Presentation on theme: "Chapter 23: The Respiratory System"— Presentation transcript:
1Chapter 23: The Respiratory System Copyright 2009, John Wiley & Sons, Inc.
2Respiratory System Anatomy StructurallyUpper respiratory systemNose, pharynx and associated structuresLower respiratory systemLarynx, trachea, bronchi and lungsFunctionallyConducting zone – conducts air to lungsNose, pharynx, larynx, trachea, bronchi, bronchioles and terminal bronchiolesRespiratory zone – main site of gas exchangeRespiratory bronchioles, alveolar ducts, alveolar sacs, and alveoliCopyright 2009, John Wiley & Sons, Inc.
3Structures of the Respiratory System Copyright 2009, John Wiley & Sons, Inc.
4Copyright 2009, John Wiley & Sons, Inc. NoseExternal nose – portion visible on faceInternal nose – large cavity beyond nasal vestibuleInternal nares or choanaeDucts from paranasal sinuses and nasolacrimal ducts open into internal noseNasal cavity divided by nasal septumNasal conchae subdivide cavity into meatusesIncrease surface are and prevents dehydrationOlfactory receptors in olfactory epitheliumCopyright 2009, John Wiley & Sons, Inc.
6Copyright 2009, John Wiley & Sons, Inc. PharynxStarts at internal nares and extends to cricoid cartilage of larynxContraction of skeletal muscles assists in deglutitionFunctionsPassageway for air and foodResonating chamberHouses tonsils3 anatomical regionsNasopharynxOropharynxLaryngopharynxCopyright 2009, John Wiley & Sons, Inc.
7Copyright 2009, John Wiley & Sons, Inc. LarynxShort passageway connecting laryngopharynx with tracheaComposed of 9 pieces of cartilageThyroid cartilage or Adam’s appleCricoid cartilage hallmark for tracheotomyEpiglottis closes off glottis during swallowingGlottis – pair of folds of mucous membranes, vocal folds (true vocal cords, and rima glottidis (space)Cilia in upper respiratory tract move mucous and trapped particles down toward pharynxCilia in lower respiratory tract move them up toward pharynxCopyright 2009, John Wiley & Sons, Inc.
8Copyright 2009, John Wiley & Sons, Inc. LarynxCopyright 2009, John Wiley & Sons, Inc.
9Structures of Voice Production Mucous membrane of larynx formsVentricular folds (false vocal cords) – superior pairFunction in holding breath against pressure in thoracic cavityVocal folds (true vocal cords) – inferior pairMuscle contraction pulls elastic ligaments which stretch vocal folds out into airwayVibrate and produce sound with airFolds can move apart or together, elongate or shorten, tighter or looserAndrogens make folds thicker and longer – slower vibration and lower pitchCopyright 2009, John Wiley & Sons, Inc.
11Copyright 2009, John Wiley & Sons, Inc. TracheaExtends from larynx to superior border of T5Divides into right and left primary bronchi4 layersMucosaSubmucosaHyaline cartilageAdventitia16-20 C-shaped rings of hyaline cartilageOpen part faces esophagusCopyright 2009, John Wiley & Sons, Inc.
12Copyright 2009, John Wiley & Sons, Inc. Location of TracheaCopyright 2009, John Wiley & Sons, Inc.
13Copyright 2009, John Wiley & Sons, Inc. BronchiRight and left primary bronchus goes to right lungCarina – internal ridgeMost sensitive area for triggering cough reflexDivide to form bronchial treeSecondary lobar bronchi (one for each lobe), tertiary (segmental) bronchi, bronchioles, terminal bronchiolesStructural changes with branchingMucous membrane changesIncomplete rings become plates and then disappearAs cartilage decreases, smooth muscle increasesSympathetic ANS – relaxation/ dilationParasympathetic ANS – contraction/ constrictionCopyright 2009, John Wiley & Sons, Inc.
15Copyright 2009, John Wiley & Sons, Inc. LungsSeparated from each other by the heart and other structures in the mediastinumEach lung enclosed by double-layered pleural membraneParietal pleura – lines wall of thoracic cavityVisceral pleura – covers lungs themselvesPleural cavity is space between layersPleural fluid reduces friction, produces surface tension (stick together)Cardiac notch – heart makes left lung 10% smaller than rightCopyright 2009, John Wiley & Sons, Inc.
