Pathology - cells (including cell death)

Question 1

Define autophagy

Answer 1

process for cells to remove organelles + denatures proteins

Question 2

Define heterophagy

Answer 2

process of cell consuming material from its environment

Question 3

Where is energy generated in a cell and what happens if this is damaged?

Answer 3

Mitochondria - ATP produced in intermembrane space by oxidative phosphorylation
Mitochondria also regulate programmed cell death (apoptosis)
If mitochondria damaged by toxins, decreased blood supply or trauma - ATP generation fails - cell dies by necrosis

Question 4

What forms of mitochondrial disease are there?

Answer 4

X-linked = fathers cannot pass to sons
Autosomal = caused by autosomal gene abnormality
Maternally-inherited = mutation in mitochondrial DNA

Question 5

What are growth factors?

Answer 5

• promote entry of cells into cell cycle
• remove block on cell cycle progression
• prevent programmed cell death (apoptosis)
• enhance synthesis of cell components (eg epiderm growth factor for skin wound healing)

Question 6

Describe the cell cycle

Answer 6

G1 = cell preparing to divide - cell grows + copies organelles
S-phase (in interphase) = DNA replicated
G2 = cell continues to grow, centrosome replication completed
M-phase = mitotic phase = cell divides its copied DNA + cytoplasm to make 2 new cells (involves mitosis + cytokinesis)

Question 7

Describe stem cells

Answer 7

• have capacity for self-renewal

- asymmetric division (one daughter cell can mature while other remains stem cell)

Question 8

Totipotent stem cell

Answer 8

• embryonic

- can give rise to all types of differentiated/mature tissues

Question 9

Adult/tissue stem cells

Answer 9

can only replace cells in tissues in which they reside

Question 10

Multipotent stem cells

Answer 10

• in bone marrow + fat

- can give rise to cartiocytes (cartilage cells), osteocytes, adepocytes (fat cells) + myocytes (muscle cells)

Question 11

What are 4 cell adaptations

Answer 11

Hypertrophy
Hyperplasia
Atrophy
Metaplasia
(reversible changes in size, number, phenotype, metabolic activity or functions of cells in response to changes in their environment)

Question 12

Hypertrophy

Answer 12

• increase in size of cells (increase in size of affected organ)
• physiological or pathological
• related to increased workload
  physiological = uterus in pregnancy
  pathological = myocardium in hypertension

Question 13

Hyperplasia

Answer 13

• increase in number of cells in organ/tissue in response to a stimulus
• can only occur if cells can divide
• can be physiological or pathological
• can occur alongside hypertrophy
• regresses if stimulus removed

Question 14

Atrophy

Answer 14

• decrease in size of organ/tissue due to decreases cell size + number
• physiological or pathological
  eg disuse atrophy, denervation atrophy, pressure atrophy, inadequate nutrition

Question 15

Metaplasia

Answer 15

• reversible change in which one differentiated cell type is replaced by another cell type
• adaptive response - replacement cell type better able to withstand adverse environment
• caused by reprogramming of stem cells

Question 16

What is necrosis?

Answer 16

• accidental/unregulated cell death
• always pathological
• damage to cell membranes - lysosomal enzyme digestion of cell
• leakage of cell contents - inflammatory reaction

Question 17

Mechanisms underlying necrosis

Answer 17

• depletion of ATP
• mitochondrial damage
• influx of calcium
• accumulation of oxygen-derived free radicals
• membrane permeability defects
• DNA + protein damage

Question 18

What is apoptosis?

Answer 18

• programmed cell death
• no inflammatory reaction
• many normal functions
• physiological (eg destruction of cells during embryogenesis) + pathological (eg viral infections)

Question 19

What are the 2 types of pathological calcification?

Answer 19

dystrophic = normal serum calcium, calcium deposited in dead/damaged tissue
Metastatic = hypercalcemia, increased PTH, increased bone turnover, vitamin D excess, sarcoidosis

Question 20

How are apoptotic cells removed?

Answer 20

• phosphatidylserine flips from inner to outer aspect of cell membrane
• recognised by macrophage receptors
• apoptotic cells secrete soluble factors which recruit macrophages
• apoptotic bodies get coated with thrombospondin or C1q which attracts macrophages
• dead cells disappear within minutes