Pathology - Cellular Adaptations

Question 1

How is cell proliferation controlled?

Answer 1

• chemical signals from the microenvironment can simulate/inhibit cell proliferation
• signalling molecules bind to a receptor, causing modulation of gene expression
• receptors usually in cell membrane, but can be in cytoplasm/nucleus

Question 2

How can a cell population be increased?

Answer 2

• shorten the cell cycle

- convert quiescent cells to proliferating cells by making them enter the cell cycle

Question 3

How does the body determine whether a cell is able to replicate?

Answer 3

It has checkpoints in mitosis, where it checks that the DNA has replicated successfully and the cell is big enough

Question 4

What is the restriction point?

Answer 4

Most critical checkpoint - the majority of cells which pass this will complete the cell cycle. Checkpoint activation delays cell cycle and triggers DNA repair mechanisms/apoptosis via p53

Question 5

What are cyclins?

Answer 5

Cyclins and cyclin dependent kinases (CDKs) are active during different phases of the cell cycle. Cyclin activates CDK, which phosphorylates the target protein (which is bound to cyclin)

Question 6

What is hyperplasia?

Answer 6

Increase in tissue or organ size due to increased cell numbers

Question 7

What is hypertrophy?

Answer 7

Increase in tissue or organ size due to increased cell size

Question 8

What is atrophy?

Answer 8

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

Question 9

What is metaplasia?

Answer 9

Reversible change of one differentiated cell type to another

Question 10

What types of tissue does hyperplasia occur in?

Answer 10

Labile/stable tissues

Question 11

What causes hyperplasia?

Answer 11

• increased functional demand/hormonal stimulation

- can occur secondary to a pathological cause but proliferation is normal response

Question 12

Is hyperplasia reversible?

Answer 12

Yah

Question 13

In which types of tissue does hypertrophy occur?

Answer 13

Labile, stable but especially permanent

Question 14

Does hypertrophy usually occur alone in tissue?

Answer 14

No, it usually occurs along with hyperplasia

Question 15

Why don’t athletes get cardiac muscle hypertrophy despite their muscle being under more strain?

Answer 15

They have a rest between exercises, so the strain on their heart goes back to normal. Obese people cannot ‘rest’ their heart, so they always have stress on it

Question 16

What is compensatory hypertrophy?

Answer 16

If one of a pair of organs is damaged/removed, the other will enlarge, eg kidneys

Question 17

What happens to a cell in atrophy?

Answer 17

The cell shrinks to a size at which survival is still possible. There are reduced structural components, which may eventually result in cell death.

Question 18

What is the relationship between cell atrophy and tissue atrophy?

Answer 18

Organ/tissue atrophy is typically due to combination of cellular atrophy and apoptosis, which is reversible up to a point

Question 19

What are ‘residual bodies’?

Answer 19

These break off from cells undergoing atrophy, and contain unnecessary organelles

Question 20

Give an example of atrophy due to reduced functional demand/workload

Answer 20

Muscle atrophy after disuse - this is reversible with activity

Question 21

Why may the hand muscles become wasted in just one part of the hand?

Answer 21

Median nerve damage leads to atrophy

Question 22

Give an example of atrophy due to inadequate blood supply

Answer 22

Thinning of skin on legs with peripheral vascular disease

Question 23

What is atrophy of the extracellular matrix called in older people?

Answer 23

Osteoporosis

Question 24

Which cell types have metaplasia?

Answer 24

Labile or stable tissues

Question 25

Is there a link between metaplasia and cancer?

Answer 25

Epithelial metaplasia can be a prelude to to dysplasia and cancer

Question 26

What is aplasia?

Answer 26

Complete failure of a specific tissue/organ to develop - this is an embryonic developmental disorder eg. Aplasia of a kidney

Question 27

What is hypoplasia?

Answer 27

Underdevelopment or incomplete development of a tissue or organ at embryonic stage due to an inadequate number of cells

Question 28

What is involution?

Answer 28

Normal programmed shrinkage of an organ which overlaps with atrophy. Eg. Occurs in uterus after childbirth

Question 29

What is reconstitution?

Answer 29

Replacement of a lost part of the body. Angiogenesis is the only mechanism for this in humans

Question 30

What is atresia?

Answer 30

Congenital imperforation of an opening, eg lack of an anus, vagina or small bowel

Question 31

What is dysplasia?

Answer 31

Abnormal maturation of cells within a tissue. This is potential reversible and an often pre-cancerous condition