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BIOL1412 03 17 2014.docx

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Department
Biological Sciences
Course
BIOL 1412
Professor
Paul Messing
Semester
Winter

Description
BIOL1412 03 17 2014  types: a. Quiet Inspiration  active process (muscle contract) (Fig. 22.12)  at startatm = al (760 mmHg) ­ no air moves, then:  diaphragm, external intercostals contract, ⇑ volume of thoracic cavity  lungs resist expansion i ⇓ (756 ⇒ 754 mmHg)  (Fig. 22.14)  higher pressure difference betweal and Pi pushes lungs out ⇒ lungs  expand ∴ Pal ⇓ (760 ⇒758 mmHg)  air moves in down P gradient (untal = atm) b. Forced Inspiration  involves diaphragm, external intercostals + sternocleidomastoids, pectoral minors,  scalenes (∴ active)  ⇑⇑ volume of thoracic cavity ∴ pressure gradient ⇑, and more air moves in c. Quiet Expiration (Fig. 22.13)  relax muscle ⇒ lungs to resting size ∴ ⇓ thoracic cavity (passive process)  volume ⇓, Pi (754 ⇒ 762 mmHg) (Fig. 22.14)  ∴ Pal (756 ⇒ 762 mmHg) ⇒ air moves out down pressure gradient d. Forced Expiration  laboured or impeded (eg. asthma) breathing  relax diaphragm, external intercostals + contract internal intercostals, abdominals  (ACTIVE Process)  Pi ⇑ ­ lung volume ⇓ ∴ Pal ⇑ and air moves out  Stretch in lungs determined by:  Compliance = effort needed to stretch lungs; low = much effect  Recoil = ability to return to resting size after stretch  both = result of elastic CT + surfactant  Lung collapse prevented by: a. Pi always below Palv (Fig. 22.14)  pneumothorax = air into pleural cavity  Pat = Pal = Pi ∴lungs collapse, thoracic wall expands b. Pressure of surfactant  = lipoprotein/phospholipid mixture  on surface of watery film on alveoli ­ ⇓ surface tension  allows easier stretc
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