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1、,respiration,第五章 呼吸生理,1.外呼吸 肺通气（外界空气与肺泡之间的气体交换过程）肺换气(肺泡与肺毛细血管之间的气体交换过程）,呼吸的三个基本环节,气体在血液中的运输3.内（组织）呼吸 血液与组织、细胞之间的气体交换过程,肺通气和肺换气,6,The goals of respiration are to provide oxygen to the tissues and to remove carbon dioxide.To achieve these goals,respiration can be divided into four major functional eve
2、nts:,7,pulmonary ventilation,which means the inflow and outflow of air between the atmosphere and the lung alveoli;(2)diffusion of oxygen and carbon dioxide between the alveoli and the blood;,8,(3)transport of oxygen and carbon dioxide in the blood and body fluids to and from the cells;and(4)regulat
3、ion of ventilation and other facets of respiration.This chapter is a discussion of pulmonary ventilation.,第一节 肺通气,一、实现肺通气的结构特点及功能,鼻、咽、喉、气管直到终末细支气管,上呼吸道,下呼吸道,二、肺通气原理,（一）肺通气的动力直接动力：肺泡与大气之间的压力差 原动力:呼吸运动呼吸肌收缩、舒张所造成的胸廓的扩大和缩小，称为呼吸运 动。,1呼吸运动（1）吸气运动：膈肌收缩时中部下移，增大了胸腔的上下径，肺容积随之增大，产生吸气。平静呼吸时膈肌收缩造成的通气量 占总通气量的4/5
4、。,当肋间外肌收缩时，增大了胸腔的前后径和左右径，肺容积随之 增大,产生吸气。,（2）呼气运动：平静呼气时，因膈肌和肋间外肌 舒张，肺依靠本身的回缩力量而回位，产生呼气。,用力呼吸：除上述肌肉外，有更多的吸气肌与呼气肌 参与呼吸运动。,用力呼吸,吸气（主动）膈肌和肋间外肌收缩，胸锁乳突肌、斜角肌也收缩,呼气（主动）膈肌和肋间外肌舒张，腹壁肌肉、肋间内肌收缩,平静呼吸,吸气（主动）膈肌和肋间外肌收缩,呼气（被动）膈肌和肋间外肌舒张,膈肌舒缩引起的呼吸运动伴以腹壁的起伏，所以称为腹式呼吸（abdominal breathing）。,由肋间肌舒缩使肋骨和胸骨运动所产生的呼吸运动，称为胸式呼吸。Tho
5、racic breathing,26,1.Mechanics Of Pulmonary Ventilation 627.4-628.3A.Muscles That Cause Lung Expansion and Contraction 629.2-630.2,27,The lungs can be expanded and contracted in two ways:by downward and upward movement of the diaphragm to lengthen or shorten the chest cavity and by elevation and dep
6、ression of the ribs to increase and decrease the antero-posterior diameter of the chest cavity.,28,Normal quiet breathing is accomplished almost entirely by the first of the two methods,that is,by movement of the diaphragm.During inspiration,contraction of the diaphragm pulls the lower surfaces of t
7、he lungs downward.,29,Then,during expiration,the diaphragm simply relaxes,and the elastic recoil of the lungs,chest wall,and abdominal structures compresses the lungs.,30,During heavy breathing,however,extra force is achieved mainly by contraction of the abdominal muscles,which pushes the abdominal
8、contents upward against the bottom of the diaphragm.,31,The second method for expanding the lungs is to raise the rib cage.when the rib cage is elevated,making the antero-posterior thickness of the chest about 20 per cent greater during maximum inspiration than during expiration.,32,Therefore,all th
9、e muscles that elevate the chest cage are classified as muscles of inspiration,and the muscles that depress the chest cage are classified as muscles of expiration.The most important muscles that raise the rib cage are the external intercostals.,33,The muscles that pull the rib cage downward during e
10、xpiration are(1)the abdominal recti,which have the powerful effect of pulling downward on the lower ribs at the same time that they and the other abdominal muscles compress the abdominal contents upward toward the diaphragm,and(2)the internal intercostals.,34,As the external intercostals they contra
11、ct,they pull ribs forward,and this causes leverage on the ribs to raise them upward,thereby causing inspiration.The internal intercostals function exactly oppositely,functioning as expiratory muscles,because they angle between the ribs in the opposite direction and cause opposite leverage.,2肺内压 肺内压是
12、指肺泡内的压力。吸气初，肺内压低于大气压，空气进入肺泡。呼气初，肺内压高于大气压，肺内气体流出。吸气末和呼气末，肺内压和大气压相等。,36,Alveolar pressure is the pressure of the air inside the lung alveoli.When the glottis声门is open and no air is flowing into or out of the lungs,the pressures in all parts of the respiratory tree,all the way to the alveoli,are equal
