Funcons of the Respiratory System

•Gas exchange •Regulaon of blood pH •Voice producon •Olfacon •Protecon

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Funcons of the Nasal Cavity

•Filtraon of inspired air •Humidificaon of inspired air •Warming of inspired air •Passageway for venlaon •Locaon of olfactory epithelium •Resonance during speech

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Respiratory membrane Capillary endothelial cell Bronchiole Fluid with surfactant Pulmonary arteriole Squamous alveolar cell Pulmonary venule Lymphocyte Alveoli Alveolar sac

(b) Great Alveolar Capillary alveolar macrophage networks cell around Terminal alveoli bronchiole

Respiratory Air Respiratory membrane: bronchiole Squamous alveolar cell CO2 Shared basement membrane Capillary endothelial cell O2

Blood (a)

(c)

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Air Air Expired air Inspired air

O PO2 116 mm Hg P 2 159 mm Hg

PCO2 32 mm Hg PCO2 0.3 mm Hg

Alveolar gas exchange Alveolar air

PO 104 mm Hg Time O2 loading 2 PCO2 40 mm Hg CO2 unloading

CO2 O2

Blood Blood

Gas transport Pulmonary circuit Inial state Equilibrium state O2 carried from alveoli to systemic ssues (a) Oxygen Deoxygenated CO2 carried blood Oxygenated blood from systemic PO 95 mm Hg ssues to PO2 40 mm Hg 2 CO alveoli PCO2 46 mm Hg P 2 40 mm Hg Air Air

Systemic circuit Time

Systemic CO2 O2 gas exchange

Blood O unloading Blood 2 CO2 loading Tissue fluid

PO2 40 mm Hg Inial state Equilibrium state PCO2 46 mm Hg

(b) Carbon dioxide 21 22

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O Reduced P 2 in Decreased Increased Elevated PO2 in blood vessels airflow airflow blood vessels

Response Result: Response Blood flow to reduced to increased venlaon matches airflow venlaon Vasoconstricon of Vasodilaon of pulmonary vessels pulmonary vessels

Decreased Increased blood flow blood flow

(a) Perfusion adjusted to changes in venlaon

Decreased Increased Reduced PCO Elevated PCO 2 blood flow blood flow 2 in alveoli in alveoli

Response Result: Response to reduced Airflow matches to increased perfusion blood flow perfusion Constricon of Dilaon of bronchioles bronchioles

Decreased Increased airflow airflow (b) Venlaon adjusted to changes in perfusion 23 24 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproducon or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproducon or display. 100 10°C 90 20°C 20 38°C 100 80 43°C O2 unloaded 70 to systemic 60 Normal body ssues 50 80 15 temperature 40 30 20

60 Percentage saturaon of hemoglobin 10 10 0 0 20 40 60 80 100 120 140

PO2 (mm Hg) 40 (a) Effect of temperature /dL of blood saturaon of hemoglobin 2 2 5 100 90 pH 7.60

20 mL O 80 pH 7.40 70 (normal blood pH) 60 pH 7.20 Percentage O 0 50 0 20 40 60 80 100 40 30 20 10 Systemic ssues Alveoli Percentage saturaon of hemoglobin 0 0 20 40 60 80 100 120 140 PO (mm Hg) Paral pressure of O (PO ) in mm Hg 25 2 26 2 2 (b) Effect of pH

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Tumors

(a) Healthy lung, mediasnal surface (b) Smoker's lung with carcinoma

a: © The McGraw-Hill Companies/Dennis Strete, photographer; b: Biophoto Associates/Photo Researchers, Inc. 31 32