Adaptations Of Cell Growth: Cell Injury

Question 1

The cell’s response may be a change in 4 things

Answer 1

number
size
phenotype
metabolism
Etc

Question 2

● Adaptations are a cell’s response to?

Answer 2

changes in its environment.

Question 3

4 types of adaptation and slight explanation

Answer 3

• Hyperplasia : increase in cell number
● Hypertrophy : increase in cell size
● Metaplasia : change in cell phenotype
● Atrophy : reduction in cell size/number

Question 4

Hypertrophy
● Increase in cell size which leads to?
● Seen in cells which?

Answer 4

1. increase in the size of the organ.
2. cannot multiply by division

May also be seen in cells which undergo division (hyperplasia/hypertrophy)

Question 5

Hypertrophy Occurs as a result of

Answer 5

synthesis of increased structural elements in the affected cells

Question 6

Can be physiologic or pathologic

● Physiologic hypertrophy results from ______ or ______

Answer 6

increased stimulation of the cell by hormones or increased functional demand.

E.g.
skeletal muscle in weightlifters

growth of the uterus in pregnancy.

Question 7

● Pathologic hypertrophy is a response to _____

Examples include?

Answer 7

Disease

In aortic stenosis,
hypertension,
also in hypertrophic cardiomyopathy

when the heart muscle pumps against resistance in certain disease conditions

Question 8

What is the mechanism of Hypertrophy

Answer 8

Increased synthesis of intracellular proteins

Question 9

The combined actions of _____, ______and g_____ lead to generation of signals which are transmitted into the cell through signal transduction pathways. These signals activate transcription factors which increase?

Answer 9

Mechanical sensors
Vasoactive agents
Growth factors

the synthesis of muscle proteins.

Question 10

Other adaptive changes can occur in hypertrophy. For example?

Answer 10

change from alpha to beta isoform of myosin heavy chain, increases expression of atrial natriuretic factor gene in states of cardiac hypertrophy.

Question 11

Hypertrophy has its limits beyond which the enlargement of muscle mass cannot cope with the stimuli. This may lead to ____ &____

Answer 11

fibrosis and myocyte death.

Question 12

Hyperplasia is?

It may occur together with hypertrophy if the cell is capable of?

Answer 12

Increase in the number of cells in a particular organ/tissue

Dividing

Question 13

Physiologic hyperplasia there’s 2 types
Give examples

Answer 13

● Functional: when there is a need to increase functional capacity e.g. breast in puberty/pregnancy.

● Compensatory: need to replace function of damaged cells e.g. liver post-resection and bone marrow after blood loss.

Question 14

Pathological hyperplasia results from excessive or inappropriate actions of _____ or _____.

Pathologic hyperplasia may be _____

Answer 14

hormones or growth factors

Pre cancerous

Question 15

3 examples of pathologic hyperplasia

Answer 15

Endometrial hyperplasia due to increase in estrogen

○ Benign prostatic hyperplasia due to androgen effects

Skin changes in response to viral infections (warts in Human Papillomavirus infections)

Question 16

Mechanism of hyperplasia

Answer 16

Growth factor driven proliferation of existing cells

Increased output of new cells from stem cells

Question 17

Atrophy is ?

● Maybe physiologic or pathologic.

Answer 17

Reduction in the size of a tissue or organ due to a reduction in cell size and number

Question 18

Example of physiologic atrophy

Answer 18

in regression of uterus to normal size post pregnancy.

Question 19

6 types of pathologic atrophy and explanation

DDINEP

Answer 19

1. Decreased workload (disuse atrophy): e.g. muscle atrophy following fracture/ prolonged bed rest
2. Denervation atrophy: muscles need nerve stimulation to metabolism and function
3. Ischaemia : due to atherosclerosis. E.g. senile atrophy in the brain & heart
4. Inadequate nutrition: skeletal muscle proteins may be used as energy source.
5. Loss of endocrine stimulation: e.g. breast, uterus
6. Pressure effects: tissue compression for long periods of time.
   E.g. by a tumour or POP cast (fracture)

Question 20

The purpose of atrophy is to?

Answer 20

create a new balance between the cell’s demands and its supply of nutrients/oxygen.

Question 21

3 mechanisms of atrophy

Answer 21

1. Increased degradation and reduced synthesis of proteins.
2. Protein synthesis is reduced due to the reduction in metabolism
3. Degradation of protein occurs through the
   ubiquitin-proteasome pathway and through autophagy.

Question 22

Metaplasia is a reversible cell change in which?

But it really is ?

Answer 22

one differentiated cell type is replaced by another cell type.

The reprogramming of stem cells to differentiate along a new pathway

Question 23

It is an adaptive change to stress such that_____ replaces _____

● However, the functional effects of the original cell may be lost and these changes may be ______

Answer 23

the cell better able to withstand the stress

the cell sensitive to the stress.

Pre cancerous

Question 24

Give the 3 metaplasmic changes and their examples

Answer 24

1. Columnar to squamous epithelial changes:
   - Respiratory tract e.g smokers, Vit A deficiency/excess
   - Excretory ducts e.g. salivary glands, bile duct
2. Squamous to columnar changes:
   - Oesophagus (Barett’s oesophagus)
3. Connective tissue metaplasia
   - Myositis ossificans

Question 25

Mechanism of metaplasia is

Answer 25

Reprogramming of stem cells found in that tissue or of undifferentiated mesenchymal cells in surrounding tissues.

The environmental stimulants program these cells towards a differentiation pathway

These precursor cells differentiate along a new pathway due to the expression of genes induced by external stimuli and transcription factors

Question 26

Effects of metaplasia

Answer 26

Fertile ground for development of malignancy.
E.g. is Barrett’s oesophagus leading to sq