13、to atmospheric pressure,which is considered to be the zero reference pressure in the airways that is,0 centimeters water pressure.,37,To cause inward flow of air into the alveoli during inspiration,the pressure in the alveoli must fall to a value slightly below atmospheric pressure(below 0).,38,Duri
14、ng normal inspiration,alveolar pressure decreases to about-1 centimeter of water.This slight negative pressure is enough to pull 0.5 liter of air into the lungs in the 2 seconds required for normal quiet inspiration.,39,During expiration,opposite changes occur:The alveolar pressure rises to about+1
15、centimeter of water,and this forces the 0.5 liter of inspired air out of the lungs during the 2 to 3 seconds of expiration.,3.胸内压,胸膜腔内的压力称为胸内压。,胸膜腔内压比大气压低，为负压。平静呼气末胸膜腔内压约为-5-3mmHg，吸气末约为-10-5mmHg。,胸内压=大气压-肺回缩力,胸内压=肺内压-肺弹性回缩力=大气压-肺弹性回缩力若以1个大气压为0，则胸膜腔内压=肺弹性回缩力,46,Pleural pressure is the pressure of the
16、 fluid in the narrow space between the lung pleura and the chest wall pleura.,47,Pleural pressure is normally a slightly negative pressure.The normal pleural pressure at the beginning of inspiration is about-5 centimeters of water,which is the amount of suction that is required to hold the lungs ope
17、n to their resting level.,48,Then,during normal inspiration,the expansion of the chest cage pulls outward on the lungs with still greater force and creates a still more negative pressure to an average of about-7.5 centimeters of water.,（二）肺通气的阻力,弹性阻力（70%）,非弹性阻力（30%）,1、弹性阻力和顺应性,（1）弹性阻力弹性组织在外力作用下变形时，有
18、对抗变形和弹性回位的倾向，为弹性阻力。,（2）顺应性(compliance),顺应性是指在外力作用下弹性组织的可扩张性。容易扩张者，顺应性大，弹性阻力小；反之则相反。,可见顺应性（C）与弹性阻力（R）成反变关系：C=1/R,顺应性用单位压力变化（P）所引起的容积变化（V）来表示，单位是L/cmH2O，即 C=V/PL/cmH2O。,54,Compliance in the respiratory system 631.2-633.1describes the distensibility of the lungs and chest wall.is inversely related to e
19、lastance,which depends on the amount of elastic tissue.is the change in volume for a given change in pressure.,肺的弹性阻力,肺表面张力（2/3）,肺组织弹性（1/3）,(3)肺的弹性阻力的来源,肺组织的弹性主要来肺组织的弹性纤维和胶原纤维。,57,Resistence to pulmonary ventilation633.2-634.4Resistant forces of the lungs.These can be divided into two parts:(1)the e
20、lastic forces of the lung tissue itself,58,The elastic forces of the lung tissue are determined mainly by the elastin and collagen fibers interwoven among the lung parenchyma.(2)the elastic forces caused by surface tension of the fluid that lines the inside walls of the alveoli and other lung air sp
21、aces.,59,Nature of Lung Elastic RecoilThe elastic recoil of the lung consists of two kinds of forcestissue forces and surface tension forces.The elasticity of lung tissue is due principally to elastin弹性蛋白fibers in alveolar walls and surrounding small airways.,肺泡表面张力,肺泡内壁有一薄层液体，它与肺泡内气体形成了液-气交界面，这里存在减
22、小液-气界面的力，使肺泡趋于缩小，称为肺泡表面张力。,肺泡表面活性物质,是由肺泡型细胞分泌的一种复杂的脂蛋白，主要成分为二棕榈酰卵磷脂。其主要作用是降低表面张力。,Laplace定律：P=2T/r p 肺泡内压T 表面张力 r 肺泡半径由于小肺泡表面活性物质的密度大，大肺泡表面活性物质分子的 稀疏，则大小肺泡内压力相等，大小肺泡的稳定性。,肺泡表面活性物质的作用,降低表面张力,维持大小肺泡的容积相对稳定,调节肺泡的回缩力，有利呼吸,使肺泡表面相对干燥，避免肺水肿,64,The surface tension accounts for about two thirds of the total
23、elastic forces in the normal lungs.The surface tension elastic forces of the lungs also increase tremendously when the substance called surfactant is not present in the alveolar fluid.,Surfactant is a surface active agent,which means that it greatly reduces the surface tension of the water.It is sec
24、reted by special surfactant-secreting epithelial cells that constitute about 10 per cent of the surface area of the alveoli.These cells are are called type II alveolar epithelial cells.,66,Surfactant is a complex mixture of several phospholipids,proteins,and ions.Surfactant consists primarily of the
25、 phospholipid,(DPPC)which is responsible for reducing the surface tension.,67,Abnormalities of Lung Elastic RecoilLung elastic recoil is increased by reduced surfactant activity resulting from decreased synthesis or inactivation.The best-known clinical disorder associated with decreased surfactant s
