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module 10 - respiratory system.docx

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Physiology 2130
Ingrid L.Stefanovic

Module 10Respiratory System IntroductionThe transport of oxygen from airbloodThe removal or CO2 from the bloodairThe control of blood acidity pHTemperature regulationForming a line of defense to airborne particlesAnatomyThe lungs are located in the thoracic cavity and are surrounded by the rib cage and the diaphragmThe airways consist of the nasal cavity and the mouth which join tg at the pharynxThe pharynx leads into the larynx voice box which then becomes the trachea o Larynx is where sound is produced by the passage of air this sound is then modified by the tongue and lips to produce the final vocal noiseso Trachea windpipe is the large conducting airway of the respiratory system rings of cartilage that help to hold it open so air can move in and out with ease it branches into R and L primary bronchiThe trachea divides into 2 main bronchi left and right which continually divide into smaller and smaller bronchioles smaller airways o Primary bronchi R and L branch one in each lobe in the lungThese bronchioles continually divide and eventually end in the alveoli which are the site of gas exchange in the lung and make up bulk of the lungs o Structure of alveoli the diffusion of gas is maximized through the large surface area for diffusion and the short distance the gases have to diffuseAnatomyBlood Vessels and Blood FlowThe pulmonary arterydelivers deoxygenated blood to the lungs branches extensively to form a dense network of capillaries around each alveolusThe structure of the capillaries and blood flow characteristics maximize gas exchange o These characteristics include thin endothelial walls large total crosssectional area and a very low blood velocityo Hence in the capillaries O2 diffuses into the blood while CO2 diffuses outFrom the capillaries the O2rich blood flows back into the left side of the heart through the pulmonary vein AnatomyHistological Structure of an Alveolus300 million alveoli in a healthy human lung each with a diameter of 03mm 1100 of an inchThe walls of the alveoli are one cell thick and are composed of alveolar epithelial cells type 1 cellsType II cells secrete a fluid called surfactant that lines the alveoliLarge numbers of capillaries surround the alveoli in close proximity Respiratory membranethe region btwn the alveolar space and the capillary lumeno This membrane can have a thickness as narrow as 03 microns is where gas exchange takes place btwn air and bloodCells of the immune system incl macrophages and lymphocytes protect the body from airborne particles that make their way into the alveoliFibers of elastin and collagen are present in the walls of the alveoli around blood vessel and bronchiPressures of the LungsIntrapleural PressureTo understand inspiration inhalation and expiration exhaling need to understand the enviro of the lungsThere are two thin pleural membranes o Parietal pleuralines and sticks to the ribso Visceral pleurasurrounds and sticks to lungsThese two layers of membrane form the intrapleural space which contains a very small amount of pleural fluid 1015ml o This fluid reduces friction btwn the 2 pleural membranes during breathing o Due to their nature and attached muscle the ribs tend to spring outward while the lungs due to the presence of elastin tend to recoil and collapseLungs want to collapse and ribs want to expand outwardPressures of the LungsAlveolar and Atmospheric PressureAlveolarintrapulmonary pressurepressure inside the lungsIntrapleural pressurethe pressure in the intrapleural spaceAtmospheric pressureoutside the body is 760 mmHg at sea levelBtwn breaths the alveolar and atmospheric pressures are the same 760 mmHg 0 differenceWhile the pressure in the intrapleural pressure756 mmHg a difference of 4 mmHgThe chest wall and lungs moving in opposite directions cause this lower intrapleural pressure Pressures of the LungsTranspulmonary PressureTranspulmonary pressuredifference btwn the alveolar and intrapleural pressures o Transpulmonary pressurealveolar pressureintrapleural pressure o Transpulmonary pressure760 mmHg756 mmHg4mmHgThe transpulmonary pressure is important bc this difference in pressure across the alveoli and intrapleural space holds the lungs openIn a healthy set of lungs the transpulmonary pressure is positive outward and keeps the lungs and alveoli open Pressures of the LungsPneumothoraxIf both the alveolar and intrapleural pressures were equal this would result in a transpulmonary pressure of 0 mmHgIn this situation there would be no pressure holding the lungs open and they would collapse producing a pneumothoraxThis occurs when the intrapleural space is punctured causing the alveolar pressure and intrapleural pressure to become equal both 760 mmHgGenerally only 1 lung collapses bc the intrapleural space of each lung is isolated from the other
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