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The Respiratory System II Physiology Physiology • The major function of the respiratory system is to supply the body with oxygen and to dispose of carbon dioxide • Events happening during respiration: 1. Pulmonary ventilation: Air must move into and out of the lungs; this process is commonly known as breathing 2. External respiration: Gas exchange between the pulmonary blood and alveoli must take place Physiology 3. Respiratory gas transport: Oxygen and carbon dioxide must be transported to and from the lungs and tissue via the blood stream 4. Internal respiration: Gas exchange between the blood and tissue cells Mechanics of Breathing • Volume changes leads to pressure change, which leads to the flow of gases to equalize the pressure • Inspiration: air is flowing into the lungs • Expiration: air is leaving the lungs • Inspiratory muscles: diaphragm and external intercostals Inspiration • At the end of a normal inspiration: - Chest is expanded - Rib cage is elevated - Diaphragm is depressed and flattened Expiration • At the end of a normal expiration: - Chest is depressed - Rib cage is descended - Diaphragm is elevated and domeshaped Forced expiration • Forced expiration: the internal intercostal muscles are activated to help depress the rib cage, and the abdominal muscles contract - Asthma: the respiratory passageways are narrowed by spasms of the bronchioles - Pneumonia: the respiration passageways are clogged with fluid or mucus Respiratory Volumes and Capacities • Tidal volume (TV): the amount of air into and out of the lungs when breathing normally and quietly (approximately 500 ml of air) • Inspiratory reserve volume (IRV): the amount of air that can be taken in forcibly over the tidal volume (approximately 21003200 ml of air) Respiratory Volumes and Capacities • Expiratory reserve volume (ERV): The amount of air can be forcibly exhaled after a tidal expiration (approximately 1200 ml) • Residual volume (RV): Even after the most strenuous expiration, about 1200 ml of air still remains in the lungs, and it can not be voluntarily expelled • Vital Capacity (VC): the total amount of exchangeable air ( TV+IRV+EVR) Dead Space Volume • The amount of air remains in the conducting zone passageways and never reaches the alveoli Respiratory Sounds • Bronchial sounds: are produced by air rushing through the large respiratory passageways • Vesicular sounds: occurs as air fills the alveoli Respiration External Respiration: • It is the actual exchange of gases between the alveoli and the blood • Gas exchanges in the body occur according to the laws of diffusion Internal Respiration: • It is the exchange of gases that takes place between the blood and the tissue cells Oxygen Transport in the Blood • Oxygen is transported in the blood in two ways: - Most attaches to hemoglobin molecules inside the red blood cells to form oxyhemoglobin - A very small amount of oxygen is carried dissolved in the plasma Carbon Dioxide Transport in the Blood • Most carbon dioxide is transported in plasma as the bicarbonate ion (HCO3-) • A smaller amount (between 20%-30%) is carried inside the red blood cells bound to hemoglobin - Carbon dioxide attaches to hemoglobin at a different site than oxygen does, so it does not interfere in any way with oxygen transport Carbon Dioxide Transport in the Blood • Before carbon dioxide can diffuse out of the blood into the alveoli, it must: - Combine with hydrogen ions (H+) to form carbonic acid (H2CO3) - carbonic acid (H2CO3) quickly splits to form water and carbon dioxide - Carbon dioxide then diffuses from the blood and enters the alveoli - HCO3- + H+ H2CO3 CO2 + H2O