lecture 25- resp

Question 1

At an air-fluid interface, the surface is under a

Answer 1

tension bc of attractive forces between fluid molecules

–> inwardly directed pressure

Question 2

Law of laplace

Answer 2

P= 2T/r

P= pressure
T= surface tension of the fluid

Question 3

how does surfactant allow alveoli to expand?

Answer 3

by decreasing the tension, which decreases the inward pressure

Question 4

what would happen to alveoli without surfactant?

Answer 4

inward pressures of alveoli would be high.
prone to inflation and collapse

Question 5

smaller alveoli have more

Answer 5

surfactant

Question 6

how is pressure and air flow distributed in alveoli

Answer 6

equally

Question 7

functional residual capacity (FRC)

Answer 7

volume of air left in the lungs after a normal expiration

Question 8

Positive transpulmonary pressure

Answer 8

is the force inflating the lungs

Question 9

what keeps the lung adhered to the chest wall?

Answer 9

pleural fluid

Question 10

pneumothorax

Answer 10

air enters the pleural sac, intrapleural pressure is not negative anymore

bond holding lung to chest wall is broken and lung collapses

pneumothorax= “air in the thorax”

Question 11

chest expansion — Pip

Answer 11

causes decreased intrapleural pressure

(V increases, pressure decreases)

Question 12

Transpulmonary pressure equation

Answer 12

Palv-Pip

the difference between the pressure in the alveoli and the pressure in the pleural cavity

Question 13

Compliance: lung

Answer 13

ability of the lungs to stretch (change volume for a given pressure)

Question 14

when is compliance decreased?

Answer 14

in restrictive pulmonary diseases
ex. fibrosis

Question 15

elastance

Answer 15

the ability of the lung to spring back after being stretched

Question 16

what allows lung elastance

Answer 16

the presence of elastin fibers in the lung interstitial space

Question 17

when is elastance decreased?

Answer 17

in emphysema (loss of elastin)

Question 18

high compliance of the lung allows them to

Answer 18

move outward with little force required

Question 19

elastic recoil of the lung creates

Answer 19

an inward pull

Question 20

Boyles law

Answer 20

P1V1=P2V2

Question 21

what happens when inspiratory muscles contract (boyle’s law)

Answer 21

lung volume increases, pressure in lungs decreases, air is ‘sucked’ into the lungs

Question 22

what happens when inspiratory muscles relax (boyle’s law)

Answer 22

lung volume decreases, pressure in lungs increases, air is blown out of lungs (following pressure gradient, via bulk flow)

Question 23

muscles used for ventilation at rest

Answer 23

external intercostals and diaphragm use at rest
(contracts, air flows in)

Question 24

what other muscles are recruited during forceful breathing?

Answer 24

intercostals and abdominals

sternocleidomastoids and scalenes

Question 25

what happens during quiet inspiration?

Answer 25

• diaphragm contracts and flattens
• muscles of inspiration contract and pull ribs up and out, sternum lifts up

–> thoracic and lung volumes increase
–> Pip and Palv decrease
–> Patm>Palv
–> air flows in

Question 26

what happens during quiet expiration?

Answer 26

-diaphragm relaxes and moves upward
-muscles of inspiration relax, ribs and sternum “fall” back down

–> thoracic and lung volumes decrease
–> Pip and Palv increase
–> Palv>Patm
–> air flows out

Question 27

what is the machine that measures changes in lung volume during ventilation?

Answer 27

spirometer

Question 28

Total pulmonary ventilation (minute ventilation)= ?

Answer 28

ventilation rate (12 breaths/min) * tidal volume (500mL)= 6 L/min

Question 29

the efficiency of breathing depends on both

Answer 29

rate and depth

Question 30

how much air is moved into/out of the respiratory system per minute?

Answer 30

6L/min
(total pulmonary ventilation)

Question 31

anatomical deadspace

Answer 31

150mL

because gas exchange does not occur in conducting pathways

Question 32

what is a better indicator of ventilation efficiency?

Answer 32

alveolar ventilation

(the amount of air moves in and out the alveoli per minute)

Question 33

alveolar ventilation=

Answer 33

ventilation rate* (Tidal volume- dead space volume)

= 12 breaths/min*(500-150mL)
= 4.2L/min

Question 34

at the end of inspiration, the dead space (150mL) is filled with

Answer 34

fresh air

Question 35

the first exhaled air comes out of the —–. Only —-mL leaves the alveoli.

Answer 35

dead space
350mL

Question 36

at the end of expiration, the dead space is filled with

Answer 36

stale air from alveoli

Question 37

end of expiration, inhale…

Answer 37

500mL of fresh air (tidal volume)

Question 38

how is the 500mL of fresh air divided when inhaled?

Answer 38

-dead space (150mL) is filled w fresh air
-only 350 mL reaches alveoli
(the first 150mL of air into the alveoli is stale from the dead space)