16Relationship of the Pleural Membranes to Lungs Copyright 2009, John Wiley & Sons, Inc.
18Copyright 2009, John Wiley & Sons, Inc. Anatomy of LungsLobes – each lung divides by 1 or 2 fissuresEach lobe receives it own secondary (lobar) bronchus that branch into tertiary (segmental) bronchiLobules wrapped in elastic connective tissue and contains a lymphatic vessel, arteriole, venule and branch from terminal bronchioleTerminal bronchioles branch into respiratory bronchioles which divide into alveolar ductsAbout 25 orders of branchingCopyright 2009, John Wiley & Sons, Inc.
19Microscopic Anatomy of Lobule of Lungs Copyright 2009, John Wiley & Sons, Inc.
20Copyright 2009, John Wiley & Sons, Inc. AlveoliCup-shaped outpouchingAlveolar sac – 2 or more alveoli sharing a common opening2 types of alveolar epithelial cellsType I alveolar cells – form nearly continuous lining, more numerous than type II, main site of gas exchangeType II alveolar cells (septal cells) – free surfaces contain microvilli, secrete alveolar fluid (surfactant reduces tendency to collapse)Copyright 2009, John Wiley & Sons, Inc.
21Copyright 2009, John Wiley & Sons, Inc. AlveolusRespiratory membraneAlveolar wall – type I and type II alveolar cellsEpithelial basement membraneCapillary basement membraneCapillary endotheliumVery thin – only 0.5 µm thick to allow rapid diffusion of gasesLungs receive blood fromPulmonary artery - deoxygenated bloodBronchial arteries – oxygenated blood to perfuse muscular walls of bronchi and bronchiolesCopyright 2009, John Wiley & Sons, Inc.
22Components of Alveolus Copyright 2009, John Wiley & Sons, Inc.
23Pulmonary ventilation Respiration (gas exchange) stepsPulmonary ventilation/ breathingInhalation and exhalationExchange of air between atmosphere and alveoliExternal (pulmonary) respirationExchange of gases between alveoli and bloodInternal (tissue) respirationExchange of gases between systemic capillaries and tissue cellsSupplies cellular respiration (makes ATP)Copyright 2009, John Wiley & Sons, Inc.
24Inhalation/ inspiration Pressure inside alveoli lust become lower than atmospheric pressure for air to flow into lungs760 millimeters of mercury (mmHg) or 1 atmosphere (1 atm)Achieved by increasing size of lungsBoyle’s Law – pressure of a gas in a closed container is inversely proportional to the volume of the containerInhalation – lungs must expand, increasing lung volume, decreasing pressure below atmospheric pressureCopyright 2009, John Wiley & Sons, Inc.
25Copyright 2009, John Wiley & Sons, Inc. Boyle’s LawCopyright 2009, John Wiley & Sons, Inc.
26Copyright 2009, John Wiley & Sons, Inc. InhalationInhalation is active – Contraction ofDiaphragm – most important muscle of inhalationFlattens, lowering dome when contractedResponsible for 75% of air entering lungs during normal quiet breathingExternal intercostalsContraction elevates ribs25% of air entering lungs during normal quiet breathingAccessory muscles for deep, forceful inhalationWhen thorax expands, parietal and visceral pleurae adhere tightly due to subatmospheric pressure and surface tension – pulled along with expanding thoraxAs lung volume increases, alveolar (intrapulmonic) pressure dropsCopyright 2009, John Wiley & Sons, Inc.
28Exhalation/ expiration Pressure in lungs greater than atmospheric pressureNormally passive – muscle relax instead of contractBased on elastic recoil of chest wall and lungs from elastic fibers and surface tension of alveolar fluidDiaphragm relaxes and become dome shapedExternal intercostals relax and ribs drop downExhalation only active during forceful breathingCopyright 2009, John Wiley & Sons, Inc.
