Functional morphology Clearance Assoc. Prof. MUDr. Markéta Bébarová, Ph.D. Department of Physiology Faculty of Medicine, Masaryk University This presentation includes only the most important terms and facts. Its content by itself is not a sufficient source of information required to pass the Physiology exam. Renal Functions > Excretion of Waste Products and Toxins > Control of Volume and Composition of Body Fluids, Osmolality > Regulation of Acid-Base Balance > Regulation of Blood Pressure >Secretion, Metabolism and Excretion of Hormones >Glukoneogenesis Structure of Kidney Cortical radiate vein Cortical radiate artery Arcuate vein Arcuate artery Interlobar vein Interlobar artery Segmental arteries Renal vein Renal artery Renal pelvis Ureter Renal medulla Renal cortex (a) Frontal section illustrating major blood vessels O 2013 Peanon Education. Ine Aorta I Renal artery 1 Segmental artery I Interlobar artery 1 Arcuate artery 1 Cortical radiate artery I Afferent arteriole Inferior vena cava t Renal vein t Interlobar vein I Arcuate vein 1 Cortical radiate vein Peritubular capillaries -or vasa recta í Efferent arteriole -► Glomerulus (capillaries) J Nephron-associated blood vessels (see Figure 25.7) (b) Path of blood flow through renal blood vessels http://classes.midlandstech.edu/carterp/Courses/bio211/chap25/chap25.htm Structure of Kidney Cortical nephron Juxtamedullary nephron • Short nephron loop * Long nephron loop • Glomerulus further from the cortex-medulla junction • Glomerulus closer to the cortex-medulla junction • Efferent arteriole supplies peritubular capillaries * Efferent arteriole supplies vasa recta Rena)- corpuscle http://classes.midla ndstech.edu/carter p/Courses/bio211/c hap25/chap25.htm Structure of Nephron thin descending limb Ganong's Review of Medical Physiology, 23rd edition Structure of Nephron - Glomerulus B Fenestrations Guy ton & Hall. Textbook of Medical Physiology C Basal lamina Endothelium mesangial cells Structure of Nephron - Glomerulus B Fenestrations Guy ton & Hall. Textbook of Medical Physiology C Basal lamina Endothelium Structure of Nephron - Glomerulus > High filtration rate in glomeruli provided by high permeability of glomerular membrane > Protein passage barrier negative charge of all layers of glomerular membrane LL 0 4.0 6.0 8.0 Effective molecular diameter (nm) Ganong 's Review of Medical Physiology Structure of Nephron - Tubulus J IB W Proximal convoluted tubule Distal convoluted tubule Loop of Henle, thin descending limb jdi Collecting duct v. Outer medulla Inner medulla > glomerulus > proximal convoluted tubule Ganong's Review of Medical Physiology, 23rd edition Proximal convoluted tubule Structure of Nephron - Tubulus J IB W Proximal convoluted tubule Distal convoluted tubule Loop of Henle, thin descending limb jdi Collecting duct v. Outer medulla Inner medulla > glomerulus > proximal convoluted tubule > loop of Henle Loop of Henle, thin descending limb Loop of Henle, thick ascending ^ Ganong's Review of Medical Physiology, 23rd edition limb Structure of Nephron - Tubulus J IB W Proximal convoluted tubule Distal convoluted tubule jdi Collecting duct v. Lo ihic Lo thin c Lacis cells Macula Glomerulus S ]•/// 0' o I Efferent arteriole Juxtaglomerular cells Renal nerves Afferent arteriole > glomerulus > proximal convoluted tubule > loop of Henle Loop of Henle, thin descending limb Loop of Henle, thick ascending ^ Ganong's Review of Medical Physiology, 23rd edition limb Structure of Nephron - Tubulus Cortical nephron > Short nephron loop • Glomerulus further from the cortex-medulla junction • Efferent arteriole supplies peritubular capillaries Juxtamedullary nephron • Long nephron loop • Glomerulus closer to the cortex-medulla junction • Efferent arteriole supplies vasa recta Renat-corpuscle http://classes.midla ndstech.edu/carter p/Courses/bio211/c hap25/chap25.htm Structure of Nephron - Tubulus J IB W Proximal convoluted tubule Distal convoluted tubule Loop of Henle, thin descending limb jdi Collecting duct v. Outer medulla Inner medulla > glomerulus > proximal convoluted tubule > loop of Henle > distal convoluted tubule Ganong's