Respiratory Physiology

Fig. 21.13

↑ container size, ↓ pressure Boyle’s Gas Law ↑ container size, ↓ pressure P1V1 = P2V2

↑ container size, ↓ pressure Inspiration: ↑ container size, ↓ pressure

↓ container size, ↑ pressure Expiration: ↓ container size, ↑ pressure

Compliance Lessens with… ossified cartilage damage (fibrosis) stroma (Stretchiness of lungs) Lessens with… ossified cartilage damage (fibrosis) stroma

Physical principles of gas exchange (Dalton’s law of partial pressure) © 2014 Pearson Education, Inc.

© 2014 Pearson Education, Inc. Figure 21.17 Partial pressure gradients promoting gas movements in the body. Inspired air: PO2 PCO2 160 mm Hg 0.3 mm Hg Alveoli of lungs: PO2 PCO2 104 mm Hg 40 mm Hg External respiration Alveoli Pulmonary arteries Pulmonary veins (PO2 100 mm Hg) Blood leaving tissues and entering lungs: Blood leaving lungs and entering tissue capillaries: PO2 PCO2 40 mm Hg 45 mm Hg PO2 PCO2 100 mm Hg 40 mm Hg Heart Systemic veins Systemic arteries Internal respiration Tissues: PO2 less than 40 mm Hg PCO2 greater than 45 mm Hg © 2014 Pearson Education, Inc.

Figure 21.17 Partial pressure gradients promoting gas movements in the body. Inspired air: PO2 PCO2 160 mm Hg 0.3 mm Hg Alveoli of lungs: PO2 PCO2 104 mm Hg 40 mm Hg External respiration Alveoli Pulmonary arteries Pulmonary veins (PO2 100 mm Hg) Blood leaving tissues and entering lungs: Blood leaving lungs and entering tissue capillaries: PO2 PCO2 40 mm Hg 45 mm Hg PO2 PCO2 100 mm Hg 40 mm Hg Heart Systemic veins Systemic arteries Internal respiration (Hand out) Tissues: PO2 less than 40 mm Hg PCO2 greater than 45 mm Hg © 2014 Pearson Education, Inc.

Figure 21.9a Alveoli and the respiratory membrane. Terminal bronchiole Respiratory bronchiole Smooth muscle Elastic fibers Alveolus Capillaries Diagrammatic view of capillary-alveoli relationships © 2014 Pearson Education, Inc.

Figure 21.9c Alveoli and the respiratory membrane. PO2 40 mmHg Red blood cell Nucleus of type I alveolar cell Alveolar pores Capillary Capillary PO2 104 mmHg Macrophage Alveolus Endothelial cell nucleus Alveolus Alveolar epithelium Respiratory membrane Fused basement membranes of alveolar epithelium and capillary endothelium Alveoli (gas-filled air spaces) Red blood cell in capillary Type II alveolar cell Type I alveolar cell Capillary endothelium Detailed anatomy of the respiratory membrane © 2014 Pearson Education, Inc.

PO2 104 mm Hg 150 100 PO2 (mm Hg) 50 40 0.25 0.50 0.75 Time in the Figure 21.18 Oxygenation of blood in the pulmonary capillaries at rest. 150 Oxygenation of blood takes 0.25 sec 100 PO2 104 mm Hg PO2 (mm Hg) 50 40 0.25 0.50 0.75 Time in the pulmonary capillary (s) Start of capillary End of capillary © 2014 Pearson Education, Inc.

What affects simple diffusion through respiratory membranes?

Consequences?

Diabetic foot ulcer

Gangrene

Solutions?

Constant O2 supplement (nasal cannula in nose)

Hyperbaric therapy: high pressure oxygen chamber (PO2 2000-3000 mmHg) drives CO off hemoglobin

Diabetic foot ulcer

98% of O2 picked up in pulmonary capillaries is carried by RBC hemoglobin molecule Red blood cell Nucleus of type I alveolar cell Alveolar pores Capillary Capillary Macrophage Alveolus Endothelial cell nucleus Alveolus Alveolar epithelium Respiratory membrane Fused basement membranes of alveolar epithelium and capillary endothelium Alveoli (gas-filled air spaces) Red blood cell in capillary Type II alveolar cell Type I alveolar cell Capillary endothelium Detailed anatomy of the respiratory membrane © 2014 Pearson Education, Inc.

Hb 98% saturated = PO2 ~100 mmHg Fully saturated: all 4 heme groups bound to O2 Hb 98% saturated = PO2 ~100 mmHg

Figure 21.22 Transport and exchange of CO2 and O2. Tissue cell Interstitial fluid (dissolved in plasma) Binds to plasma proteins Slow Chloride shift (in) via transport protein Fast Carbonic Anhydrase (Carbamino- hemoglobin) Red blood cell (dissolved in plasma) Blood plasma Oxygen release and carbon dioxide pickup at the tissues Alveolus Fused basement membranes (dissolved in plasma) Slow Chloride shift (out) via transport protein Fast Carbonic anhydrase (Carbamino- hemoglobin) Red blood cell (dissolved in plasma) Blood plasma © 2014 Pearson Education, Inc. Oxygen pickup and carbon dioxide release in the lungs

Hemoglobin Dissociation Curve Hand out: Hemoglobin Dissociation Curve

Anemic hypoxia: too little Hb from too few rbcs or improperly made rbcs Ischemic hypoxia: systemic blockage by MI or localized by thrombus or emboli Hypoxemic hypoxia: arterial PO2 low, probable diffusion problem in lungs

Diagrams of gas transport Hand out: Diagrams of gas transport

Neural mechanisms Higher brain centers (cerebral cortex—voluntary Figure 21.24 Neural and chemical influences on brain stem respiratory centers. Neural mechanisms Higher brain centers (cerebral cortex—voluntary control over breathing) + Other receptors (e.g., pain) and emotional stimuli acting through the hypothalamus – + – Respiratory centers (medulla and pons) Peripheral chemoreceptors + Stretch receptors in lungs + – Central chemoreceptors – Irritant receptors + Receptors in muscles and joints © 2014 Pearson Education, Inc.

Normal resp. rate 12-16 rpm Pons Medulla Pontine respiratory centers Figure 21.23 Locations of respiratory centers and their postulated connections. Pons Medulla Pontine respiratory centers interact with medullary respiratory centers to smooth the respiratory pattern. Ventral respiratory group (VRG) contains rhythm generators whose output drives respiration. Pons Medulla Dorsal respiratory group (DRG) integrates peripheral sensory input and modifies the rhythms generated by the VRG. Normal resp. rate 12-16 rpm To inspiratory muscles External intercostal muscles © 2014 Pearson Education, Inc. Diaphragm

Factors Influencing Breathing Rate Stimulus to ↑ respiration rate & depth IF ___ PCO2, ___ PO2, ___ [H+] Stimulus to ↓ respiration rate & depth ↑ ↓ ↑ (≤60mmHg) ↓ ↑ ↓

Apnea Hyperventilation Hyperpnea

Lung Diseases Chronic Obstructive Pulmonary Disease (COPD) Asthma Pulmonary Tuberculosis Lung Cancer

Figure 21.27 The pathogenesis of COPD. • Tobacco smoke • Air pollution α-1 antitrypsin deficiency Continual bronchial irritation and inflammation Breakdown of elastin in connective tissue of lungs Chronic bronchitis Emphysema • Excess mucus production • Destruction of alveolar walls • Chronic productive cough • Loss of lung elasticity • Airway obstruction or air trapping • Dyspnea • Frequent infections • Hypoventilation • Hypoxemia • Respiratory acidosis © 2014 Pearson Education, Inc.