The Respiratory System



The Respiratory SystemGas Exchange at a Major and Minor ScaleChristin DeMoss3638556906260Audience & ScopeIntroductory physiology students will utilize this description to gain a more precise understanding of the respiration process.? These physiology students will have prior knowledge of the subject through lectures and online readings. This description will not serve as a replacement to the lectures and readings, but will instead serve to enhance, clarify, and better organize existing knowledge. This description will extend the students' respiration knowledge and will comprehensively outline the process to help the students understand the material.? Introduction The respiratory system is a physiological process involving inspiration, expiration, and gas exchange. The average adult human breathes about 8 to 16 times a minute1. With an average respiratory rate of 12 breaths a minute and 1,440 minutes in a day, the average adult takes approximately 17,280 breaths a day. It is imperative introductory physiology students understand this frequent, life sustaining physiological process. The process of respiration occurs in a stepwise sequence that involves inhaling oxygenated air and exhaling deoxygenated air. The components that convert air from oxygenated to deoxygenated are elaborated throughout this technical description. The major components of the respiration process are displayed below in diagram 1. In addition to the steps of respiration, it is equally important to fully understand how respiration is controlled. This technical description also elaborates on the basics of homeostatic regulation. Diagram 1: Simplified process of respirationOverviewThe respiratory system is comprised of two divisions, the conduction division (major scale) and the respiratory division (minor scale)2. Table 1 shows the major components of each division. Table 1: Conduction and Respiration Division Overview1. The Conduction Division Nose and nasal cavity Oral cavity Pharynx LarynxTracheaBronchial Tree These components can be observedIn figure 1. 2. The Respiration Division The Alveoli (site of gas exchange) The alveoli and the capillaries that surround them can be observed in figure 2. Figure 1: Figure 2: Figure 3: The pathway of inspired air through both the conducting and respiration divisions. Figure 3 demonstrates the pathway that inspired air takes during the process of respiration. As shown in the figure, oxygenated air is inspired and travels through the components of the conduction division to the alveoli located at the terminal ends of the bronchioles. Once oxygenated air reaches the alveoli, O2 diffuses across the membrane into the blood, while CO2 from the blood diffuses into the alveoli. Once in the blood, the O2 is transported to the heart and pumped through the body. The CO2 in the alveoli is carried with the deoxygenated air back through the conduction system and expired through the mouth and nose. The details of the respiratory system are elaborated on in the following sections. Division I: Conduction 1. Inspiration: For air to be inspired, the diaphragm must first contract and pull the lungs downward. This contraction increases the volume of the lungs while decreasing the intrapulmonary pressure in the lungs. Once the atmospheric pressure becomes greater than the decreased pressure in the lungs, air rushes into the nose and mouth.2 Figure 4 demonstrates this process. Figure 4: Inhalation vs. Exhalation Atmospheric pressure > intrapulmonary pressureIntrapulmonary pressure > atmospheric pressureFigure 5: Respiratory anatomy Inspired Air2. Mouth/nasal cavity -> pharynx -> larynx -> trachea: Inspired air travels into the body through the mouth and nasal cavity where it is warmed and cleaned along the way. As the air moves through the pharynx then to the trachea, it is further cleaned and humidified2. The larynx located at the top of the trachea functions to ensure only air enters the lungs. 