Transcript Chapter 17
Chapter 17 Mechanics of Breathing About this Chapter • The respiratory system • Gas laws • Ventilation Respiratory System Functions • External Respiration • Exchange of gases between the atmosphere and the blood • Homeostatic regulation of body pH • Protection from inhaled pathogens and irritating substances • Vocalization Respiratory System Principles of Bulk Flow • Flow from regions of higher to lower pressure • Muscular pump creates pressure gradients • Resistance to flow • Diameter of tubes Respiratory System CO2 • Overview of external and cellular respiration O2 Exchange I: atmosphere to lung (ventilation) Airways Alveoli of lungs CO2 O2 Exchange II: lung to blood O2 CO2 Pulmonary circulation Transport of gases in the blood Systemic circulation CO2 O2 CO2 Exchange III: blood to cells O2 Cellular respiration Cells Nutrients ATP Figure 17-1 Respiratory System Components • Conducting system • Alveoli • Bones and muscle of thorax Respiratory System ANATOMY SUMMARY THE LUNGS AND THORACIC CAVITY Pharynx Nasal cavity Vocal cords Tongue Esophagus Upper respiratory system Larynx Trachea Lower respiratory system Right lung Right bronchus Left lung Diaphragm Left bronchus (a) The respiratory system Figure 17-2a Muscles Used for Ventilation Sternocleidomastoids Scalenes Internal intercostals External intercostals Diaphragm Abdominal muscles Muscles of inspiration Muscles of expiration (b) Muscles used for ventilation Figure 17-2b The Respiratory System Air-filled balloon Fluid-filled balloon Air space of lung Pleural fluid Pleural membrane Figure 17-3 Branching of Airways ANATOMY SUMMARY THE LUNGS AND THORACIC CAVITY Larynx Trachea Cartilage ring Left primary bronchus Secondary bronchus Bronchiole Alveoli (e) Branching of airways Figure 17-2e Branching of the Airways Figure 17-4 Conditioning Air • Warming air to body temperature • Adding water vapor • Filtering out foreign material Ciliated Respiratory Epithelium Cilia move mucus to pharynx Dust particle Mucus layer traps inhaled particles. Watery saline layer allows cilia to push mucus toward pharynx. Cilia Goblet cell secretes mucus. Nucleus of columnar epithelial cell Basement membrane Ciliated epithelium of the trachea Figure 17-5 Alveolar Structure – Note cell types of alveoli Figure 17-2g Pulmonary Circulation • Right ventricle pulmonary trunk lungs pulmonary veins left atrium • Note oxygenation Anatomy Review PLAY Interactive Physiology® Animation: Respiratory System: Anatomy Review Gas Laws Table 17-1 Gas Laws • Pgas = Patm % of gas in atmosphere Table 17-2 Boyle’s Law • Gases move from areas of high pressure to areas of low pressure Figure 17-6 Spirometer Bell Inspiration Expiration Inspiration Expiration Air 0.5 Volume (L) Water 0 Time Figure 17-7 Lung Volumes and Capacities Figure 17-8 Air Flow • Flow P/R • Alveolar pressure or intrapleural pressure can be measured • Single respiratory cycle consists of one inspiration followed by one expiration Movement of the Diaphragm Figure 17-9a Movement of the Diaphragm Figure 17-9b Movement of the Diaphragm Figure 17-9c Dimensions of the Thoracic Cavity During Inspiration Figure 17-10a Dimensions of the Thoracic Cavity During Inspiration Figure 17-10b Pressure Changes During Quiet Breathing Inspiration Expiration Inspiration Expiration +2 Alveolar pressure (mm Hg) Trachea A1 A4 A3 +1 0 A5 Bronchi –1 A2 –2 Lung B1 Intrapleural pressure (mm Hg) B3 –3 –4 –5 Diaphragm Right pleural cavity –6 B2 Left pleural cavity 750 Volume of air moved (mL) 500 C2 250 C1 C3 0 1 2 3 4 5 Time (sec) 6 7 8 Figure 17-11 Subatmospheric Pressure in the Pleural Cavity P = –3 mm Hg Intrapleural pressure is subatmospheric. Ribs Intrapleural space Pleural membranes Diaphragm Elastic recoil of the Elastic recoil of lung chest wall tries to pull creates an inward pull. the chest wall outward. (a) Normal lung at rest Figure 17-12a Subatmospheric Pressure in the Pleural Cavity • Pneumothorax results in collapsed lung that cannot function normally P = Patm Knife Lung collapses to unstretched size Intrapleural space Pleural membranes The rib cage expands slightly. If the sealed pleural cavity is opened to the atmosphere, air flows in. (b) Pneumothorax Figure 17-12b Compliance and Elastance • Compliance: ability to stretch • High compliance • Stretches easily • Low compliance • Requires more force • Restrictive lung diseases • Fibrotic lung diseases • Inadequate surfactant production • Elastance: returning to its resting volume when stretching force is released Law of LaPlace • Surface tension is created by the thin fluid layer between alveolar cells and the air Figure 17-13 Surfactant • More concentrated in smaller alveoli • Mixture containing proteins and phospholipids • Newborn respiratory distress syndrome • Premature babies • Inadequate surfactant concentrations Air Flow Table 17-3 Pulmonary Ventilation PLAY Interactive Physiology® Animation: Respiratory System: Pulmonary Ventilation Ventilation • Total pulmonary ventilation is greater than alveolar ventilation because of dead space • Total pulmonary ventilation = ventilation rate tidal volume Ventilation Dead space filled with fresh air 150 mL 1 2700 mL The first exhaled air comes out of the dead space. Only 350 mL leaves the alveoli. 2 Exhale 500 mL (tidal volume) Atmospheric air Dead space is filled with fresh air. Only 350 mL of fresh air reaches alveoli The first 150 mL of air into the alveoli is stale air from the dead space. 1 End of inspiration 3 At the end of expiration, the dead space is filled with “stale” air from alveoli. 4 Inhale 500 mL of fresh air (tidal volume). 2 150 mL 150 350 RESPIRATORY CYCLE IN ADULT 2200 mL 150 2200 mL 4 Dead space filled with stale air KEY PO2 = 150 mm Hg (fresh air) PO2 ~ ~ 100 mm Hg (stale air) 150 mL 2200 mL 3 Figure 17-14 Ventilation • Alveolar ventilation = ventilation rate (tidal volume – dead space volume) Table 17-4 Ventilation Table 17-5 Ventilation Table 17-6 Ventilation • As alveolar ventilation increases, alveolar PO2 increases and PCO2 decreases Figure 17-15 Ventilation Table 17-7 Ventilation • Local control mechanisms attempt to match ventilation and perfusion Figure 17-16a Ventilation Figure 17-16b Ventilation Figure 17-16c Ventilation • Auscultation = diagnostic technique • Obstructive lung diseases • Asthma • Emphysema • Chronic bronchitis Summary • Respiratory system • Cellular respiration, external respiration, respiratory system, upper respiratory tract, pharynx, and larynx • Lower respiratory tract, trachea, bronchi, bronchioles, alveoli, Type I and Type II alveolar cells • Diaphragm, intercostal muscles, lung, pleural sac, and pleural fluid • Gas Laws: Dalton’s law and Boyle’s law Summary • Ventilation • Tidal volume, vital capacity, residual volume, and respiratory cycle • Alveolar pressure, active expiration, intrapleural pressures, compliance, elastance, surfactant, bronchoconstriction, and bronchodilation • Total pulmonary ventilation, alveolar ventilation, hyperventilation, and hypoventilation