BIOL 112- The Respiratory System Part B.pdf

BIOL: The Respiratory System Instructor: Pamela Paynter-Armour  Objectives Describe the various respiratory volumes and capacities Outline the difference between internal respiration and external respiration. Describe how oxygen is transported fr...

BIOL: The Respiratory System Instructor: Pamela Paynter-Armour  Objectives Describe the various respiratory volumes and capacities Outline the difference between internal respiration and external respiration. Describe how oxygen is transported from the lungs to body cells.  Objectives Describe how carbon dioxide is transported from body cells to the lungs. Explain how the brain controls breathing and how normal breathing patterns can be disrupted. Outline various homeostatic imbalances of the respiratory system  Respiratory Volumes  Used to assess a person’s respiratory status › Tidal volume (TV) › Inspiratory reserve volume (IRV) › Expiratory reserve volume (ERV) › Residual volume (RV) ⁸  Respiratory Volumes  Tidal Volume (TV): Volume inspired or expired with each normal breath. = 500 ml  Inspiratory Reserve Volume (IRV): Maximum volume that can be inspired over the inspiration of a tidal volume/normal breath. Used during exercise/exertion.=3100 ml  Expiratry Reserve Volume (ERV): Maximal volume that can be expired after the expiration of a tidal volume/normal breath. = 1200 ml  Residual Volume (RV): Volume that remains in the lungs after a maximal expiration. CANNOT be measured by spirometry.= 1200 ml (De Anza College, 2012)  Respiratory Capacities  Inspiratory capacity (IC)  Functional residual capacity (FRC)  Vital capacity (VC)  Total lung capacity (TLC) ⁸  Respiratory Capacities  Inspiratory Capacity ( IC): Volume of maximal inspiration:IRV + TV = 3600 ml  Functional Residual Capacity (FRC): Volume of gas remaining in lung after normal expiration, cannot be measured by spirometry because it includes residual volume: ERV + RV = 2400 ml  Vital Capacity (VC): Volume of maximal inspiration and expiration:IRV + TV + ERV = IC + ERV = 4800 ml  Total Lung Capacity (TLC): The volume of the lung after maximal inspiration. The sum of all four lung volumes, cannot be measured by spirometry because it includes residual volume:IRV+ TV + ERV + RV = IC + FRC = 6000 ml (De Anza College, 2012) (University of Hawaii, n.d.).  Dead Space  Some inspired air never contributes to gas exchange  Anatomical dead space: volume of the conducting zone conduits (~150 ml)  Alveolar dead space: alveoli that cease to act in gas exchange due to collapse or obstruction  Total dead space: sum of above nonuseful volumes ⁸  Pulmonary Function Tests  Spirometer: instrument used to measure respiratory volumes and capacities  Spirometry can distinguish between › Obstructive pulmonary disease— increased airway resistance (e.g., bronchitis) › Restrictive disorders—reduction in total lung capacity due to structural or functional lung changes (e.g., fibrosis or TB) ⁸  Pulmonary Function Tests  Minute ventilation: total amount of gas flow into or out of the respiratory tract in one minute  Forcedvital capacity (FVC): gas forcibly expelled after taking a deep breath  Forced expiratory volume (FEV): the amount of gas expelled during specific time intervals of the FVC ⁸  Pulmonary Function Tests  Increases in TLC, FRC, and RV may occur as a result of obstructive disease  Reduction in VC, TLC, FRC, and RV result from restrictive disease ⁸  Alveolar Ventilation  Alveolarventilation rate (AVR): flow of gases into and out of the alveoli during a particular time AVR = frequency X (TV – dead space) (ml/min) (breaths/mi (ml/breath) n)  Dead space is normally constant  Rapid, shallow breathing decreases AVR ⁸ Nonrespiratory Air Movements  Most result from reflex action  