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PP A > Session 7 > Flashcards

Session 7 Flashcards

1
Q

What determines the size of a cell population?

A
  • Rate of cell proliferation
  • Rate of cell differentiation
  • Rate of cell death by apoptosis
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2
Q

When is increase in cell population seen?

A
  • Increased proliferation

- Decreased cell death

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3
Q

When does cell proliferation occur?

A

Occurs in physiological and pathological conditions

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4
Q

When can excessive physiological stimulation become pathological?

A

Prostatic hypertrophy

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5
Q

What regulates normal cell proliferation?

A

Proto-oncogenes

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6
Q

How is cell proliferation controlled?

A
  • Largely by chemical signs from the microenvironment which either stimulate or inhibit cell proliferation.
  • when a signalling molecule binds to a receptor, it results in the modulation of gene expression
  • Receptors usually in cell membrane but can be in the cytoplasm or nucleus
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7
Q

Give example of what kind of receptors are found in the cytoplasm or nucleus

A

Steroid receptors (mostly activated by sex hormones)

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8
Q

What can the chemical signals make the cell do?

A
  • Survive - resist apoptosis
  • Divide - enter the cell cycle
  • Differentiate - take on specialised form and function
  • Die - undergo apoptosis
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9
Q

How can a cell population increase its numbers?

A

Increased growth occurs by

  • shortening the cell cycle
  • conversion of quiescent cells to proliferating cells by making them enter the cell cycle
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10
Q

Define mitosis

A

Nuclear division

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11
Q

Define cytokinesis

A

Cell division

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12
Q

Can cells with damaged DNA replicate? Why?

A

NO.

  • The cell cycle has important check points
  • If the DNA is damaged or the DNA has not been replicated, the cell will try and correct this issue
  • If the issue can’t be resolved, the cell will be driven to apoptosis
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13
Q

What is the restriction (R) point?

A
  • Most critical checkpoint

- Majority of the cells that pass R pint will complete cell cycle - point of no return

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14
Q

What happens if the R point is activated?

A
  • Delays the cell cycle

- Triggers DNA repair mechanisms or apoptosis via p53

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15
Q

What is the significance between the R point and cancer?

A

The R point is the most commonly altered checkpoint in cancer cells

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16
Q

What substances control the cell cycle?

A
  • Cyclins and cyclin dependent kinases (CDKs)

- CDKs become active by binding with cyclins

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17
Q

How do these substances control the cell cycle?

A

The cyclin binds to the enzyme and activates the CDK. The CDK then phosphorylates the target protein.

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18
Q

How many times can cells divide?

A

Humans - 61.3
This is the Hayflick number - ie the number of times a normal human cell population will divide until cell division stops.

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19
Q

How can cells adapt?

A
  • Hyperplasia
  • Hypertrophy
  • Atrophy
  • Metaplasia
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20
Q

Define hyperplasia

A

Cell increase in number

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21
Q

Define hypertrophy

A

Cells increase in size

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22
Q

Define atrophy

A

Cells become smaller

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23
Q

Define metaplasia

A

Cells are replaced by cells of a different type

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24
Q

Are cellular adaptations reversible?

A

Atrophy is the least reversible

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25
Q

What is hyperplasia?

A

Increase in tissue or organ size due to increased cell number

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26
Q

In which types of tissues does hyperplasia occur?

A
  • Labile or stable tissues
27
Q

What causes hyperplasia?

A

Increased functional demand or hormonal stimulation

28
Q

Risk of hyperplasia?

A

Repeated cell divisions exposes the cell to risk of mutations and neoplasia

29
Q

Is hyperplasia reversible?

A

Yes

30
Q

What controls hyperplasia?

A
  • Remains under physiological control

- Can occur secondary to a pathological cause but the proliferation itself is a normal response

31
Q

Examples of physiological hyperplasia

A
  • Proliferative endometrium under influence of oestrogen

- Bone marrow produces erythrocytes in response to hypoxia

32
Q

Examples of pathological hyperplasia

A
  • Eczema

- Thyroid goitre in iodine deficiency

33
Q

What is hypertrophy?

A

Increase in tissue or organ size due to increased cell size

34
Q

In which types of tissues does hypertrophy occur?

A
  • Labile, stable but especially permanent tissues
35
Q

What causes hypertrophy to occur?

A

Increased functional demand or hormonal stimulation

36
Q

Examples of physiological hypertrophy?