31Copyright 2009, John Wiley & Sons, Inc. AirflowAir pressure differences drive airflow3 other factors affect rate of airflow and ease of pulmonary ventilationSurface tension of alveolar fluidCauses alveoli to assume smallest possible diameterAccounts for 2/3 of lung elastic recoilPrevents collapse of alveoli at exhalationLung complianceHigh compliance means lungs and chest wall expand easilyRelated to elasticity and surface tensionAirway resistanceLarger diameter airway has less resistanceRegulated by diameter of bronchioles & smooth muscle toneCopyright 2009, John Wiley & Sons, Inc.
32Lung volumes and capacities Minute ventilation (MV) = total volume of air inhaled and exhaled each minuteNormal healthy adult averages 12 breaths per minutemoving about 500 ml of air in and out of lungs (tidal volume)MV = 12 breaths/min x 500 ml/ breath= 6 liters/ minCopyright 2009, John Wiley & Sons, Inc.
33Spirogram of Lung Volumes and Capacities Copyright 2009, John Wiley & Sons, Inc.
34Copyright 2009, John Wiley & Sons, Inc. Lung VolumesOnly about 70% of tidal volume reaches respiratory zoneOther 30% remains in conducting zoneAnatomic (respiratory) dead space – conducting airways with air that does not undergo respiratory gas exchangeAlveolar ventilation rate – volume of air per minute that actually reaches respiratory zoneInspiratory reserve volume – taking a very deep breathCopyright 2009, John Wiley & Sons, Inc.
35Copyright 2009, John Wiley & Sons, Inc. Lung VolumesExpiratory reserve volume – inhale normally and exhale forcefullyResidual volume – air remaining after expiratory reserve volume exhaledVital capacity = inspiratory reserve volume + tidal volume + expiratory reserve volumeTotal lung capacity = vital capacity + residual volumeCopyright 2009, John Wiley & Sons, Inc.
36Exchange of Oxygen and Carbon Dioxide Dalton’s LawEach gas in a mixture of gases exerts its own pressure as if no other gases were presentPressure of a specific gas is partial pressure PxTotal pressure is the sum of all the partial pressuresAtmospheric pressure (760 mmHg) = PN2 + PO2 + PH2O + PCO2 + Pother gasesEach gas diffuses across a permeable membrane from the are where its partial pressure is greater to the area where its partial pressure is lessThe greater the difference, the faster the rate of diffusionCopyright 2009, John Wiley & Sons, Inc.
37Partial Pressures of Gases in Inhaled Air PN2=0.786x 760mm Hg= mmHgPO2=0.209= mmHgPH2O=0.004= 3.0 mmHgPCO2=0.0004= 0.3 mmHgPother gases=0.0006= 0.5 mmHgTOTAL= mmHgCopyright 2009, John Wiley & Sons, Inc.
38Copyright 2009, John Wiley & Sons, Inc. Henry’s lawQuantity of a gas that will dissolve in a liquid is proportional to the partial pressures of the gas and its solubilityHigher partial pressure of a gas over a liquid and higher solubility, more of the gas will stay in solutionMuch more CO2 is dissolved in blood than O2 because CO2 is 24 times more solubleEven though the air we breathe is mostly N2, very little dissolves in blood due to low solubilityDecompression sickness (bends)Copyright 2009, John Wiley & Sons, Inc.
39External Respiration in Lungs OxygenOxygen diffuses from alveolar air (PO2 105 mmHg) into blood of pulmonary capillaries (PO2 40 mmHg)Diffusion continues until PO2 of pulmonary capillary blood matches PO2 of alveolar airSmall amount of mixing with blood from conducting portion of respiratory system drops PO2 of blood in pulmonary veins to 100 mmHgCarbon dioxideCarbon dioxide diffuses from deoxygenated blood in pulmonary capillaries (PCO2 45 mmHg) into alveolar air (PCO2 40 mmHg)Continues until of PCO2 blood reaches 40 mmHgCopyright 2009, John Wiley & Sons, Inc.
40Copyright 2009, John Wiley & Sons, Inc. Internal RespirationInternal respiration – in tissues throughout bodyOxygenOxygen diffuses from systemic capillary blood (PO2 100 mmHg) into tissue cells (PO2 40 mmHg) – cells constantly use oxygen to make ATPBlood drops to 40 mmHg by the time blood exits the systemic capillariesCarbon dioxideCarbon dioxide diffuses from tissue cells (PCO2 45 mmHg) into systemic capillaries (PCO2 40 mmHg) – cells constantly make carbon dioxidePCO2 blood reaches 45 mmHgAt rest, only about 25% of the available oxygen is usedDeoxygenated blood would retain 75% of its oxygen capacityCopyright 2009, John Wiley & Sons, Inc.