Examples include: cough, sneeze, crying, laughing, hiccups, and yawns ⁸  Gas Exchanges Between Blood, Lungs, and Tissues  External respiration  Internal respiration  To understand the above processes, first consider › Physical properties of gases › Composition of alveolar gas ⁸  Basic Properties of Gases: Dalton’s Law of Partial Pressures  Totalpressure exerted by a mixture of gases is the sum of the pressures exerted by each gas  The partial pressure of each gas is directly proportional to its percentage in the mixture ⁸  Basic Properties of Gases: Henry’s Law  When a mixture of gases is in contact with a liquid, each gas will dissolve in the liquid in proportion to its partial pressure  At equilibrium, the partial pressures in the two phases will be equal  The amount of gas that will dissolve in a liquid also depends upon its solubility › CO2 is 20 times more soluble in water than O2 › Very little N2 dissolves in water ⁸ Composition of Alveolar Gas  Alveolicontain more CO2 and water vapor than atmospheric air, due to › Gas exchanges in the lungs › Humidification of air › Mixing of alveolar gas that occurs with each breath ⁸  External Respiration  Exchange of O2 and CO2 across the respiratory membrane  Influenced by › Partial pressure gradients and gas solubility › Ventilation-perfusion coupling › Structural characteristics of the respiratory membrane ⁸  Partial Pressure Gradients and Gas Solubilities  Partial pressure gradient for O2 in the lungs is steep › Venous blood Po2 = 40 mm Hg › Alveolar Po2 = 104 mm Hg  O2 partial pressures reach equilibrium of 104 mm Hg in ~0.25 seconds, about 1/3 the time a red blood cell is in a pulmonary capillary ⁸  PO 104 mm Hg 2 Time in the pulmonary capillary (s) Start of End of capillary capillary  Partial Pressure Gradients and Gas Solubilities  Partial pressure gradient for CO2 in the lungs is less steep: › Venous blood Pco2 = 45 mm Hg › Alveolar Pco2 = 40 mm Hg  CO2 is 20 times more soluble in plasma than oxygen  CO2 diffuses in equal amounts with oxygen ⁸ Inspired air: Alveoli of lungs: PO2 160 mm Hg PO2 104 mm Hg PCO 0.3 mm Hg PCO 40 mm Hg 2 2 External respiration Pulmonary Pulmonary arteries veins (PO2 100 mm Hg) Blood leaving Blood leaving tissues and lungs and entering lungs: entering tissue PO2 40 mm Hg capillaries: PCO2 45 mm Hg PO2 100 mm Hg PCO2 40 mm Hg Heart Systemic Systemic veins arteries Internal respiration Tissues: PO2 less than 40 mm Hg PCO greater than 45 mm Hg 2  Ventilation-Perfusion Coupling  Ventilation: amount of gas reaching the alveoli  Perfusion: blood flow reaching the alveoli  Ventilation and perfusion must be matched (coupled) for efficient gas exchange ⁸  Ventilation-Perfusion Coupling  Changes in Po2 in the alveoli cause changes in the diameters of the arterioles › Where alveolar O2 is high, arterioles dilate › Where alveolar O2 is low, arterioles constrict ⁸  Ventilation-Perfusion Coupling  Changes in Pco2 in the alveoli cause changes in the diameters of the bronchioles › Where alveolar CO2 is high, bronchioles dilate › Where alveolar CO2 is low, bronchioles constrict ⁸  Mismatch of ventilation and O2 perfusion ventilation and/or autoregulates Pulmonary arterioles Match of ventilation serving these alveoli and perfusion perfusion of alveoli causes local arteriole ventilation, perfusion P and P diameter constrict CO2 O2 (a) Mismatch of ventilation and O2 perfusion ventilation and/or autoregulates Pulmonary arterioles Match of ventilation perfusion of alveoli causes local serving these alveoli and perfusion arteriole ventilation, perfusion P and P diameter dilate CO2 O2 (b) Thickness and Surface Area of the Respiratory Membrane  Respiratory membranes › 0.5 to 1 m thick › Large total surface area (40 times that of one’s skin)  Thicken if lungs