water - 副本

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,water,演讲：徐丹,单词：刘晓彬,回答：童莉,ppt：张敏敏,Water,water as a percentage of body weight,水作为身体重量的百分比,functions of water,special characteristics of water,水的特殊特性,Water is of vital importance to the body and constitutes the greatest portion of body weight.The human body consists of 45%to 75%water,depending on age and sex.,水是至关重要的,是对身体体重最大的一部分。人的身体有,45%,至,75%,的水,根据年龄和性别有所不同。,Water as a percentage of body weight,Water Compartment,Infant (%),Adult(%),Man,Woman,Elderly Person(%),Extracellular,Intravascular,Interstitial,Intracellular,Total body water,4,25,4,11,5,10,5,15,48,45,35,25,77,60,50,45,Water(H,2,o)is vital to human life.The body cannot carry on most of its activities without it.,Water performs many significant functions in the human body.It provides an efficient medium for delivery of nutrients to the cells and export of waste products from the cells.It is especially important in regulation of blood pressure and fluid and electrolyte balance.,流体和电解质的平衡,Primary solvent,主要溶剂,within the body,Primary compound in all body fluids,在所有体液中主要化合物,Suspension agent,Helps regulate body temperature,body pH,and fluid pressures inside and outside cells,Assists or participates in chemical reactions,May be end product of chemical reactions,可能是化学反应的最终产物,Transports nutrients and oxygen to cells,Transports waste products away from cells,Acts as bumper to protect cells and organs,Lubricates to prevent outer walls(parietal)from rubbing against inner walls(visceral)of organs,Water in solution with other substances,Participates in maintenance of blood pressure,Helps regulate acid-base and fluid-electrolyte balance,Facilitates the use of water-soluble victamins(C and B-complex),便于使用的水溶性,victamins,Water in Solution with Other substances,Special characteristics of water,A great difference in temperature is needed to bring about a physical change in water.,Water directly and indirectly participates in all chemical reactions that occur in the body.,Water is a good solvent.,Water exerts pressure against the walls or vessels that contain it.,A graet different in temperature is needed to bring about a physical change in water,.,Water boils at 100(212,）,and freezes at 0(32).Water can become a solid,a liquid,or a gas with only a temperature change.Water temperature,however,change relatively slowly.It needs heat to change from a liquid to a gas.The evaporation process(change from liquid to gas)removes heat from the body,.,Water directly and indirectly participates in all chemical reactions that occur in the body.,Chemically,each water molecule(H,2,O）is made up of two elements,hydrogen and oxygen.During metabolism,numerous chemical change in the body separate water molecule,s,into their component elements for use elsewhere.,Hydrogen is the main component of the pH system of the body.Oxidation is the process through which the body uses oxygen,to f,or,m needed new substances.,Indirectly,water acts as the solution in which other chemicals ionize(dissociate).,When substances change into ions,they become available to participate in other chemical reactions.,Water is a good solvent.,A,solvent,is a liquid(that dissolves solutes).A,solute,is the substance dissolved in a solvent.Many compounds,such as salts and sugars,dissolve easily in water.Nutrients and wastes are transported as solutes in water.Body water contains two main types of solutes:nonelectrolytes and electrolytes.Nonelectrolytes include proteins,glucose,carbon dioxide,oxygen,and organic acids.Electrolytes are solutes that generate an electrical charge when dissolved in water.,Water functions as a suspension agent.,M,any larger molecules,such as lipids and proteins,are easily suspended in water.These suspensions must be kept in motion,or the larger molecules will settle to the bottom.An individuals blood pressure partially depends on intravascular water as a suspension agent,with specific amounts of proteins,electrolytes,and minerals as solutes.,Water exerts pressure against the walls or vessels that contain it.,This pressure is known as hydrostatic pressure and occurs because water has weight and volume.The amount of pressure depends on the depth of the liquid.Regardless of the amount,water in a tall,thin container exerts more hydrostatic pressure than water in a shallow container.,Osmotic pressure,is pressure that develops when a semipermeable membrane separates two solutions containing different concentrations of solutes.,In other words,the amount of solutes in water affects the pressure that the water can exert against surrounding membranes.,The greater the amount of solutes,the greater the amount of pressure.This principle is normally maintained within very narrow limits.Human body cells have an osmotic pressure nearly equal to that of the circulating fluid of the blood.Solutions exerting equal pressures on opposite sides of the membrane are said to be,isotonic.,Stronger solutions,compared to those on the opposing side of a mambrane,are said to be,hyperton