorrhage –> muscle replaced by bone (myositis ossificans), quite rare

Question 16

What are three possible mechanisms of metaplasia?

Answer 16

1) Re-programming of stem cells that exist in normal tissue
2) Induction by cytokines, growth factors, or other environmental signals
3) Retinoic acid

Question 17

What are the two BROAD types of cell injury and death?

Answer 17

Reversible

Irreversible (necrosis and apoptosis)

Question 18

What are seven causes of cell injury?

Answer 18

Oxygen deprivation (hypoxia or ischemia)
Physical agents (trauma)
Chemical agents and drugs
Infectious agents
Immunologic reactions
Genetic derangements
Nutritional imbalances

Question 19

What are the two major morphologic alterations involved in reversible cell injury?

Answer 19

Cellular swelling

Fatty change

Question 20

What are the cytoplasmic and nuclear morphologic alterations involved in irreversible cell injury?

Answer 20

Cytoplasmic eosinophilia
Karyolysis - nucleus becomes pale and disappears
Pyknosis - chromatin condenses, nucleus shrinks and becomes deeply basophilic
Karyorrhexis - nucleus undergoes fragmentation

Question 21

What are the five patterns of tissue necrosis?

Answer 21

Coagulative 
Liquefactive
Fat necrosis
Caseous
Fibrinoid

Question 22

What are the major characteristics of coagulative necrosis?

Answer 22

Progressive loss of cell structure
Coagulation of cellular constituents
Persistence of cellular outlines, until inflammatory cells arrive and degrade them
Changes in cytoplasmic staining (eosinophilia)
Changes in nuclear morphology (pyknosis, karyolysis, karyorrhexis)

Question 23

What are the major characteristics of liquefactive necrosis?

Answer 23

Dissolution of necrotic cells
Typically seen in an abscess - large numbers of neutrophils release hydrolytic enzymes that break down the dead cells and form pus
Common in the CNS

Question 24

What are the major characteristics of caseous necrosis?

Answer 24

Occurs with granulomatous inflammation in response to certain microorganisms (TB)
Chronic inflammatory response - “cheesy” area of cellular debris in the center of a caseating granuloma

Question 25

What are the major characteristics of fat necrosis?

Answer 25

Formation of insoluble salts from the binding and precipitation of free fatty acids (mobilized from adipose tissue by lipases) with calcium ions
Appear chalky white upon gross examination
Basophilic after H&E stain

Question 26

What are the major characteristics of fibroid necrosis?

Answer 26

Occurs in the wall of arteries in cases of vasculitis
Necrosis of smooth muscle cells in the tunica media and endothelial damage
Plasma proteins (fibrin) are depositing in the area of necrosis