become waterlogged and edematous, and gas exchange becomes inadequate  Reduction in surface area with emphysema, when walls of adjacent alveoli break down ⁸  Internal Respiration  Capillary gas exchange in body tissues  Partial pressures and diffusion gradients are reversed compared to external respiration › Po2 in tissue is always lower than in systemic arterial blood › Po2 of venous blood is 40 mm Hg and Pco2 is 45 mm Hg ⁸ Inspired air: Alveoli of lungs: PO2 160 mm Hg PO2 104 mm Hg PCO 0.3 mm Hg PCO 40 mm Hg 2 2 External respiration Pulmonary Pulmonary arteries veins (PO2 100 mm Hg) Blood leaving Blood leaving tissues and lungs and entering lungs: entering tissue PO2 40 mm Hg capillaries: PCO2 45 mm Hg PO2 100 mm Hg PCO 40 mm Hg 2 Heart Systemic Systemic veins arteries Internal respiration Tissues: PO2 less than 40 mm Hg PCO greater than 45 mm Hg 2 The Transport of Oxygen and Carbon Dioxide in the Blood  Transport of Respiratory Gases by Blood  Oxygen (O2) transport  Carbon dioxide (CO2) transport ⁸  O2 Transport  Molecular O2 is carried in the blood › 1.5% dissolved in plasma › 98.5% loosely bound to each Fe of hemoglobin (Hb) in RBCs › 4 O2 per Hb ⁸  O2 and Hemoglobin  Oxyhemoglobin (HbO2): hemoglobin-O2 combination  Reduced hemoglobin (HHb): hemoglobin that has released O2 ⁸  O2 and Hemoglobin  Loading and unloading of O2 is facilitated by change in shape of Hb › As O2 binds, Hb affinity for O2 increases › As O2 is released, Hb affinity for O2 decreases  Fully (100%) saturated if all four heme groups carry O2  Partially saturated when one to three hemes carry O2 ⁸  O2 and Hemoglobin  Rate of loading and unloading of O2 is regulated by › Po2 › Temperature › Blood pH › Pco2 › Concentration of BPG(2,3- bisphosphoglycerate) ⁸  Influence of Po2 on Hemoglobin Saturation  Oxygen-hemoglobin dissociation curve  Hemoglobin saturation plotted against Po2 is not linear  S-shaped curve  Shows how binding and release of O2 is influenced by the Po2 ⁸  O2 unloaded to resting tissues Additional O2 unloaded to exercising tissues Exercising Resting Lungs tissues tissues  Influence of Po2 on Hemoglobin Saturation  In arterial blood › Po2 = 100 mm Hg › Contains 20 ml oxygen per 100 ml blood (20 vol %) › Hb is 98% saturated  Furtherincreases in Po2 (e.g., breathing deeply) produce minimal increases in O2 binding ⁸  Influence of Po2 on Hemoglobin Saturation  Invenous blood › Po2 = 40 mm Hg › Contains 15 vol % oxygen › Hb is 75% saturated ⁸  Influence of Po2 on Hemoglobin Saturation  Hemoglobin is almost completely saturated at a Po2 of 70 mm Hg  Further increases in Po2 produce only small increases in O2 binding  O2 loading and delivery to tissues is adequate when Po2 is below normal levels ⁸  Influence of Po2 on Hemoglobin Saturation  Only 20–25% of bound O2 is unloaded during one systemic circulation  If O2 levels in tissues drop: › More oxygen dissociates from hemoglobin and is used by cells › Respiratory rate or cardiac output need not increase ⁸  O2 unloaded to resting tissues Additional O2 unloaded to exercising tissues Exercising Resting Lungs tissues tissues  Other Factors Influencing Hemoglobin Saturation  Increases in temperature, H+, Pco2, and BPG › Modify the structure of hemoglobin and decrease its affinity for O2 › Occur in systemic capillaries › Enhance O2 unloading › Shift the O2-hemoglobin dissociation curve to the right  Decreases in these factors shift the curve to the left ⁸  Decreased carbon dioxide 10°C (PCO2 20 mm Hg) or H+ (pH 7.6) 20°C 38°C 43°C Normal arterial carbon dioxide (PCO2 40 mm Hg) Normal body or H+ (pH 7.4) temperature Increased carbon dioxide (PCO2 80 mm Hg) or H+ (pH 7.2) (a) PO (mm Hg) (b) 2 ⁸  Factors that Increase Release of O2 by Hemoglobin  As cells metabolize glucose › Pco2 and H+ increase in concentration in capillary blood  Declining pH weakens the hemoglobin- O2 bond (Bohr effect) › Heat production increases  Increasing temperature directly and indirectly decreases Hb affinity for O2 ⁸  Homeostatic Imbalance  Hypoxia › Inadequate O2 delivery to tissues › Due to a variety of causes  Too few RBCs  Abnormal or too little Hb  Blocked circulation  Metabolic poisons  Pulmonary disease  Carbon monoxide ⁸  CO2 Transport  CO2 is transported in the blood in three forms › 7 to 10% dissolved in plasma › 20% bound to globin of hemoglobin (carbaminohemoglobin) › 70% transported as bicarbonate ions (HCO3–) in plasma ⁸  Transport and Exchange of CO2  CO2 combines with water to form carbonic acid (H2CO3), which quickly dissociates: CO2 + H 2O  H2CO3  H+ + HCO3– Carbon Water Carbonic Hydrogen Bicarbonate dioxide acid ion ion  Transport and Exchange of CO2  Mostof the above occurs in RBCs, where carbonic anhydrase reversibly and rapidly catalyzes the reaction ⁸  Hydrogen ions released bind to Hb, triggering the Bohr effect.  Hbbuffering results in little change in pH under resting conditions. Transport and Exchange of CO2  Insystemic capillaries › HCO3– quickly diffuses from RBCs into the plasma lungs › The chloride shift occurs: outrush of HCO3– from the RBCs is balanced as Cl– moves in from the plasma ⁸  Tissue cell Interstitial fluid CO2 CO2 (dissolved in plasma) Binds to Slow plasma CO2 CO2 + H2O H2CO3 HCO3– + H+ proteins CO2 HCO3– Chloride Fast Cl– shift CO2 CO2 + H2O H2CO3 HCO3– + H+ Carbonic Cl– (in) via CO2 anhydrase transport HHb protein CO2 CO2 + Hb HbCO2 (Carbamino- hemoglobin) Red blood cell HbO2 O2 + Hb CO2 O2 O2 O2 (dissolved in plasma) Blood plasma (a) Oxygen release and carbon dioxide pickup at the tissues Transport and Exchange of CO2  Inpulmonary capillaries › HCO3– moves into the RBCs and binds with H+ to form H2CO3 › H2CO3 is split by carbonic anhydrase into CO2 and water › CO2 diffuses into the alveoli ⁸  Alveolus Fused basement membranes CO2 CO2 (dissolved in plasma) Slow CO2 CO2 + H2O H2CO3 HCO3– + H+ HCO3– Chloride CO2 Fast H2CO3 HCO3– + H+ Cl– shift CO2 + H2O Carbonic Cl– (out) via anhydrase transport CO2 CO2 + Hb HbCO2 (Carbamino- protein hemoglobin) Red blood cell O2 + HHb HbO2 + H+ O2 O2 O2 (dissolved in plasma) Blood plasma (b) Oxygen pickup and carbon dioxide release in the lungs  Haldane Effect  Theamount of CO2 transported is affected by the Po2  Thelower the Po2 and hemoglobin saturation with O2, the more CO2 can be carried in the blood ⁸  Haldane Effect  At the tissues, as more carbon dioxide enters the blood › More oxygen dissociates from hemoglobin (Bohr effect) › As HbO2 releases O2, it more readily forms bonds with CO2 to form carbaminohemoglobin ⁸  Influence of CO2 on Blood pH  HCO3– in plasma is the alkaline reserve of the carbonic acid–bicarbonate buffer system  If H+ concentration in blood rises, excess H+ is removed by combining with HCO3–  IfH+ concentration begins to drop, H2CO3 dissociates, releasing H+ ⁸ Influence of CO2 on Blood pH  Changes in respiratory rate can also alter blood pH › For example, slow shallow breathing allows CO2 to accumulate in the blood, causing pH to drop  Changes in ventilation can be used to adjust pH when it is disturbed by metabolic factors ⁸  Control of Respiration  Involves neurons in the reticular formation of the medulla and pons ⁸ Medullary Respiratory Centers (Austin, 2004) Medullary Respiratory Centers 1. Dorsal respiratory group (DRG) › Near the root of cranial nerve IX › Integrates input from peripheral stretch and chemoreceptors ⁸  Medullary Respiratory Centers 2. Ventral respiratory group (VRG) › Rhythm-generating and integrative center › Sets eupnea (12–15 breaths/minute) › Inspiratory neurons excite the inspiratory muscles