Kidney Physiology Nikkina Hankins nikkina hankinsbison howard edu

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Kidney Physiology Nikkina Hankins nikkina. hankins@bison. howard. edu

Kidney Physiology Nikkina Hankins nikkina. [email protected] howard. edu

 • 1200 m. L of blood pass through each glomeruli each minute •

• 1200 m. L of blood pass through each glomeruli each minute • Kidneys consume 20 -25% of all oxygen used by the body • Filtrate contains everything found in blood plasma except proteins • Urine contains unneeded substances • Kidneys process 180 L • How much do we urinate in one day?

Urine Formation • Glomerular filtration • Tubular reabsorption • Tubular secretion • Regulation of

Urine Formation • Glomerular filtration • Tubular reabsorption • Tubular secretion • Regulation of Urine 4

Glomerular Filtration • Renal corpuscle • Produces cell free and protein free filtrate •

Glomerular Filtration • Renal corpuscle • Produces cell free and protein free filtrate • Passive process

Filtration Membrane • Allows free passage of water and solutes smaller than plasma •

Filtration Membrane • Allows free passage of water and solutes smaller than plasma • Fenestrated endothelium of glomerular capillaries • Basement membrane • Foot processes of podocytes of the glomerular capsule

Pressures that Affect Filtration • • • Outward pressures • Hydrostatic pressure in glomerular

Pressures that Affect Filtration • • • Outward pressures • Hydrostatic pressure in glomerular capillaries - HPgc • Colloid osmotic pressure in the capsular space Inward pressures • Hydrostatic pressure in the capsular space - HPcs • Colloid osmotic pressure in the glomerular capillaries - OPgc Net filtration pressure - NFP

Glomerular Filtration Rate • Volume of filtrate formed each minute HPgc = 55 mm

Glomerular Filtration Rate • Volume of filtrate formed each minute HPgc = 55 mm Hg OPgc = 30 mm Hg • Net filtration pressure • Total surface area available for filtration • Filtration membrane permeability HPcs = 15 mm Hg NFP = Net filtration pressure = outward pressures – inward pressures = (HPgc) – (HPcs + OPgc) = (55) – (15 + 30) = 10 mm Hg

Regulation of GFR • Intrinsic control - renal autoregulation • Myogenic mechanism • Tubuloglomerular

Regulation of GFR • Intrinsic control - renal autoregulation • Myogenic mechanism • Tubuloglomerular feedback mechanism

Regulation of GFR • Extrinsic control - neural and hormonal mechanism • Sympathetic nervous

Regulation of GFR • Extrinsic control - neural and hormonal mechanism • Sympathetic nervous system mechamism • RAA mechanism

Tubular Reabsorption • Reclaims most tubule contents and returns it to the blood •

Tubular Reabsorption • Reclaims most tubule contents and returns it to the blood • Selective transepithelial process • Active tubular reabsorption • Passive tubular reabsorption

Transcellular Route of Reabsorption • Sodium • Glucose • Amino Acids • Vitamins •

Transcellular Route of Reabsorption • Sodium • Glucose • Amino Acids • Vitamins • Water

Reabsorptive Capabilities of Different Areas of the Kidney • Proximal convoluted tubule - PCT

Reabsorptive Capabilities of Different Areas of the Kidney • Proximal convoluted tubule - PCT • Nephron loop • Descending limb • Ascending limb • Distal convoluted tubule - DCT • Collecting duct

Tubular Secretion • Moves selected substances from peritubular capillaries through tubule cells into the

Tubular Secretion • Moves selected substances from peritubular capillaries through tubule cells into the filtrate • PCT is main site of secretion • Disposing substances that are tightly bound to plasma proteins • Eliminate substances and end products that have been reabsorbed by passive processes • Ridding body of excess K • Controlling blood p. H

Clinical Evaluation of Kidney Function • Renal Clearance • Urine

Clinical Evaluation of Kidney Function • Renal Clearance • Urine

Countercurrent Mechanisms • Fluid flows in the opposite directions through adjacent segments of the

Countercurrent Mechanisms • Fluid flows in the opposite directions through adjacent segments of the same tube connected by a hairpin turn. • Multiplier • Exchanger • Medullary osmotic gradient allows kidneys to vary urine concentration

Renal Clearance • Volume of plasma from which kidneys clear a particular substance in

Renal Clearance • Volume of plasma from which kidneys clear a particular substance in a minute • C = renal clearance rate m. L/min • U = concentration of substance in urine mg/m. L • V = flow rate of urine formation m. L/min • P = concentration of substance in plasma mg/m. L

Creatinine Clearance • Clears the kidneys with a C of 140 m. L/min •

Creatinine Clearance • Clears the kidneys with a C of 140 m. L/min • Freely filtered and barely secreted • Used to measure the renal clearance and activity

Cockcroft Gault Equation • Obtain SCr from blood analysis • SCr is inverse to

Cockcroft Gault Equation • Obtain SCr from blood analysis • SCr is inverse to GFR • Need age, weight (kg) and SCr • m. L/min

Urine • Color and transparency • Odor • p. H • Specific gravity •

Urine • Color and transparency • Odor • p. H • Specific gravity • Micturition

Diuretics

Diuretics

Renal Disorders • Acute kidney injury • Chronic kidney disease

Renal Disorders • Acute kidney injury • Chronic kidney disease

Acute Renal Injury • Rapid decrease in GFR over a period of minutes to

Acute Renal Injury • Rapid decrease in GFR over a period of minutes to days • Accumulation of waste products and inability to regulate fluids, electrolytes, and acid base balance • Prerenal • Intrinsic • Postrenal

Look Ups • RIFLE • AKIN • KDIGO

Look Ups • RIFLE • AKIN • KDIGO

Chronic Kidney Disease • Progressive deterioration in renal function as shown by an increase

Chronic Kidney Disease • Progressive deterioration in renal function as shown by an increase in BUN and SCr and decline in Cl. Cr and development of uremic symptoms for at least 3 months • Diabetes is the number one cause of CKD • Hypertension is the number two cause of CKD

Look Ups • Stages of CKD • Equation used for pediatrics Cr. Cl •

Look Ups • Stages of CKD • Equation used for pediatrics Cr. Cl • NKFF/DOQI