42Rate of Pulmonary and Systemic Gas Exchange Depends onPartial pressures of gasesAlveolar PO2 must be higher than blood PO2 for diffusion to occur – problem with increasing altitudeSurface area available for gas exchangeDiffusion distanceMolecular weight and solubility of gasesO2 has a lower molecular weight and should diffuse faster than CO2 except for its low solubility - when diffusion is slow, hypoxia occurs before hypercapniaCopyright 2009, John Wiley & Sons, Inc.
43Transport of Oxygen and Carbon Dioxide Oxygen transportOnly about 1.5% dissolved in plasma98.5% bound to hemoglobin in red blood cellsHeme portion of hemoglobin contains 4 iron atoms – each can bind one O2 moleculeOxyhemoglobinOnly dissolved portion can diffuse out of blood into cellsOxygen must be able to bind and dissociate from hemeCopyright 2009, John Wiley & Sons, Inc.
45Relationship between Hemoglobin and Oxygen Partial Pressure Higher the PO2, More O2 combines with HbFully saturated – completely converted to oxyhemoglobinPercent saturation expresses average saturation of hemoglobin with oxygenOxygen-hemoglobin dissociation curveIn pulmonary capillaries, O2 loads onto HbIn tissues, O2 is not held and unloaded75% may still remain in deoxygenated blood (reserve)Copyright 2009, John Wiley & Sons, Inc.
46Oxygen-hemoglobin Dissociation Curve Copyright 2009, John Wiley & Sons, Inc.
47Copyright 2009, John Wiley & Sons, Inc. Hemoglobin and OxygenOther factors affecting affinity of Hemoglobin for oxygenEach makes sense if you keep in mind that metabolically active tissues need O2, and produce acids, CO2, and heat as wastesAcidityPCO2TemperatureCopyright 2009, John Wiley & Sons, Inc.
48Copyright 2009, John Wiley & Sons, Inc. Bohr EffectAs acidity increases (pH decreases), affinity of Hb for O2 decreasesIncreasing acidity enhances unloadingShifts curve to rightPCO2Also shifts curve to rightAs PCO2 rises, Hb unloads oxygen more easilyLow blood pH can result from high PCO2Copyright 2009, John Wiley & Sons, Inc.
49Copyright 2009, John Wiley & Sons, Inc. Temperature ChangesWithin limits, as temperature increases, more oxygen is released from HbDuring hypothermia, more oxygen remains bound2,3-bisphosphoglycerateBPG formed by red blood cells during glycolysisHelps unload oxygen by binding with HbCopyright 2009, John Wiley & Sons, Inc.
50Fetal and Maternal Hemoglobin Fetal hemoglobin has a higher affinity for oxygen than adult hemoglobinHb-F can carry up to 30% more oxygenMaternal blood’s oxygen readily transferred to fetal bloodCopyright 2009, John Wiley & Sons, Inc.
51Carbon Dioxide Transport Dissolved CO2Smallest amount, about 7%Carbamino compoundsAbout 23% combines with amino acids including those in HbCarbaminohemoglobinBicarbonate ions70% transported in plasma as HCO3-Enzyme carbonic anhydrase forms carbonic acid (H2CO3) which dissociates into H+ and HCO3-Copyright 2009, John Wiley & Sons, Inc.
52Copyright 2009, John Wiley & Sons, Inc. CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-Chloride shiftHCO3- accumulates inside RBCs as they pick up carbon dioxideSome diffuses out into plasmaTo balance the loss of negative ions, chloride (Cl-) moves into RBCs from plasmaReverse happens in lungs – Cl- moves out as moves back into RBCsCopyright 2009, John Wiley & Sons, Inc.
54Copyright 2009, John Wiley & Sons, Inc. End of Chapter 23Copyright 2009 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permission Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publishers assumes no responsibility for errors, omissions, or damages caused by the use of theses programs or from the use of the information herein.Copyright 2009, John Wiley & Sons, Inc.