via the phrenic and intercostal nerves › Expiratory neurons inhibit the inspiratory neurons ⁸  Pons Medulla Pontine respiratory centers interact with the medullary respiratory centers to smooth the respiratory pattern. Ventral respiratory group (VRG) contains rhythm generators whose output drives respiration. Pons Medulla Dorsal respiratory group (DRG) integrates peripheral sensory input and modifies the rhythms generated by the VRG. To inspiratory muscles Diaphragm External intercostal muscles  Pontine Respiratory Centers  Influence and modify activity of the VRG  Smooth out transition between inspiration and expiration and vice versa ⁸  Genesis of the Respiratory Rhythm  Not well understood  Most widely accepted hypothesis › Reciprocal inhibition of two sets of interconnected neuronal networks in the medulla sets the rhythm ⁸ Depth and Rate of Breathing  Depth is determined by how actively the respiratory center stimulates the respiratory muscles  Rate is determined by how long the inspiratory center is active  Both are modified in response to changing body demands ⁸  Chemical Factors  Influence of Pco2: › If Pco2 levels rise (hypercapnia), CO2 accumulates in the brain › CO2 is hydrated; resulting carbonic acid dissociates, releasing H+ › H+ stimulates the central chemoreceptors of the brain stem › Chemoreceptors synapse with the respiratory regulatory centers, increasing the depth and rate of breathing ⁸ Depth& Rate of Breathing: PCO2 (Austin, 2004)  Depth and Rate of Breathing  Hyperventilation: increased depth and rate of breathing that exceeds the body’s need to remove CO2 › Causes CO2 levels to decline (hypocapnia)  May cause cerebral vasoconstriction and cerebral ischemia  Apnea: period of breathing cessation that occurs when Pco2 is abnormally low ⁸  Chemical Factors  Influence of Po2 › Peripheral chemoreceptors in the aortic and carotid bodies are O2 sensors  When excited, they cause the respiratory centers to increase ventilation  Substantial drops in arterial Po2 (to 60 mm Hg) must occur in order to stimulate increased ventilation ⁸ Brain Sensory nerve fiber in cranial nerve IX (pharyngeal branch of glossopharyngeal) External carotid artery Internal carotid artery Carotid body Common carotid artery Cranial nerve X (vagus nerve) Sensory nerve fiber in cranial nerve X Aortic bodies in aortic arch Aorta Heart  Chemical Factors  Influence of arterial pH › Can modify respiratory rate and rhythm even if CO2 and O2 levels are normal › Decreased pH may reflect  CO2 retention  Accumulation of lactic acid  Excess ketone bodies in patients with diabetes mellitus › Respiratory system controls will attempt to raise the pH by increasing respiratory rate and depth ⁸  Summary of Chemical Factors  Rising CO2 levels are the most powerful respiratory stimulant  Normally blood Po2 affects breathing only indirectly by influencing peripheral chemoreceptor sensitivity to changes in Pco2 ⁸  Summary of Chemical Factors  When arterial Po2 falls below 60 mm Hg, it becomes the major stimulus for respiration (via the peripheral chemoreceptors)  Changes in arterial pH resulting from CO2 retention or metabolic factors act indirectly through the peripheral chemoreceptors ⁸  Influence of Higher Brain Centers  Hypothalamic controls act through the limbic system to modify rate and depth of respiration › Example: breath holding that occurs in anger or gasping with pain  A rise in body temperature acts to increase respiratory rate  Cortical controls are direct signals from the cerebral motor cortex that bypass medullary controls › Example: voluntary breath holding ⁸  Pulmonary Irritant Reflexes  Receptors in the bronchioles respond to irritants  Promotereflexive constriction of air passages  Receptors in the larger airways mediate