Sesh 7.1- Cellular Adaptations

Question 1

What determines the size of a cell population?

Answer 1

Rate of cell proliferation, differentiation and apoptosis

Question 2

____________ regulate normal cell proliferation.

Answer 2

Proto-oncogenes

Question 3

Name 2 ways in which cell populations can increase in size.

Answer 3

1. Shortening cell cycle

2. Converting quiescent cells in G0 to proliferating cells

Question 4

Which phases of the cell cycle are visible by light microscopy?

Answer 4

mitosis and cytokinesis

Question 5

Where are the 2 cell cycle checkpoints and what are their functions?

Answer 5

Checkpoint after G1- is DNA damaged?
Checkpoint after G2- is all DNA replicated
-Prevent cells in normal state with damaged DNA from replicating

Question 6

What is the restriction point (R)?

Answer 6

Most critical checkpoint in cell cycle near end of G1. Once cells pass point, will continue to replicate regardless. Most commonly altered checkpoint in cancer cells

Question 7

What are cyclins and CDKs?

Answer 7

Cyclins bind CDKs (and CDKs substrate) to activate them, allowing them to phosphorylate target proteins, to allow the cell to go round the cell cycle.

Question 8

What is the Hayflick limit?

Answer 8

The limited number of times a normal cell can divide due to telomere shortening.
61.3 times in humans

Question 9

List the 4 ways in which cells can adapt.

Answer 9

1. Hyperplasia
2. Hypertrophy
3. Atrophy
4. Metaplasia

Question 10

What is metaplasia?

Answer 10

Cells are replaced by cells of a different type.

Question 11

Which cellular adaptation is not reversible?

Answer 11

Atrophy.

Question 12

In which types of tissue does hyperplasia occur?

Answer 12

Labile or stable tissues.

Question 13

Why does hyperplasia increase risk of neoplasia?

Answer 13

Increased no of cell divisions, means increased risk of mutation in nuclear division.

Question 14

Why does hyperplasia occur?

Answer 14

Due to increased functional demand or hormonal stimulation.

Can also be secondary to pathological cause.

Question 15

Give examples of physiological hyperplasia.

Answer 15

• Proliferative endometrium w/ oestrogen stim

- Hypoxia causes bone marrow to produce erythrocytes

Question 16

Give 2 examples of pathological hyperplasia.

Answer 16

• Eczema- hyperplasia of epidermis

- Thyroid goitre in Iodine deficiency

Question 17

Which types of tissue does hypertrophy occur in?

Answer 17

Permanent especially (can only undergo hypertrophy, not hyperplasia)
Also labile and stable tissues- often alongside hyperplasia.

Question 18

Why does tissue hypertrophy occur?

Answer 18

Increased functional demand or hormonal stimulation….

Cells contain more structural components- workload is shared between greater no of these

Question 19

Give 2 examples of physiological hypertrophy.

Answer 19

1. Skeletal muscle

2. Pregnant uterus (hypertrophy & hyperplasia)

Question 20

Give 3 examples of pathological hypertrophy.

Answer 20

1. Ventricular hypertrophy due to hypertension…can’t grow enough capillaries to compensate so heart is always hypoxic
2. Hypertrophy of smooth muscle in bladder wall in response to enlarged prostate
3. Hypertrophied bowel proximal to stricture

Question 21

What is compensatory hypertrophy?

Answer 21

Hypertrophy of organ in response to damage to part of that organ or to 1 of a paired organ e.g. If have 1 kidney removed, remaining kidney will hypertrophy.

Question 22

Define atrophy.

Answer 22

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

Question 23

What happens within the cell during atrophy?

Answer 23

• Shrinks to a size at which survival is still possible
• Reduced structural components e.g. Muscle fibres (gets rid of things it no longer needs into residual bodies)
• May result in cell death

Question 24

Is tissue atrophy only due to cellular atrophy?

Answer 24

No, is a combination of cellular atrophy AND apoptosis.

Question 25

Is tissue atrophy reversible?

Answer 25

Yes but only up to a point...if get fibrotic tissue, not reversible.

Question 26

Give 2 examples of physiological atrophy.

Answer 26

1. Ovarian atrophy in post-menopausal women | 2. Uterine atrophy after childbirth

Question 27

Give reasons why pathological atrophy can occur.

Answer 27

1. Disuse- reduced functional demand or workload e.g. Skel muscle w/ cast on 2. Denervation atrophy 3. Inadequate blood supply 4. Inadequate nutrition (brain is last organ that would atrophy) 5. Loss of endocrine stimuli 6. Persistent injury 7. Senile atrophy (cells reach Hayflick limit) 8. Pressure e.g. From tumour

Question 28

What is atrophy of extracellular matrix?

Answer 28

Loss of bone matrix rather than Ca2+ etc. get if inactive or in space and not putting weight on bones. Increased fracture risk.

Question 29

Define metaplasia.

Answer 29

Reversible change of 1 differentiated cell type to another.

Question 30

Do you get metaplasia across germ layers?

Answer 30

No..e.g. Usually epithelium changes to diff type of epithelium.

Question 31

Which cell types can metaplasia occur in?

Answer 31

Labile or stable.

Question 32

Give examples of metaplasia.

Answer 32

1. Cigarette smoke causes bronchial pseudostratified ciliated epithelium-->stratified squamous 2. Persistent acid reflux causes stratified squamous epithelium--> gastric glandular epithelium (Barrett's oesophagus) 3. Bone marrow damage can cause spleen to diff to be able to produce blood cells 4. If start to exercise sooner than should after skel muscle exercise, get metaplasia of fibroblasts to osteoblasts

Question 33

Can metaplasia predispose to cancer?

Answer 33

Yes, but not known why. E.g. Barrett's epithelium and oesophageal cancer Intestinal metaplasia of stomach and gastric adenocarcinoma

Question 34

What is aplasia?

Answer 34

Complete failure of tissue or organ to develop (an embryonic developmental disorder), or whose cells have ceased to proliferate (e.g. Bone marrow in aplastic anaemia or post-chemo).

Question 35

What is hypoplasia?

Answer 35

Under/incomplete development of tissue/organ at EMBRYONIC STAGE due to inadequate no of cells. Congenital condition. E.g. Hypoplastic left heart syndrome

Question 36

What is involution?

Answer 36

Normal programmed shrinkage of organ. Some overlap with atrophy. E.g. Uterus after childbirth

Question 37

What is reconstitution and can it happen in humans?

Answer 37

- Replacement of a lost part of the body | - Generally doesn't but can if cut 1/2 finger off before 4 yrs old, will grow back.

Question 38

What is atresia?

Answer 38

Means 'no orifice'. | It is congenital imperforation of an opening e.g. Anus

Question 39

What is dysplasia?

Answer 39

An abnormal maturation of cells within a tissue. | Often pre-cancerous.