Lung Structure and Function Flashcards
ventilation (usual values and equation)
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)
how is ventilation measured? and how is flow calculated?
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
what do ATPS, BTPS, and STPD mean?
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)
what do you convert ATPS to for O2 consumption and CO2 production rates?
STPD
what do you convert ATPS to for lung volumes?
BTPS
what does the ideal gas law mean for lungs and spirometers?
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)
what is water vapor pressure at 37 C?
47 mmHg
zones of the lung
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
what is the anatomic dead space?
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
what are the 4 functional specializations of the respiratory system?
- ventilatory apparatus
- pulmonary gas exchanger
- pulmonary circulatory system
- tissue gas exchanger
what does the respiratory zone include?
gas (O2 and CO2) exchange with blood (simple diffusion)
epithelial cells: Type I (line alveoli), II (secrete surfactant
what is surfactant?
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
blood-gas barrier
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
when is equilibrium in alveoli reached?
when partial pressure of O2 or CO2 is same in alveolar gas and pulmonary capillary blood
how many alveoli are there, and how big are they?
300 million alveoli, with 250 micron diameter, covered by 1000 pulmonary capillaries
-surface area is 70 square meters
composition of air
78% nitrogen
21% oxygen
0.03% carbon dioxide
1% argon
what is the partial pressure for dry and wet gases?
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
solubility of gases
dissolved gases don’t contribute to blood volume or BP
-partial pressure of a gas in solution refers only to dissolved gas
what is shunt flow? and how does it affect O2 and CO2?
bronchial flow that represents 1% of cardiac output
-dilutes [O2] slightly, but no effect on CO2
what artery are conducting airways perfused by?
bronchial artery
what is the oxygenated blood in pulmonary vein a mixture of?
- blood that has equilibrated with alveolar gas
- small amount of blood with mixed venous blood
is the amount of O2 dissolved in plasma enough to meet tissue needs?
no, thus we need control mechanisms
respiratory quotient
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
respiratory exchange ratio
ratio of expired CO2 to inspired O2 at lung
what happens if you cannot breathe out CO2 fast enough?
CO2 builds up and equilibriates in blood, causing acidosis
CO2 + H2O H2CO3 H+ + HCO3-