the cough and sneeze reflexes ⁸  Inflation Reflex  Hering-Breuer Reflex › Stretch receptors in the pleurae and airways are stimulated by lung inflation  Inhibitory signals to the medullary respiratory centers end inhalation and allow expiration to occur  Acts more as a protective response than a normal regulatory mechanism ⁸  Higher brain centers (cerebral cortex—voluntary control over breathing) Other receptors (e.g., pain) + and emotional stimuli acting – through the hypothalamus + – Respiratory centers (medulla and pons) Peripheral + chemoreceptors O2 , CO2 , H+ + – Stretch receptors in lungs Central Chemoreceptors – CO2 , H+ + Irritant receptors Receptors in muscles and joints  Homeostatic Imbalances  Chronic obstructive pulmonary disease (COPD) › Exemplified by chronic bronchitis and emphysema › Irreversible decrease in the ability to force air out of the lungs › Other common features  History of smoking in 80% of patients  Dyspnea: labored breathing (“air hunger”)  Coughing and frequent pulmonary infections  Most victims develop respiratory failure (hypoventilation) accompanied by respiratory acidosis ⁸  Tobacco smoke -1 antitrypsin Air pollution deficiency Continual bronchial Breakdown of elastin in irritation and inflammation connective tissue of lungs Chronic bronchitis Emphysema Bronchial edema, Destruction of alveolar chronic productive cough, walls, loss of lung bronchospasm elasticity, air trapping Airway obstruction or air trapping Dyspnea Frequent infections Abnormal ventilation- perfusion ratio Hypoxemia Hypoventilation  Homeostatic Imbalances  Asthma › Characterized by coughing, dyspnea, wheezing, and chest tightness › Active inflammation of the airways precedes bronchospasms › Airway inflammation is an immune response caused by release of interleukins, production of IgE, and recruitment of inflammatory cells › Airways thickened with inflammatory exudate magnify the effect of bronchospasms ⁸  Homeostatic Imbalances  Tuberculosis › Infectious disease caused by the bacterium Mycobacterium tuberculosis › Symptoms include fever, night sweats, weight loss, a racking cough, and spitting up blood › Treatment entails a 12-month course of antibiotics ⁸  Homeostatic Imbalances  Lung cancer › Leading cause of cancer deaths in North America › 90% of all cases are the result of smoking › The three most common types 1. Squamous cell carcinoma (20–40% of cases) in bronchial epithelium 2. Adenocarcinoma (~40% of cases) originates in peripheral lung areas 3. Small cell carcinoma (~20% of cases) contains lymphocyte-like cells that originate in the primary bronchi and subsequently metastasize ⁸  Developmental Aspects  Olfactoryplacodes invaginate into olfactory pits by the fourth week  Laryngotracheal buds are present by the fifth week  Mucosae of the bronchi and lung alveoli are present by the eighth week ⁸  Future mouth Pharynx Frontonasal elevation Eye Olfactory Foregut placode Olfactory Stomodeum placode Esophagus (future mouth) Trachea Liver Laryngotracheal Bronchial bud buds (a) 4 weeks: anterior superficial view of the embryo’s head (b) 5 weeks: left lateral view of the developing lower respiratory passageway mucosae  Developmental Aspects  Bythe 28th week, a baby born prematurely can breathe on its own  During fetal life, the lungs are filled with fluid and blood bypasses the lungs  Gasexchange takes place via the placenta ⁸  Developmental Aspects  At birth, respiratory centers are activated, alveoli inflate, and lungs begin to function  Respiratory rate is highest in newborns and slows until adulthood  Lungs continue to mature and more alveoli are formed until young adulthood  Respiratory efficiency decreases in old age ⁸  Apply Your Knowledge Describe what happens to carbon dioxide in the blood. ANSWER: Carbon dioxide can combine with hemoglobin and form carboxyhemoglobin. Most reacts with water in plasma to form carbonic acid. The carbonic acid ionizes and releases hydrogen and bicarbonate ions. The hydrogen ions then attach to hemoglobin. They are exhaled as a waste product from the lungs. (Booth, Whicker, Wyman, Pugh &Thompson, 2009). Super!  