71 - Basic Lung Physiology

Question 1

Basic functions of the lungs
1)
2)
3)

Answer 1

1) Oxygenate pulmonary arterial blood
2) Remove CO2 from the blood
3) Maintain acid-base balance (CO2 is the most plentiful acid in the body)

Question 2

O2 supply given by resp system at rest

Answer 2

250mL/minute of O2

Question 3

CO2 removed from body by resp system at rest

Answer 3

200mL/minute

Question 4

Maximum O2 able to be supplied by resp system

Answer 4

4000mL/minute

Question 5

Maximum CO2 able to be removed from the body by resp system

Answer 5

4000mL/minute

Question 6

Results of inadequate lung function
1)
2)

Answer 6

1) Hypoxaemia (leading to tissue hypoxia)

2) Hypercapnoea and respiratory acidosis

Question 7

PaO2 aimed to be maintained by resp system

Answer 7

100mmHg

Question 8

PaCO2 aimed to be maintained by resp system

Answer 8

40mmHg

Question 9

pH aimed to be maintained by resp system

Answer 9

7.4

Question 10

Aspects of the upper airway

Answer 10

1) Nasopharynx
2) Oropharynx
3) larynx

Question 11

Aspects of lower airways

Answer 11

Trachea, bronchi, bronchioles

Question 12

Aspects of lung parenchyma

Answer 12

Alveoli, capillaries, interstitial spaces

Question 13

Components of respiratory system anatomy
1)
2)
3)
4)
5)
6)

Answer 13

1) Upper airways
2) Lower airways
3) Lung parenchyma
4) Pulmonary vasculature
5) Chest wall, pleura, respiratory muscles
6) Peripheral chemoreceptors, respiratory centre in the brain

Question 14

‘Trap door’ structure over the larynx

Answer 14

Epiglottis

Question 15

Thickness of alveolar membrane

Answer 15

Two cells thick. Shared basal lamina

Question 16

General rule for relationship between pressure in pulmonary circulation versus systemic circulation

Answer 16

Systemic pressure is ~ 10x that of pulmonary circulation

Question 17

Three broad physiological concepts for the lungs

Answer 17

Ventilation
Gas exchange
Perfusion of lungs

Question 18

Only time that lungs are being inflated by positive pressure being pushed into lungs

Answer 18

When sick, on a ventilator

Question 19

Effect of contracting external intercostals

Answer 19

Increases antero-posterior dimensions of the thorax

Question 20

Resistances to expansion of thorax

Answer 20

Resistance (friction of air going through airways), elasticity of lung tissue

Question 21

How should breathing appear under normal circumstances, at rest?

Answer 21

Shouldn’t be visible.

Question 22

Gas pressure in pulmonary arteries

Answer 22

40mmHg O2

46mmHg CO2

Question 23

Gas pressures in the athmosphere

Answer 23

150mmHg O2

~0mmHg of CO2 (less than you’d think)

Question 24

Gas pressures in pulmonary veins

Answer 24

98mmHg O2

40mmHg CO2

Question 25

Gas pressures in alveoli

Answer 25

PO2 is 100mmHg

PCO2 is 40mmHg

Question 26

Effect of difference in gas pressures between alveoli and pulmonary arteies

Answer 26

O2 into circulation, CO2 out

Question 27

Threats to the resp system
1)
2)
3)

Answer 27

1) Inhalation of foreign objects
2) Circulation
3) Flooding of alveoli

Question 28

Difference between signs of symptoms

Answer 28

Symptoms are what patients are complaining of.

Signs are what are detected in examination.

Question 29

Are there nociceptors in the lungs?

Answer 29

No

Question 30

Which lung structure is innervated with nociceptors?

Answer 30

Pleura.

Question 31

Quality of pleural pain

Answer 31

Sharp, very localised, very painful.

Question 32

Structures involved if there is coughing, wheezing?

Answer 32

Airways

Question 33

Structures involved if there is lung pain

Answer 33

Pleura

Question 34

Peripheral sign of respiratory disease

Answer 34

Nail clubbing (increased nail movement, strange club shape)

Question 35

Most useful signs in the respiratory exam
1)
2)

Answer 35

1) Percussion of chest

2) Stethoscope breath signs (extra signs: wheezes, crepitations, pleural rub)