Lung Physiology

Question 1

What is breathing an example of?

Answer 1

Respiratory pump

Question 2

How much air is moved through the lungs?

Answer 2

5 litres of air a minute (minute volume)

Question 3

What is transpulmonary pressure? P(tp)

Answer 3

Difference in pressure between the inside & outside of the Lung

Question 4

What is the equation for transpulmonary pressure?

Answer 4

Alveolar pressure - intrapleural pressure

Question 5

What is intrapleural pressure? P(ip)

Answer 5

The pressure in the pleural space, also known as intrathoracic pressure

Question 6

What is alveolar pressure? P(alv)

Answer 6

Air pressure in pulmonary alveoli

Question 7

What contracts in inspiration & how?

Answer 7

Neurally induced contraction of diaphragm & external intercostal muscles

Question 8

What is the most important inspiratory muscle?

Answer 8

Diaphragm

Question 9

Where are the impulses stimulating contraction coming from and going to?

Answer 9

Transmitted to diaphragm via phrenic nerve from C3,4 & 5

Question 10

What happens in inspiration?

Answer 10

1. Diaphragm contracts, flattens -enlarging thorax, increase volume
2. External intercostal muscles contract
3. Ribs move up & out - further increasing thoracic volume
4. Intrapleural pressure decreases as thorax expands
5. Transpulmonary pressure becomes more positive
6. Lungs expand- transpulmonary pressure is greater than elastic recoil exerted by lungs
7. After lung expands, alveolar pressure becomes negative
8. Inward airflow

Question 11

What happens at the end of inspiration?

Answer 11

Passive recoil, lung size not changing & the glottis is open
Alveolar pressure= atmospheric pressure, since elastic recoil of lungs is balanced by transpulmonary pressure, no inward airflow

Question 12

What are the 2 types of expiration?

Answer 12

Expiration-passive

Forced expiration- active

Question 13

What happens during expiration?

Answer 13

1. Motor neurons decrease their firing to the diaphragm & external so muscles relax
2. Diaphragm relaxes & becomes dome shaped - decreasing thoracic volume
3. Lungs & chest wall passively collapse- elastic recoil
4. Intrapleural pressure increases,transpulmonary pressure decreases, less than the elastic recoil resulting in lungs passively collapsing
5. Alveolar pressure exceeds atmospheric pressure - air flows out down pressure gradient

Question 14

What does expiration at rest rely on?

Answer 14

Relaxation of external intercostal muscles & diaphragm

Elastic recoil of lungs

Question 15

What happens during forced expiration?

Answer 15

Same as passive expiration, internal intercostal muscles & abdominal muscles contract.

Ribs more more down & in, actively decreasing thoracic volume, increase in intra abdominal pressure

Forcing relaxed diaphragm further up into thorax, further decreasing thoracic volume

Greater than normal air expired

Question 16

Which airway has the greatest resistance?

Answer 16

Trachea-small surface area

Question 17

What accessory muscles aid active respiration (inspiration)?

Answer 17

Sternocleidomastoid
Seratus anterior
Latissmus dorsi
Pec major

Question 18

What are the accessory muscles aid active expiration?

Answer 18

Internal intercostal muscles

Abdominal muscles