Growth adaptations

Question 1

What are the two principles by which organ size is increased?

Answer 1

1. Hypertrophy

2. Hyperplasia

Question 2

What is the definition of ‘Hypertrophy’

Answer 2

1. Increase in the size of the cell

2. Involves gene activation, protein synthesis and production of new organelles

Question 3

Which cells can only undergo hypertrophy?

Answer 3

1. Cardiac muscle cells
2. Skeletal muscle cells
3. Nerve cells

Question 4

What is the definition of ‘Hyperplasia’

Answer 4

Production of new cells from stem cells

Question 5

Which is the notable exception for pathological hyperplasia?

Answer 5

BPH - does not increase risk of prostate cancer.

Question 6

What is the definition of ‘atrophy’

Answer 6

Decrease in stress (disuse/hormonal stimulation/blood supply) leads to decrease in organ size.

• decrease in cell number via apoptosis
• decrease in cell size via ubiquitin-proteosome degredation and autophagy of cellular components

Question 7

Describe the process of ‘Ubiquitin-proteosome degradation’

Answer 7

A cell’s mechanism to mark a protein for destruction
mechanism;
1. Several copies of ubiquitin added to a misfolded/unneeded protein
2. polyubiquitinated protein enters the proteasome
3. protein hydrolyzed into peptide fragments by a proteosome

Question 8

Describe the process of ‘Autophagy of cellular components’.

Answer 8

Autophagy is the natural degradation of the cell that removes unnecessary or dysfunctional components via autophagic vesicles.

These vacuoles fuse with lysosomes whose hydrolytic enzymes breakdown cellular components.

Question 9

What is the definition of ‘metaplasia;

Answer 9

1. . Change in stress of an organ leads to change in cell type
2. Metaplastic cells are better able to handle this new cells.
3. Metplasia occurs via reprogramming of stem cells which produce a new cell type
4. Metaplasia in theory is reversible if new stressor is removed.

Question 10

Describe the process of metaplasia in ‘Barret’s oesophagus’.

Answer 10

1. Gord causes change from ‘non keratinising squamous epithelium to ‘non cilated columnar cells’.
2. Under persistent stress - can result in adenocarcinoma

Question 11

Describe how vitamin A deficiency can lead to metaplasia?

Answer 11

1. Vitamin A is important in differentiation of specialised epithelial surfaces such as conjunctiva covering the eye
2. Vit A deficiency
   Thin squamous lining of conjunctiva undergoes metaplasia into stratified keratinizing squamous epithelium.
3. This process is called ‘Keratomalacia’

Question 12

Describe how connective (mesenchymal) tissue can undergo metaplasia?

Answer 12

‘Myositis ossificans’ - connective tissue within muscle changes to bone during healing after trauma.

Question 13

What is the definition of dysplasia?

Answer 13

1. Disordered cellular growth causing proliferation of precancerous cells
2. Is reversible but can progress to carcinoma if stress persists

Question 14

What is the definition of aplasia?

Answer 14

A failure of cell production during embryogenesis e.g. unilateral renal agenesis

Question 15

What is the defintion of Hypolasia?

Answer 15

A decrease in cell production during embryogenesis resulting in a small orgsn
e.g. steak ovary in Turner syndrome