Anatomy Exam 4 study guideThe Respiratory System• Major Functions of the respiratory systemo To supply the body with oxygen and dispose of carbon dioxideo Respiration- four distinct processes must happen Pulmonary ventilation• Moving air into and out of the lungs External respiration• Gas exchange between the lungs and the blood• Respiratory tubes include epithelia cells• Slide 4: Conduction Zone: Bronchio Air reaching the bronchi is: Warm and cleansed of impurities Saturated with water vaporo Bronchi subdivide into secondary bronchi, each supplying a lobe of the lungso Air passages undergo 23 orders of branching in the lungs• Little tubes is the respiratory zoneo 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 bronchioleso Respiratory bronchioles lead to alveolar ducts, then to terminal clusters of alveolar sacs composed of alveolio Walls of capillary and alveolar sac are both epithelia cells (slide 7) Lumen of alveolar sac air Lumen of capillaries bloodo 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 wallso Their fused basal laminas• Alveolar walls:o Area single layer of type 1 epithelial cellso Permit gas exchange by simple diffusiono Secrete angiotensin converting enzyme (ACE)• Blood Supply (irrigation) to the lungs:o Lungs are perfused by 2 circulations: Pulmonary• Pulmonary arterieso Supply systemic venous blood to be oxygenated• Pulmonary veinso Carry oxygenated blood from respiratory zones to the heart Bronchial• Bronchial arterieso Help supply the lungs with oxygenated blood• Breathingo Breathing, or pulmonary ventilation, consists of 2 phases: Inspiration• Air flows into the lungs Expiration• Gases exit the lungs• Pressure Relationships in the Thoracic Cavityo Respiratory pressure is always described relative to atmospheric pressure• Atmospheric pressure (Patm)o Pressure exerted by the air surrounding the bodyo Negative respiratory pressure is less than Patmo Positive respiratory pressure is greater than Patm• Slide 14: don’t need to know details on the diagram• Pressure relationshipso 760 atm at sea levelo 200 atm at Mt. Everesto 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 expirationo 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 sizeo Opposing force- Elasticity of the chest wall pulls the thorax outward to enlarge the lungs• Lung Collapseo Caused by equalization of the intrapleural pressure with the intrapulmonary pressureo Transpulmonary pressure keeps the airways open Transpulmonary pressure• Difference between the intrapulmonary and intrapleural pressures• Pulmonary Ventilationo A mechanical process that depends on volume changes in the thoracic cavityo 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 gravityo Thoracic cavity volume decreaseso Elastic lungs recoil passively and intrapulmonary volume decreaseso 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 ventilationo 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 Resistanceo As airway resistance rises, breathing movements become more strenuouso Severely constricted or obstructed bronchioles: Can prevent life-sustaining ventilation Can occur during acute asthma attacks which stops ventilationo Epinephrine release via the sympathetic nervous system dilates bronchioles and reduces air resistanceo 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 lungso Primary- to eliminate CO2 from the bloodo 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 Gaso 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• The mixing of alveolar gas that occurs with each breath• O2= 13.7%, CO2=
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