Urine formation Artery Afferent 一Glomerular -Efferent arteriole capillary arteriole 1.Glomerular filtration 2.Tubular secretion owman's」 3.Tubular reabsorption Peritubular Tubule capillary 0 -Vein Urinary excretion Excretion Filtration Reabsorption Secretion
Urine formation Excretion = Filtration – Reabsorption + Secretion
Clearance concept Clearance is an assessment of renal function
Clearance concept • Clearance is an assessment of renal function
Clearance of a substance: Kidney cvs Exterior Def:the volume of plasma from which the subs is removed (cleared)by the kidney per unit time
Clearance of a substance: Kidney CVS Exterior Def: the volume of plasma from which the subs is removed (cleared) by the kidney per unit time
Amount of a substance (x)excreted =VXUx Ux Urine concentration of x V Urine flow
Amount of a substance (x) excreted = V X Ux Ux = Urine concentration of x V = Urine flow
Excreted Filtered Secreted Reabsorbed Secreted Excreted (Filtered Reabsorbed
Excreted = Filtered + Secreted - Reabsorbed
Amount of subs x transferred from CVS to the outside via the kidney Plasma concentration of x(Px)X Plasma volume that contains subs x Cx Plasma volume that contains x
Amount of subs x transferred from CVS to the outside via the kidney Plasma concentration of x (Px) X Plasma volume that contains subs x Cx = Plasma volume that contains x
Excreted Transferred from CVS to outside via the kidney Cx X Px=Ux X V Cx Clearance of X Px Plasma concentration of X Ux Urine concentration of X V Urine flow Ux X V=Mass of X excreted per unit time
Cx X Px = Ux X V Cx = Clearance of X Px = Plasma concentration of X Ux = Urine concentration of X V = Urine flow Ux X V = Mass of X excreted per unit tim e Excreted = Transferred from CVS to outside via the kidney
Ux X V CX= Px
Ux X V Cx = --------------- Px
Glomerular filtration rate (GFR) Concentration of inulin in plasma =4 mg/L Glomerular capillary Volume of fluid Bowman's filtered(GFR) =7.5LU/h space
Glomerular filtration rate (GFR)
Measurement of GFR Use of a substance,which is 1.freely filtered, 2.non-toxic, 3.not reabsorbed by nor secreted from renal tubules Inulin (MW=5500) UIn X V CIn=-=120 ml/min Pin
Measurement of GFR Use of a substance, which is 1. freely filtered, 2. non-toxic, 3. not reabsorbed by nor secreted from renal tubules Inulin (MW= 5500) UIn X V CIn = --------------- = 120 ml/min PIn