Lung Structure and Function

Question 1

ventilation (usual values and equation)

Answer 1

flow of air into and out of the lungs

7.5 Liter/min = frequency of breathing (15 breaths/min) * Tidal Volume (0.5 Liter/breath)

Question 2

how is ventilation measured? and how is flow calculated?

Answer 2

spirometer collects expired gas for 1 minute or adds tidal volumes for 1 minute
flow is the slope of the recording of volume VS time

Question 3

what do ATPS, BTPS, and STPD mean?

Answer 3

Ambient Temp and Pressure at Saturation: 25 C, 760 mmHg (1 atm), and 24 mmHg saturation
Body Temp and Pressure at Saturation: 37 C, 760 mmHg, 47 mmHg saturation
Standard Temp and Pressure if Dry: 0 C, 760 mmHg, 0 mmHg (water vapor pressure is zero)

Question 4

what do you convert ATPS to for O2 consumption and CO2 production rates?

Answer 4

STPD

Question 5

what do you convert ATPS to for lung volumes?

Answer 5

BTPS

Question 6

what does the ideal gas law mean for lungs and spirometers?

Answer 6

Since PV = nRT, PV/T of lung = PV/T of spirometer
V (lung) = V (spirometer) * Psp/Pl * Tl/Tsp
V (lung) = 1.07 V (spirometer)

Question 7

what is water vapor pressure at 37 C?

Answer 7

47 mmHg

Question 8

zones of the lung

Answer 8

conductive zone - first 16 branches (no gas exchange) including trachea, bronchi, bronchioles, and terminal bronchioles
respiratory zone - last 7 branches (passive diffusion) including respiratory bronchioles, alveolar ducts, and alveolar sacs

Question 9

what is the anatomic dead space?

Answer 9

the conducting zone (1 mL per lb body weight)

• ciliated surface (pseudostratified columnar epithelium) propels mucous secreted by goblet cells
• trachea has cartilaginous rings for structural support

Question 10

what are the 4 functional specializations of the respiratory system?

Answer 10

1. ventilatory apparatus
2. pulmonary gas exchanger
3. pulmonary circulatory system
4. tissue gas exchanger

Question 11

what does the respiratory zone include?

Answer 11

gas (O2 and CO2) exchange with blood (simple diffusion)

epithelial cells: Type I (line alveoli), II (secrete surfactant

Question 12

what is surfactant?

Answer 12

a lipoprotein with DPPC (dipalmitoylphosphatidylcholine phospholipid, AKA lethicin) that coats alveoli

• lowers surface tension, making it easier to inhale
• increases mechanical stability of the lung

Question 13

blood-gas barrier

Answer 13

very thin, about 1.5 micron
-O2 has to cross surfactant-coated alveolar epithelium, alveolar interstitial space, capillary endothelium, plasma, and RBC membrane to finally combine with Hb

Question 14

when is equilibrium in alveoli reached?

Answer 14

when partial pressure of O2 or CO2 is same in alveolar gas and pulmonary capillary blood

Question 15

how many alveoli are there, and how big are they?

Answer 15

300 million alveoli, with 250 micron diameter, covered by 1000 pulmonary capillaries
-surface area is 70 square meters

Question 16

composition of air

Answer 16

78% nitrogen
21% oxygen
0.03% carbon dioxide
1% argon

Question 17

what is the partial pressure for dry and wet gases?

Answer 17

Dry: Pi = Fi* Pt
Wet: Pi = Fi * (Pt - Pwater)

Pi = partial pressure of "i" when equilibriated
Fi = fraction of "i" in air
Pt = total pressure

Question 18

solubility of gases

Answer 18

dissolved gases don’t contribute to blood volume or BP

-partial pressure of a gas in solution refers only to dissolved gas

Question 19

what is shunt flow? and how does it affect O2 and CO2?

Answer 19

bronchial flow that represents 1% of cardiac output

-dilutes [O2] slightly, but no effect on CO2

Question 20

what artery are conducting airways perfused by?

Answer 20

bronchial artery

Question 21

what is the oxygenated blood in pulmonary vein a mixture of?

Answer 21

• blood that has equilibrated with alveolar gas

- small amount of blood with mixed venous blood

Question 22

is the amount of O2 dissolved in plasma enough to meet tissue needs?

Answer 22

no, thus we need control mechanisms

Question 23

respiratory quotient

Answer 23

ratio of tissue metabolic production of CO2 and consumption of O2

• depends on metabolic substrate being oxidized
• -fat = 0.7, carb = 1.0, mixed = 0.85

Question 24

respiratory exchange ratio

Answer 24

ratio of expired CO2 to inspired O2 at lung

Question 25

what happens if you cannot breathe out CO2 fast enough?

Answer 25

CO2 builds up and equilibriates in blood, causing acidosis

CO2 + H2O H2CO3 H+ + HCO3-