Gas exchange unit

Question 1

Which generation is the trachea?

Answer 1

0

Question 2

Which generation is the bronchi?

Answer 2

1

Question 3

Why does resistance to airflow decrease as you go down the airway?

Answer 3

Dichotamous branching means cross sectional area increases down the airways and so at the terminal bronchioles there is little resistance to airflow

Question 4

Why do the alveoli surround the airways?

Answer 4

To maximise the space

Question 5

How do the type 1 epithelial arrange themselves?

Answer 5

The type 1 epithelial cell takes the shape of whatever is underneath it because it is thin e.g. blood vessels.

Question 6

What are caveolae and their role?

Answer 6

Caveolae - they contain lots of lipid and are invaginations of membrane. They are thought to facilitate cell-cell talk. Lots suggest lots of cross talking.

Question 7

Where is surfactant stored, and how do they appear?

Answer 7

In amellar bodies in type 2 cells. Appear as whirls inside the lamellar body. Holes inside the bodies show where surfactant has left.

Question 8

Where is unused surfactant stored?

Answer 8

In the corner of the alveolus as tubular myelin

Question 9

What is the surface area of the whole lung equivalent to?

Answer 9

Tennis court surface

Question 10

Describe the thickness of surfactant in the lung

Answer 10

It is like a large glass of water spread across a tennis court surface

Question 11

How does surfactant reduce surface tension - talk about its composition?

Answer 11

Surfactant is 10% protein (important is spreading and surfactant’s role). 90% is lipid of which 90% is phospholipid. This has a lipophilic and hydrophilic ends so reduces surface tension.

Question 12

How can pulmonary vasculature vary?

Answer 12

From muscular to non-muscular

Question 13

What is fibrosing alveolitis?

Answer 13

More fibroblasts, more collagen deposition, damage to airways means more type 2 cells, more surfactant and so it increases the distance between air and blood

Question 14

What is idiopathic interstitial fibrosis?

Answer 14

Increased collagen deposition, activated mast cells recruiting fibroblasts

Question 15

How can bacteria affect the efficiency of gas exchange?

Answer 15

Bacteria make endotoxin which cause oedema - this can increase the distance between the capillary and alveolus. It can also cause increase type 1 cell cytoplasmic volume (overlies vessels) so increase the distance between the capillary and alveolar space.

Question 16

What is respiratory distress syndrome and what can cause it?

Answer 16

Caused by some kind of trauma e.g. an accident or infection. Hyaline membrane (glassy) over airways and alveoli making it hard for anything to cross. More inflammatory cells. Occurs a few days after trauma. Over about 2 weeks can cause fibrosis and more inflammation. This is dangerous and may require oxygen, can be fatal.