26、ynthesis is the respiratory distress syndrome of the newborn.,68,Surfactant production may also beimpaired following the interruption of pulmonary perfusion,as in pulmonary thromboembolism血栓栓塞.Hydrostatic pulmonary edema and adult respiratory distress syndrome are associated with surfactant inactiva
27、tion due to alveolar flooding.,69,The consequences of decreased surfactant activity include decreased lung compliance due to increasedsurface tension and alveolar collapse(atelectasis肺萎陷),decreased lung volumes(TLC,total lung capacity,RV residual volume,and FRC functional residual capacity),and incr
28、eased elastic work of breathing.,70,The decreased lung compliance of interstitial or infiltrative浸润性的lung diseases results from two mechanisms decreased distensibility and lung shrinkage,71,Pathologically these diseases are characterized by alveolar filling with inflammatory exudate渗出物and/or replace
29、ment of alveoli by fibrosis,and this loss of alveolar units or lungshrinkage decreases compliance(see above).,72,In addition,these disorders may alter theconnective tissue elements of the lung.resulting in increased lung elastic recoil.As a result,TLC,RV,and functional residual capacity are decrease
30、d,and the elastic work of breathing is increased in these disorders.,2、非弹性阻力包括:惯性阻力 粘滞阻力 气道阻力,惯性阻力是气流在发动、变速、换向时因气流和组织的惯性所产生的。平静呼吸时，惯性阻力小，可忽略不计。,粘滞阻力来自呼吸时组织相对位移所发生的磨擦。,气道阻力来自气体分子间和气体分子与气道之间的磨擦，是非弹性阻力的主要成分，约占80%-90%。,R与1/r4成正比,影响r的因素：,1、气道管壁平滑肌的神经调节,2、化学因素的影响,（三）呼吸功,三、基本肺容积和肺容量,（一）基本肺容积（pulmonary volu
31、me)1潮气量 每次呼吸时吸入或呼出的气量为潮气量（tidal volume）。平静呼吸时，潮气量为500ml。运动时增大。,2补吸气量平静吸气末，再尽力吸气所能吸入的气量为补吸气量（inspiratory reserve volume），正常为1500-2000ml。,3补呼气量 平静呼气末，再尽力呼气所能呼出的气量为补呼气量（expiratory reserve volume），正常为900-1200ml。,4余气量 最大呼气末尚存留于肺中不能再呼出的气量为余气量（residual volume）。正常为1000-1500ml。,（二）肺容量（pulmonary capacities）是基
32、本肺容积中两项或两项以上的联合气量。1深吸气量 从平静呼气末作最大吸气时所能吸入的气量为深吸气量，它是潮气量和补吸气量之和。,2功能余气量 平静呼气末尚存留于肺内的气量为功能余气量。是余气量和补呼气量之和。,3肺活量最大吸气后，从肺内所能呼出的最大气量称作肺活（vital capacity），是潮气量、补吸气量和补呼气量之和。正常成年男性平均约为3500ml，女性为2500ml。,4.时间肺活量先深吸气，然后以最快的速度呼出气体，同时分别测量第1、2、3s末呼出的气量，计算其所占肺活量的百分数（正常人各为83%、96%和99%肺活量。),时间肺活量不仅反映肺活量容量的大小，而且反映了呼吸所遇阻
33、力的变化，所以是评价肺通气功能的较好指标。,90,Pulmonary Volumes And Capacities628.3-629.1A.Pulmonary Volumes1.The tidal volume is the volume of air inspired or expired with each normal breath;it amounts to about 500 milliliters.,91,2.The inspiratory reserve volume is the maximum extra volume of air that can be inspired
34、over and above the normal tidal volume;it is usually equal to about 3000 milliliters.,92,3.The expiratory reserve volume is the maximum extra volume of air that can be expired by forceful expiration after the end of a normal tidal expiration;this normally amounts to about 1100 milliliters.,93,4.The
35、residual volume is the volume of air remaining in the lungs after the most forceful expiration.This volume averages about 1200 milliliters.,94,Pulmonary CapacitiesIn describing events in the pulmonary cycle,it is sometimes desirable to consider two or more of the volumes together.Such combinations a
36、re called pulmonary capacities.,95,The vital capacity equals the inspiratory reserve volume plus the tidal volume plus the expiratory reserve volume.This is the maximum amount of air a person can expel from the lungs after first filling the lungs to their maximum extent and then expiring to the maxi
37、mum extent(about 4600 milliliters).,96,The total lung capacity is the maximum volume to which the lungs can be expanded with the greatest possible effort(about 5800 milliliters);it is equal to the vital capacity plus the residual volume.,97,All pulmonary volumes and capacities are about 20 to 25 per
