Lung/Trachea Development

Question 1

Lungs are derived from which two tissues?

Answer 1

Endoderm

Mesoderm

Question 2

Endoderm gives rise to which lung structures?

Answer 2

Trachea, larynx, bronchi, alveoli

Question 3

Mesoder gives rise to which lung structures?

Answer 3

Cartilage, muscle and connective tissue

Question 4

Buds made from branching morphogenesis form which lung structures?

Answer 4

Trachea -> Bronchi -> Bronchioles -> Alveoli

Question 5

The trachea, bronchi etc rise from what?

Answer 5

The respiratory diverticulum

Question 6

How is respiratory diverticulum formed?

Answer 6

The foregut splits in to the oesophagus and the trachea as a result of the hox code

Question 7

In humans when do lung buds form?

Answer 7

During the forth week?

Question 8

The outgrowth of the respiratory diverticulum is dependent on signals from where?

Answer 8

The adjacent mesoderm/mesenchyme

Question 9

Which model organism was used to understand tracheal development?

Answer 9

Drosophila

Question 10

Bud extension occurs because nearby mesenchyme expresseds which gene?

Answer 10

FGF

Question 11

Exposure of high FGF induces the expression of which genes in the tip of the bud?

Answer 11

BMP4, Shh and Sprouty2

Question 12

Where is BMP4 expressed at the highest level in the bud?

Answer 12

In the leading edge tip cells

Question 13

What is the effect of the high BMP4 in the leading edge tip cell?

Answer 13

It autonomously inhibits epithelial cell proliferation so it limits branch extension and causes the bud to flatten

Question 14

What is the effect of the Shh which is expressed by the tip cells?

Answer 14

It diffuses to the mesenchyme and inhibits FGF10 expression in the mesenchyme nearest the tip
This splits the expression of FGF10 promoting th enext round of branching

Question 15

What is the action of sprouty2?

Answer 15

Sprouty2 limits the action of FGF10 so that branching is restricted to one end of the branch

Question 16

Which of the genes expressed in the leading tip cell as a result of FGF is activated later?

Answer 16

Sprouty2

Question 17

Why is sprouty activated later?

Answer 17

It is an inhibitor of FGF10 so it sets up a negative feedback loop to limit the time FGF can cause any action

Question 18

By the end of 6 months of gestation how many generations of subdivisions have formed?

Answer 18

17

Question 19

How many more divisions occur in postnatal life?

Answer 19

23

Question 20

The formation of alveoli attracts what?

Answer 20

Endothelial blood cells which come in to close contact and provide an extensive network for gas exchange

Question 21

What fraction of adult alveoli is present at birth?

Answer 21

A sixth

Question 22

Why is a conditional knockout used?

Answer 22

This is where the gene is lost at the right place and the right time
It is used as otherwise the organism would die before you could look at the effect of losing a gene on a particular organ

Question 23

Give an example of a conditional knockout experiment in mice mammary glands

Answer 23

Rac1 knockout in the mammary glands mean they do not undergo branching morphogenesis
They have a ‘baobab tree’ phenotype

Question 24

What happens if a cell loses its apico-basal polarity?

Answer 24

It thinks it no longer needs to be in an epithelium, meaning it leaves and potentially causes cancer

Question 25

List examples of other organs that use branching morphogenesis

Answer 25

Salivary gland, Prostate, Mammary gland, Pancreas