Anatomy Of Chest Wall And Mechanics Of Breathing

Question 1

What does Boyle’s law state?

Answer 1

That the pressure exerted by a gas is inversely proportional to its volume

Question 2

What does Dalton’s law state?

Answer 2

That 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

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

Question 4

What does Henry’s law state?

Answer 4

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

Question 5

How many lobes is the right lung externally divided into?

Answer 5

Three

Question 6

State the three external lobes of the right lung

Answer 6

Superior lobe
Middle lobe
Inferior lobe

Question 7

How many lobes is the left lung externally divided into?

Answer 7

Two

Question 8

State the two external lobes of the left lung

Answer 8

Superior lobe

Inferior lobe

Question 9

What encloses each lung

Answer 9

Two pleural membranes

Question 10

What passes through the thorax between the pleural sacs?

Answer 10

The esophagus and aorta

Question 11

What coats the outer surface of the lungs?

Answer 11

Visceral pleural membrane (inner most pleura)

Question 12

What coats the inner surface of the ribs?

Answer 12

Parietal pleural membrane (outermost pleura)

Question 13

What is located between the parietal pleura and the visceral pleura

Answer 13

The pleural cavity which is filled with intrapleural fluid

Question 14

Define pleurisy

Answer 14

Inflammation of the pleura

Question 15

Describe the importance of the relationship between the pleural membranes

Answer 15

• Provides lubrication
• Protects lungs from damaging interactions
• Allow lungs to move within the body cavity with minimal friction from other organs

Question 16

Describe the movement of gases in relation to pressure

Answer 16

Gases always move from high pressure to low pressure

Question 17

State the muscles used for inspiration

Answer 17

• diaphragm
• external intercostals
• sternocleidomastoids
• scalenes

Question 18

State the muscles used for expiration

Answer 18

• internal intercostals

- the abdominals

Question 19

Describe expiration at rest

Answer 19

Passive

Question 20

Describe the movement of the diaphragm during inspiration

Answer 20

Diaphragm contracts, thoracic volume increases

Question 21

Describe the movement of the diaphragm during expiration

Answer 21

Diaphragm relaxes, thoracic volume decreases

Question 22

Describe the ‘pump handle’ motion of the ribs

Answer 22

Ribs usually lie lower to the axis, during inspiration the ribs elevate over the axis which increases the anterior-posterior dimension of the rib cage.

During expiration the ribs lower below the axis again decreasing the volume of the rib cage

Question 23

Describe the ‘bucket handle’ motion of the rib cage

Answer 23

The ribs normally lie at a 45 degree angle. During inspiration the ribs move up to increase the lateral dimension of the rib cage.

During expiration the ribs move down again decreasing the lateral dimension of the ribs.

Question 24

Describe asthma

Answer 24

The over-reactive constriction of bronchial smooth muscle which increases resistance, making expiration difficult

Question 25

Define pneumothorax

Answer 25

If the sealed pleural cavity is opened to the atmosphere, air flows in causing a collection of free air in the chest cavity which causes the lung to collapse

Question 26

Define the intra-thoracic (alveolar) Pressure (Pa)

Answer 26

Relates tot he pressure inside the thoracic cavity, essentially the pressure inside the lungs.

This may be negative or positive compared to atmospheric pressure.

Question 27

Define intra-pleural pressure (Pip)

Answer 27

This relates to the pressure inside the pleural cavity.

This is always negative in healthy lungs

Question 28

Define transpulmonary pressure (Pt)

Answer 28

This is the difference between alveolar pressure and intra-pleural pressure.

This is always positive (in health) because Pip is always negative.

Pt = Pa-Pip

Question 29

Describe the flow of air between breaths at the end of an unforced expiration

Answer 29

The atmospheric pressure = alveolar pressure, therefore no air is flowing.

Question 30

How to the dimensions of the lungs and thoracic cage remain stable between breaths at the end of an unforced expiration?

Answer 30

As a result of opposing elastic forces.

Question 31

Describe the fact of opposing elastic forces

Answer 31

The lungs being stretched and attempting to recoil, combined with the chest wall being compressed and attempting to move outward creates a sub atmospheric intrapleural pressure and hence a transpulmonary pressure that oppose the forces of elastic recoil.

Question 32

What does airway resistance determine?

Answer 32

How much air flows into the lungs at any given pressure difference between atmosphere and alveoli.

Question 33

What is the major determinant of airway resistance?

Answer 33

The radii of the airways

Question 34

What does the volume of the lungs depend on?

Answer 34

• The transpulmonary pressure

- how ‘stretchable’ the lungs are