38、 cent less in women than in men,and they are greater in large and athletic people than in small and asthenic无力的people.,98,To perform a forced vital capacity(FVC)maneuver,the subject inhales to total lung capacity,exhales as forcefully and rapidly as possible to residual volume,and then returns toTLC
39、 by a rapid forceful inhalation.,99,During forced inspiration,flow increases rapidly above residual volume becausethe inspiratory muscles function most advantageously at low lung volumes.As inspiration progresses,flow remainshigh because airway resistance falls as lung volume increases.Near TLC flow
40、 decreases as the inspiratory muscles shorten,and inspiratory force decreases.,=1218500=69L/min,四、肺通气量,（一）每分通气量和每分最大通气量,每分通气量=呼吸频率潮气量,101,The minute respiratory volume is the total amount of new air moved into the respiratory passages each minute;this is equal to the tidal volume times the respirato
41、ry rate.The normal tidal volume is about 500 milliliters,and the normal respiratory rate is about 12 breaths per minute.Therefore,the minute respiratory volume averages about 6 L/min.,每分最大通气量尽力作深快呼吸时，每分钟所能吸入或呼出的最大气量为最大通气量。,（二）无效腔（dead space)和肺泡通气量,生理无效腔,解剖无效腔（150ml）,肺泡无效腔,104,Dead space 636.5-6a.Ana
42、tomic dead space is the volume of the conducting airways.is normally approximately 150 ml,105,Some of the air a person breathes never reaches the gas exchange areas but instead goes to fill respiratory passages where gas exchange does not occur,such as in the nose,pharynx,and trachea.,106,This air i
43、s called dead space air because it is not useful for the gas exchange process;the space in the respiratory passages where no gas exchange takes place is called the dead space.,107,Normal Dead Space Volume.The normal dead space air in a young adult man is about 150 milliliters.This increases slightly
44、 with age.,108,The volume of all the space of the respiratory system besides the alveoli and their other closely related gas exchange areas;this space is called the anatomic dead space.,109,On occasion,some of the alveoli themselves are nonfunctional or are only partially functional because of absen
45、t or poor blood flow through adjacent pulmonary capillaries.Therefore,from a functional point of view,these alveoli must also be considered dead space.,110,When the alveolar dead space is included in the total measurement of dead space,this is called physiologic dead space,in contradistinction to th
46、e anatomic dead space.,111,In a normal person,the anatomic and physiologic dead spaces are nearly equal because all alveoli are functional in the normal lung,but in a person with partially functional or nonfunctional alveoli in some parts of the lungs,sometimes the physiologic dead space is as much
47、as 10 times the volume of the anatomic dead space,or 1 to 2 liters.,112,Alveolar ventilation per minute is the total volume of new air entering the alveoli and adjacent gas exchange areas each minute.It is equal to the respiratory rate times the amount of new air that enters these areas with each br
48、eath.,113,VA=Freq.(VT-V0)where VA is the volume of alveolar ventilation per minute,Freq is the frequency of respiration per minute,VT is the tidal volume,and V0 is the physiologic dead space volume.,114,Thus,with a normal tidal volume of 500 milliliters,a normal dead space of 150 milliliters,and a r
49、espiratory rate of 12 breaths per minute,alveolar ventilation equals 12 X(500-150),or 4200 ml/min.,115,Alveolar ventilation is one of the major factors determining the concentrations of oxygen and carbon dioxide in the alveoli.,每次吸入的气体，一部分留在从鼻至呼吸性细支气管之间的呼吸道内，这部分气体不参与肺泡与血液的气体交换，故称为解剖无效腔，其容积约为150ml。,进入肺泡内的气体，也可因血流在肺内分布不均而未能都与血液进行气体交换，未能发生气体交换的这一部分肺泡容量称为肺泡无效腔。,500ml,肺泡通气量,每分钟进入肺泡，能与血液进行气体交换的新鲜气体量。,肺泡通气量=（潮气量-无效腔）呼吸频率,深慢呼吸和浅快呼吸的效率比较,
