Unformatted text preview: ation
goal: move air out of lungs
needs: increase pressure, higher than atmospheric pressure
mechanics: v in thoracic volume -> ^intrapulmonary pressure causing expiration Question: How do you think the mechanics described above change during exercise?
breathe more frequently to make up for increased need of O2 and to expel the increased levels of CO2
to breathe more deeply, need increased gradient. use inspirational muscles more to increase volume as much as possible, will create as large of
gradient as possible III. PULMONARY PRESSURES (cont.)
2. Intrapleural Pressure
goal: keeping the lungs from collapsing. needs: something that will pin the lungs to thoracic cavity wall mechanics: parietal if everything removed, ribs would
go outward ribs
visceral a. Parietal pleura
thin membrane lining the ribs, down to diaphragm and around the heart lung tissue is elastic
lung wants to collapse
naturally b. Visceral pleura
thin membrane that lines the lungs, c. Intrapleural space connective
tissue force countered in equal manner thin layer of water intrapleural pressure is "negative" as compared to atmospheric
intrapulmonary pressure. hence why its considered negative. needs to be lower than both athmospheric and intrapulmonary pressures Question: What happens if something punctures the pleura?
air will go into intraplueral space What would happen to intrapleural pressure?
will decrease What would happen to the lung on the injured side?
lung would collapse What would happen to the lung on the UNinjured side?
not affected at ﬁrst, could collapse later on What would happen to the chest wall on the injured side?
ribs will pop out on injured side What is this medical condition called?
pneumothorax IV. PHYSICAL PROPERTIES OF THE LUNGS
1. Pulmonary compliance: change in lung volume/change in pressure
how easy it is to expand the lung, outward measure.
we don't control lung, it is passive tissue, why its important.
as intrapulmonary pressure changes, how much air actually makes it
into the lung?
under normal conditions, lungs pretty compliant. only need about 3 mmHg needed to fill up
500mL. at 5mmHg we get about a liter of air.
point of diminishing return. limit to how much air we can get in. we will reach capacity of
fibrosis: non elastic fibers weave their way into lungs, compliance goes
down. needed 5x more pressure change for same amount of air. Will have to put a lot more
effort in to get same amount of air. more O2 used and CO2 produced. need to breath more
required. Emphysema: walls between alveoli break down, larger and larger alveoli, point of
one giant alveolus. easier to expand lung. can get a lot of air into lung, but no place for gas
exchange. 2. Elasticity: due to elastin fibers. like rubber bands, when left alone will snap back.
Elasticity is the opposite of compliance.
Elastic tension: increases during inspiration and decreases during expiration 3. Surface tension:
Natural tendency of water molecules to attract to ea...
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This note was uploaded on 09/30/2013 for the course P 215 taught by Professor Mynark during the Fall '12 term at Indiana.
- Fall '12