PP A > Session 7 > Flashcards

Session 7 Flashcards

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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
What is hyperplasia?
Increase in tissue or organ size due to increased cell number
26
In which types of tissues does hyperplasia occur?
- Labile or stable tissues
27
What causes hyperplasia?
Increased functional demand or hormonal stimulation
28
Risk of hyperplasia?
Repeated cell divisions exposes the cell to risk of mutations and neoplasia
29
Is hyperplasia reversible?
Yes
30
What controls hyperplasia?
- Remains under physiological control | - Can occur secondary to a pathological cause but the proliferation itself is a normal response
31
Examples of physiological hyperplasia
- Proliferative endometrium under influence of oestrogen | - Bone marrow produces erythrocytes in response to hypoxia
32
Examples of pathological hyperplasia
- Eczema | - Thyroid goitre in iodine deficiency
33
What is hypertrophy?
Increase in tissue or organ size due to increased cell size
34
In which types of tissues does hypertrophy occur?
- Labile, stable but especially permanent tissues
35
What causes hypertrophy to occur?
Increased functional demand or hormonal stimulation
36
Examples of physiological hypertrophy?
- Skeletal muscle | - Pregnancy - uterus (hypertrophy + hyperplasia)
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Examples of pathological hypertrophy?
- Hypertension leads to hypertrophy of the cardiac muscle | - Hypertrophy of the smooth muscle in bladder due to prostrate getting bigger
38
Why don't athletes get cardiac muscle hypertrophy?
They do - but athletes rest. When you have hypertension - there is no rest for the cardiac muscle.
39
What is compensatory hypertrophy?
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
What is atrophy?
Shrinkage of a tissue or organ due to an acquired decrease in size and/or number of cells.
41
What is happening to the cell in atrophy?
- 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
Is tissue atrophy only a result of cell atrophy?
- Organ/tissue atrophy typically due to combination of cellular atrophy and apoptosis - Is reversible but only up to a point
43
What happens in tissue atrophy?
Apoptosis
44
What examples are there of physiological atrophy?
Ovarian atrophy in post menopausal women
45
What examples are there of pathological atrophy?
- 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
What can cerebral atrophy lead to?
Alzeihmers
47
What is metaplasia?
Reversible change of one differentiated cell type to another
48
What causes metaplasia?
Altered stem cell differentiation
49
Why does metaplasia occur?
May represent adaptive substitution of cells that are sensitive to stress by cell types better able to withstand the adverse environment.
50
What does metaplasia often lead to?
Metaplasia sometimes a prelude to dysplasia and cancer
51
Where does metaplasia occur?
- Only in labile or stable cell types | - No metaplasia across germ layers
52
Examples of metaplasia
- 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
Does metaplasia predispose to cancer?
- 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
What is aphasia?
- 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
Example of aplasia
- Thymic aplasia - infections and auto-immune problems | - Aplasia of the kidney
56
What is hypoplasia?
- 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
Examples of hypoplasia
Renal Breast Testicular in Klinefelter's syndrome Chambers of the heart
58
What is involution?
- Overlaps with atrophy | - Normal programmed shrinkage of an organ
59
Examples of involution
- Uterus after childbirth | - Thymus in early life
60
What is reconstitution?
Replacement of a lost part of the body
61
Can reconstitution occur in humans?
If a child clearly cuts the end of their finger, it can grow back.
62
What is atresia?
- No orifice | - Congenital imperforation of an opening
63
Example of atresia
Anus, vagina and small bowel
64
What is dysplasia?
- Abnormal maturation of cells within a tissue - Potentially reversible - Often pre-cancerous condition
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