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Unformatted text preview: Monday, November 14, 2011 8:00 AM Chapter Sixteen – Respiratory System Diffusion from high to low… air into the blood Steps of Respiration • Red=blood • O2 and CO2 are the respiratory gasses. • Everything is driven by diffusioin. NO ATP. Just concentration gradients of the gasses. Respiration • Comprises 3 related functions: o Ventilation (breathing). o Gas Exchange(a)air/blood;(b)blood/tissues o Oxygen Utilization by tissues in cellular respiration. • External respiration (1&2a together). o Ventilation moves air in & out of lungs for gas exchange with blood and alveoli. • Internal respiration (2b&3 together). o Gas exchange between blood & tissues; O 2 used by tissues. Gas exchange passive - diffusion (v. rapid in lung). Lung Alveoli and Pulmonary Capillaries • Gas exchange occurs across alveoli (300 million, 60-80 m 2 total surface area). • Only 2 thin cells between lung air & blood: 1 alveolar + 1 endothelial. • DIFFUSION FAST: Large SA + thin barrier • Simple squamous epithelium • Alvioulus- contains macrophages (killer cells). • Surfactant- stops alveolar from collapsing (type I) • Big surface area. (tennis court size) Thoracic Cavity • 2 lungs and heart • Lungs o Plurel Membrane (serous)- 2 layers with fluid in between layers. o Viseral (internal)/Parietal (external) Plural. o Plureal cavity (space between membranes) • Heart o Paracardial Membrane- around heart. • Visceral & parietal pleurae normally stick to each other so that lungs remain in contact with chest walls & expand & contract with thoracic cavity Physical Aspects of Ventilation • Ventilation results from pressure differences brought about by changes in lung volumes • Air moves from higher to lower pressure. • Compliance, elasticity, & surface tension of lungs influence ease of ventilation. • Intrapleural space is thin fluid layer between visceral pleura covering lungs & parietal pleura lining thoracic cavity walls • Pressure difference brought by changes in lung volume (breathing in=increasing lungs) Boyle’s Law • P = 1/V Muscles involved in Breathing • Diaphram-dome shaped at rest, when contracted it flatens out. Quiet Breathing • Inspiration occurs mainly because diaphragm contracts, increasing thoracic volume vertically. • External intercostal muscles contribute to inspiration a little by raising ribs, increasing thoracic volume laterally. • Expiration at rest is due to passive recoil. Deep Breathing • Deep Inspiration involves contraction of external intercostals, plus pectoralis minor & sternocleido-mastoid muscles to elevate ribs. • Forced Expiration involves contraction of internal intercostals & abdominal muscles....
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