Respiratory L3.1

Question 1

1) How do lungs enable gas exchange?

2) How much oxygen must blood pick up at rest to meet needs?

3) State 3 factors needed for efficient gas exchange in the lungs

4) Why is a large SA important for gas exhange?

Answer 1

1) Allow air on one side + blood on other side of thin membrane to exchange gases. Allowing oxygen to enter blood + CO2 to exit

2) At rest, 5 liters of blood must pick up 12 mmol of oxygen per minute.

3) Large surface area
Large no of small components (alveoli
proximity to blood

4) More O2 diffuse into blood + more CO2 removed, more efficient gas exchange

Question 2

1) How many divisions are there in the airway tree?

2) What does trachea branch into?

3) After primary bronchi, what do airways divide into?

4) What do bronchi become as they divide further?

Answer 2

1) >20

2) Primary bronchi

3) Secondary (LOBAR) bronchi, then tertiary (segmenal) bronchi

4) Bronchioles, then terminal bronchioles

Question 3

1) What occurs in the respiratory airways?

2) what are the components of respiratory airways?

3) Wht is large no of alveoli important?

Answer 3

1) gas exchange
2) respiratory bronchioles, alveolar ducts, alveoli
3) Large SA, efficient gas exchange

Question 4

1) Describe blood supply of alveoli

2) How are the blood vessels in pulmonary circulation structured?

Answer 4

1) Each alveolus surrounded by capillary, allow for efficient gas exchange between alveoli + blood

2) Form branhing network, simlar tree like structure of airway

Question 5

1) What characterises pulmpnary circulation in terms of resistance and pressure?

2) How does pulmonary circulation compare to systemic circulation in terms of blood flow?

3) What is the typical mean pulmonary arterial pressure?

4) What is the systolic and diastolic pressure in the pulmonary circulation?

5) Why does the low pressure in pulmonary circulation prevent fluid build up in the lungs?

Answer 5

1) LOW RESISTANCE, ,LOW PRESSURE

2) Pulmonary is SUPPLY-DRIVEB, meaning it receives entire carediac output, unlike systemic which is demand led.

3) 14-18 mm Hg.

4) Systolic: 20-25 mm Hg.
Diastolic: 4-12 mm Hg.

5) LOW PRESSURE ensures fluid does not leak inti lungs. However, in certain diseases, this can be disrupted, causing fluid accumulation

Question 6

1) What does the hydrostatic pressure gradient do in the lungs?

2) What is the role of oncoric (colloid osmotic) pressure gradient?

3) How do hydrostatic + oncotic pressure gradients interact? (i.e. how is fluid balance maintained in lungs?)

Answer 6

1) Drives flyid out of pulmonary microcirculation into intersitium (space surrounding blood vessels and lung tissue)

2) OPPOSES HYDROSTATIC PRESSURE: favours movement of fluid back into blood vessels

3) Hydrostatic pressure pushes fluid out of blood vessels, oncotic pressure pylls fluid back in, helping maintain FLUID BALANCE IN LUNGS

Question 7

What is the abnormality shown?

Answer 7

PULMONARY OEDEMA

Question 8

1) How do gases move from alveolus to blood?
2) What three factors affect gas exchange in lungs?
3) How does SA affect gas exchange?
4) What role do gradients play in gas exchange?
5) How does nature of barrier affect gas exchange ?

Answer 8

1) Gases move via diffusion from area of high conc to low conc
2) Area, gradients, diffusion resistance
3) Large SA (provided by high no of alveoli) = more efficient gas exchange
4) Difference in partial pressure of oxygen and carbon diocide drives diffusion between alveols and blood
5) Thinner barrier (alveolar capillary membrane) allows gas to diffuse more easily bewteen alveolus + blood

Question 9

EMPHYSEMA

Answer 9

DAMAGED ALVEOLI

Question 10

1) What creats gadients needed for gas exchange in the lungs?

2) How does composition of alveolar air differ from atmosphere?

3) What is mixed venous blood and how does its composition differ?

4) What is the typical pO₂ and pCO₂ in mixed venous blood?

Answer 10

1) Alveolar air composition + gases in blood returning to lungs

2) Alveolar air has a different composition:

pO₂ is normally 13.3 kPa
pCO₂ is normally 5.3 kPa

3) Mixed venous blood returns from lungs to body, lower oxygen, higher CO2 levels

4) pO₂: 6.0 kPa
pCO₂: 6.5 kPa, but it varies with metabolism.

Question 11

1) How does the partial pressure of oxygen (pO₂) compare between alveolar gas and returning blood?
2) How does the partial pressure of carbon dioxide (pCO₂) compare between alveolar gas and returning blood?
3) What direction will oxygen and carbon dioxide diffuse based on their gradients?

Answer 11

1) The pO₂ in alveolar gas is higher than in the returning blood.
2) The pCO₂ in alveolar gas is lower than in the returning blood.
3) Oxygen will diffuse into the blood.
Carbon dioxide will diffuse out of the blood into the alveoli.

Question 12

Describe the diffusion resistance and nature of the barrier. What are the barriers that the gases must diffuse through to get into the blood?

