20081020

20081020 - Lecture 21 Respiration page#1 Lecture 21...

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Lecture 21 Respiration page #1 Lecture 21 Respiration (cont’d) Ventilation of the lungs: pressure relationships alveolar pressure atmospheric pressure transpulmonary pressure intrapleural pressure P alv – P ip = -4 mm Hg during expiration P alv – P ip = -7 mm Hg during inspiration P alv ~ 0 mm Hg because elastic recoil just balances P ip . 0 -4 -2 -8 -6 2 0.5 0 inspiration expiration 4s time Resp. pressures (mm Hg) total breath vol. (liters) Ventilation: Flow = Δ P/R Δ P = P atmos - P alv R = resistance to air flow (normally not important unless airway constricts) R = ( η L/r 4 )(8/ π ) r 4 is the biggest effect on R ex. 2 x r Æ 16X in R 3 x r Æ 81X in R where η = viscosity L = length of airway r = radius
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Lecture 21 Respiration page #2 Work of breathing: 1. compliance work: overcomes elastic forces 2. tissue resistance work: overcomes viscosity of lungs 3. airway resistance work: overcomes resistance of airway passages 3-5% of body energy is used for breathing at rest – can 50-fold during exercise. STRUCTURAL ASPECTS OF GAS EXCHANGE Bronchial Cells The conducting air way is a pseudostratified epithelium, i.e., all cell types touch the basement membrane -- only six types extend from the basement membrane to the lumen. 1. Basal cell - the stem cell of the airway
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This note was uploaded on 11/16/2011 for the course PNB 2250 taught by Professor Renfro during the Spring '08 term at UConn.

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20081020 - Lecture 21 Respiration page#1 Lecture 21...

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