Overview of Respiration and Respiratory Mechanics

Question 1

What is the difference between the internal and external respiration?

Answer 1

Internal refers to the intracellular mechanisms which consume O2 and produces CO2.

External refers to the sequence of events that leads to the exchange of O2 and CO2 between the external enviroment and cells.

Question 2

What are the 4 stages of external respiration?

Answer 2

Ventilation; gas exchange between alveoli and blood; gas transport in the blood; gas exchange at the tissue level.

Question 3

What 4 systems are involved in external respiration?

Answer 3

Respiratory, cardiovascular, haematology, nervous.

Question 4

During ventilation, what to do with pressure has to occur?

Answer 4

There has to be a higher atmospheric pressure compared to the intra-alveolar pressure.

Question 5

How does the intra-alveolar have a lower pressure than atmospheric pressure?

Answer 5

Usually the same pressure but when the thorax and lung expand (due to contraction of inspiratory muscles) Boyle’s law comes into effect and reduced the intra-alveolar’s pressure.

Question 6

What is Boyle’s Law?

Answer 6

At any constant temperature the pressure exerted by a gas varies inversely with the volume of the gas. (the more volume, the more room for gas to go and therefore reduce concentration in a single area.

Question 7

What is the linkage of lungs to thorax?

Answer 7

The forces that hold the thoracic wall and the lungs in close opposition.

Question 8

What are the two forces that hold the thoracic wall and lungs in close opposition?

Answer 8

The intrapleural fluid cohesiveness and the negative intrapleural pressure.

Question 9

What is the intrapleural cohesiveness?

Answer 9

The water molecules in the intra-pleural fluid are attracked to each other and so allow pleural membranes to stick together.

Question 10

What is the negative intrapleural pressure?

Answer 10

The difference between the intra- alveolar pressure and the intra-pleural pressure is -4mm Hg. This means that the intra-alveolar can expand more.

Question 11

What is the atmospheric, intra-alveolar and intrapleural pressure normally?

Answer 11

Atmospheric - 760
Intra-alveolar - 760
intrapleural - 756

Question 12

What type of process is inspiration?

Answer 12

Active

Question 13

What happens to the thorax in inspiration and how does this happen?

Answer 13

It increases it’s volume as it is increased vertically by the contraction of the diaphragm.

Question 14

Where does the phrenic nerve originate and what does it do?

Answer 14

It originates from cervical 3, 4 and 5. It sends motor signals to the diaphragm.

Question 15

What happens to the ribs and sternum during inspiration and why?

Answer 15

The lift up and the sternum moves out. This is because the external intercostal muscle contracts.

Question 16

What is expiration?

Answer 16

exhalation

Question 17

What type of process is expiration and how is it brought about?

Answer 17

It is a passive process and it brought about by the relaxation of the inspiratory muscles.

Question 18

What happens to the chest wall and lungs during expiration?

Answer 18

They recoil back to their preinspiratory states because of their elastic properties.

Question 19

What does this recoil cause?

Answer 19

The intra-alveolar pressure to rise as it has a smaller volume due to Boyle’s law. The air then leaves the lungs down the pressure gradient untill the intra-alveolar pressure equals atmospheric pressure.

Question 20

How does the intrapleural pressure change during

Answer 20

It goes from 756 mmHg to 754 during inspiration and then back up during expiration.

Question 21

pneumothorax is?

Answer 21

Air in the pleural space

Question 22

What three different things can the pneumothorax be?

Answer 22

Spontaneous, traumatic, iatrogenic.

Question 23

What can occur from pneumothorax?

Answer 23

This can abolish the transmural pressure gradient. This can lead to a lung collapsing.

Question 24

What are the symptoms of pneumothorax?

Answer 24

Shortness of breath and chest pain. Physical signs include hyperresonant percussion note and decreased/absent breath sounds.

Question 25

What causes the lungs to recoil during expiration?

Answer 25

Elastic connective tissue in the lungs. The most important bit is alveolar surface tension.

Question 26

What is alveolar surface tension?

Answer 26

Attraction between water molecules at liquid air interface.

Question 27

What is the problem with water alone lined the alveoli?

Answer 27

It would be too strong so the alveoli would collapse

Question 28

What is LaPlace’s Law?

Answer 28

It is when the Radius of the buble is small then the surface tension would be too high and so it would cause inward directed collapsing pressure. (P=2T/r)

Question 29

What is the solution to prevent the surface tension being too high if the alveoli was lined with only water molecules?

Answer 29

Pulmonary surfactant - a mixture of lips and proteins that lowers alveolar surface tension by interspersing between water molecules lining the alveoli.

Question 30

Surfactant affects what in a variable in a alveoli?

Answer 30

Size - the bigger alveoli are less affected by it compared to smaller alveoli and so the smaller alveoli is less likely to collapse.

Question 31

What is Respiratory Distress Syndrome?

Answer 31

When premature babies do not have enough pulmonary surfactant. (This isn’t guaranteed in premature babies)

Question 32

What is the symptoms for respiratory distress syndrome?

Answer 32

The baby makes very strenuous inspiratory efforts in attemp to overcome the high surface tension and inflate the lungs.

Question 33

What is the alveolar independence?

Answer 33

This is a factor to help keep alveoli open. This is where if a alveolus starts to collapse then the surrounding alveoli are stretched and then recoil exerting expanding forces in the collapsing alveolus to open it.

Question 34

Forces keeping the alveoli open?

Answer 34

transmural pressure gradient, pulmonary surfactant, alveolar interdependence

Question 35

What forces promote the collapse of the alveolar?

Answer 35

Elasticity of stretched lung connective tissue and alveolar surface tension.