L64: Gas Exchange

Question 1

In alveoli and capillaries, what gradient do gases move from?

Answer 1

Down a concentration/ pressure gradient

Question 2

Airways branch into smaller and more numerous bronchioles until terminating to a group of alveoli, describe the respiratory tree:

Answer 2

Trachea >
Bronchi >
Nonrespiratory bronchioles >
Respiratory bronchioles >
Alveoli

Question 3

What happens through each division of the respiratory tree?

Answer 3

• Increase in number of units;
• Decrease in diameter;
• Increase in SA.

Question 4

What is a conducting airway?

Answer 4

Bronchi containing cartilage and non-respiratory bronchioles

Question 5

What is a respiratory airway?

Answer 5

Bronchi with alveoli where gas exchange occurs

Question 6

What is a respiratory unit?

Answer 6

The physiological unit of the lung, a gas exchanging unit

Question 7

What is the difference between a terminal and respiratory bronchiole?

Answer 7

A respiratory bronchiole has alveoli

Question 8

How many alveolar sacs do adults typically have?

Answer 8

~300-400 million

Question 9

What is the diameter of alveoli? (polygonal in shape)

Answer 9

~250μm

Question 10

What type of cells do alveolar epithelium comprise of?

Answer 10

Type I and type II (septal) cells

Question 11

What is the most dominant type of alveolar epithelial cell?

Answer 11

Type I, these cover 97% of the surface area

Question 12

What is the primary function of type I alveolar epithelial cells?

Answer 12

Site of gas exchange

Question 13

What is the primary function of type II alveolar epithelial cells?

Answer 13

To produce pulmonary surfactant, this reduces surface tension

Question 14

What is the primary function of alveolar macrophages?

Answer 14

Removal of debris

Question 15

How are alveoli specialised to carry out their function?

Answer 15

• Large surface area (~100m^2);
• Thin walls (~0.5μm);
• Good diffusion characteristics.

Question 16

What are the blood supplies for the lung?

Answer 16

• Pulmonary Circulation (heart and lungs);

- Bronchial Circulation (O2 to parenchyma)

Question 17

What does the lymphatic system do?

Answer 17

Supports the body from pathogens through supporting the immune response and removes lymph fluid

Question 18

What is the total volume of blood in pulmonary circulation ?

Answer 18

500mLs

Question 19

At rest, how much blood is in the alveolar-capillary network?

Answer 19

75mLs

Question 20

During exercise, how much blood is in the alveolar-capillary network?

Answer 20

150-200mLs, through recruitment of more capillaries

Question 21

How are alveolar capillaries specialised to perform their function?

Answer 21

• Thin-walled;
• Highly compliant;
• Larger diameter
• Lower resistance than in systemic circulation.

Question 22

Describe the alveolar-capillary network:

Answer 22

• Network for gas exchange;
• Dense, mesh-like network of capillaries, alveoli and rbc;
• 1-2μm between alveoli and rbc;
• abc pass through capillaries in <1 second, sufficient for gas exchange.

Question 23

In pulmonary circulation, X gas enters and Y gas leaves

Answer 23

X: Oxygen, Y: Carbon Dioxide

Question 24

In systemic circulation, X gas enters and Y gas leaves

Answer 24

X: Carbon Dioxide, Y: Oxygen

Question 25

What are the pressures of O2 and CO2 in pulmonary circulation?

Answer 25

O2 (venous blood): 40
O2 (alveolar air): 100

[air to blood]

CO2 (venous blood): 46
CO2 (alveolar air): 40

[blood to air]

Question 26

What are the pressures of O2 and CO2 in systemic circulation?

Answer 26

O2 (arterial blood): 100
O2 (tissues): 40

[blood to tissues]

CO2 (arterial blood): 40
CO2 (tissues): 46

[tissues to blood]