respiration - gas exchange

Question 1

What is the inspiratory reserve volume (IRV)?

Answer 1

the maximum volume of additional air that can be inhaled after a normal breath

Question 2

What is the inspiratory capacity?

Answer 2

The volume of air breathed in from quiet expiration to maximum inspiration.

Question 3

What is the vital capacity?

Answer 3

The maximum volume of air that can be expired from the lungs after a maximum inspiration.

Question 4

What is residual volume?

Answer 4

The volume of air left in the lungs after max expiration

Question 5

What is functional residual capacity?

Answer 5

The volume of air left in the lungs after quiet expiration

Question 6

What homeostasis does breathing maintain?

Answer 6

Blood gas homeostasis

Question 7

What is the partial pressure of oxygen at rest?

Answer 7

PO2 = 100 +- 2 mmHg

Question 8

What is the partial pressure of carbon dioxide at rest?

Answer 8

PO2 = 40+-2 mmHg

Question 9

What is the ventilation rate at rest?

Answer 9

6-7 L/min (12-15 breaths/min, 500ml/breath)

Question 10

What volume of O2 is consumed per minute?

Answer 10

250ml/min

Question 11

What volume of CO2 is expired per minute?

Answer 11

200ml/min

Question 12

How to calculate the partial pressure of a gas

Answer 12

fraction of gas x barometric pressure

Question 13

Which part of the lung makes up the conducting airways?

Answer 13

Trachea, bronchi and nonrespiratory bronchioles

Question 14

Why are conducting airways considered to be anatomic dead space?

Answer 14

They don’t participate in gas exchange and take up 150ml volume (30% of breath doesn’t reach alveoli)

Question 15

What structures form the respiratory airways?

Answer 15

bronchioles with alveoli where gas exchange occurs (terminal bronchioles, respiratory bronchioles, alveoli)

Question 16

What volume is the conducting airways?

Answer 16

150 ml

Question 17

What volume is the respiratory airways?

Answer 17

2500ml

Question 18

How long is the respiratory airways?

Answer 18

5mm

Question 19

What is a respiratory unit?

Answer 19

the basic physiological unit of the lung involved in gas exchange consisting of respiratory bronchioles, alveolar ducts and alveoli.

Question 20

How many alveoli are there in adults?

Answer 20

300-400 million alveolar sacs

Question 21

Shape of alveoli

Answer 21

polygonal, 250 um diameter

Question 22

What cells make up the alveoli?

Answer 22

type 1 and type 2 (septal) epithelial cells / pneumocytes

Question 23

Function of type 1 pneumocytes

Answer 23

primary site of gas exchange

Question 24

What percentage of the alveoli surface are is type 1 epithelial cells?

Answer 24

97%

Question 25

What are type 2 pneumocytes also known as?

Answer 25

Septal / surfactant cells

Question 26

How much of the alveolar surface area is occupied by type 2 pneumocytes / surfactant / septal cells?

Answer 26

3%

Question 27

Function of type 2 pneumocytes

Answer 27

Produce pulmonary surfactant which reduces surface tension, allowing the lungs to expand duringeach breath.

Question 28

What cells remove debris from alveolar sacs?

Answer 28

Alveolar macrophages

Question 29

What feature of the lung may mean that babies born prematurely (before 28 weeks) might not survive?

Answer 29

Their septal/surfactant cells have not yet differentiated

Question 30

Why are alveoli efficient for gas exchange?

Answer 30

large surface area (100m2), very thin walls (0.5um), large capillary network

Question 31

What are the 2 blood circulations in the lungs?

Answer 31

pulmonary circulation and bronchial circulation

Question 32

Function of the pulmonary circulation

Answer 32

brings deoxygenated blood from the RV to the lungs where it is oxygenated and returned to the LA and then pumped around the rest of the body.

Question 33

Function of the bronchial circulation

Answer 33

brings oxygenated blood to the lung parenchyma (part of systemic circulation)

Question 34

What is the total blood volume in the pulmonary circulation?

Answer 34

500ml (10% of total)

Question 35

What is the volume of blood in the alveolar-capillary network at rest?

Answer 35

75ml

Question 36

What is the volume of blood in the alveolar-capillary network during exercise?

Answer 36

150-200ml

Question 37

How does the volume of blood in the alveolar-capillary network increase (more than x2) during exercise?

Answer 37

New capillaries are recruited and there is an increase in blood pressure.

Question 38

How do arteries in the pulmonary circulation differ compared to the systemic circulation?

Answer 38

thinner walls, larger diameter, lower resistance and lower pressure.

Question 39

What is the distance between the alveoli and an erythrocyte?

Answer 39

1-2um

Question 40

What structures must O2 diffuse through to reach Hb?

Answer 40

type 1 pneumocyte, basement membrane (fused basal lamina), endothelial cell, erythrocyte plasma membrane.

Question 41

How long does it take erythrocytes to pass through capillaries?

Answer 41

less than 1 second - very efficient as it is enough time for O2 and CO2 gas exchange

Question 42

Does O2 or CO2 have a greater pressure gradient between the alveolar air and venous blood?

Answer 42

O2 has a steeper conc gradient

Question 43

Ventilation definition

Answer 43

process by which air moves in and out of lung

Question 44

perfusion definition

Answer 44

process by which deoxygenated blood passes through the lung and becomes oxygenated

Question 45

What is the V/Q ratio?

Answer 45

The relationship between ventilation and perfusion which is a major determinant of normal gas exchange and levels of PO2 and PCO2.

Question 46

V/Q in healthy lungs

Answer 46

0.8