Mechanics of Pulmonary Ventilation

Question 1

What is Boyles law?

Answer 1

Pressure varies inversely with volume

Question 2

Why is Boyles law applicable to breathing?

Answer 2

Volume changes within the thoracic cavity create a pressure difference between inside pressure and atmospheric pressure, causing air to flow down it [gradient] in or out of the body

Question 3

When is inside pressure = to outside pressure?

Answer 3

When there is no breathing. 760mmHg in the lung and outside

Question 4

How do you get air into the lungs?

Answer 4

Decrease pressure and Increase volume

-greater volume= more space = decrease pressure = air flow in

Question 5

What allows the increase of volume within the thoracic cavity?

Answer 5

The external intercostal muscles and the Diaphragm

Question 6

How does the increase in volume in the thoracic cavity happen?

Answer 6

Diaphragm: accounts for 75% of the volume increase
-muscle contracts to pull down the diaphragm

External intercostal muscle: Muscle contracts allowing the thoracic wall (ribs) to expand up and out

Question 7

How do you get air out of the lungs?

Answer 7

Decrease volume and increase pressure

-decrease volume=less air space=increases pressure =air flows out

Question 8

What allows the decrease in volume in the thoracic cavity?

Answer 8

Relaxing of the external intercostal muscles and the diaphragm

Question 9

How does the decrease in volume in the thoracic cavity happen?

Answer 9

Diaphragm gets pulled back up, external intercostal muscle stop contracting

Question 10

How does inhalation during exercise differ from inhalation at rest?

Answer 10

The more forceful the inhalation causes the diaphragm to pull deeper, creating more volume space
-everything else is the same

Question 11

How does exhalation during exercise differ from exhalation at rest?

Answer 11

Internal intercostal muscles contract causing the thoracic wall (ribs) to contract down and in (opposite to external intercostal muscles)

Oblique muscles contract

Rectus abdominus contracts (6pack)
-when contracts, causes the organs underneath to shift a little helping to push the diaphragm back up

Question 12

Do the lungs fully deflate?

Answer 12

Never no matter how hard you exhale

Question 13

Why don’t the lungs fully deflate?

Answer 13

Due to the intrapleural pressure in the intratpleural space

-757mmHg

Question 14

Why is having intraleural pressure advantageous?

Answer 14

Lungs don’t collapse even at the end of expiration

Allows for easy expansion of the lung, and there is no resistance against inflation

Question 15

What happens during a pneumothorax?

Answer 15

When interleura pressure and intrapulmonary pressure become the same pressure by the lung tissue springing back into the chest cavity (causing collapse) and the thoracic wall springing outward

Question 16

What are the 2 ways in which you can get a pneumothorax?

Answer 16

1. Hole in visceral pleura: Gas will flow from high to low until pressures are the same . Causing the lung to collapse
2. Hole through chest wall/periatal pleura: Air goes from the environment into the body
   - in both cases the intrapleural space goes from only having fluid to having fluid and air

Question 17

What is lung compliance?

Answer 17

Change in lung volume which is due to change in lung pressure
-how much pressure needed to fill the lung

Question 18

What is compliance?

Answer 18

The stretchability of the lung

-More compliant the lung, the easier it is to stretch and increase volume during inhalation

Question 19

What 2 factors influence the compliance of the lung?

Answer 19

Elastic tissue components of the lung

Surface tension inside the alveoli

Question 20

Why does having too much elastin (elastic tissue) a bad thing?

Answer 20

If you have too much elastin it will become harder for the lung to expand enough, decreasing the compliance

Question 21

What is surface tension?

Answer 21

Force that develops at the surface of a liquid due to the attraction between water molecules

Question 22

What is surfactant?

Answer 22

Protein+ phospholipids that make a thin layer over the liquid in the alveoli.

Question 23

What does surfactant do?

Answer 23

Prevents H2O molecules from sticking together

Prevents lung collapse

Increases compliance

Question 24

Which group of people dose not having enough surfactant affect?

Answer 24

Premies

-dont have fully developed lungs and can not make enough surfactant to have a normal compliant lung