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Pathological Processes > 10. Cellular Adaptations > Flashcards

10. Cellular Adaptations Flashcards

1
Q

What 3 things does the size of a cell population depend on?

A

Rate of cell proliferation.
Cell differentiation.
Cell death by apoptosis.

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2
Q

What regulates normal cell proliferation?

A

Proto-oncogenes

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3
Q

How is cell proliferation controlled?

A

Chemical signals from the microenvironment, binds to a receptor in cell membrane, cytoplasm or nucleus, resulting in modulation of gene expression which can either stimulate or inhibit cell proliferation.

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4
Q

In what two ways can a cell population increase its numbers?

A

Shortening of the cell cycle.

Conversion of quiescent cells (G0) to proliferating cells by making them enter the cell cycle.

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5
Q

What are the two checkpoints in mitosis? What do they check?

A 
G1 checkpoint/restriction checkpoint (after G1 which is cell growth, before S which is DNA synthesis) - cell big enough, environment favourable, DNA damaged. Majority of cells that pass this will complete cell cycle. Checkpoint activation delays cell cycle, triggers DNA repair mechanisms or apoptosis via p53.
G2 checkpoint (after G2 which is cell growth, before mitosis) - if all DNA is replicated and is the cell is big enough.
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6
Q

What is the most commonly altered checkpoint in cancer cells?

A

Restriction point

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7
Q

What is progression through the cell cycle regulated by?

A

Proteins called cyclins and enzymes called cyclin-dependant kinases.

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8
Q

How do cyclin dependant kinases become activated?

A

Binding to and complexing with cyclins.

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9
Q

How do activated cyclin-dependant kinases drive the cell cycle?

A

By phosphorylating proteins that are critical for progression of the cell to the next stage of the cell cycle.

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10
Q

What is the activity of cyclin-cyclin-dependant complexes regulated by?

A

Cyclin-dependant kinase inhibitors. So some growth factors work by stimulating the production of cyclins and some work by shutting off the production of cyclin-dependant inhibitors.

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11
Q

What is the average number of times that a human cell can divide?

A

61.3

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12
Q

What is hyperplasia?

A

Cells increase in number above normal, so increased tissue or organ size

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13
Q

What is hypertrophy?

A

Cells increase in size, so increase in tissue or organ size

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14
Q

What is atrophy?

A

Size and/or number of cells become smaller, so there is shrinkage of the tissue or organ.

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15
Q

What is metaplasia?

A

Cells are replaced by cells of a different type

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16
Q

How can cells adapt?

A

Via hyperplasia, hypertrophy, atrophy and metaplasia

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17
Q

Are cellular adaptations reversible?

A

Hyperplasia and metaplasia are reversible, least reversible is atrophy. All cellular adaptations are irreversible once reaches cell injury.

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18
Q

In what type of tissues does hyperplasia occur?

A

Labile or stable.

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19
Q

What causes hyperplasia (increase in cell number)?

A

Increased functional demand or hormonal stimulation.

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20
Q

What are cells at risk of in hyperplasia due to the repeated cell divisions?

A

Mutations and neoplasia

21
Q

Give a physiological example of hyperplasia

A

Proliferative endometrium under the influence of oestrogen in the menstrual cycle

22
Q

Give a pathological example of hyperplasia

A

Eczema.

Thyroid goitre in iodine deficiency.

23
Q

In what type of tissues does hypertrophy occur?

A

Labile, stable, but especially permanent tissues

24
Q

What causes hypertrophy?

A

Increased functional demand or hormonal stimulation

25
Q

In what tissue types does hypertrophy usually occur with hyperplasia?

A

Labile and stable

26
Q

How does hypertrophy help the cells cope with increased functional demand?

A

Cells contain more structural components so the workload is shared by a greater mass of cellular components.