Review of Medical Physiology, 23rd edition Distal convoluted tubule Structure of Nephron - Tubulus J IB W Proximal convoluted tubule Distal convoluted tubule Loop of Henle, thin descending limb jdi Collecting duct v. Outer medulla Inner medulla > glomerulus > proximal convoluted tubule > loop of Henle > distal convoluted tubule > collecting duct Ganong's Review of Medical Physiology, 23rd edition Collecting duct Urine Formation Afferent arteriole Glomerular capillaries Bowman's capsule Efferent arteriole 1. Filtration 2. Reabsorption 3. Secretion 4. Excretion Peritubular capillaries Renal vein v Urinary excretion Excretion = Filtration - Reabsorption + Secretion Guyton &Hall. Textbook of Medical Physiology 1) Glomerular filtration 2) Tubular reabsorption 3) Tubular secretion 4) Urine excretion Urine Formation A. Filtration only B. Filtration, partial reabsorption Substance A Substance Urine Urine Guyton & Hall. Textbook of Medical Physiology creatinine other waste products electrolytes C. Filtration, complete reabsorption D. Filtration, secretion Substance Substance D amino acids glucose Urine PAH toxins organic base and acids Urine Formation A. Filtration only Substance A B. Filtration, partial reabsorption _ Substance C. Filtration, complete reabsorption (ft Substance C D. Filtration, secretion Substance D Urine Urine Guyton &Hall. Textbook of Medical Physiology Urine creatinine other waste products Substance Concentration in Urine (U) Plasma (P) U/P Ratio Glucose [mg/dL) 0 100 0 Na+ tmEq/L) 90 140 0.6 Urea tmg/dL} 900 15 60 Creatinine tmg/dL) 150 1 150 Urine PAH toxins organic base and acids Urine Formation - Glomerular Filtration Proximal tubule Capillary loops Bowman's space Bowman's capsule Podocytes B GFR = 125 ml/min = 180 l/day FF = 0.2 20% of plasma filtered! Afferent arteriole Efferent arteriole Epithelium Basement * membrane Endothelium Fenestrations Guyton & Hall. Textbook of Medical Physiology 800 600 :§ 400 E 200 - 0 Renal blood flow Glomerular filtration 70 140 210 Arterial pressure (mm Hg) Ganong's Review of Medical Physiology, 23rd edition Urine Formation - Glomerular Filtration Glomerular filtration rate (GFR) depends on: 1) Capillary filtration coefficient Kf (permeability and area of glomerular membrane; mesangial cells) 2) Balance of hydrostatic and coloid osmotic forces GFR = Kf • net filtration pressure Urine Formation - Glomerular Filtration Glomerular filtration rate (GFR) depends on: 1) Capillary filtration coefficient Kf (permeability and area of glomerular membrane; mesangial cells) 2) Balance of hydrostatic and coloid osmotic forces GFR = Kf • net filtration pressure Urine Formation - Glomerular Filtration GFR = Kr net filtration pressure 800 600 ^ 400 200 Renal blood flow Glomerular filtration 70 1 40 210 Arterial pressure (mm Hg) Afferent arteriole Ganong's Review of Medical Physiology, 23rd edition Glomerular Glomerular hydrostatic colloidosmotic pressure pressure \ (60 mmHg) (32 mm Hg) Bowman's capsule pressure (18 mm Hg) Efferent arteriole nB = 0 Guyton & Hall. Textbook of Medical Physiology Under physiological conditions: net filtration pressure = PG + ttb - PB - ttg = 60 + 0 - 18 - 32 = 10 mmHg GFR = Kf (PG + n"ß — Pß — TTG) Urine Formation - Glomerular Filtration Vas afferens, vas efferens • input and output of high-pressure glomerular capillary net glomerular blood flow = P - P 1 v.a. 1 v.e. RV.a. + Rv.e. + • t resistance of vas aff. or vas eff. -> [ renal blood flow (if the arterial pressure is stable) • control the glomerular filtration pressure: constriction of vas aff. -> I glomerular pressure -> I filtration constriction of vas eff. ->• t glomerular pressure ->• t filtration Urine Formation - Tubular Processes Peritubular capillary Tubular cells FILTRATION Lumen Paracellular path Transcellular path Solutes REABSORPTION EXCRETION Guyton & Hail. Textbook of Medical Physiology Urine Formation - Tubular Processes Active Transport Mechanisms 1) Primary active transport 2) Secondary active transport 3) Pinocytosis (big molecules, e.g. proteins, namely in the proximal tubule) Urine Formation - Tubular Processes Active Transport