A
  • Skeletal muscle

- Pregnancy - uterus (hypertrophy + hyperplasia)

37
Q

Examples of pathological hypertrophy?

A
  • Hypertension leads to hypertrophy of the cardiac muscle

- Hypertrophy of the smooth muscle in bladder due to prostrate getting bigger

38
Q

Why don’t athletes get cardiac muscle hypertrophy?

A

They do - but athletes rest. When you have hypertension - there is no rest for the cardiac muscle.

39
Q

What is compensatory hypertrophy?

A

This is a type of regenerative growth that can take place in a number of human organs after the organ is either damaged, removed or cease to function.

40
Q

What is atrophy?

A

Shrinkage of a tissue or organ due to an acquired decrease in size and/or number of cells.

41
Q

What is happening to the cell in atrophy?

A
  • Shrinkage in the size of the cell to a size at which survival is still possible
  • Reduced structural components of the cell
  • May eventually result in cell death
42
Q

Is tissue atrophy only a result of cell atrophy?

A
  • Organ/tissue atrophy typically due to combination of cellular atrophy and apoptosis
  • Is reversible but only up to a point
43
Q

What happens in tissue atrophy?

A

Apoptosis

44
Q

What examples are there of physiological atrophy?

A

Ovarian atrophy in post menopausal women

45
Q

What examples are there of pathological atrophy?

A
  • Reduced functional demand/workload = atrophy of disuse; muscle atrophy after disuse, reversible with activity
  • Loss of innervation = denervation atrophy; wasted hand muscles after median nerve damage
  • Inadequate blood supply; thinning of skin on legs with peripheral vascular disease
  • Inadequate nutrition; wasting of muscles with malnutrition (brain is the last organ to atrophy in malnutrition)
  • Loss of endocrine stimuli; breast & reproductive organs
  • Persistent injury; polymyositis (inflammation of the muscle)
  • Aging = senile atrophy;brain, heart
  • Pressure; tissues around an enlarging benign tumour (probably secondary to ischaemia)
46
Q

What can cerebral atrophy lead to?

A

Alzeihmers

47
Q

What is metaplasia?

A

Reversible change of one differentiated cell type to another

48
Q

What causes metaplasia?

A

Altered stem cell differentiation

49
Q

Why does metaplasia occur?

A

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

50
Q

What does metaplasia often lead to?

A

Metaplasia sometimes a prelude to dysplasia and cancer

51
Q

Where does metaplasia occur?

A
  • Only in labile or stable cell types

- No metaplasia across germ layers

52
Q

Examples of metaplasia

A
  • Bronchial pseudostratified ciliated epithelium to stratified squamous epithelium due to effect of cigarette smoke
  • Stratified squamous epithelium to gastric glandular epithelium with persistent acid reflux (Barrett’s oesophagus)
53
Q

Does metaplasia predispose to cancer?

A
  • Epithelial metaplasia can be a prelude to dysplasia and cancer
    Eg - Barrett’s epithelium and oesophageal adenocarcinoma
    - Intestinal metaplasia of the stomach and gastric adenocarcinoma
54
Q

What is aphasia?

A
  • Complete failure of a specific tissue or organ to develop
  • An embryonic developmental disorder
  • Also used to describe and organ whose cells have ceased to proliferate eg aplasia of bone marrow in aplastic anaemia
55
Q

Example of aplasia

A
  • Thymic aplasia - infections and auto-immune problems

- Aplasia of the kidney

56
Q

What is hypoplasia?

A
  • Underdevelopment or incomplete development of tissue or organ at embryonic stage, inadequate number of cells
  • In a spectrum with aplasia
  • Not opposite of hyperplasia as it is a congenital condition
57
Q

Examples of hypoplasia

A

Renal
Breast
Testicular in Klinefelter’s syndrome
Chambers of the heart

58
Q

What is involution?

A
  • Overlaps with atrophy

- Normal programmed shrinkage of an organ

59
Q

Examples of involution

A
  • Uterus after childbirth

- Thymus in early life

60
Q

What is reconstitution?

A

Replacement of a lost part of the body

61
Q

Can reconstitution occur in humans?

A

If a child clearly cuts the end of their finger, it can grow back.

62
Q

What is atresia?

A
  • No orifice

- Congenital imperforation of an opening

63
Q

Example of atresia

A

Anus, vagina and small bowel

64
Q

What is dysplasia?

A
  • Abnormal maturation of cells within a tissue
  • Potentially reversible
  • Often pre-cancerous condition

PP A (13 decks)

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