Physiology - Introduction to the respiratory system

Question 1

What makes up the composition of dry atmospheric air?

Answer 1

O2 - 20.95%
CO2 - 0.03%
N - 78.09%
Ar - 0.93%

Question 2

Why is respiration important?

Answer 2

Needed to replace energy (i.e. for metabolism)
- a process similar to charcoal combustion

note: most metabolism occurs outside lung in tissue

Question 3

What types of alveolar cells are there?

Answer 3

Type 1 pneumocytes = squamous epithelial cell
- gas exchange

Type 2 pneumocytes = thicker cell
- produce surfactant that lines alveoli

Question 4

What is connective tissue of the lung made out of?

Answer 4

Collagen fibres
Elastin fibres

This if interspersed between the capillaries in the alveoli walls

Question 5

What forms the lung parenchyma and what’s it’s appearance?

Answer 5

By the linkage of connective tissue and alveoli

Appears sponge-like

Question 6

What interconnects neighbouring alveoli?

Answer 6

Pores of Kohl

- small air passages

Question 7

What is the formula for time of molecule diffusion in one direction?

Answer 7

(x^2) is proportional to t

x = distance
t = time

Question 8

Where does diffusion in the lungs occur?

Answer 8

Across the alveolar-capillary membrane in both directions

Question 9

What is convection?

Answer 9

The bulk flow of substances driven by pressure constant difference
- pressure gradient drives air along airways

The transportation method over long distance
- occurs through capillaries, vessels, heart

Question 10

What is ventilation?

Answer 10

The rate at which gas enters or leaves the lungs

Question 11

What are the eight volume and capacities which make up the ventilation (spirometry) graph?

Answer 11

Residual volume
Expiratory reserve volume
Tidal volume
Inspiratory reserve volume

Functional residual capacity
Inspiratory capacity
Vital capacity
Total lung capacity

Question 12

How are lungs expanded to fill the pleural cavity?

Answer 12

When intrapulmonary (alveolar) pressure is relatively -ve
 - i.e. intrapulmonary pressure < atmospheric pressure

Question 13

What is the definition of a pneumothorax in terms of pressures?

Answer 13

Intrapleural pressure >= atmospheric pressure

note: intrapleural=intrathoracic

Question 14

What pressure changes occur during inspiration?

Answer 14

Intrapleaural pressure become relatively more negative

Question 15

When does expiration occur?

Answer 15

When intrapulmonary pressure > atmospheric pressure

Question 16

What is lamina flow and where does it occur?

Answer 16

Constant resistance to flow for a tube of given dimensions

Flow is lamina by the time it gets to small airways

Question 17

What is turbulent flow and where does it occur?

Answer 17

Flow rate is high and occurs in large diameter, irregularly branches tubes

E.g. upper airways (nose, pharynx, larynx)

Question 18

What is the dead space?

Answer 18

Two types:

Anatomical dead space
- inhaled air that doesn’t mix with air in the alveoli

Physiological dead space
- volume of inhaled air that doesn’t take part in gas exchange

Question 19

How does oxygen diffuse from alveoli to venous blood?

Answer 19

When the pO2 in alveoli > pO2 in venous blood

Question 20

What if the formula for dead space?

Answer 20

Dead space = tidal volume - air volume entering alveoli

Question 21

How is dead space affected in a disease such as emphysema?

Answer 21

Physiological dead space can be increased

Question 22

How does ventilation vary throughout the lung?

Answer 22

Lower lobes more ventilated on standing and slow inspiration and normal expiration, even more after forced

The difference of ventilation between lobes is reduced if subject is lying down

Question 23

What are the three causes of uneven pulmonary ventilation?

Answer 23

Volume of lower chest can increases more

Diaphragm descent expands lower lobes more

Lung compliance in not uniform

Question 24

What is the pulmonary systolic pressure?

Answer 24

25 mmHg

Question 25

What is the pulmonary diastolic pressure?

Answer 25

8 mmHg

Question 26

What proportion of systemic vascular resistance is the pulmonary vascular resistance?

Answer 26

one tenth

Question 27

What is the formula that links vascular resistance to cardiac output?

Answer 27

Pressure gradient = Cardiac output x vascular resistance

Question 28

Describe a Va/Q ratio of 0?

Answer 28

Poorly ventilated

Question 29

Describe a Va/Q ratio tending to infinity?

Answer 29

Poorly perfused

Question 30

How does COPD affect Va/Q ratio?

Answer 30

Becomes high

- due to loss of alveolar walls resulting in destruction of alveoli

Question 31

Describe the process of respiratory ventilation

Answer 31

=> Higher centres

=> Pons

=> Medulla

=> Lower respiratory neurons

=> Lung stretch receptors

Question 32

What are the higher centres of respiratory ventilation?

Answer 32

Cerebral cortex

Hypothalamus

Question 33

What does the medulla do in control of the resp. ventilation?

Answer 33

The central respiratory rhythm generator

Receives inputs from

• peripheral chemoreceptors (carotid and aortic bodies)
• the vagus nerve

Upper respiratory motor neurones for the:

• contralateral phrenic nerve
• the intercostal nerve

Question 34

What are the lower respiratory neurones and what do they do?

Answer 34

Contralateral phrenic nerve
- activates the diaphragm

Intercostal nerves
- activate intercostal muscles

Question 35

What are the upper respiratory neurones and what do they do?

Answer 35

Dorsal respiratory neurones
- inspiratory neurones

Ventral respiratory neurones

• receive signal from dorsal respiratory neurones
• both insp. and exp. neurones

Question 36

How does the cycle of pulmonary ventilation continue?

Answer 36

Activating chemoreceptors (in medulla)

Activating lung stretch receptors sending signals to higher centres