West Respiratory Phys Flashcards
List other functions of the lung besides gas exchange
Metabolizes some compounds, filters unwanted materials from the circulation, acts as a reservoir for blood
Fick’s law of diffusion?
The amount of gas that moves across a sheet of tissue is proportional to the area of the sheet but inversely proportional to its thickness
V = A/T x D x (P1-P2) where A = area, T = thickness, D - diffusion constant, P1, P2 = partial pressure of gas on either side of sheet
How thick is the blood-gas barrier?
3 micrometers
About how many alveoli in the human lung? How thick are they?
About 500 million; each is 1/3 mm diameter
Describe the airways in terms of large structures–>smaller structures using the terms trachea, alveoli, etc
Trachea–>R&L mainstem bronchi–>lobar bronchi–>segmental bronchi–>terminal bronchioles–>respiratory bronchioles–>alveolar ducts–>alveolar sacs
What components of the airway are part of the conducting zone? Transitional and respiratory zones?
Conducting- trachea, bronchi, bronchioles, terminal bronchiolesTransitional/respiratory- respiratory bronchioles, alveolar ducts, alveolar sacs
Describe the diffusion path from alveolar gas to the interior of the erythrocyte
See pg 3Layer of surfactant–>alveolar epithelium–>interstitium–>capillary endothelium–>plasma
What is the function of the conducting airways?
Lead inspired air to the gas-exchanging regions of the lung (example is bronchi)They make up the anatomic dead space b/c they don’t participate in gas exchange
What helps increase the volume in the thoracic cavity during inspiration?
Contraction of diaphragm, intercostal muscles raising the ribs
Why does inhaled dust frequently settle in the terminal bronchioles?
Because the velocity of gas falls rapidly in the region of the terminal bronchioles
A normal breath of 500 ml requires how much distending pressure for the lung?
<3 cm h2o
T/F- Initially the pulmonary arteries, veins, and bronchi are far apart but become closer together towards the periphery of the lung?
False- they become further apart towards the periphery
What is the diameter of a capillary segment in the lung?
about 7-10 micrometers, just big enough for a RBC
What are some reasons why the capillaries in the lung can be easily damaged?
Extremely thin, inflation of the lung can raise the wall stresses of the capillaries and cause structural changes– this can cause leakage of plasma and even RBC into alveolar spaces
What is the function of surfactant?
Dramatically lowers the surface tension of the alveolar lining layer- increases stability of alveoli, although collapse of small airways is still possible
Mechanism of filtering out particles in the different areas of the airways?
Nose- filters out large particlesConducting airways- filters small particles via mucociliary ladder into epiglottis, where they are swallowedAlveoli- no mucociliary ladder; macrophages engulf the particles and they are removed via lymphatics or blood flow
What is functional residual capacity?
Volume of gas in the lung after normal expiration
Definition of total ventilation?
Total volume of air leaving the lung each minute (volume of each breath x RR in bpm)
What does Boyle’s law state?
Pressure x volume is constant at constant temperature (P1 x V1) = (P2 x V2)
Describe the alveolar ventilation equation
Va=[Vco2/Pco2] x K
The partial pressure of CO2 is proportional to the fractional concentration of the gas in the alveoli, or PCO2=FCO2 x K, where K is a constant
How do you measure dead space ? (what equation/method?)
Bohr’s method
[VD/VT] = [PACO2-PECO2] / PACO2
*E=mixed expired, A=alveolar
T/F: Ventilation per unit volume is greater near the bottom of the lung as opposed to the top of the lung?
True
T/F: In the lateral position, the dependent lung is best ventilated?
True
[Mult Choice]
Concerning the blood-gas barrier of the human lung:
A. The thinnest part of the blood-gas barrier is about 3 micrometers thick
B. The total area of the blood-gas barrier is about 1 square meter
C. About 10% of the area of the alveolar wall is occupied by capillaries
D. If the pressure in the capillaries rises to unphysiologically high levels, the blood-gas barrier can be damaged
E. O2 crosses the blood-gas barrier by active transport
D