The Respiratory System 1 Mechanics of breathing PET Final Exam Study Guide Exam 4 27 at 10am a There are two different zones in the lungs i Conducting Zone Trachea Terminal bronchioles 1 There is cartilage and no muscle in the bronchi so no contraction can occur 2 PNS Contraction SNS Dilation ii Respiratory Zone Respiratory bronchioles Alveoli 1 Alveoli surrounded by capillaries of pulmonary veins so gas exchange occurs here a The wall of the alveolus is one layer of epithelial cells i Why There is no muscle here and this allows for the simple diffusion of gases Respiration at the cellular level b Alveoli secrete ACE c Alveoli exchange gases with the pulmonary veins by simple diffusion so there is oxygenation of the blood in the pulmonary capillary 2 Smooth muscle is present within the bronchioles of this region so these airways can contract There is no cartilage b The larger tubes the bronchi have rigid cartilage and cannot contract they need to stay open for air to flow The bronchioles have smooth muscle so they can contract bronchiole constriction c Breathing Pulmonary Ventilation consists of inspiration and expiration d Pneumotaxic inhibits inspiration Apneustic gives us breathing rhythm by pons 2 Pressure relationships in the thoracic cavity a Alveolar Pressure decreases relative to atmospheric pressure as the Inspiration diaphragm contracts moves down as air flows into lungs so thoracic cavity expands lungs Alveolar Pressure increases as the diaphragm moves up relaxes as gases exit b Expiration c The diaphragm is a voluntary muscle not part of the Autonomic Nervous System d Respiratory pressure is always described relative to atmospheric pressure i 1 mmHg pressure difference is needed for air to move 3 Pulmonary Ventilation Physical Factors a The act of breathing the exchange of air between the atmosphere and the lungs Air travels from areas of high pressure to areas of low pressure b O2 diffuses from alveoli to the capillary and goes into the blood while CO2 diffuses from the blood to the alveolus to be expired c Flow Change in Pressure Resistance Notice this is the same formula for BF i Amount of gas flowing into and out of alveoli is directly proportional to change in pressure between atmosphere and alveoli ii Greatest resistance is in the medium bronchi d Muscles of inhalation Diaphragm Sternocleidomastoid scalenes external intercostal e Muscles of exhalation Internal intercostal External Internal oblique transversus rectus abdominus Abdominals Inspiration f i Alveolar pressure decreases to 758 mmHg 1 PET Final Exam Study Guide Exam 4 27 at 10am ii Thoracic cavity increases in size and volume within the lungs expand iii The diaphragm is contracted Oxygen diffuses into capillaries to go to blood g Expiration i The diaphragm relaxes and the thoracic cavity decreases in size as lungs recoil ii Alveolar pressure increases to 762 mmHg iii Carbon dioxide exits blood and diffuses into alveolus to complete exchange 4 Dead Space and Alveolar Ventilation a The anatomical dead space is the Conducting Zone which pushes air to the alveoli i The Conducting Zone holds no alveoli so it isn t possible for gas exchange to take place We call this space the Anatomical Dead Space the air that remains in the nose mouth trachea bronchi and bronchioles ii During rest with each inspiration 500mL of air enters the Conducting Zone TV to reach the alveoli respiratory zone iii 150 ml of this air remains in the dead space or the Conducting Zone iv So anatomical dead space 150mL Alveolar air 350 mL Tidal Volume 500mL i AVR measures the flow of fresh gases into and out of the alveoli during a particular b Alveolar Ventilation time ii AVR ml min frequency breath min x TV dead space ml breath iii Deep slow breathing increases AVR iv Rapid shallow breathing decreases AVR v Pulmonary Ventilation is always greater than Alveolar Ventilation because we would use the whole Tidal Volume 5 Gas exchange between blood lungs and tissues a Gas exchange takes place in primarily two places in the body i 1st Exchange Between alveoli and pulmonary capillaries Oxygen in the lungs diffuses into the blood carbon dioxide in the blood diffuses into the lungs the force behind this is partial pressure Oxygen moves from the lungs into the blood because the pressure in the lungs is higher than the pressure of Oxygen in the blood ii 2nd Exchange At the cell level given the higher partial pressure of Oxygen in the blood versus the tissues Oxygen dissociates from the Hb and moves from the blood into the mitochondria of the tissues b Movement of air Inspiration DRG Control in Medulla i The alveolus has a partial pressure of O2 of 100 mmHg while the venous blood pulmonary artery has a partial pressure of 40 mmHg for Oxygen ii The blood gets oxygen from the alveolus iii The Oxygen pressure increases in the venous blood and the Oxygen pressure in the alveoli is maintained iv Blood leaves lung capillary to the systemic circulation with partial pressure of Oxygen of 100 mmHg no difference results in discontinued diffusion c Movement of air Expiration VRG Control in Medulla i After leaving the systemic tissue cells in the pulmonary capillaries the alveolus has a partial pressure of CO2 of 40 mmHg while the venous blood pulmonary artery has a partial pressure of 45 mmHg for CO2 2 ii Carbon Dioxide has a higher partial pressure in the venous blood so the venous blood offloads the CO2 to the alveoli where the partial pressure is lower PET Final Exam Study Guide Exam 4 27 at 10am 6 External respiration partial pressure gradients a Dalton s Law of Partial Pressures total pressure exerted by a mixture of gases is the sum of the pressures exerted independently by each gas the mixture The partial pressure of each gas is directly proportional to its percentage in the mixture b Partial Pressure concentration x Total Pressure c The three main gases Water Vapor Nitrogen Oxygen i Atmospheric pressure of these three gases is higher in the atmosphere than the partial pressure for each gas in our lungs ii This allows for diffusion of the gas from high to low atmosphere inside iii Although CO2 has a lower partial pressure gradient it is 20x more soluble than Oxygen Therefore it takes a higher change in pressure to move oxygen because it is less diffusible 7 Transport of respiratory gases by blood Oxy Hb dissociation curve when all four hemes of the molecule are bound to O2 a Saturated hb b Each hemoglobin molecule has 4 places for oxygen to bind c At
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