Mechanisms 1) Primary active transport Peritubular capillary Interstitia fluid Tubular epithelial cells Tubular lumen Basement membrane channels Intercellular space Na- i- ^ (-3 mv) ^-Tight junction Brush border (luminal membrane) Guyton & Hall. Textbook of Medical Physiology Urine Formation - Tubular Processes Active Transport Mechanisms 1) Primary active transport - Na+/K+ ATPase - H+ATPase - Ca2+ATPase Urine Formation - Tubular Processes 2) Active Transport Mechanisms Secondary active transport Interstitial fluid Tubular cells Co-transport ----- Glucose (ATP) -70 mV ■----Amino acids TT01" < ^ < Na+ < j K Na+ O ^ Am Tubular lumen Glucose symport ino acids k+ (atp}^ -70mv ^ ( ) antiport Counter-transport Guyton & Hall. Textbook of Medical Physiology Urine Formation - Tubular Processes Active Transport Mechanisms Substances using active transport show the so called transport maximum (given by saturation of the transporter). for example glucose transport maximum: -320 mg/min t ~c Q -Q t_ O w ID CD W O _^ Splay ----"Ideal" - Actual Plasma glucose (PG) 900 n - ?> 300-o 100 200 300 400 500 600 700 800 Plasma glucose concentration (mg/100 ml) Guyton & Hall. Textbook of Medical Physiology I \ K$i Urine Formation - Tubular Processes Active Transport Mechanisms Substances using active transport show the so called transport maximum (given by saturation of the transporter). reabsorption substance Transport Maximum Glucose 375 mg/min Phosphate 0.10 mM/min Sulfate 0.06 mM/min Amino acids 1.5 mM/min Urate 15 mg/min Lactate 75 mg/min Plasma protein 30 mg/min secretion Substance Creatinine Para-ami nohippuric acid Transport Maximum 16 mg/min SO mg/min Guyton & Hall. Textbook of Medical Physiology Urine Formation - Tubular Processes Active Transport Mechanisms Substances using active transport without the transport maximum (the gradient-time transport). - reabsorption of Na+ in the proximal tubule The higher concentration of Na+ in the proximal tubule, the higher velocity of its reabsorption. The slower flow of fluid in the proximal tubule, the more , Na+ is reabsorpbed. In the distal parts of tubule, Na+ reabsorption shows the transport maximum (non-leaky tight junctions, smaller transport) - may be increased, e.g. by aldosteron. Urine Formation - Tubular Processes 1) 2) 3) 1) Peritubular capillary Active Transport Mechc Primary active transport Secondary active transport Pinocytosis (big molecules, e.g. proteins, namely in the pi ■ i i i i i i i i i Tubular i epithelial cells ] Tubular lumen -Na+ (-70 mV) -Basal channels 3 mv) _^-Tight junction Brush border (luminal membrane) Interstitial Basement fluid membrane Intercellular space Passive Transport Mechanisms Reabsorption of H20 by osmosis ■ in the proximal tubule (highly permeable for H20) ■ active reabsorption of solutes -> lumen-intersticium concentration gradient -> H20 osmosis into intersticium 2) Reabsorption of solutes by diffusion ■ CI" (Na+ into intersticium, reabsorption of H20 by osmosis) ■ urea (reabsorption of H20 by osmosis) I Urine Formation - Tubular Processes Peritubular capillary Tubular umen Interstitial fluid i-3 mvj Tight junction Brush border (luminal membrane) Basement membrane Intercellular space Lumen negative potential Na~ reabsorption H20 reabsorption Luminal Cl~ concentration Luminal urea concentration \ Passive Cl~ reabsorption Passive urea reabsorption Guyton & Hall. Textbook of Medical Physiology Urine Formation - Tubular Processes Peritubular capillary Tubular cells FILTRATION Lumen Paracellular path Transcellular path Solutes REABSORPTION EXCRETION Guyton & Hail. Textbook of Medical Physiology Urine Formation - Tubular Processes Physical Forces in Peritubular Capillaries and in Renal Intersticium - tubular reabsorption is controlled by hydrostatic and coloid osmotic forces (similary to GFR) GFR = Kf • net filtration pressure net reabsorptive force TRR = K Urine Formation - Tubular Processes Physical Forces in Peritubular Capillaries and in Renal Intersticium Peritubular Interstitial Tubular Tubular capillary fluid cells lumen Urine Formation - Tubular Processes Tubuloglomerular feedback Glomerulotubular