Lung anatomy and function

Question 1

1

Answer 1

Total lung capacity

the volume of air contained in the lungs at the end of maximal inspiration.

TLC = VC + RV

Question 2

2

Answer 2

Functional residual capacity

the resting volume at which the elastic recoil pressure of the lung inward equals the elastic recoil pressure of the chest wall outward, where alveolar and mouth pressure are both at 0 and there is no airflow.

This is the volume in the lungs just after passive expiration.

FRC = RV + ERV

Question 3

3

Answer 3

Residual volume

the air that is still contained in the lungs even after maximum contraction of the expiratory muscles. This volume cannot be measured by spirometry.

Question 4

4

Answer 4

Expiratory reserve volume

the fraction of gas that remains in the lungs after expiration. It can be exhaled by maximum contraction of the expiratory muscles.

Question 5

5

Answer 5

Inspiratory reserve volume

the (relatively large) volume of air that the lungs can still receive at termination of normal inspiration, achieved by maximum contraction of the inspiratory muscles.

Question 6

6

Answer 6

Vital capacity

the maximum volume of air that can be inhaled or exhaled: occurs when maximum inspiration is followed by maximum expiration.

VC = IRV + V_T + ERV

Question 7

7

Answer 7

Inspiratory capacity

the volume of air that can be inspired following a normal, quiet expiration.

IC = V_T + IRV

Question 8

8

Answer 8

Tidal volume (V_T) - in this case at rest

the volume of air flowing through the airways during each inspiration or expiration.

Question 9

Alveolar respiration (V_A)

Answer 9

volume of fresh air reaching the alveoli per minute.

Can be estimated = RR x (V_T - V_D)

Breathing pattern has great influence on alveolar ventilation: deep, slow breathing elevates alveolar ventilation whereas polypnoea reduces it.

Question 10

Anatomical dead space (V_D)

Answer 10

the conducting airways which do not participate in gas exchange and the air contained within them.

30-60% of V_T at rest.

Question 11

What is the relevance of the V:Q ratio?

Answer 11

• Optimal gas exchange requires good ventilation (V): blood flow (Q) ratio
• In quadrupeds (compared to humans), V:Q ratio is good
• Ventilation and perfusion are well-matched in different parts of the lung as long as the lung is healthy; disease may mismatch air/blood supply

Question 12

Describe the compensatory mechanism that exists to maintain good matching of ventilation and blood flow

Answer 12

• Compensatory mechanism: constriction of arterioles to poorly ventilated alveoli
• This means a greater proportion of pulmonary blood flow goes to well-ventilated regions of the lungs

Question 13

A ventilation/perfusion mismatch tends to affect levels of which gas more: oxygen or carbon dioxide?

Answer 13

• Affects O₂ more than CO₂
• Because CO₂ diffuses most rapidly of the two
• However, if mismatch exceeds a certain level, even CO₂ exchange is affected

Question 14

1

Answer 14

Costal pleura

Question 15

2

Answer 15

Diaphragmatic pleura

Question 16

3

Answer 16

Mediastinal pleura

Question 17

4

Answer 17

Visceral (pulmonary) pleura

Question 18

5

Answer 18

Cranial mediastinum

Question 19

5’

Answer 19

Cupula pleurae

Question 20

6

Answer 20

Plica venae cavae

Question 21

7

Answer 21

Costodiaphragmatic recess

Question 22

Porcine lungs

1

Answer 22

Right cranial lobe

Question 23

Porcine lungs

2

Answer 23

Right middle lobe

Question 24

Porcine lungs

3

Answer 24

Right caudal lobe

Question 25

Porcine lungs 5

Answer 25

Divided left cranial lobe

Question 26

Porcine lungs 6

Answer 26

Trachea

Question 27

Porcine lungs 7

Answer 27

Tracheal bronchus

Question 28

Porcine lungs 8

Answer 28

Right cardiac notch

Question 29

Porcine lungs 9

Answer 29

Basal border