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Respiratory Physiology Study Notes.docx
Respiratory Physiology Study Notes.docx

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Western University
Physiology 2130

Respiratory Physiology Study Notes The Functions of the Respiratory System  Provides oxygen to the blood and the cells to produce ATP  Removes carbon dioxide from the blood (waste product)  Regulates [H+] (blood PH) 7.35-7.40  Speech  Microbe defense  Influences arterial concentration of chemical messenger’s  Traps and dissolves small blood clots  GAS EXCHANGE Basic Lung Anatomy Blood Vessels and Blood Flow  Five factors that maximize simple diffusion across the Blood gas barrier: o Short diffusion distance (0.2 microns) o Very large surface area o Gradient for diffusion o Lipid soluable substances (CO2 and O2) o Slow blood flow Diagram of the Alveoli and Blood Supply Mechanisms of Pulmonary Ventilation  Boyles law o States that pressure varies inversely with the volume o Pressure= 1/ volume o Meaning that a closed volume of gas, when the volume increases the pressure decreases o Inverse relationship  Physical environment of the lungs o Atmospheric pressure (760mmHg) o Alveolar pressure (varies) between breathes (760mmHg)  This should be greater that the intraplueral space, if it is lower the lung will collapse o Intrapleural space (756mmHg) between breathes  Transpulmonary pressure o Alveolar pressure – intrapleural pressure o 760 – 756 = +4mmHg o The significance of this is it is an outward force keeping lungs inflated, so the lungs don’t collapse when exhaling  Pneumothorax o Pressure in the lungs equalizes intrapleural space o Usually due to a puncture in the lung o 760 – 760 = 0 – keeping inflated, lungs collapse Diagram of the lungs (pressure)  Inhalation and exhalation o The movement of air requires a pressure gradient o In order to move in there must be a high pressure eon the outside and a low pressure on the inside o Process Inhalation Exhalation Alveolar pressure Increased Decreased Thoracic volume Increased Decreased Movement of air In Out Rest Active Passive (no contraction) Active muscles External intercostal and None the diaphragm Exercise Active Active External intercostal Causes increase in muscles and the alveolar pressure diaphragm Active muscles during External intercostal Internal intercostal exercise muscles and the Rectus abdominus diaphragm Internal/external obliques Diagram of the process involved in Inspiration Diagram of the process involves in Expiration Elastic properties of the Lungs  Pulmonary compliance o Defined as the change in lung volume as a result of a change in alveolar pressure o Compliance = change in lung volume/ change in lung pressure o Measure of the stretch ability of the lungs, the more compliant, the more it will stretch o Two major factors effecting  The elastic tissue components  Surface tension: of the surfactant o An increase in either of the above will decrease the compliance of the lungs, and increase the likelihood that the lungs will collapse o Elastic tissue compliance: fibers of elastin and collagen are present on alveolar walls throughout the lungs o It decreases the compliance by  Accounts for 1/3 of the elastic behaviour of the lungs  The more elastin, the more the lungs want to collapse/recoil, the harder it is for them to expand o Surface tension: is the forced developed at the surface of a liquid due to the intermolecular attraction between water molecules  Liquid that lines the alveoli – the surface tension accounts for 2/3 of the elastic behaviour of the lungs (it is a very powerful recoiling force). It prevents the lungs from expanding and promotes lung collapse causing a decrease in compliance.  Properties of pulmonary surfactant:  It is a phospholipid protein complex that is both hydrophilic and hydrophobic  Water wants to collapse the lung because the molecules are attracted to each other  Surfactant diminishes attractive force  It can lie on the surface of a liquid and reduce surface tension  It is produced late in fetal life  Deep breathing stimulates surfactant production  Before 34 weeks, no surfactant Diagram showing alveolar surfactant Lung Volumes  Tidal volume: air you can breathe in/out at rest, ~500ml, increases with exercise (TV)  Vital capacity: maximum air that you can breathe in/out. This naturally decreases with age. ~4500ml (VC)  Inspiratory Capacity; max air that you can breathe in (TV+IRV)  Inspiratory reserve volume: additional air you can breathe in if you need to. (IRV)  Expiratory Capacity: maximum air that you can breathe out (TV + ERV)  Expiratory reserve volume: additional air that you can breathe out if you need to (ERV)  Residual volume: air remain in the lungs after max exhale (RV)  Total lung capacity: (RV + VC) everything  Forced vital capacity: max you can breathe out as fast as you can (FVC) Diagram of an FVC curve Respiratory diseases  Asthma: can be triggered by exercise, sudden changes in humidity and temperature and allergies o Hyper responsive bronchioles, swell, bronchoconstriction o Increased airway resistance, decreased air flow  Chronic Bronchitis o Smoking damages prot
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