Week 3: Cellular Stress

Question 1

Define adaptation

Answer 1

cells attempt to maintain an internal steady-state (homeostasis), but when exposed to an adverse stimulus undergo various adaptations to establish a new “steady-state”.

Question 2

Define stem cell

Answer 2

defined as an undifferentiated cell of a multicellular organism which can give rise to indefinitely more cells of the same type, and from which certain other kinds of cells arise by differentiation

Question 3

List and describe the different types of stem cells

Answer 3

-Embryonic stem cells – totipotent – can give rise to any cell type in the body
-Tissue stem cells – in adults, stem cells replace damaged cells and maintain tissue populations

Question 4

Define proliferation

Answer 4

defined as a rapid increase in the number or amount of something

Question 5

Define atrophy

Answer 5

a decrease in tissue mass due to shrinkage of cells
-can be both physiological and pathological

Question 6

Define hypertrophy

Answer 6

an increase in the size of existing cells resulting in an increase in the size of the organ; often in response to increased workload
-can be both physiologic and pathologic

Question 7

_____ and _____ also can occur together, and obviously both result in an enlarged organ

Answer 7

hypertrophy and hyperplasia

Question 8

What is a physiological example of hypertrophy?

Answer 8

hypertrophy of skeletal muscle occurs as a normal physiological response in weight training

Question 9

What is a pathological example of hypertrophy?

Answer 9

the cardiac enlargement that occurs with hypertension or aortic valve disease

Question 10

Define hyperplasia

Answer 10

an increase in the number of cells (caused by cell division)
-can be both physiologic and pathologic

Question 11

What is a physiological example of hyperplasia?

Answer 11

when part of a liver is resected, mitotic activity in the remaining cells beings as early as 12 hours later, eventually restoring the liver to its normal size

Question 12

What is a pathologic example of hyperplasia?

Answer 12

excessive hormonal or growth factor stimulation (abnormal menstrual bleeding)

Question 13

Define metaplasia

Answer 13

the substitution of one type of cell for another cell type

Question 14

What is an example of metaplasia?

Answer 14

cells in the bronchi of smokers change from ciliated columnar epithelial cells to squamous cells

Question 15

Define dysplasia

Answer 15

an alteration in the size, shape, and/or organization of the cells in a tissue

Question 16

What are the causes of cell injury?

Answer 16

-Hypoxia
-Physical agents
-Chemical agents
-Biological/infectious agents
-Immunologic reactions
-Genetic alterations
-Nutritional imbalances

Question 17

_____ _____ can also lead to cell injury.

Answer 17

Cellular aging

Question 18

What four components are particularly vulnerable to cell injury?

Answer 18

1. Cell membranes critical for ionic and osmotic homeostasis
2. Mitochondria and the generation of energy via ATP
3. Protein synthetic machinery
4. Cellular DNA

Question 19

What are the 4 major mechanisms of cell injury?

Answer 19

1. Damage to mitochondria results in a reduction in ATP and an increase in reactive oxygen species&raquo_space; damage to lipids, proteins, and DNA.
2. Entry of calcium into the cell results in increased mitochondrial permeability and activation of multiple cellular enzymes.
3. If the plasma membrane is damaged there can be a loss of cellular components, and if the lysosomal membrane is damaged, leaked lysosomal enzymes can inadvertently digest cellular components.
4. Protein misfolding and DNA damage should trigger pro-apoptotic proteins to initiate programmed cell death. If the checkpoint or repair mechanism is faulty, damaged cells can avoid apoptosis which may result in cancer development.

Question 20

What are two types of reversible cell injury?

Answer 20

Hydropic swelling and Fatty change

Question 21

Describe hypropic swelling

Answer 21

injury caused by a variety of agents; produces a characteristic cellular or hydropic swelling when seen under the microscope.

Question 22

What is another name for fatty change?

Answer 22

Steatosis

Question 23

Describe fatty change

Answer 23

the abnormal accumulation of triglycerides within cells.
-Is linked to the intracellular accumulation of triglyceride fat either because of increased delivery of fat to the cell (e.g., in starvation, diabetes); an impairment of fat metabolism within the cell (e.g., in liver cells in alcoholism); or decreased synthesis of apolipoproteins for transport out of the cell (e.g., in protein malnutrition, CCl4 (carbon tetrachloride) toxicity).

Question 24

Define necrosis

Answer 24

is an uncontrolled process of cell death in response to overwhelming injury and is characterized by certain structural changes

Question 25

What are the structural changes that necrosis is characterized by?

Answer 25

a. eosinophilia (pinkness) of the cytoplasm
b. pyknosis (shrinkage)
c. karyorrhexis (the pyknotic nucleus fragments or breaks up)
d. karyolysis (dissolution) of the nucleus

Question 26

What are the different types of necrosis?

Answer 26

1. coagulative
2. liquefactive
3. fat
4. caseous

Question 27

Describe coagulative necrosis and provide an example

Answer 27

the most common form of necrosis – microscopically all the changes described above are seen. Typical of ischemia e.g., in heart (myocardial) cells (heart attack)

Question 28

Describe liquefactive necrosis and provide an example

Answer 28

rapid loss of tissue architecture and digestion of the dead cells. Most often seen in CNS. Typical of bacterial infection or death of brain tissue (following infarction or stroke)

Question 29

Describe fat necrosis and provide an example

Answer 29

specific to fat (adipose) tissue. Released enzymes digest fat that complexes with calcium to form chalky-white deposits, e.g., pancreatitis; damage to breast tissue

Question 30

Describe caseous necrosis and provide an example

Answer 30

soft, friable, “cheesy” material. Characteristic of tuberculosis

Question 31

Describe apoptosis

Answer 31

the morphologic manifestation of programmed cell death and is distinct from necrosis

Question 32

Apoptosis is an _____-dependent process specifically designed to switch off unneeded or damaged cells and _____ them.

Answer 32

energy; eliminate

Question 33

Apoptosis can occur under either

Answer 33

physiological or pathological circumstances

Question 34

Give two pathological examples of apoptosis

Answer 34

-Following radiation injury
-some cancers

Question 35

Describe the process of apoptosis

Answer 35

Apoptotic cells initiate their own death by the activation of proteases that breakdown the cell nucleus and cytoskeleton. In the initial stages, the cell nucleus collapses due to chromatic condensation and fragmentation. Then the cells shrink and is cleaved into cytoplasmic buds enclosing organelles (apoptotic bodies). Finally, there is phagocytosis of the extruded apoptotic bodies.

Question 36

List the differences between apoptosis and necrosis

Answer 36

Apoptosis:
-Programmed cell death following a tightly regulated programme
-Cells degrade their own DNA and proteins via intrinsic enzymes
-May be physiologic or pathologic
-Cell shrinks

Necrosis:
-Characterized by loss of membrane integrity and leakage of cellular contents
-Results in host inflammatory reaction in surrounding tissue
-Always pathologic
-Cell swells

Question 37

Define anoxia

Answer 37

absence or almost complete absence of oxygen from inspired gases, arterial blood, or tissues

Question 38

Define hypoxia

Answer 38

decrease below normal levels of oxygen in inspired gases, arterial blood, or tissues