Sistem Pernafasan

Lingkup bahasan 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 Figure 17-2 b: Anatomy Summary

Paru: permukaan untuk pertukaran gas Luas: 75 m2; berdinding tipis dan lembab Dilindungi oleh tulang iga (costae), otot dan kulit Diafrgama dan tulang iga berperan sebagai pompa

Fungsi sistem pernafasan Pertukaran Oksigen (O2) dari udara ke darah dari darah ke sel Pertukaran CO2 dari sel ke darah dari darah ke udara Pengendalian pH darah Pembentukan suara Melindungi alveoli Figure 17-1: Overview of external and cellular respiration

Aliran udara dari luar hingga alveoli Udara disaring, dihangatkan dan lembab Melalui hidung (mulut), trachea, bronchi dan bronchiolus Luas permukaan yang dilalui semakin sangat besar Figure 17-4: Branching of the airways

Sifat fisika gas Gas dimampatkan; peningkatan tahanan akan menurunkan kekuatan arus Udara merupakan campuran gas; setiap gas dapat berdifusi secara independen

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

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

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

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

Gas exchange in the alveoli 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

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

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

Summary of Oxygen Transport

Gas Transport in the Blood: Carbon Dioxide Excess CO2 in blood (Hypercapnia) Leading to: acidosis, CNS depression & coma 7% in plasma, 23% bound to Hb & 70% as HCO3- acts as a buffer [H+]

Gas Transport in the Blood: Carbon Dioxide Figure 18-13: Carbon dioxide transport in the blood

Regulation of Ventilation: Central pattern generator Integrates input from cortex, limbic & chemoreceptors Rhythmic contractions of ventilation

Regulation of Ventilation: Central pattern generator Figure 18-15: Reflex control of ventilation

Regulation of Ventilation: Pons Center Dorsal respiratory group – inspiration Ventral respiratory group – forced breathing

Regulation of Ventilation: Chemoreceptors Carotid & aortic bodies: O2, CO2 & H+ receptors Medullary CO2 receptor Low [O2], high [CO2] & low [H+]  ventilation

Regulation of Ventilation: Chemoreceptors

Summary of Regulatory Ventilation Reflexes

Protective Reflexes Bronchoconstriction Irritant receptors Toxic particles Irritating particles (i.e. pollen) Hering-Breuer Reflex prevents over inflation Unconscious reflexes take over voluntary breathing

Summary Oxygen is transported bound to Hb and this is affected by temperature, pH, CO2 Carbon dioxide is transported in plasma, bound to Hb and acts as the buffer bicarbonate Respiration is regulated by CNS central pattern generator, pons center and peripheral carotid and aortic receptors Feedback reflexes coordinate circulation and ventilation to maintain blood O2, CO2, and H+ concentrations