2. Anatomy of chest wall and mechanics of breathing

Question 1

What does Boyle’s Law state?

Answer 1

The pressure exerted by a gas is inversely proportional to its volume

Question 2

What does Dalton’s Law state?

Answer 2

The total pressure of a gas mixture is the sum of the pressures of the individual gases

Question 3

What does Charles’ Law state?

Answer 3

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

Question 4

What does Henry’s Law state?

Answer 4

The amount of gas dissolved in a liquid is determined by the pressure of the gas and its solubility in the liquid

Question 5

Describe the direction of movement of gases.

Answer 5

Move from areas of high pressure to areas of low pressure

Question 6

How are the lungs divided?

Answer 6

• Right lung contains 3 lobes

- Left lung contains 2 lobes

Question 7

What are the lobes of the right lung?

Answer 7

• Superior lobe
• Middle lobe
• Inferior lobe

Question 8

What are the lobes of the left lung?

Answer 8

• Superior lobe

- Inferior lobe

Question 9

What are the 2 components of the pleural membrane?

Answer 9

• Parietal pleural membrane

- Visceral pleural membrane

Question 10

What does the pleural fluid do?

Answer 10

• Acts as a lubricant

- Anchors the visceral and pleural membranes which sticks the lungs and ribs together

Question 11

What is pleurisy?

Answer 11

Inflammation of the pleura

Question 12

What does the visceral pleural membrane do?

Answer 12

Coats the outer surface of the lungs

Question 13

What does the parietal pleural membrane do?

Answer 13

Coats the inner surface of the ribs

Question 14

What passes through the thorax between the pleural sacs?

Answer 14

The eosaphagus and the aorta

Question 15

What is found between the surfaces of the pleural membranes?

Answer 15

Intrapleural fluid

Question 16

Why are the lungs effectively stuck to the ribcage?

Answer 16

Through the relationship of the pleural membranes

Question 17

What is the normal value for intrapleural pressure?

Answer 17

-3 mmHg

Question 18

What muscles are involved in inspiration?

Answer 18

• External intercostal muscles
• Diaphragm
• Sternocleidomastoids
• Scalenes

Question 19

What muscles are involved in expiration?

Answer 19

It is passive at rest but during severe respiratory load the internal intercostal muscles and abdominal muscles can be used

Question 20

What do the external intercostal muscles do?

Answer 20

Pull the ribs up and out to increase the space of the thoracic cavity

Question 21

What do the internal intercostal muscles do?

Answer 21

Pull the ribs down and in to decrease the space of the thoracic cavity

Question 22

What dimension of the rib cage does the pump-handle motion increase?

Answer 22

Anterior-posterior

Question 23

What dimension of the ribcage does the bucket handle motion increase?

Answer 23

Lateral dimension

Question 24

What is asthma cause by?

Answer 24

The over-reactive constriction of bronchial smooth muscle which increases resistance and makes expiration difficult

Question 25

What happens during pneumothorax?

Answer 25

If the sealed pleural cavity is opened to the atmosphere, air flows in which causes the lung to collapse to upstretched size

Question 26

What is the intra-thoracic (alveolar) pressure (Pa)?

Answer 26

• Pressure inside the thoracic cavity.

- May be negative or positive compared to atmospheric pressure

Question 27

What is the intra-pleural pressure (Pip)?

Answer 27

• Pressure inside the pleural cavity

- ALWAYS negative

Question 28

What is the trans pulmonary pressure (Pt)?

Answer 28

• Difference between alveolar pressure and intra-pleural pressure.
• ALWAYS positive

Question 29

What is the bulk flow of air between the atmosphere and alveoli proportional and inversely proportional to?

Answer 29

• Proportional to the difference between the atmospheric and alveolar pressures
• Inversely proportional to the airway resistance

Question 30

How is a subatmospheric intrapleural pressure and hence a transpulmonary pressure that opposes the force of elastic recoil established?

Answer 30

• Between breaths at the end of an unforced expiration there is no air flowing and the dimensions of the lungs and thoracic cage are stable as the result of opposing elastic forces.
• The lungs are stretched and are attempting to recoil whereas the chest wall is compressed and attempting to move outward.

Question 31

What determines airway resistance?

Answer 31

Radii of airways

Question 32

What determines how much air flows into the lungs at any given pressure difference between atmosphere and alveoli?

Answer 32

Airway resistance