Unit 2, L2, Lung Mechanics A

Question 1

Why does air flow in and out of alveoli?

Answer 1

Air flows down a pressure gradient, so during inspiration, alveolar pressure is below atmospheric pressure and air flows in. During expiration, alveolar pressure is above atmospheric pressure and air flows out

Question 2

How are the lungs connected to the chest

Answer 2

Not through any ligaments or tendons, its all through controlling pressure in pleural space

Question 3

What is Boyle’s law

Answer 3

At a fixed temperature, the volume of a gas is inversely proportional to the pressures exerted by the gas

Question 4

What is the equation for Boyle’s law

Answer 4

P = 1/V

Question 5

Thoracic cavity is separated by what from the abdominal cavity

Answer 5

Diaphragm

Question 6

Major muscles of inspiration

Answer 6

External intercostals and diaphragm

Question 7

Muscles of active expiration

Answer 7

Internal intercostal muscles and abdominal musclees

Question 8

Accessory muscles of inspiration

Answer 8

Scalenus and sternocleidomastoid

Question 9

The diaphragm

Answer 9

Stimulated by phrenic nerve, accounts for 75% of increase in thorax cavity volume, its a major inspiratory muscle. Stimulation causes the muscle to flatten and move downward, enlarges the cavity in the vertical direction

Question 10

External intercostal muscles

Answer 10

Stimulated by the intercostal nerves, stimulation causes the ribs to move up and outward, enlarges the cavity in both lateral and anteroposterior directoin

Question 11

Deep forceful inspiration uses what muscles and what is different from a tidal inspiration

Answer 11

Needs to engage the accessory inspiratory muscles, so contraction of the neck muscles raises the sternum and elevates the first two ribs, enlarges the upper portion of the thorax

Question 12

Expiration is active or passive

Answer 12

Mostly passive, inspiratory muscles relax. Diaphragm relaxes, allowing the muscle to assume its natural dome shape, and intercostal muscles relax, causing the rib cage to fall down due to gravity

Question 13

Forced expiration is active or passive

Answer 13

Active, requires contraction of expiratory muscles. Abdominal muscle contraction increases abdominal pressure and pushes the diaphragm upward. The internal intercostal muscles contraction flatten the rib cage by pulling the ribs downward and inwards

Question 14

What determines the volume of air in the lungs?

Answer 14

Balance between elastic properties of the lung and properties of the muscles of the chest wall

Question 15

Elastic properties of the lung are primarily dependent on two factors

Answer 15

Surface tension of airways and elastic properties of cells and tissue. Both of these are an inward directed force

Question 16

RV is

Answer 16

Residual volume

Question 17

Positive side of 0, in terms of pressure, will do what to the lungs

Answer 17

They will want to collapse, want to get smaller when you release them

Question 18

Negative side of 0, in terms of pressure, will do what to the lungs

Answer 18

Make them want to get bigger when you release them

Question 19

For most of our volume, the chest wall is at a (negative or positive) expanding force

Answer 19

Negative

Question 20

Lungs always have a (expanding or collapsing) force

Answer 20

Collapsing, lungs don’t give a shit, they just wanna collapse and end this life

Question 21

What is FRC

Answer 21

Functional residual capacity, is the equilibrium point of the lungs and the chest wall, pulling equally on each other, also the volume left after a tidal exhale

Question 22

Transmural pressure is what

Answer 22

Pressure inside relative to pressure outside of a compartment

Question 23

Transmural pressure across the lung wall

Answer 23

PL (translung or transpulmonary pressure) = PA (alveolar pressure) - PpI (pleural pressure) so 760-756 = 4 mmHg

Question 24

Transmural pressure across the chest wall

Answer 24

Pw (Pressure across the chest wall) = Ppl (pleural pressure) - Pb (Barometic pressure, atmospheric pressure) so 756-760 = - 4 mmHg

Question 25

Pressure across respiratory system equation

Answer 25

Prs (pressure across respiratory system) = PL (translung, transpulmonary pressure) + Pw (pressure across the chest wall), which can be simplified down to be PA (alveolar pressure) - Pb (atmospheric pressure)

Question 26

Puncture any barrier in the lungs and what will happen

Answer 26

Pneumothorax, lungs will collapse

Question 27

Pleural space is an (open or closed) system

Answer 27

Closed, there is no airflow. Changes in volume change pressure with no dissipation

Question 28

Alveolar space is (closed or open) system

Answer 28

Open, there is air flow. Changes in volume will change pressure transiently, but air flow will return pressure to steady-state