Answer 12

1. Firstly, diffuse through gas in alveolus
2. Second, epithelial cells of alveolus
3. Then, tissue fluid
4. Endothelial cell of capillary
5. Plasma and red blood cell membrane

5 cell membranes, 3 layers of cytoplasm, 2 layers of
tissue fluid

Question 13

1) How does molecular weight affect gas diffusion through gases?

2) Which diffuses slower through gas, carbon dioxide or oxygen?

3) How does solubility affect gas diffusion through liquids?

4) Which gas is more soluble, carbon dioxide or oxygen?

5) Why does CO₂ diffuse faster than O₂ in liquids, despite being larger?

Answer 13

1) Gases diffuse at a rate inversely proportional to their molecular weight. Larger molecules diffuse slower.
2) Carbon dioxide diffuses slower than oxygen through gases because it has a larger molecular weight.
3) Gases diffuse at a rate proportional to their solubility. More soluble gases diffuse faster.
4) Carbon dioxide is much more soluble than oxygen, allowing it to diffuse 21 times faster through liquids.
5) Although CO₂ is a larger molecule, it is much more soluble in liquids, allowing it to diffuse 21 times faster than O₂.

Question 14

1) Which gas, CO₂ or O₂, diffuses faster overall?

2) How do diseases that increase fluid in the lungs affect gas exchange?

3) What is the limiting step in gas exchange and why?

Answer 14

1) CO₂ diffuses much faster than O₂.

2) Affect oxygen diffusion more than CO2 diffusion because of above (point 1)

3) Exchange of oxygen. Becasue O2 diffuses slower than CO2.

Question 15

1) How thick is the gas diffusion barrier in the normal lung?

2) How long do blood cells spend in capillary during gas exchange?

3) How quickly is oxygen exchange completed in the capillary?

4) What happens to partial pressure of gases in blood leaving alveolar capillary in normal lung?

Overall question: In a normal lung, is gas diffusion a limiting factor for oxygen exchange?

Answer 15

1) 0.6 μm thick.
2) 1 second
3) 0.5 seconds after the blood cell arrives in the capillary = plenty of
leeway
4) In normal lung, partial pressure of gases in blood leaving alveolar capillary are in equilbrium with alveolar air by the time blood cell exits capillary

Answer to overall question:
No. Sufficient time for oxygen to diffuse into blood before blood cell moves on from capillary. Use points above in answer

Question 16

1) What is ventilation?
2) What happens to respiratory bronchioles and alveolar ducts when the lungs expand?
3) Why does air flow into the lungs during expansion?

Answer 16

1) Expansion of the lung
2) Volume of respiratory bronchioles + alveolar ducts increases
3) Due to pressure gradient created by increased lung volume, causing lower pressure in lungs compared to atmosphere

Question 17

1) What device is used to measure ventilation?
2) How does the subject breath during spirometry?
3) How does the spirometer maintain constant pressure during ventilation?

Answer 17

1) Spirometer
2) Closed chamver over water, allowing spirometer to track changes in lung volume
3) Spirometer matches volume changes during breathing to keep pressure in chamber constant

Question 18

1) What is tidal volume?
2) What is inspiratory reserve volume?
3) What is expiratory reserve volume?

Answer 18

1) Vol of air moves in and out of lungs with each normal breath
2) Extra vol od air that can be breathed in after a normal breath
3)Extra vol of air that can be breathed out after a normal breath

Question 19

1) What is residual volume?
2) Does residual volume change during breathing?
3) Can residual volume be measured by a spirometer?

Answer 19

1) Amount of air left in lungs after maximal expiration
2) No, even during deep exhalation
3) No. Measured by HELIUM DILUTION

Question 20

1) What is the difference between lung volume and lung capacities?
2) What are the 4 lung capacity measures?
3) Which 2 of the 4 lung capacity measures can be measured by spirometry?

Answer 20

1) Lung volume change with different breathing patterns. Lung capacities do notm measured from fixed points in breathing cycle
2) Vital Capacity*, Total Lung Capacity, Inspiratory Capacity+, Functional residual capacity

• ONLY ONES THAT CAN BE Measured by spirometry

Question 21

1) What is inspiratory capacity?
2) When do you measure this?

Answer 21

1) Biggest breat that can be taken from resting expiratory level (after normal exhale)
2) After normal exhalation (resting expiratory level)

Question 21

1) What is vital capacity? How is it measured?
2) Does VC change in diseases?
3) What is the formula for TLC?

Answer 21

1) Measured from max inspiration to max expiration
2) Yes e,g, COPD, restrictive lung disease
3) TLC = VC + RV (residual volume)

Question 22

What is the functional residual capacity?
FRC Calculation

Answer 22

Volume of air in lungs at resting expiratory level

FRC = Expiratory reserve

Question 23

Typical values (do not learn, only for understanding)

Need to know what affects tehse values

Answer 23

• Sex
• Age
• Race
• State of health

Question 24

What is the pulmonary ventilation rate?

Answer 24

Amount ofa air moved into and out of the lungs per minute

Product of
1. tidal vol
2. Respiratory rate (breaths per min)

PVR = TV x RR

NOT ALL AIR TAKEN IN WITH EACH BREATH INVOLVED IN GAS EXCHANGE, some air stays in conducting pathways