7. Cellular Adaptations

Question 1

What 3 processes influence the size of a cell population?

Answer 1

Rate of proliferation, cell differentiation and cell death by apoptosis.

Question 2

Which genes regulate normal cell proliferation?

Answer 2

Proto-oncogenes

Question 3

What 2 processes could lead to an increase in cell numbers?

Answer 3

Increased proliferation or decreased cell death.

Question 4

Name the phases of the cell cycle, in the correct order.

Answer 4

G1, S, G2, M

Question 5

What happens to cells which exit the cell cycle?

Answer 5

Enter G0 until further growth signals occur.

Can undergo terminal differentiation where there is a permanent exit from the cell cycle.

Question 6

What 2 mechanisms can lead to increased growth of a tissue?

Answer 6

1. Shortening of cell cycle

2. Conversion of cells in G0 to proliferating cells, making them re-enter the cell cycle.

Question 7

Which phase of the cell cycle is visible under a light microscope?

Answer 7

Mitosis

Question 8

What is the name given to the cell cycle between M phases?

Answer 8

Interphase

Question 9

How is cell cycle progression controlled?

Answer 9

Checkpoints - sense damage to the DNA, ensuring cells with damaged DNA do not replicate.

Question 10

What is the most critical cell cycle checkpoint? Explain its significance.

Answer 10

The restriction (R) point towards the end of G1. The majority of cells that pass this point will go on to complete the cell cycle - no more signals are needed.

Question 11

What occurs if checkpoints are activated (e.g by DNA damage)?

Answer 11

P53 protein - suspends cell cycle, triggers DNA repair mechanisms, if damage irreparable then trigger apoptosis.

Question 12

Other then R, where are the other checkpoints in the cell cycle and what are their main functions?

Answer 12

G1/S transition - checks for DNA damage before replication

G2/M transition - checks for DNA damage after replication

Question 13

Defective cell cycle checkpoints are associated with which disease?

Answer 13

genetic instability in cancer cells.

Question 14

Which enzymes play a role in the control of the cell cycle?

Answer 14

Cyclin-dependent kinases (CDK)

Question 15

What is the name of the proteins which bind to the CDK enzyme to control the cell cycle?

Answer 15

Cyclins

Question 16

How do CDK and cyclins control the cell cycle?

Answer 16

Cyclin binds to CDK, activating the enzyme. The activated kinase phosphorylates proteins to drive the cell cycle.

Question 17

What is hyperplasia?

Answer 17

Growth by increasing cell number

Question 18

Which tissues can undergo hyperplasia?

Answer 18

Stable and labile

Question 19

What causes hyperplasia and hypertrophy?

Answer 19

Increased functional demand or hormonal stimulation

Question 20

What is a physiological example of hyperplasia?

Answer 20

Proliferation of bone marrow to produce erythrocytes in response to hypoxia.
Proliferative endometrium under oestrogen influence

Question 21

What is a pathological example of hyperplasia?

Answer 21

Thryoid goitre

Eczema - epidermis hyperplasia

Question 22

What is hypertrophy?

Answer 22

Increase in tissue or organ size due to increased cell size

Question 23

Which tissues undergo hypertrophy?

Answer 23

Particularly permanent tissues

Stable and labile too usually in combination with hyperplasia.

Question 24

What is an example of physiological hypertrophy?

Answer 24

Skeletal muscle

Pregnant uterus - hypertrophy of SM cells

Question 25

What is an example of pathological hypertrophy?

Answer 25

Cardiac hypertrophy | If enlarged pancreas, SM of bladder hypertrophies due to increased resistance

Question 26

What is an example of compensatory hypertrophy?

Answer 26

If one kidney is removed or damaged, the other enlarged by both hyperplasia and hypertrophy

Question 27

What is atrophy?

Answer 27

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

Question 28

What may be visible under an electron microscope in cells undergoing atrophy?

Answer 28

Residual bodies - packing of inessential components of the cell

Question 29

What is an example of physiological atrophy?

Answer 29

Ovarian atrophy in post-menopausal women | Uterus after childbirth

Question 30

What is an example of pathological atrophy?

Answer 30

Disuse atrophy Denervation atrophy Inadequate blood supply Ageing

Question 31

Is atrophy reversible?

Answer 31

Yes, up to a point...

Question 32

What is metaplasia?

Answer 32

Change of one differentiated cell type to another due to altered stem cell differentiation

Question 33

Is metaplasia reversible?

Answer 33

Yes

Question 34

What cellular adaptation can be a prelude to dysplasia and cancer?

Answer 34

Metaplasia

Question 35

When might metaplasia occur?

Answer 35

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

Question 36

Does metaplasia occur across germ layers?

Answer 36

No. | E.g epithelium -> epithelium

Question 37

What tissues can undergo metaplasia?

Answer 37

Stable or labile

Question 38

How can smoking cause metaplasia, what is a possible long term complication?

Answer 38

bronchial epithelial changes from pseudostratified columnar, ciliated epithelium to stratified squamous epithelium. Can lead to squamous cell carcinoma.

Question 39

Other than smoking, what is another example of metaplasia?

Answer 39

Barrett's oesophagus - stratified squamous epithelium becomes gastric glandular epithelium in response to gastric reflux.

Question 40

How does the spleen demonstrate metapalsia?

Answer 40

Myeloid metaplasia - Extramedullary haemotopoiesis to produce blood cells

Question 41

Barretts oesophagus is linked to which cancer?

Answer 41

Oesophageal adenocarcinoma

Question 42

Intestinal metaplasia of the stomach is linked to which cancer?

Answer 42

Gastric adenocarcinoma

Question 43

What effect does tamoxifen have on the endometrium?

Answer 43

Can cause endometrial hyperplasia and progression to endometrial cancer.

Question 44

What are some common causes of LV hypertrophy?

Answer 44

Aortic stenosis, Hypertension, IHD, Mitral regurgitation, aortic regurgitation.

Question 45

How does LV hypertrophy increase risk of sudden death?

Answer 45

No increase in capillary numbers, so increased oxygen demand which is not met by an increased supply. Fibrous tissue can cause arrhythmia and failure.

Question 46

What are some common causes of cerebral atrophy?

Answer 46

Alzheimer's disease | Huntington's disease

Question 47

What is a common cause of intestinal metaplasia of the stomach?

Answer 47

Chronic Helicobacter pylori infection

Question 48

What function is lost when bronchial squamous metaplasia occurs?

Answer 48

Mucus secretion and cilia to waft mucus along,

Question 49

What metaplasia occurs in columnar epithelium lining ducts secondary to chronic irritation by stones, how is this beneficial?

Answer 49

Stratified squamous epithelium- more resistant to mechanical abrasion

Question 50

Give an example of when flat, non-secreting epithelium is replaced by secreting epithelium?

Answer 50

Lower oesophagus in Barrett's oesophagus