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USC BISC 307L - Respiratory System
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Functions of Respiratory Systemblood buffers (bicarbonate)respiratory regulation of body pH is much slower than blood buffers but kidneys fastestLungs and Thoracic CavityUpper is divided into 3 (right pleural cavity, pericardial cavity, and left pleural cavity)Pleural cavity is where the lung sits and is lined with the pleural membranesIn the intrapleural space there is pleural fluid which is a slippery mucus used for breathing and movement (prevents friction or damage)Muscles involved in inspirtartion (external intercostal muscles, diaphragm, and scaines, and sternociedomastoids)Expiration (abdominal muscles and internal intercostal muscles)Lung Lobules and AlveoliBe familiar with parts (larynx to bronchi know are rigid tubes with cartilage)The bronchioles are collapsible with no cartilage but do have smooth muscle (open and close with breathing movement) can cause bronchiole constriction or dilationAlveoli – gas exchange only occurs hereCluster of grapes2 types of epithelial cells lining: Type 1 (flat, gas exchange) Type 2 (thicker, secrete mucus containing surfactant to coat inside)surrounded by capillaries- distance about 0.1-1.5 micrometers from alveolar air to the RBC- thin cellsProperties of GasesPartial pressure of oxygen is about 160mmHg at sea levelThe pressure of oxygen goes down as you go up in altitudeBut oxygen is always 21% of whatever the pressure is at that altitudeBoyles Law: pressure inversely proportional to volume. If you change lung volume you will cange the pressure- this is important for generating pressure gradients that drive air flow into and out of the lungsPressure Changes in Quiet Breathingmeasuring the pressure in the alveoli (difference between atmospheric pressure and alveolar pressure creates pressure gradient)Intrapleural pressure is the pressure in that tiny spaceTime 0: just expired haven’t inspired yet- no air is going into or out of the system because there is no pressure gradient pressure in the alveolar but the intrapleural pressure is less than the atmospheric pressure so there is a pressure pushing air out of the lung – the outside of the lung is stuck. Intrapleural pressure is always negative (below atmospheric pressure and alveolar pressure)Thoracic cavity grows more than the lungs so when the lungs are fully inflated their volume is less than the cavity it occupiesThe lungs want to pull away from the wall so this is what creates the negative pressure in the intrapleural spaceInspiration: diaphragm pushes down, volume of the pleural cavity increases and the pressure falls creating a pressure gradient and air come in. As it expands, the lung expands too, but because it is elastic is wants to recoil away from the wall but it cant. The more you stretch the lungs, the pleural pressure gets even more negativeTranspulmonary pressure (alveolar pressure- intrapleural pressure) It goes up from time 0 to inspiration (as the lung gets more stretched)How strongly the outside of the lung is attached to the inside of the chest wallExpiration: usually passive (exhale by ceasing to inhale because lungs are elastic and want to recoil) diaphragm pushed back up. Decrease in volume of pleural cavity, pressure goes up and air goes out of the lungs. As the lungs become less stretched the intrapleural pressure becomes more negativePneumothoraxAir at atmospheric pressure being introduced to intrapleural space and the intrapleural pressure goes to zero and causes the lung to collapsePhysical Properties of LungsPulmonary fibrosisVarious causes—due to poor compliance of lung (what makes lung compliant is the elastic connective tissue between the alveoli combined with the surface tension- this gets replaced with stiff collagen instead of elastin) makes breathing very difficultElasticityOnce you have a change in volume it goes back to former volumeElastin fibers and residual surface tension in alveolar fluid – at surface of air water divide this forms surface tension due to hydrogen bonding. Also causes alveolus to shrinkSurfactantsInterfere with surface tension at the sir water divide secreted by alveolar alveoliReduce the surface tension making it possible for the alveoli to expand.Do not reduce it down to zeroTotal residual surface tension is what contributes to the elasticity of the lungLaw of LaplaceWhat the pressure of the air in the alveolus will be depending on surface tension and radius2T/rtwice as much pressure in the one on the rightwe are wrong in assuming the surface tension is the same. AS the alveolus decreases in size, the surface tension also decreases – there is a given amount of alveolar fluid in each alveoli so as it gets smaller, the density of the surfactant molecules goes up making the surface tension less and less.The more you inflate the alveoli, the surface tension goes up- important contributor to the elasticity of the lungFailure of surfactant to be secreted in newborns is the number 1 cause of respiratory distress (surfactant is developed late in fetal life)Diffusion and Solubility of Gasesgases only move by diffusionthe rate of diffusion is proportional to the area, concentration gradient, and permeability but inversely so to the membrane thicknessamount of gas in air is determined by pressure but in fluids it is determined by concentrationAt equilibrium then the partial pressure of O2 in water = partial pressure of O2 in air so we give them both mmHg unitsHow much oxygen is in there depends on the pressure, temperature 9higher the temperature the less gas), and the solubility (O2 is not very soluble in water- CO2 is more so)Fish that need a lot of oxygen live in cold waterBecause oxygen is not very soluble, the oxygen carried in our blood is not soluble carried by hemoglobinBISC 307L 1st Edition Lecture 33 Current Lecture- Functions of Respiratory Systemoo blood buffers (bicarbonate)o respiratory regulation of body pH is much slower than blood buffers but kidneys fastest- Lungs and Thoracic Cavityomain body cavity divided into two by the diaphragm (upper and lower)o Upper is divided into 3 (right pleural cavity, pericardial cavity, and left pleural cavity)o Pleural cavity is where the lung sits and is lined with the pleural membraneso In the intrapleural space there is pleural fluid which is a slippery mucus used for breathing and movement (prevents friction or damage)o Muscles involved in inspirtartion (external intercostal muscles, diaphragm, and scaines, and sternociedomastoids)o Expiration (abdominal muscles


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