week 6: respiratory physiology: pulmonary ventilation and gas exchange

Question 1

what does pulmonary ventilation refer to

Answer 1

mechanical process that allows the flow of air between atmosphere and lungs occurs due to differences in pressure

Question 2

atmospheri pressure

Answer 2

pressure in air at sea level
approx 760mm Hg

Question 3

intra-alveolar pressure

Answer 3

pressure of air within alveolar
at rest is equal to atmospheric pressure 0mm Hg
varies during phases of ventilation

Question 4

what drives ventilation

Answer 4

differences in atmospheric pressure and intra-alveolar pressure

Question 5

when atmospheric pressure exceeds intra-alveolar pressure

Answer 5

inspiration occurs

Question 6

when intra-alveolar pressure exceeds atmospheric pressure

Answer 6

expiration occurs

Question 7

intrapleural pressure

Answer 7

pressure inside pleural space
at rest: -4 mmHg
varies with phases of ventilation
always less than intra-alveolar pressure

Question 8

why is intrapleural pressure always negative during normal breathing

Answer 8

because opposing forces exerted by chest walls and lungs pull parietal and visceral pleura apart

chest wall pulls outwards, lungs pull inwards

Question 9

transpulmonary pressure

Answer 9

difference between intra-alveolar pressure and intrapleural pressure
measure of distending force across the lung

Question 10

increase in transpulmonary pressure creates

Answer 10

larger distending pressure across the lung
alveoli therefore expand

Question 11

why do chest wall and lungs not separate when forces move them apart

Answer 11

surface tensions of intra-pleural fluid
keep parietal and visceral pleura from pulling apart

Question 12

why is breathing a mechanical process

Answer 12

muscular force required
(diaphragm contracting)

Question 13

(breathing mechanics) rib cage and diaphragm at rest,

Answer 13

pressure inside and outside lungs equal
no movement of air

Question 14

(breathing mechanics) inhalation

Answer 14

intercoastal muscles contact, rib cage expands
diaphragm contracts,
increase vol of chest
pressure of chest lowered
air moves down pressure gradient into lungs

Question 15

(breathing mechanics) exhalation

Answer 15

intercostal muscles relax, rib cage drops inwards and downwards
diaphragm relaxes
pressure of chest deceases
air forced out

Question 16

inhalation Boyles law

Answer 16

increase in alveolar volume and decrease in alveolar pressure
inflow of air

Question 17

exhalation Boyles law

Answer 17

decrease alveolar volume
increase alveolar pressure
outflow of air

Question 18

two factors affecting pulmonary ventilation

Answer 18

pressure gradients
airway resistance

Question 19

lung compliance

Answer 19

measure of how easily lungs can be stretched
= change in volume/ change in transpulmonary pressure

Question 20

larger lung compliance

Answer 20

advantageous
smaller change in pressure required to inspire air, less work at breathing, less work for muscles

Question 21

compliance dependent on :

Answer 21

elasticity of lung tissue
surface tension of fluid lining alveoli

Question 22

pulmonary surfactant

Answer 22

substance produced by type 2 alveoli cells
decrease surface tension
increase compliance
decrease work of breathing

Question 23

compliance decreased if

Answer 23

scarring occurs (e.g pulmonary fibrosis)
production of surfactant reduced

Question 24

lung compliance too high,

Answer 24

negatively impacts lung function

Question 25

increase in resistance

Answer 25

seen in obstructive airway diseases
requires significantly greater pressure gradients to be produced
increases work of breathing

Question 26

minute ventilation

Answer 26

VE
total amount of air that flows in or out of lungs per min
tidal vol x breaths per minute
average : 500ml x 12= 600ml/min

Question 27

alveolar ventilation

Answer 27

only a proportion of air breathed in participates in gas exchange
30% of tidal vol fills trachea, bronchi and bronchioles (dead space volume)

Question 28

exchange of O2 and CO2 occurs due to

Answer 28

diffusion across respiratory membrane

Question 29

atmospheric air vs alveolar air

Answer 29

atmospheric air
PO2: 160
PCO2: 0.3
alveolar air
PO2: 100
PCO2: 40

residual vol, gas moved from atmosphere to lung mixes with residual volume

Question 30

increased PCO2 in red blood clel causes

Answer 30

most of molecules to be converted to bicarbonate, some bind to hemoglobin, small proportion dissolved in blood
bicarbonate transported out of rbc into plasma
H+ ions buffered by binding to hemoglobin

Question 31

decrease PCO2 by

Answer 31

CO2 diffuses from blood to alveolar air
bicarbonate enters rbc, H+ released from hemoglobin
bicarbonate and H+ converted to CO2
diffuses into alveoli