Anatomy of chest wall and mechanics of breathing

Question 1

Boyle’s Law

Answer 1

Pressure exerted by a gas is inversely proportional to its volume

Question 2

Dalton’s Law

Answer 2

Total pressure of a gas mixture = the sum of the pressures of the individual gases

Question 3

Charles’ Law

Answer 3

The volume occupied by a gas is directly related to absolute temperature

Question 4

Henry’s Law

Answer 4

That the amount of gas dissolved in a liquid is determined by the pressure of the gas and it’s solubility in the liquid

Question 5

Pleural cavities are filled with

Answer 5

Intrapleural fluid

Question 6

Inflammation of the pleura is?

Answer 6

Pleurisy

Question 7

Intrapleural pressure is?

Answer 7

Sub-atmospheric - lower than normal atmospheric pressure (-3mmHg)

Question 8

Elastic recoil of the chest tries to?

Answer 8

Pull the chest wall outward

Question 9

Elastic recoil of the lungs…

Answer 9

Creates an inward pull

Question 10

When the sealed pleural cavity is punctured, why does the lung collapse?

Answer 10

Since the intrapleural pressure is sub-atmospheric, when the cavity is punctured, air rushes in and fills it, also the inward pull of the lung causes it to collapse and the outward pull of the chest cause the rib cage to expand slightly

Question 11

According to Boyle’s law, as the volume of gas increases, the pressure…

Answer 11

Decreases

Question 12

What muscles are used during inspiration?

Answer 12

External intercostals Diaphragm
Sternocleidomastoid
Scalenes

Question 13

Is expiration passive at rest or does it also use muscles?

Answer 13

Passive at rest

Question 14

When does expiration use muscles and what muscles are used?

Answer 14

During severe respiratory load

Internal intercostals and abdominal muscles

Question 15

When the diaphragm contracts, the thoracic cavity…?

Answer 15

Increases by moving down

Question 16

What nerve innervates the diaphragm and how?

Answer 16

Phrenic nerve

From underneath

Question 17

What causes asthma?

Answer 17

Over-reactive constriction of bronchial smooth muscle which increases resistance making expiration difficult

Question 18

A pneumothorax is…

Answer 18

An abnormal collection of air/gases in the pleural space

Question 19

A pneumothorax causes…

Answer 19

The uncoupling of the lung from the chest wall (lung collapse)

Question 20

What is alveolar pressure/intra-thoracic pressure (Pa)? When is it negative or positive?

Answer 20

Pressure inside the thoracic cavity/alveoli. At rest after a normal expiration it will be equal to atmospheric pressure.

On inspiration, as the thoracic cavity increases in volume the pressure in alveoli goes negative so air rushes in easier from atmosphere

On expiration, when inspiratory muscles relax, the alveolar air is compressed raising Pa to above atmospheric levels pushing air out.

Question 21

What is the intra-pleural pressure (Pip)? Positive or Negative?

Answer 21

Pressure inside the pleural cavity and is always negative in healthy lungs

Question 22

What is transpulmonary pressure (Pt)? Is it negative or positive?

Answer 22

Difference between alveolar pressure and intra-pleural pressure. ALWAYS positive in healthy individuals.

Question 23

Why is the transpulmonary pressure always positive?

Answer 23

Because since the Pip is always negative the PT = Pa – Pip. Which will become a +.

Pip is always move negative than Pa so even if both are negative it will still turn out to be a positive for the Pt

Question 24

Transpulmonary pressure opposes forces of…

Answer 24

Elastic recoil

Question 25

The bulk flow of air between the atmosphere and alveoli is proportional to ____ and inversely proportional to _____

Answer 25

1) The difference between atmospheric and alveolar pressures
2) Airway resistance

Question 26

Major determinant of the resistance of airways?

Answer 26

Radii of airways