2 Breathing Mechanics

Question 1

What does Boyle’s law dictate?

Answer 1

Pressure exerted by gas is inversely proportional to its volume. ( P proportional to 1/V)

Question 2

What is dalton’s law?

Answer 2

Total pressure of a gas mixture is the sum of the pressures of all individual gases (duh)

Question 3

What is charles’ law?

Answer 3

Volume of a gas is proportional to temperature.

V proportional T

Question 4

What is Henry’s law?

Answer 4

Amount of gas dissolved in a liquid depends on its solubility & pressure

Question 5

What parts make up the upper respiratory system?

Answer 5

Mouth
Nasal Cavity
Pharynx
Larynx

Question 6

What parts make up the lower respiratory tract?

Answer 6

Trachea
Bronhi
Lungs

Question 7

What binds the lower respiratory system?

Answer 7

Ribs
Spine
Diaphragm

Question 8

What is differnet about the external anatomy of the lungs?

Answer 8

The right lung has 3 lobes whereas the left only has 2

Question 9

What are the lobes of the lung called?

Answer 9

Superior and inferior

The right lung also has a middle lobe

Question 10

What encloses each lung?

Answer 10

Two pleural membranes seperated by a thin space of pleural fluid

Question 11

What is the pericardial cavity?

Answer 11

The space around the heart

Question 12

What is the inner pleural membrane called

Answer 12

The one around the lung (inner) is the visceral pleura

Question 13

What is the outer pleural membrane called?

Answer 13

The one coating the inner rib surface (outer) is the Parietal pleura

Question 14

What is inflammation of the pleura called?

Answer 14

Pleurisy

Question 15

What do pleura do?

Answer 15

effectively stick the lungs to the ribs. This way the elastic recoil of the chess wall keeps the lung stretched open.

Question 16

What is pneumothorax?

Answer 16

When air gets into the pleural cavity causing the lung to detach from the ribs and collapse

Question 17

What muscles are involved in inspiration?

Answer 17

External intercostal muscles
diaphragm
Sternocleidomastoids
Scalenes

Question 18

What muscles are involved in expiration?

Answer 18

Its passive at rest

But under heavy respiratory load the internal intercostal muscles & abdominal muscles are used.

Question 19

What are the scalenes?

Answer 19

3 pairs of muscles in the lateral neck connecting the transverse processes of cervical vertebrae to the first 2 ribs

Question 20

How does air enter the lungs?

Answer 20

• Muscles cause lung to expand increasing volume.
• Due to boyle’s law the pressure decreases.
• Air moves from higher pressure outside to lower pressure in lung

Question 21

What abnormal action occurs during asthma?

Answer 21

Over-constriction of the bronchial smooth muscle

Question 22

How does asthma cause breathing problems?

Answer 22

The over-constricted smooth muscle decreases the airway diameter
Thus the air flow resistance increases
Expiration becomes difficult

Question 23

What are the 3 relevant pressures in breathing?

Answer 23

Intra-thoracic pressure (Alveolar) (Pa)
Intra-pleural pressure (Pip)
Transpulmonary pressure (Pt)

Question 24

What is intra-thoracic (alveolar) pressure?

Answer 24

Pa:
Pressure inside the thoracic cavity (lungs).
-ve or +ve compared to atmospheric pressure

Question 25

What is intra-pleural pressure?

Answer 25

Pip:
Pressure inside pleural cavity.
Always -ve

Question 26

What is transpulmonary pressure?

Answer 26

Pt:
alveolar pressure - intra-pleural pressure.
Always +ve because Pip is always -ve.

Question 27

Is Alveolar pressure +ve or -ve?

Answer 27

Either as compared to atmospheric pressure

Question 28

Is intra-pleural pressure -ve or +ve?

Answer 28

Always -ve

Question 29

How is transpulmonary pressure determined?

Answer 29

Pt = Pa - Pip

Question 30

What is the measurment of pressure?

Answer 30

mm Hg

‘millimetres of mercury’

Question 31

How does alveolar pressure change?

Answer 31

During inspiration it decreases then returns to normal

During expiration it increases then returns to normal

Question 32

How does intrapleural pressure change?

Answer 32

It decreases during inspiration

Returns to normal during expiration

Question 33

What effects bulk flow of air between atmosphere & alveoli?

Answer 33

Proportional to differnce between atmospheric & alveolar pressure.
Inversely proportional to airway resistance.

Question 34

Equation for bulk flow of air?

Answer 34

F = (Patm - Pa)/R

Question 35

When does Patm = Pa?

Answer 35

Between breaths at the end of unforced expiration

Question 36

What factor determines how much air flows into the lungs?

Answer 36

• Airway resistance

- Pressure difference between atmosphere & alveoli