Overview of the respiratory system

Question 1

What is meant by internal respiration?

Answer 1

The mechanisms of O2 consumption and CO2 production by cells

Question 2

What is meant by external respiration?

Answer 2

The sequence of events that leads to the exchange of O2 and CO2 between cells and the outside environment

Question 3

What are the 4 steps of external respiration?

Answer 3

Ventilation
Exchange of O2 and CO2 in alveoli
Transport of O2 and CO2 in blood
Exchange of O2 and CO2 between blood and tissue

Question 4

What is meant by ventilation?

Answer 4

The mechanical process of moving air between the atmosphere and the alveolar sacs

Question 5

What forces keep the alveoli open?

Answer 5

Transmural pressure gradient
Pulmonary surfactant (Reduced surface tension)
Alveolar interdependance

Question 6

What forces promote alveolar collapse?

Answer 6

Elastic recoil of lungs and chest wall
Alveolar surface tension

Question 7

How do the lungs adhere to the chest wall?

Answer 7

Transmural pressure gradient, as the sub-atmospheric, inter-pleural pressure creates a pressure gradient across the lung wall and chest wall
Interpleural fluid molecules adhere to each other, meaning the pleural membranes stick together

Question 8

What is meant by intrapleural or intrathoracic pressure?

Answer 8

Pressure in the pleural cavity

Question 9

What is meant by intrapulmonary pressure?

Answer 9

Pressure in the lungs

Question 10

How do you convert from mmHg to kPa?

Answer 10

mmHg ÷ 7.5 = kPa

Question 11

What is pneumothorax?

Answer 11

Air in the pleural space

Question 12

How does pneumothorax cause problems?

Answer 12

It can abolish the transmural pressure gradient, meaning that the pressure in the pleural cavity is no longer lower than that of the lungs, so the lungs can collapse

Question 13

What are some symptoms of pneumothorax?

Answer 13

Shortness of breath
Chest pain

Question 14

What are some of the physical signs of pneumothorax?

Answer 14

Hyper-resonant percussion note
Decreased breath sounds

Question 15

What are the main causes pneumothorax?

Answer 15

Spontaneous
Iatrogenic
Traumatic

Question 16

What is Boyle’s law?

Answer 16

At any constant temperature, the pressure exerted by a gas varies inversely with the volume of the gas

Question 17

What occurs during inspiration?

Answer 17

the thorax and lungs expand due to contraction of inspiratory muscles (Diaphragm and external intercostal muscles)
This increases intra-thoracic and intra-alveolar pressure as volume increases
This creates a pressure gradient into the lungs

Question 18

What occurs during expiration?

Answer 18

The wall and stretched lungs recoil to return to original size
This causes idntraalveolar pressure to rise as volume decreases
The air then moves out of the lungs, down a pressure gradient

Question 19

What is surfactant and what is its purpose?

Answer 19

It is a phospholipid and protein rich substance with a much lower surface tension than water, decreasing adhesion and so allowing alveoli to open

Question 20

Which law determines that the smaller the alveoli, the higher its tendency to collapse?

Answer 20

LaPlace’s law

Question 21

What occurs in respiratory distress syndrome of the newborn?

Answer 21

Developing foetal lungs are unable to synthesise surfactant until later on in pregnancy, so premature babies may not have enough
This means the baby must make strenuous effort to overcome the high surface tension in the lungs

Question 22

What is meant by alveolar interdependence?

Answer 22

If an alveolus starts to collapse, it stretches the surrounding alveoli, which recoil and open the collapsing alveolus