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Respiratory Physiology.docx

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Physiology 2130

Respiratory Physiology - responsible for transport of oxygen in the air to the blood and removal of CO2 from blood to air 7 functions: 1) Provides O2 2) Removes CO2 3) Regulates blood pH 4) Speech 5) Microbial defense 6) Chemical messenger concentrations 7) Traps and dissolves small blood clots Lung Anatomy- Thoracic Cavity: lungs suspended in thoracic cavity and surrounded by chest wall. Space between lungs and chest wall is called intrapleural space (.5mm) intrapleural fluid = 1-5ml. Under lungs is the diaphragm - Trachea- 1 - right and left primary bronchi- 2 - right lung (3 lobes) and left lung (2 lobes) - bronchioles- 35 - terminal bronchioles- 600 - respiratory bronchioles- 5000 - alveolar ducts - alveoli- 3-6 billion and SA 75m2 Conduction Zone “anatomical dead space”: provides tow resistance to air flow, microbe defence, filters, warm and moisten air and conduct into lungs Respiratory Zone: where gas exchange of 02 and C02 occurs Blood Vessels and Blood Flow: - Pulmonary artery branches into capillaries that wrap around the alveoli - Blood gas barrier .05um Maximize diffusion across BGB ( flicks law) rate of diffusion= gradient x SA / thickness: 1) thin membrane (short diffusion distance) 2) high surface area (75m2) 3) high pressure gradient 4) blood velocity (slow blood flow) 5) lipid solubility of substance ( CO2 and 02 lipid soluble) Pulmonary Ventilation- Boyles Law: pressure is inversely proportional to volume as shown by: pressure 1/volume - this means that as volume increases, pressure decreases and as volume decreases pressure increases (inverse relationship) - atmospheric pressure = 760mmHg - intrapulmonary pressure= 760mmhg - inward force of elastic lungs and outward force of elastic ribs Inhalation (contraction): - external intercostal muscles and diaphragm Contract - high pressure outside, low inside therefore air moves into lungs from high to low - during exercise forced inhalation, contraction of above muscles increases volume of thoracic, and decreases alveolar pressure Expiration (relaxation): - relax external intercostal and diaphragm muscles - high pressure inside, low outside so air moves out - during exercise, contraction of obliques, rectus dominus and intercostal muscles - these muscles decrease the volume causing increase in alveolar pressure… get an ab workout!  Lungs never deflate completely after exhalation Lung Compliance “stretchbility”: Compliance= change in lung volume/change in lung pressure - compliance is a measure of stretchability of the lung. The more compliant the lung, the easier it will stretch (increase vol) 2 Factors Influencing Compliance: 1) the elastic tissue components of the lung itself 2) surface tension inside the alveoli - an increase in either of the above will decrease compliance and increase chance that lungs will collapse Intrapleaural pressure: - allows for easy expansion of lungs (no resistance to inflation) - makes sure lungs don’t collapse at end of expiration Transpulmonary Pressure= intrapulmonary pressure/intrapleural pressure - should be +5mmHg - pneumothorax (collapsed lung) occurs when air is in space around lungs ( transpulm pressure less that 5) Elastic Tissue Component of the Lung: fibers of elastin and collagen are present in alveolar walls and throughout the lung - accounts for 1/3 of elastic behavior in lungs - the more the elastin, the more the lungs want to collapse/recoil, and the harder it is to inflate the lungs (decreases compliance) Surface tension: a force developed at the surface of a liquid due to attraction between water molecules - thin film of liquid on alveoli with surface tension and accounts for 2/3 of elastic behavior of lungs - prevents lungs from expanding and promotes lung collapse, decreasing compliance Pulmonary Surfactant: a phospholipid protein complex that is both hydrophobic and hydrophilic - reduces surface tension (prevents alveolar collapse) - microbe defense - produced late in fetal life and stimulated by deep breathing *Neonatal respiratory distress syndrome:poor lung function- administer surfactant Tidal Volume (TV)- The amount of air breathed in or out
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