gul_lect - 1 LECTURE NOTES ON HUMAN RESPIRATORY SYSTEM...

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1 LECTURE NOTES ON HUMAN RESPIRATORY SYSTEM PHYSIOLOGY (Dr. GÜL ERDEMLI) CONTENTS 1. MECHANICS OF BREATHING: 2. REGULATION AND CONTROL OF BREATHING: 3. VENTILATION 4. LUNG VOLUMES AND PULMONARY FUNCTION TESTS 5. DIFFUSION 6. PERFUSION 7. GAS TRANSPORT TO THE PERIPHERY 8. ACID-BASE REGULATION 9. RESPIRATORY SYSTEM UNDER STRESS 10. RECOMMENDED FURTHER READING: 11. SELF ASSESSMENT
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2 1. MECHANICS OF BREATHING : INSPIRATION: Inspiration is the active part of the breathing process, which is initiated by the respiratory control centre in medulla oblongata (Brain stem). Activation of medulla causes a contraction of the diaphragm and intercostal muscles leading to an expansion of thoracic cavity and a decrease in the pleural space pressure. The diaphragm is a dome-shaped structure that separates the thoracic and abdominal cavities and is the most important muscle of inspiration. When it contracts, it moves downward and because it is attached to the lower ribs it also rotates the ribs toward the horizontal plane, and thereby further expands the chest cavity. In normal quite breathing the diaphragm moves downward about 1 cm but on forced inspiration/expiration total movement could be up to 10 cm. When it is paralysed it moves to the opposite direction (upwards) with inspiration, paradoxical movement . The external intercostal muscles connect adjacent ribs. When they contract the ribs are pulled upward and forward causing further increase in the volume of the thoracic cavity. As a result fresh air flows along the branching airways into the alveoli until the alveolar pressure equals to the pressure at the airway opening. EXPIRATION: Expiration is a passive event due to elastic recoil of the lungs. However, when a great deal of air has to be removed quickly, as in exercise, or when the airways narrow excessively during expiration, as in asthma, the internal intercostal muscles and the anterior abdominal muscles contract and accelerate expiration by raising pleural pressure. COUPLING OF THE LUNGS AND THE CHEST WALL: The lungs are not directly attached to the chest wall but they change their volume and shape according to the changes in shape and volume of the thoracic cavity. Pleura covering the surfaces of the lungs (visceral) or the thoracic cavity (parietal) together with a thin (20 μm) layer of liquid between them create a liquid coupling.
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3 PRESSURE-VOLUME RELATIONSHIPS: In the pulmonary physiology absolute pressure means atmospheric pressure (760 mm Hg at sea levels). The pressures and the pressure differences of the respiratory system are expressed as relative pressures to the atmospheric pressure. When it is said that alveolar pressure is zero, it means that alveolar pressure = atmospheric pressure. If one excises animal lung and places it in a jar, one could measure the changes in volume with a
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This note was uploaded on 05/05/2011 for the course BIOL 400 taught by Professor Dr.biology during the Spring '11 term at University of Tennessee.

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gul_lect - 1 LECTURE NOTES ON HUMAN RESPIRATORY SYSTEM...

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