Anatomy Exam 4 study guide The Respiratory System Major Functions of the respiratory system o To supply the body with oxygen and dispose of carbon dioxide o Respiration four distinct processes must happen Pulmonary ventilation External respiration Moving air into and out of the lungs Gas exchange between the lungs and the blood Respiratory tubes include epithelia cells Slide 4 Conduction Zone Bronchi o Air reaching the bronchi is Warm and cleansed of impurities Saturated with water vapor o Bronchi subdivide into secondary bronchi each supplying a lobe of the lungs o Air passages undergo 23 orders of branching in the lungs Little tubes is the respiratory zone o Alveoli plural of alveolar sac in respiratory zone comes from the pulmonary artery from the heart with unoxygenated blood blood gets oxygenated in the alveolar sacs and returns to heart oxygenated via the pulmonary vein and into the left Big tubes are the conducting zone Bronchioles Consist of cubodial epithelium Have a complete layer of circular smooth muscle Lack cartilage support and mucus producing cells Respiratory Zone o Presence of alveoli begins as terminal bronchioles feed into respiratory bronchioles o Respiratory bronchioles lead to alveolar ducts then to terminal clusters of alveolar sacs composed of alveoli o Walls of capillary and alveolar sac are both epithelia cells slide 7 Lumen of alveolar sac air Lumen of capillaries blood o CO2 moves from blood to alveolus and from alveolus to outside of the body Approximately 300 million alveoli o Account for most of the lungs volume o Provide large surface area for gas exchange The air blood barrier is composed of o Alveolar and capillary walls o Their fused basal laminas Alveolar walls o Area single layer of type 1 epithelial cells o Permit gas exchange by simple diffusion o Secrete angiotensin converting enzyme ACE Blood Supply irrigation to the lungs o Lungs are perfused by 2 circulations Pulmonary Pulmonary arteries Pulmonary veins o Supply systemic venous blood to be oxygenated o Carry oxygenated blood from respiratory zones to the heart Bronchial Bronchial arteries Breathing o Breathing or pulmonary ventilation consists of 2 phases o Help supply the lungs with oxygenated blood o Respiratory pressure is always described relative to atmospheric pressure Inspiration Expiration Air flows into the lungs Gases exit the lungs Pressure Relationships in the Thoracic Cavity Atmospheric pressure Patm o Pressure exerted by the air surrounding the body o Negative respiratory pressure is less than Patm o Positive respiratory pressure is greater than Patm Slide 14 don t need to know details on the diagram Pressure relationships o 760 atm at sea level o 200 atm at Mt Everest o In thoracic cavity we need pressure of 759 757 to breathe in a difference of 3 2 1 mm compared to atmospheric pressure o Diaphragm The diaphragm is an inspiratory muscle Diaphragm contracts were produced inspiration Abdominal muscles are the main expiratory muscles Diaphragm Relaxes expiration o Two forces act to pull the lungs away from the thoracic wall promoting lung collapse Elasticity of lungs causes them to assume smallest possible size Surface tension of alveolar fluid draws alveoli to their smallest possible size o Opposing force Elasticity of the chest wall pulls the thorax outward to enlarge the lungs Lung Collapse o Caused by equalization of the intrapleural pressure with the intrapulmonary pressure o Transpulmonary pressure keeps the airways open Transpulmonary pressure Difference between the intrapulmonary and intrapleural pressures Pulmonary Ventilation o A mechanical process that depends on volume changes in the thoracic cavity o Volume changes lead to pressure changes which lead to the flow of gases to equalize pressure Expiration diaphragm relaxes moves up o Inspiratory muscle that relaxes and the rib cage descends due to gravity o Thoracic cavity volume decreases o Elastic lungs recoil passively and intrapulmonary volume decreases o Intrapulmonary pressure rises above atmospheric pressure 1 mmHg o Gases flow out of the lungs down the pressure gradient until intrapulmonary pressure is zero Physical Factors influencing ventilation o Airway Resistance Friction is the major nonelastic source of resistance to airflow Air flow delta pressure resistance Delta p Its hard to change the size of the lumen of the large tubes because they are made of cartilage However bronchioles have smooth muscle that allows us to be able to contract and constrict the tube bronchoconstriction Gas flow is inversely proportional to resistance with the greatest resistance being in the medium sized bronchi Airway Resistance o As airway resistance rises breathing movements become more strenuous o Severely constricted or obstructed bronchioles Can prevent life sustaining ventilation Can occur during acute asthma attacks which stops ventilation o Epinephrine release via the sympathetic nervous system dilates bronchioles and reduces air resistance o PNS activity increases air resistance Delete slide 28 Slide 29 o Anatomical dead space like the trachea Is dead space because there are no alveoli there and it doesn t do gas exchange Conduction 150mL Respiratory 350mL Alveolar Ventilation similar to C O o AVR measures the flow of fresh gases into and ot of the alveoli during a particular time AVR mL min frequency breaths min x TV dead space mL breath Slow deep breathing increases AVR Rapid shallow breathing decreases AVR Purpose of the lungs o Primary to eliminate CO2 from the blood o Secondary to reoxygenate the blood Basic properties of Gases o Dalton s Law of Partial Pressure Total pressure exerted by a mixture of gases is the sum of the pressures exerted independently by each gas in the mixture The partial pressure of each gas is directly proportional to its percentage in the mixture Partial pressure conc X total pressure Composition of Alveolar Gas o Contain more carbon dioxide and water vapor These differences result from Gas exchange in the lungs oxygen diffuses from the alveoli and carbon dioxide diffuses into the alveoli Humidification of air by conducting passages O2 13 7 CO2 5 2 H20 6 2 The mixing of alveolar gas that occurs with each breath Partial Pressure Gradients and Gas Solubility o Although carbon dioxide has a lower partial pressure gradient It is 20 times more soluble membranes than oxygen It diffuses in equal amounts with oxygen Oxygen Transport Role of Hemoglobin o Each Hemoglobin molecule binds four
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