balance Glomerulotubular balance Renal arteriolar pressure Glomerular capillary pressure GFR Solute reabsorption in proximal tubule Solute reabsorption in thick ascending limb Salt and fluid delivery to the distal tubule Tubuloglomerular feedback Ganong's Review of Medical Physiology, 23rd editiaď Urine Formation - Tubular Processes Proximal Tubule 1) complete reabsorption of substances playing key roles for the organism (glucose, amino acids) 2) partial reabsorption of substances important for the organism (ions - Na+, K+, CI", etc.) 65% 3) reabsorption of water 4) secretion of H+ 5) reabsorption of HC03 Result: isoosmotic fluid, notably decreased volume Urine Formation - Tubular Processes Loop of Henle 1) thin descending part - passive reabsorption of water (osmosis) 2) thick ascending part - active reabsorption of ions (Na+/K+/2CI" symport), secretion of H+, reabsorption of HC03 Urine Formation - Tubular Processes Loop of Henle 1) thin descending part - passive reabsorption of water (osmosis) 2) thick ascending part - active reabsorption of ions (Na+/K+/2CI" symport), secretion of H+, reabsorption of HC03" * Ethacrynic acid • Bumetanide Urine Formation - Tubular Processes Distal tubule 1) juxtaglomerular apparatus 2) active reabsorption of solutes similar to the thick ascending loop of Henle, also no permeability for urea and water -the so called dilution segment (dilutes the tubular fluid) Urine Formation - Tubular Processes Collecting duct (+ end of distal tubule) 1) principal cells - reabsorption of Na+ and water (ADH), secretion of K+ Late distal tubule and collecting tubule Intercalated cells Renal interstitial fluid Tubular cells Tubular lumen (-50 mV) Aldosterone antagonists • Spironolactone • Eplerenone Na' channel blockers • Amiloride • Triamterene Urine Formation - Tubular Processes Collecting duct (+ end of distal tubule) 1) principal cells - reabsorption of Na+ and water (ADH), secretion of K+ 2) intercalated cells - secretion of H+, reabsorption of HC03 and K+ Late distal tubule and collecting tubule Principal cells Intercalated cells Renal interstitial fluid Tubular cells CI"--- XL" ci- HC03- + H+ 4 HjC03 Carbonic anhydrase CO, H20 + Tubular lumen ci- Urine Formation - Tubular Processes Collecting duct - medullar part 1) reabsorption of Na+ and CI", water (ADH), urea 2) secretion of H+, reabsorption of HC03" Medullary Urine Formation - Tubular Processes 0.02H Proximal tubule Loop of Henle Distal tubule Collecting i tubule pronounced secretion in comparison with H20 pronounced reabsorption in comparison with H20 Guyton &Hall. Textbook of Medical Physiology Renal Clearance = the volume of plasma that is cleared of the substance by kidneys per unit time Using clearance, we can quantified the excretion ability of kidneys, the velocity of renal blood flow and even basic functions of kidneys (GFR, tubular reabsorption and secretion). V-Us v-us [ml/min] Renal Clearance Determination of renal plasma flow velocity (RPF) Clearance of a substance that is fully cleared from plasma in glomerulotubular apparatus. PAH (paraaminohippuric acid) cleared by 90% PPAH = 0.01 mg/ml (< Renal plasma flow RPF = 5.85 x 1 mg/min 0.01 mg/ml = 585 ml/min Renal venous PAH = 0.001 mg/ml UPAH = 5.85 mg/ml V = 1 ml/min Guyton &HaU. Textbook of Medical Physiology Correction to the extraction ratio of PAH (EPAH): PAH PpAH " VpAH PAH = 0.9 585 ml/min * RPF =-= 650 ml/min 0.9 Renal Clearance - 1 mg/ml Determination of glomerular filtration rate (GFR) Clearance of a substance that is fully filtered in the glomerulus and is not reabsorbed/secreted in tubules. Inulin Creatinine Amount filtered = Amount excreted GFR X Pinuijp = UirU|in X V GFR = Uinulin x V inulin GFR = 125 ml/min Uinulin= 125 m9/ml V = 1 ml/min Guyton &Hall. Textbook of Medical Physiology Renal Clearance Calculation of Filtration Fraction (FF) FF is the fraction of plasma filtered through the glomerular membrane. PP _ GFR = 125 ml/min = _^ -20% of plasma is filtered RPF 650 ml/min in the glomerulus Calculation of Tubular Reabsorption/Secretion A. GFR • Ps > V • Us substance reabsorbed B. GFR • Po < V • Uo substance secreted