Apply Your Knowledge ANSWER: Match the following: ___ C Amount of air that moves during a normal breath A. Total lung ___ B Amount of air that always capacity remains in the lungs B. Residual A ___ Total amount of air the lungs volume can hold C. Tidal volume D Amount of air forcefully ___ D. Vital capacity exhaled after deepest inhalation possible Good Job! (Booth, Whicker, Wyman, Pugh &Thompson, 2009). References 1. Austin, V. (2006). The Respiratory System. Retrieved from http://www.google.tt/url?sa=t&rct=j&q=&e src=s&source=web&cd=3&ved=0CC0QFjA C&url=http%3A%2F%2Ffacweb.northseattle.edu%2Frvieira%2Fap214%2FHAP7_22- a.ppt&ei=mXIXU8fOJ4rqkQebs4DQBg&usg =AFQjCNGv4QtyLzoGbcO1ikUO3LkObqrb Ng References Cont’d 2. Austin, V. (2004). The Respiratory System. Retrieved from http://www.google.tt/url?sa=t&rct=j&q=&e src=s&source=web&cd=4&ved=0CDAQFjA D&url=http%3A%2F%2Fpodcasting.jessamin e.kyschools.us%2Fgroups%2Fjctcwelchwiki %2Fwiki%2Fdcacb%2Fattachments%2F20a3 a%2F22- References Cont’d 3. Booth, Whicker, Wyman, Pugh, Thompson. (2009). The Respiratory System. Retrieved from http://www.google.tt/url?sa=t&rct=j&q=&esrc =s&source=web&cd=1&ved=0CCEQFjAA&url =http%3A%2F%2Fhighered.mcgraw- hill.com%2Fsites%2Fdl%2Ffree%2F0073520837% 2F589002%2FChapter_28_Respiratory_System. ppt&ei=9XQYU7eRJYqokQffw4GwCQ&usg=A FQjCNFD7AJVlAFpXU_cmKzLtP3tOfGVDg&bv m=bv.62577051,d.eW0 References Cont’d 4. De Anza College. (2012).Anatomy of Respiratory System. Retrieved from http://www.google.tt/url?sa=t&rct=j&q=&e src=s&source=web&cd=3&sqi=2&ved=0C C0QFjAC&url=http%3A%2F%2Ffacultyfiles.d eanza.edu%2Fgems%2Fkandulaanita%2FR espsystemppt.ppt&ei=uW4XU9y0MNG2kAe 3r4GoAg&usg=AFQjCNG65ZYTpa3WTxZvG HyWHLtou_MjfA References Cont’d 5. Hendon, L. (2008). The Respiratory System. Retrieved from http://www.google.tt/url?sa=t&rct=j&q=&e src=s&source=web&cd=8&ved=0CEwQFjA H&url=http%3A%2F%2Flpc1.laspositascolleg e.edu%2Flpc%2Fbhinck%2FAnat1%2F21_01 LectureOutline%2F21_01LectureOutlines%2 FHA5_MM_ch21_1.ppt&ei=mXIXU8fOJ4rqk Qebs4DQBg&usg=AFQjCNHhrIzCUjrxfeWeh 82ncikmCGDYWg References Cont’d 6. Los Angeles Valley College.(n.d.). The Respiratory System. Retrieved from http://www.google.tt/url?sa=t&rct=j&q=&esrc =s&source=web&cd=1&sqi=2&ved=0CCEQFj AA&url=http%3A%2F%2Fwww.lavc.edu%2Finstr uctor%2Fwatson_k%2Fdocs%2FLecture%25202 1%2520- %2520%2520Respiratory%2520System.ppt&ei= uW4XU9y0MNG2kAe3r4GoAg&usg=AFQjCNF2 2IpgHUOk- Gw6vPh0n3NqboeMUQ&bvm=bv.62286460,d. eW0  References Cont’d 7. Meeking, J. (2010a). The Respiratory System: Part A. Retrieved from http://www.google.tt/url?sa=t&rct=j&q=&e src=s&source=web&cd=7&ved=0CD8QFjA G&url=http%3A%2F%2Fwww.aw- bc.com%2Fppt%2Fmarieb_hap%2Fchap27 b.ppt&ei=pXgXU6f- B42qkQfFpYCoAQ&usg=AFQjCNEkCKOn09 g3viAbXHkcMn_YZnt-QA  References Cont’d 8. Meeking, J. (2010b). The Respiratory System: Part B. Retrieved from http://www.google.tt/url?sa=t&rct=j&q=&e src=s&source=web&cd=2&ved=0CCcQFjA B&url=http%3A%2F%2Fwww.hccfl.edu%2Fm edia%2F374639%2Fch_22_lecture_outline_b.ppt&ei=FnsXU9bDGM75kQeI0YHICQ&usg= AFQjCNHCDAYUOp5TR2tvZwfH8pakI8O6kA  References Cont’d 9. University of Hawaii. (n.d.). Respiratory System. Retrieved from http://www.google.tt/url?sa=t&rct=j&q=&e src=s&source=web&cd=4&ved=0CDMQFjA D&url=http%3A%2F%2Fwww.wcc.hawaii.ed u%2Ffacstaff%2Fmiliefsky- m%2FMarieb%2520ZOOL%2520142%2520%2 520PPT%2F022%2520Respiratory.ppt&ei=mX IXU8fOJ4rqkQebs4DQBg&usg=AFQjCNFKS CuHpb5CDzc0G4yHE-hZjdOqBg