27
Q

Give an example of physiological hypertrophy

A 
Skeletal muscle.
Pregnant uterus (hypertrophy and hyperplasia).
28
Q

Give an example of pathological hypertrophy

A

Right ventricular hypertrophy in increased BP.
Bowel stricture, proximal bowel becomes hypertrophied to push material though.
Enlarged prostate gland, hypertrophy of smooth muscle cells of bladder to push urine through urethra.

29
Q

Why dont athletes get cardiac muscle hypertrophy?

A

Rest after exercise, pathological heart hypertrophy is when heart cannot rest eg high BP.

30
Q

What is compensatory hypertrophy?

A

Where in a pair of organs one becomes enlarged to compensate for lack, or decreased function, of other. Eg if one kidney is removed, or small from birth. (Hypertrophy and hyperplasia occurs).

31
Q

How does atrophy help cells to survive?

A

Cells shrink to a size at which survival is still possible, by reducing the structural components of the cell. However may eventually result in cell death.

32
Q

Give an example of physiological atrophy

A

Ovarian atrophy in post-menopausal women.

Uterus atrophy after birth.

33
Q

Give 4 examples of pathological atrophy

A

Atrophy of disuse - eg muscle (such as due to plaster cast) due to reduced functional demand/workload, reversible with activity.
Denervation atrophy - eg wasted hand muscles after median nerve damage.
Inadequate blood supply - eg thinning of skin on legs with peripheral vascular disease.
Inadequate nutrition - eg wasting of muscles with malnutrition.
Loss of endocrine stimuli - eg breast, reproductive organs.
Persistent injury - eg polymyositis (inflammation of muscle).
Senile atrophy - eg brain and heart.
Pressure - eg tissues around an enlargening benign tumour secondary to ischaemia.

34
Q

What causes metaplasia?

A

Altered stem cell differentiation.

35
Q

How does metaplasia help a tissue withstand stress better?

A

Adaptive substitution of cells that are sensitive to stress by cell types that are better able to withstand the adverse environment.

36
Q

What is sometimes a prelude to dysplasia and cancer? Give an example of a cancer in which this is sometimes the case

A

Epithelial metaplasia.

Eg Barrett’s epithelium and oesophageal adenocarcinoma. Intestinal metaplasia of the stomach and gastric adenocarcinoma.

37
Q

In what cell types does metaplasia occur?

A

Labile or stable. There is no metaplasia across germ layers.

38
Q

Give an example of metaplasia

A

Bronchial pseudostratified ciliated epithelium becoming stratified squamous epithelium due to the effect of cigarette smoke.
Stratified squamous epithelium becoming gastric glandular epithelium with persistant acid reflux in Barrett’s oesophagus.

39
Q

What is aplasia?

A

Complete failure of a specific tissue or organ to develop. Is an embryonic developmental disorder.
Also used to describe an organ whose cells have ceased to proliferate (eg aplasia of bone marrow in aplastic anaemia).

40
Q

Give an example of aplasia

A

Thymic aplasia in infections and auto-immune problems.

Aplasia of the kidney.

41
Q

What is hypoplasia?

A

Underdevelopment or incomplete development of the tissue or organ at embryonic stage, inadequate number of cells.

42
Q

Give an example of hypoplasia

A

Renal hypoplasia.
Breast hypoplasia.
Testicular hypoplasia in Klinefelter’s syndrome.
Hypoplasia of the chambers of the heart.

43
Q

What is involution?

A

Normal programmed shrinkage of an organ, so overlaps with atrophy.

44
Q

Give an example of involution

A

Uterus after birth.

Thymus in early life.

45
Q

What is reconstitution?

A

Replacement of a lost part of the body

46
Q

Give an example of reconstitution

A

Small child cuts off end of finger, can grow back.

47
Q

What is atresia?

A

Congenital imperforation of an opening

48
Q

Give an example of atresia

A

No anus, vagina, small bowel

49
Q

What is dysplasia?

A

Abnormal maturation of cells within a tissue, which is potentially reversible and often a pre-cancerous condition.

Pathological Processes (14 decks)

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