MoD S7 - Cellular adaptations

Question 1

What is a growth factor and what codes for their production?

Answer 1

Local chemical mediator involved in cell proliferation

Proto-oncogenes code for growth factors

Polypeptide chain that binds to specific cell surface receptors and stimulates the transcription of genes that control the entry of the cell into the cell cycle

Question 2

List the phases of the cell cycle and where the key checkpoints occur

Answer 2

G1, S, G2, Mitosis and Cytokinesis

Restriction point - End of G1

G1/S transition

G2/M

Question 3

What is the restriction point and why is it relevant to cancer?

Answer 3

Checkpoint that occurs at end of G1

Once a cell has passed G1 it is likely to complete the entire cell cycle

The restriction point is the most commonly altered checkpoint in cancerous cells leading to unchecked cell growth

Question 4

What processes occur in a cell once a checkpoint has been activated?

Answer 4

p53 delays the cell cycle, stimulates DNA repair mechanisms and if damage is too extensive then activates apoptosis

Question 5

What stages of the cell cycle are visible under a light microscope?

Answer 5

M phase (mitosis and cytokinesis)

Question 6

What changes occur to the cell cycle in order to increase tissue growth?

Answer 6

Shortening of cell cycle or stimulation of quiescent cells to enter the cell cycle

Question 7

Outline how the cell cycle is controlled including the relevant proteins and enzymes

Answer 7

• Different cyclins are produced at each stage of the cell cycle
• These activate cyclin-dependant kinase
• This once activated, phosphorylates regulatory proteins that enable progression to the next stage of the cell cycle such as RB protein
• CDK is controlled by CDK inhibitor molecules

Question 8

What is regeneration?

Answer 8

Replacement of cell losses by identical cells to maintain tissue or organ size

Question 9

What is the Hayflick number in humans and what does it represent?

Answer 9

61.3 - number of cell divisions that can occur

Question 10

What is reconstitution?

Answer 10

Replacement of a lost part of the body, involving coordinated regeneration of multiple cell types

Question 11

What is hyperplasia and what tissues are capable of it?

Answer 11

Increase in tissue or organ size due to increased cell number

Labile and stable cells are capable of this process

Question 12

What is a potential consequence of hyperplasia as the number of cell divisions increases?

Answer 12

Increased risk of mutation due to high rate of cell division

Question 13

List a pathological and physiological example of hyperplasia in the body

Answer 13

Pathological - Thyroid goitre due to iodine deficiency, psoriasis

Physiological - Endometrium under influence of oestrogen, bone marrow release of erythrocytes in hypoxia

Question 14

What is hypertrophy and which types of cells are more likely to undergo this process?

Answer 14

Increase in tissue or organ size due to an increase in cell size

Permanent cell populations are more likely to undergo hypertrophy but it can occur alongside hyperplasia in labile and stable cells

Question 15

Why does hypertrophy occur?

Answer 15

Due to increased functional demand or hormonal stimulation

Question 16

List a pathological and physiological example of hypertrophy in the body

Answer 16

Pathological‐ ventricular hypertrophy in cardiac pathologies, urinary bladder when prostate gland is enlarged

Physiological‐ skeletal muscle in body building, pregnant uterus

Question 17

What is atrophy and what is a possible physiological example of atrophy in the body?

Answer 17

Shrinkage of tissue or organ due to an acquired decrease in cell number and/or size

• Occurs in the ovaries post-menopause

Question 18

List the pathological types of atrophy and an example of each

Answer 18

Disuse e .g. muscles after bed rest

Denervation e .g. median nerve damage causes atrophy of thenar muscles in hand

Inadequate blood supply e .g. thinning of skin on legs in peripheral vascular disease

Inadequate nutrition e .g. muscle wastage

Ageing (senile) e.g. brain and heart decrease in size

Persistent injury e .g. polymyositis of the muscles

Pressure e.g. tissues around a benign tumour

Loss of endocrine stimuli e.g. breast tissue

Question 19

What is metaplasia and why does it occur?

Answer 19

Reversible change of one differentiated cell type to another

Due to altered stem cell differentiation

Adaptive substitution of cell sensitive to stress with differentiated cell better able to withstand the adverse environment

Question 20

What are the limitations to metaplasia?

Answer 20

Only occurs in cells that can replicate and cannot occurs across germ layers

Question 21

Where would toxins from cigarette smoking cause metaplasia and what are the consequences of this in terms of function?

Answer 21

Bronchial psuedostratified columnar ciliated epithelium is replaced by stratified squamous

Results in loss of function as can no longer produce mucus and the mucociliary escalator is inhibited

Question 22

Outline the similarities and differences between in aplasia and hypoplasia

Answer 22

Similarities‐ both are embryonic developmental defects

Differences‐ aplasia is complete failure of a tissue to develop whereas hypoplasia is incomplete
development

Question 23

What is involution and when may it occur as a physiological process?

Answer 23

Normal programmed cell shrinkage

Occurs in the uterus after childbirth

Question 24

What is atresia

Answer 24

Failure of an orifice to develop

Question 25

What is dysplasia and why is it a potential cause for concern?

Answer 25

Abnormal cells present within a tissue

Often pre-cancerous