Mechanics of Breathing Chapter 17 Mechanics of Breathing

About this Chapter Structure and function of the respiratory pumps How gasses are exchanged with blood The role of pressures and surfactants in rate of exchange How respiration is regulated

Respiratory System: Overview Lungs: exchange surface 75 m2 Thin walled Moist Ribs & skin protect Diaphragm & ribs pump air PLAY Animation: Respiratory System: Anatomy Review

Respiratory System: Overview Figure 17-2 b: Anatomy Summary

Functions of the Respiratory System: Overview Exchange O2 Air to blood Blood to cells Exchange CO2 Cells to blood Blood to air Regulate blood pH Vocalizations Protect alveoli Figure 17-1: Overview of external and cellular respiration

The Airways: Conduction of Air from Outside to Alveoli Filter, warm & moisten air Nose, (mouth), trachea, bronchi & bronchioles Huge increase in cross sectional area Figure 17-4: Branching of the airways

Key Gas Laws Reviewed Gas is compressible & flow  with  resistance Air is a mix of gasses, each diffuses independently

Key Gas Laws Reviewed Solubility of a gas depends on: Partial pressure of that gas (example: O2 =156 mmHg) Temperature Solubility in a particular solvent Water: solvent for life O2 into water: 0.1 m moles/L (poor) CO2 into water: 3.0 m mole/L (good) PLAY Animation: Respiratory System: Pulmonary Ventilation

Ventilation: The Pumps Inspiration Expiration Diaphragm Low energy pump Concavity – flattens Thorax: ribs & muscles Pleura: double membrane Vacuum seal Fluid-lubrication

Ventilation: The Pumps Figure 17-11 a: Surfactant reduces surface tension PLAY Animation: Respiratory System: Pulmonary Ventilation

Respiratory Damage & Diseases Pneumothorax ("collapsed lung") Fibrotic Lung Disease Emphysema Asthma NRDS

Respiratory Damage & Diseases Figure 17-11b: Surfactant reduces surface tension

Factors Affecting Ventilation Airway Resistance Diameter Mucous blockage Bronchoconstriction Bronchodilation Alveolar compliance Surfactants Surface tension Alveolar elasticity Figure 17-2e: Anatomy Summary

Lung Volumes: Spirometer Measurements Tidal volume: Inspiratory reserve Expiratory reserve Residual Vital capacity

Lung Volumes: Spirometer Measurements Figure 17-12: The recording spirometer

Lung Volumes: Spirometer Measurements Figure 17-14: Total pulmonary and alveolar ventilation

Efficiency of Breathing: Normal & High Demand Total Pulmonary Ventilation (rate X tidal vol about 6 L/min) Alveolar ventilation (– dead air space – 4.5 L/min) Little variation [O2] & [CO2] Exercise- High Demand  Depth of breathing Use inspiratory reserve

Efficiency of Breathing: Normal & High Demand Figure 17-14: Total pulmonary and alveolar ventilation

Efficiency of Breathing: Normal & High Demand Figure 17-2 g: Anatomy Summary

Gas Exchange in the Alveoli Thin cells: exchange Surfactant cells Elastic fibers Recoil Push air out Thin basement membrane Capillaries cover 90% of surface

Gas Exchange in the Alveoli Figure 17-2 h : Anatomy Summary

Gas Exchange in the Alveoli Figure 17-6: Ciliated respiratory epithelium

Matching Ventilation with Alveolar Blood Flow (Perfusion) Mostly local regulation Low [O2] in alveoli  vasoconstriction of arteriole Reduced blood flow at rest (lung apex ) saves energy High blood [CO2]  bronchodilation

Matching Ventilation with Alveolar Blood Flow (Perfusion) Figure 17-6: Ciliated respiratory epithelium

Summary Diaphragm & rib cage are pumps for inspiration Alveolar surface exchanges O2 & CO2 with blood The gasses in air act independently & move down a pressure gradient Airway resistance can limit ventilation efficiency Typically ventilation matches blood perfusion via local regulators of vasodilation & bronchodilation