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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,*,Urinary concentration and dilution,Concentrative urine,浓缩尿,:,Osmolality of urine plasma osmolality,(300mOsm/L H,2,O),Diluted urine,稀释尿,:,Osmolality of urine plasma osmolality,Formation of Diluted Urine,I,sosmotic reabsorption of water at proximal tubule,Impermeable of water at,thick ascending limb,ADH,Reabsorption of water at distal tubule and collecting duct,Diluted urine,Formation of Concentrative Urine,ADH,Reabsorption of water at distal tubule and collecting duct,Concentrative Urine,ADH,-key element of urinary concentration and dilution,What is the drive force of water reabsorption at,distal tubule and collecting duct?,The Osmotic Gradient of the Renal Medulla,Formation of Osmotic Gradient of the Renal Medulla,Permeability of the Tubular System,Permeability of the Tubular System,H,2,O,NaCl,Urea,Thin descending limb,+,_,_,Thick ascending limb,_,Actively transport,_,Thin ascending limb,_,+,+,Distal tubule,+ADH,Actively transport,_,Cortical collecting duct,+ADH,Actively transport,_,Inner medullary,collecting duct,+ADH,Actively transport,+,The countercurrent theory,1.Countercurrent multiplication,逆流倍增,A,C,B,Formation of Osmotic Gradient of the Renal Medulla,Na,+,H,2,O,1.Countercurrent multiplication,Na,+,H,2,O,Establishing,of Osmotic Gradient of the Renal Medulla,Outer medulla:,reabsorption of NaCl at,thick ascending limb,hyperosmolality,Inner medulla:,1)urea recycling,2)reabsorption of NaCl at,thin ascending limb,hyperosmolality,The Countercurrent Theory,2.Countercurrent exchange,逆流交换,2.Countercurrent exchange,Maintenance,of the Osmotic Gradient in the Medulla,Vasa,recta,Maintenance,of the Osmotic Gradient in the Medulla,The vasa recta:Countercurrent exchanger,Summary:Formation of Concentrated or Dilute Urine,In the presence of ADH,Collecting duct permeable to water,excretion of a concentrated urine,In the absence of ADH,Collecting duct impermeable to water,excretion of a diluted urine,Factors that affect the concentration and dilution of the urine,1)Damage of renal medulla,Resulting in an impairment of the concentrating ability,2)Loop diuretics,such as frusemide,inhibiting the Na,+,/K,+,/2Cl,-,co-transport system in the thick ascending limb,Factors that affect the concentration and dilution of the urine,3)Lack of urea in the body,such as malnutrition,reducing the osmotic gradient established in the renal medulla,4)Increased velocity of blood flow in the vasa recta,carrying away amount of NaCl,reducing the osmotic gradient in the medulla,Humoral Control of Renal F,unctions,Antidiuretic hormone(,抗利尿激素，,ADH),Synthesis in supraoptic and paraventricular nuclei,（视上核与室旁核）,Release from the posterior pituitary,Mechanism of ADH Antidiuresis,Increasing water permeability of collecting duct,Insertion of aquaporins,水通道,in apical membrane,Diabetes Insipidous,尿崩症,Regulation of ADH Release,Plasma osmolality,Plasma osmolality,(+),hypothalamic,osmoreceptors,production and release of ADH,urine,Blood volume,Blood volume,(+),baroreceptor reflex&atrial stretch receptors,ADH release,urine,Blood volume,Water diuresis,水利尿,Physiologic water diuresis is a response to water load:,Slightly decreased plasma osmolality(,drinking bulk water,),ADH,Increased urine flow until plasma osmolality increases,Humoral Control of Renal F,unctions,Aldosterone,醛固酮,Secreted by the glomerulosa,球状带,of the adrenal cortex,To increase the reabsorption of Na,+,in the distal tubule and early collecting duct,coupled to secretion of K,+,Mechanism of Aldosterone Action,To increase number of Na,+,channels,To increase activity of Na,+,pumps,Regulation of Aldosterone Secretion,1.Renin-Angiotensin System,（肾素,-,血管紧张素系统）,Regulation of Aldosterone Secretion,2.Plasma concentrations of sodium and potassium,K,+,Aldosterone secretion,Na,+,Aldosterone secretion,3.Adrenocorticotrophin(,促肾上腺皮质激素，,ACTH),Necessary for Aldosterone secretion,but little effect in controlling the secretion,rate,Ingesting,too much,potassium,stimulates,aldosterone secretion from the adrenal cortex;,aldosterone increases,sodium reabsorption at,the“expense”of increased potassium secretion.,Also shown here is an,indication that more,potassium in the filtrate,leads to greater potassium excretion in the urine.,Decreased blood volume,and ingesting,too much,potassium,both stimulate,aldosterone secretion from,the adrenal cortex;,aldosterone increases,sodium reabsorption at,the“expense”of increased,potassium secretion.,Humoral Control of Renal F,unctions,Atrial natriuretic peptides(,心房钠尿肽，,ANP),Synthesis in the cardiac atrial muscle cell,Leading to increased excretion of salt&water,Its mechanism:,Regulation of ANP Release,Stretch of the atrium,Extracellular fluid volume,and blood volume,Plasma sodium concentration,Renal Clearance,血浆清除率,Defined as the volume of plasma required to supply the amount of a substance X to be excreted in urine per unit time,Use of Clearance Methods to Quantify Kidney Function,U,x,V=GF R+E,G=GFR,F,=Filtration concentration,Use of Clearanc
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