3. Bronchial Tree: The trachea splits into two bronchi, the right primary bronchus and left primary bronchus. Each primary bronchus continues to branch to the smallest bronchi called respiratory bronchioles2. Figure 6 shows the succession of bronchi branching and figure 7 shows a visual of the brachial tree. Figure 6: Brachial TreeFigure 7: Visual of Brachial Tree *Please note that the terminal bronchioles are too small to be shown on this diagram. Division 2: Respiration4. Alveoli: The alveoli located at the terminal end of the terminal bronchioles and are surrounded by a dense covering of capillaries. Figure 8 displays the alveoli structure. Figure 8: Alveoli5. Gas exchange: When air reaches the alveoli, the O2 from the air diffuses across the alveolar membrane and into the blood. At the same time, CO2 from the deoxygenated blood diffuses into the alveoli. The oxygenated blood returns to the heart to be pumped to the rest of the body. The deoxygenated air travels back through the conducting division of the respiratory system to be expired through the mouth and nose. Figure 9 demonstrates this process. Figure 9: Gas ExchangeThe O2 is moving from the alveoli to the capillary and the CO2 is moving from the capillary to the alveoli. Alveoli **Expelled air returns to the conduction division of the Respiratory System after Gas Exchange**6. Brachial Tree: The deoxygenated air travels back through the brachial tree. Figure 10: Brachial Tree7. Trachea -> Larynx -> Pharynx -> Mouth/nasal cavity: As the deoxygenated air moves back through the conduction division, the trachea, larynx, pharynx, and mouth/nasal cavity all act to dehumidify the air. Reducing the amount of water in exhaled air reduced the amount of water lost via breathing. 8. Expiration: Once gas exchange has occurred, the diaphragm relaxes and compresses the lungs. This compression decreases the lung volume and increases the intrapulmonary pressure of the lungs. Deoxygenated air can be expired when the pressure inside the lungs is greater than the atmospheric pressure.2 Please refer to figure 4 on page 4. Homeostatic RegulationHomeostatic regulation also occurs in a stepwise process like respiration2. Homeostatic regulation is comprised of:The respiration control center-Located at the base of the brainIncludes the medulla oblongata and ponsControls breathing rateNeurons run from control center to diaphragmChemoreceptorsLocated in arteriesMonitor CO2, H+, and O2 blood concentrationsNeuronsAfferent (from muscle to control center)Efferent (from control center to muscle) It is important to note that carbon dioxide in the blood combines with water and yields hydrogen protons and bicarbonate. Equation 1 demonstrates this process below: Equation 1:Since CO2 breaks down into H+ and HCO3- in the blood, high levels of H+ signify high levels of CO2 and low levels of H+ signify low levels of CO2. How the body reacts to the level of H+ in the blood is summarized below. Table 2: Homeostatic Regulation OverviewHigh H+ in BloodChemoreceptors detect a change in equilibriumChemoreceptors send a message to the respiratory control center via afferent neuronsEfferent neurons from the control center tell the diaphragm to contract more quicklyBreathing increases and CO2 is expelledLow H+ in BloodChemoreceptors detect a change in equilibriumChemoreceptors send a message to the respiratory control center via afferent neuronsEfferent neurons from the control center tell the diaphragm to contract less frequentBreathing decreases, increasing CO2 concentration ConclusionThere is no doubt that the respiratory process functions as one of the most important physiological pathways. A full understanding of this process is necessary to comprehend other physiological processes. This technical description, in conjunction with lectures and online readings, serves to clarify and organize respiration for introductory physiology students. ReferencesContent1. Dugdale, David C. "Rapid Shallow Breathing: MedlinePlus Medical Encyclopedia." U.S National Library of Medicine. U.S. National Library of Medicine, 25 May 2011. Web. 18 Oct. 2012. <. "Respiratory System Tutorial." Biology 142: Physiology Laboratory: Spring 2012. N.p., n.d. Web. 18 Oct. 2012. < 1"THE RESPIRATORY SYSTEM." Respiratory System. N.p., 18 May 2010. Web. 23 Oct. 2012. < 2"Respiratory System Tutorial." Biology 142: Physiology Laboratory: Spring 2012. N.p., n.d. Web. 18 Oct. 2012. < 4"The Mechanics of Breathing." Respiration_page. N.p., n.d. Web. 23 Oct. 2012. < 5"RESPIRATORY MANAGEMENT IN SPINAL CORD INJURY: NORMAL BREATHING AND THE RESPIRATORY TRACT." Normal Breathing and the Respiratory Tract. N.p., n.d. Web. 23 Oct. 2012. < 7"Bronchi, Bronchial Tree, & Lungs." SEER Training: Bronchi, Bronchial Tree, & Lungs. N.p., n.d. Web. 23 Oct. 2012. < 8 "File:Alveoli Diagram.png." Wikipedia. N.p., n.d. Web. 23 Oct. 2012. < 9"Human Respiration." Human Respiration, Excretion, and Locomotion. N.p., n.d. Web. 23 Oct. 2012. <;*Note- Figures 3, 6, and 10 along with tables 1 and 2 were hand made and no reference was used. EquationsEquation 1"Respiratory System Tutorial." Biology 142: Physiology Laboratory: Spring 2012. N.p., n.d. Web. 18 Oct. 2012. <;. ................
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