Kidney and urine formation Renal structure & function Urine formation Urinary y concentration and dilution Regulation of urine formation 1 Kidney and urine formation 1.Renal structure & function 1)General functions Excretion Regulation of the internal environment Water balance Na +,K + balance Acid-base balance Production of renin, erythropoietin, etc. 2 1
3 Kidney and urine formation 1.Renal structure & function 2)Renal structure Nephron Cortical nephron: 80-90% Juxtamedullary nephron Renal corpuscle: filtration Renal tubule: reabsorption, secretion Collecting duct Juxaglomerular J x l m l apparatus Juxaglomerualr cell Renin Macula densa Receptor : Na + 4 2
5 6 3
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Macula densa cells Granular cells 9 Kidney and urine formation 1.Renal structure & function 3)Renal circulation (22%) Autoregulation of RBF Constant Myogenic 80~180mmHg AP AA constriction AP AA dilation Neuro-humoral regulation of RBF Sympathetic vasoconstrictor nerve NE, E 10 5
Kidney and urine formation 2.Urine Formation 1)Glomerular Filtration GFR: 125ml/min(180L/day) (Ultrafiltration) Filtration membrane K f Effective filtration pressure =glomerular capillary ~ - (plasma colloid osmotic ~ + capsular pressure) Afferent end=55-(30+15)=10mmhg 11 12 6
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15 Kidney and urine formation 2.Urine formation 2)Tubular reabsorption and secretion Primary Active transportation Secondary active transportation passive Transportation i.proximal tubule Reabsorption: 180L/day 1.5L/day 67% Na +,Cl -,K +,H 2 O; 85% HCO - 3 ; all glucose, aa Secretion: H + H + -Na + exchange ii.loop henle Descending thin limb H 2 O passive reabsorption through tight junction Ascending limb Impermeable to H 2 O ; Na + -2Cl - -K + symporter 16 8
Kidney and urine formation 2.Urine formation (2)Tubular reabsorption and secretion iii.distal tubule &collecting duct Ionic balance & water balance Early part of the distal tubule Impermeable to H 2 O; Active reabsorption NaCl Later part ~ & collecting ducts 1 H + secretion (Intercalated cells) (Acid-base balance) 2 Na + reabsorption (8% )& K + secretion ( Na +,K + balance) 3H 2 O reabsorption(10%-15%) (Water balance) 17 100 300 300 100 600 400 400 600 1000 800 1000 1200 1200 18 9
The reabsorption of glucose in the proximal tubule: Secondary active transportation Normal: 125mg/min (100mg/100ml); Tm=375mg/min 19 20 10
Bicarbonate reabsorption in the proximal tubule: 21 The processes responsible for the uptake of Na + and Cl - in the thick ascending limb of the loop of Henle tubule: 22 11
Secretion of H + by the intercalated cells of distal tubule and collecting ducts: 23 The tubule secretion of K + in the distal tubule and collecting duct: 24 12
Na + Renin secrection Angiotension II, III production Aldosterone release Na + channel(p cells) Na +,K + -ATPase Na + reabsorption K + secrection 25 Na + ANP (Atrial natriuretic peptide) Na + excretion 26 13
The control of H 2 O uptake by ADH in the distal tubule and collecting duct: 27 Plasma crystal osmotic pressure + Osmoreceptor ADH secretion Urine volume Blood volume Osmotic pressure Blood volume Barorecptor Vagus nerve Center _ Symp. nerve + Vagus nerve _ Blood pressure _ 28 14
29 Water diuresis 30 15
3.Urinary Concentration and Dilution 100 300 300 100 600 400 400 600 Out medulla: NaCl 1000 800 1000 1200 1200 Inner medulla: Urea, NaCl 31 High ADH Many Water Channels Low ADH Few Water Channels Cortex Collecting Duct Medulla Small Volume Concentrated Urine Large Volume Dilute Urine 32 16
Mechanism of countercurrent multiplication: Descending limb: 1. Highly permeable to H2O 2. Not reabsorb Na+ Ascending limb: 1. actively transports NaCl 2. always Impermeable to H2O 33 Role of vasa recta for maintaining the high solute concentration of renal medulla Countercurrent exchange 34 17
Kidney and urine formation 4.Regulation of Urine formation (negative feedback) 1)ADH (Antidiuretic hormone ) 2)Renin-angiotensin-aldosterone system Na + -conserving system 3)Renal sympathetic nerves 4)ANP(Atrial natriuretic peptide) (Atrial myocarial cells) Na + -losing system 35 Volume contraction Sympathetic activity Renin ANP Angiotensin II ADH Na+,H 2 O excretion Aldosterone 36 18
Volume expansion Sympathetic activity Renin ANP Angiotensin II ADH Na+,H 2 O excretion Aldosterone 37 19