Lecture 5

Question 1

What is the nutritive blood supply to the lungs called?

Answer 1

Bronchial circulation

Question 2

Describe bronchial circulation

Answer 2

Circulation supplied by the bronchial arteries to supply oxygenated blood to airway smooth muscle, nerves and lung tissue. It is part of the systemic circulation.

Question 3

Where do the pulmonary arteries originate from?

Answer 3

The right ventricle of the heart

Question 4

Describe the pulmonary circulation

Answer 4

It is a unique system that supplies the dense capillary network around the alveoli with deoxygenated blood and returns oxygenated blood to the heart.

Question 5

Where does the pulmonary vein end?

Answer 5

In the left atrium

Question 6

What type of system is the pulmonary circulation?

Answer 6

High flow, low pressure

Question 7

Down what gradient does air diffuse during gas exchange?

Answer 7

The partial pressure gradient

Question 8

What is the average PAO2?

Answer 8

100 mmHg

13.3 kPa

Question 9

What is the average PACO2?

Answer 9

40 mmHg

5.3 kPa

Question 10

What is the average PaO2?

Answer 10

100 mmHg

13.3 kPa

Question 11

What is the average PaCO2?

Answer 11

40 mmHg

5.3 kPa

Question 12

What is the average venous PO2?

Answer 12

40 mmHg

5.3 kPa

Question 13

What is the average venous PCO2?

Answer 13

46 mmHg

6.2 kPa

Question 14

Why is the rate of diffusion of CO2 not as low as expected in comparison to O2?

Answer 14

Because carbon dioxide is more water soluble than oxygen

Question 15

What does fibrosis of the lungs do?

Answer 15

Restricts the stretching of the lungs so reduces compliance. It also reduces diffusion by creating a physical barrier.

Question 16

What is Emphysema?

Answer 16

The destruction of barriers between alveoli creating large holes in the lungs, reducing surface area.

Question 17

What is the primary cause of Emphysema?

Answer 17

Smoking

Question 18

What is the ideal ratio of ventilation to perfusion?

Answer 18

1

Question 19

What is the distribution of blood flow in the lungs influenced by?

Answer 19

Hydrostatic pressure and alveolar pressure

Question 20

What is vascular resistance?

Answer 20

The resistance that must be overcome to push blood through the circulatory system

Question 21

Why is blood flow low at the apex of the lungs?

Answer 21

Because arterial pressure is less than alveolar pressure so the arterioles are compressed increasing vascular resistance

Question 22

Where is there the greatest amount of mismatch in ventilation and perfusion?

Answer 22

At the apex of the lungs

Question 23

What local control mechanism can be used to try to keep ventilation and perfusion matched?

Answer 23

Blood vessels can constrict in areas of low ventilation and blood flow is diverted to areas of better ventilation

Question 24

What happens when ventilation is less than blood flow?

Answer 24

PCO2 is increased and PO2 is decreased so blood flowing past does not get oxygenated

Question 25

What happens when ventilation is greater than blood flow?

Answer 25

Pulmonary vasodilation and bronchial constriction

Question 26

What is alveolar dead space?

Answer 26

Alveoli that are ventilated but not perfused

Question 27

Define shunt

Answer 27

Shunt describes blood moving through areas of the lung that are poorly ventilated

Question 28

What is physiological dead space?

Answer 28

Alveolar dead space and anatomical dead space