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BIOC34H3 (46)

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5 Pages
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Department
Biological Sciences
Course Code
BIOC34H3
Professor
Stephen Reid

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Lecture 10 Study Notes
Lung compliance: a measure of the ease of expansion of the lungs and thorax
oCompliance = Lung Volume / (Palv Pip) OR Lung
Volume/TRANSPULMONARY PRESSURE
Transpulmonary pressure: refers to the driving force behind
lung expansion
Not the same as driving force for air flow
Driving force for air flow is Patm Palv
oLow compliance: small change in lung volume with given pressure change
oHigh compliance: large change in lung volume with given pressure change
Recoil pressure: pressure exerted when chest wall relaxes and lung volume
decreases
oRecoil pressure is what causes the Pip to be negative. Look back at previous
lecture
Emphysema: lungs are overcompliant
oAlveolar walls break down, causing lungs to become loose and floppy
Fibrosis: lungs are rigid and less compliant
Compliance is influenced by surface tension
oA liquid layer adheres to the surface of alveoli
oHydrogen bonding
So during inspiration, we expand:
oLung tissue (via transpulmonary pressure changes)
oSurface tension to allow gas exchange
Laplaces Law
oP = 2T/r
www.notesolution.com
oLaplaces law = pressure required to prevent alveolar collapse at rest
oThe smaller the alveoli (radius), the more pressure needed to prevent collapse
Pulmonary Surfactant: detergent like substance that reduces surface tension
oProduced by type II cells in the lungs
oInterfered with H bonding that holds liquid in surface tension together
Pulmonary surfactant is more in small alveoli than in larger alveoli
oAlveolar pressure within the lungs is equal throughout, and as noted before,
greater distending pressure is needed to prevent alveolar collapse in small
lungs
oThe larger quantity of pulmonary surfactant levels the playing field, as there
is also higher surface tension on small alveoli
Infant distress syndrome: can result from failure of type II cells in the lungs to
produce pulmonary surfactant
oAbnormal serotonin levels
Air Flow = (Patmospheric Palveolar) / R
Alveolar Pressure/Lung Pressure is influenced by two things:
oMoles of air in lungs
oVolume of the lung
Three main factors affect airway resistance:
oPassive forces (short term)
Change in transpulmonary pressure i.e pressure that drives lung
expansion
Palv Pip
oContraction of bronchiole smooth muscle (long term changes)
oMucus secretion
www.notesolution.com

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Description
Lecture 10 Study Notes • Lung compliance: a measure of the ease of expansion of the lungs and thorax o Compliance = Lung Volume / ( P alv– P ip OR Lung Volume/TRANSPULMONARY PRESSURE Transpulmonary pressure: refers to the driving force behind lung expansion • Not the same as driving force for air flow Driving force for air flow isP atm – P alv o Low compliance: small change in lung volume with given pressure change o High compliance: large change in lung volume with given pressure change • Recoil pressure: pressure exerted when chest wall relaxes and lung volume decreases o Recoil pressure is what causes the Pip to be negative. Look back at previous lecture • Emphysema: lungs are overcompliant o Alveolar walls break down, causing lungs to become loose and floppy • Fibrosis: lungs are rigid and less compliant • Compliance is influenced by surface tension o A liquid layer adheres to the surface of alveoli o Hydrogen bonding • So during inspiration, we expand: o Lung tissue (via transpulmonary pressure changes) o Surface tension to allow gas exchange • Laplace’s Law o P = 2T/r www.notesolution.com o Laplace’s law = pressure required to prevent alveolar collapse at rest o The smaller the alveoli (radius), the more pressure needed to prevent collapse • Pulmonary Surfactant: detergent like substance that reduces surface tension o Produced by type II cells in the lungs o Interfered with H bonding that holds liquid in surface tension together • Pulmonary surfactant is more in small alveoli than in larger alveoli o Alveolar pressure within the lungs is equal throughout, and as noted before, greater distending pressure is needed to prevent alveolar collapse in small lungs o The larger quantity of pulmonary surfactant levels the playing field, as there is also higher surface tension on small alveoli • Infant distress syndrome: can result from failure of type II cells in the lungs to produce pulmonary surfactant o Abnormal serotonin levels • Air Flow = (P – P / R atmospheric alveolar) • Alveolar Pressure/Lung Pressure is influenced by two things: o Moles of air in lungs o Volume of the lung • Three main factors affect airway resistance: o Passive forces (short term) Change in transpulmonary pressure i.e pressure that drives lung expansion • P alv – P ip
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