1、5 RespirationChemical reduction of molecular oxygen to form water is the primary source of energy for animals.The principal site for the reaction occurs within the mitochondria.Without this reaction life cannot exist for more than seconds.Coincidental with the reduction of O2 is the production of CO
2、2;this comes mainly from oxidative phosphorylation of glucose which also occurs principally in the mitochondrion.Repiration includes:The gases must be moved between the environment and the lungs,usually referred to as“pulmonary ventilation”The gases must be exchanged between the spaces in lung and t
3、he blood Exchange of gases between the blood and the various tissues must occur Finally transfer of gases must occur within the tissue to sites of utilization(for O2)and from the sites of production(for CO2)5.1 pulmonary ventilationGas exchange between the environment and the lungs,usually referred
4、to as“pulmonary ventilation”The structures needed for pulmonary ventilation:airway,alveoli lvilai (单数 alveolus),and thorax 5.1.1肺通气的原理肺通气的原理 5.1.1.1 肺通气的动力肺通气的动力直接动力肺泡与外界环境之间的压力差原动力节律性呼吸运动Respiratory movements(呼吸运动）呼吸运动）Respiratory muscle:diaphragm(膈),intercostal muscle,et al Thoracic cavity Inspira
5、tory movement&Expiratory movement 呼吸运动的形式：腹式呼吸和胸式呼吸平静呼吸和用力呼吸Intrapulmonary pressures 肺内压 平静呼吸 吸气时 -2-1 mmHg(-0.266-0.133Kpa)呼气时 1 2 mmHg(0.133 0.266Kpa)用力呼吸(forced breathing)用力吸气-100-30 mmHg 用力呼气60 140 mmHgThe pressure in thoracic cavity(intrapleural pressures)胸膜腔内压 pulmonary ventilation:As long as
6、interplueral pressure remains less than atmospheric pressure,the dimensions of the lungs follow closely the dimensions of the thoracic cavity.Lung movements results from contraction of respiratory muscles associated with the movement of structures in thoracic cavity wall and of the diaphragm.Pleura：
7、surrounding each lung is a serous(含浆液的）membrane,the pleura.The out layer adheres to the inner thoracic wall and the diaphragm.The inner layer covers the lung the potential space between the two layers is called the pleural cavity,the layers normally move easily over each other with movement of the t
8、horax.Pressure in the interpleural space is always negative.（平静呼吸时）气胸（Pneumothorax)胸膜腔内压肺内压肺回缩压当呼吸暂停时胸膜腔内压大气压肺回缩压若以大气压为“0”胸膜腔内压肺回缩压胸腔负压也可作用于腔静脉和胸导管，影响静脉血和淋巴的回流。5.1.1.2 肺通气的阻力肺通气的阻力肺通气的阻力有两种：弹性阻力（70%），包括肺的弹性阻力和胸廓的弹性阻力非弹性阻力（30%），包括气道阻力等弹性阻力和顺应性（Compliance）CV/P(L/cmH2O)肺表面活性物质（肺表面活性物质（pulmonary surfact
9、ant)是复杂的脂蛋白混合物，主要成分是二软脂酰卵磷脂（DPPC）和表面活性物质结合蛋白（SP）。作用是降低肺泡液气界面的表面张力，而肺的回缩力减小。生理意义：维持肺泡的稳定性；减少肺间质和肺泡内组织液生成，防止肺水肿；降低吸气阻力，减少呼吸做功。早产婴儿5.1.2肺通气功能的评价肺通气功能的评价 5.1.2.1 Pulmonary volume and Pulmonary CapacityTimed vital capacity四种基本肺容积：潮气量、补吸气量、补呼气量、残气量。肺容量是指肺容中两项或两项以上的联合气量5.1.2.2 Pulmonary ventilation volume
10、and alveolar ventilation volume Minute ventilation volume 0.5*120.5*18 69 L/min,maxmum 70150 L/min Dead space and alvoelar ventilation anatomical dead space physiological dead space alveolar ventilation5.2 Gas Exchanges5.2.1 The principle of gas exchages Factors affecting diffusion rate partial pres
11、ure difference P solubility of gas S area available for dissusion A temperrature T distance to diffuse(thickness of the diffusion barrier)d molecular weight of gas MW P T A S D d MWThe partial pressure of respiratory gases at different parts of the body 5.2.2 Gas Exchanges in the Lung The exchange o
12、f gases in the lung between the inspired air and the blood is governed by several important physiological mechanisms.In an ideal cardiorespiratory system,perfect equilibration between the air and the blood might be expected.This would provide optimal efficiency in gas exchange.Unfortunately,the lung
13、 is always somewhat inefficient,even in normal individuals.This inefficiency is manifested(表示)as a difference between alveolar Po2 and arterial Po2.With lung disease or some circulatory abnormalities,the difference can be large.Pulmonary capillary gas equilibration Under the normal circumstances,the
14、 blood spends an average of 0.75 seconds in the pulmonary capillary.With a normal diffusion capacity,enough oxygen crosses the membrane to bring the red cell hemoglobin to equilibrium with the avoelar Po2 in 0.25 seconds or less.Factors affecting gas exchange in the lung The thickness of alveolocapi
15、llary(respiratory)membrane surface lining(surfactant),alveolar epithelium,basement of membranes,capillary endothelium.The area of respiratory membrane about 3x108 alveoli total 70 m2,40 m2 at resting state (Ventilation/perfusion ratio V/Q:4.2/5=0.845.2.3 Gas exchange in the tissues组织换气的机制和影响因素与肺换气相似
16、，不同的是气体的交换发生于液相，而且扩散膜两侧的O2和CO2分压随细胞代谢的强度和组织的血流量而异。5.3 Transport of respiratory gases5.3.1 The forms of O2 and CO2 carried in blood Oxygen is carried in the blood in two forms:in physical solution and in combination with hemoglobin.Approximately 1.5%of the O2 carried in the systematic arterial blood
17、at normal PO2 is dissolved in the plasma,The rest is held in loose chemical combination with the hemoglobin found in the red blood cell.Carbon dioxide is stored in three forms in blood,in physical solution,as bicarbonate,and in combination with protein,as carbamino compound.Although the dissolved O2
18、 and CO2 are very small parts they are very important.5.3.2 Transport of O2 Hemoglobin is a conjugated protein consisting of a ferrous iron-porphyrin compound(heme)joined to the protein globulin.Each Fe2+molecule of Hb combines loosely and reversibly with one molecule of O2.Fully oxygenated hemoglob
19、in carries 1.39 ml O2/g of Hb.If the Fe2+is oxidized to Fe3+,the compound is no longer able to transport O2 4 moles O2/1mole Hb=4*22.4 L/64458g=1.39 ml/g Oxygen capacity(氧容量)normally 20 ml/100ml blood Oxygen content(氧含量)Oxygen saturation(氧饱和度)=content/capacity Oxygen dissociation(equilibrium)curve 氧
20、解离曲线 oxygen dissociation curve The position of O2 equilibrium curve can change owing to other physiological factors.The major factors affecting O2 affinity are Pco2,pH,temperature and 2,3-diphosphoglycerate.CO2 and pH Bohr effect advantage Temperature 2,3-diphosphoglycerate CO and the structure of H
21、b Fully oxygenated hemoglobin releases more protons than the deoxygenated Hb.As a result,in a solution at 7.25,the release of 1 mM of O2 from HbO2 permit 0.7 mM of H+to be taken up without a change in pH;thus delivery of O2 aids in buffering acids produced locally in the tissue.影响氧解离曲线的因素影响氧解离曲线的因素factors effect oxygen dissociation curve
