Kidney Day : IntroductionSlide 2Formation of UrineSlide 4Slide 5Summary of Tubular Reabsorption and SecretionKidney Function: Regulation of Body Fluids, their volume and osmolarity; How is this accomplished? THE COUNTERCURRENT MECHANISMThe Countercurrent MechanismSite of FiltrationLocation of the GlomerulusGlomerular Filtration MechanismWhat are PODOCYTES?The Juxtaglomerular (JG) ApparatusThe Juxtaglomerular ApparatusThe Juxtaglomerular Apparatus (JG)Juxtaglomerular ApparatusRenin-Angiotensin-AldosteroneSlide 18Slide 19Slide 20Effects of Angiotensin IIMaintaining Water BalanceSlide 23Regulation of Water and Electrolyte ReabsorptionMaintaining Water and Electrolyte BalanceSlide 26Maintaining Acid-Base Balance in BloodSlide 28Blood BuffersKidney Day : Kidney Day : Introduction Introduction The Kidney’s FunctionsFunctions of Kidneys:1. Produce Urine (as a function of ridding body of Nitrogenous waste and other wastes. 2. Regulate water balance3. Regulate acid-base of body fluids4. Calcium Homeostatis ( Calcitriol)5. In times of starvation ( Gluconeogenesis)6. Secretes Erythropoieten 7. Secretes Renin ( Controls Blood pressure)8. Detoxify free radicals with use of peroxisomes.Formation of UrineFormation of UrineFigure 15.5Summary of Tubular Summary of Tubular Reabsorption and SecretionReabsorption and SecretionKidney Function: Regulation of Kidney Function: Regulation of Body Fluids, their volume and Body Fluids, their volume and osmolarity; How is this osmolarity; How is this accomplished? accomplished? THE COUNTERCURRENT MECHANISMTHE COUNTERCURRENT MECHANISMThe Countercurrent The Countercurrent MechanismMechanismUnit 1 - Objective 7????Site of FiltrationSite of FiltrationGlomerulus◦the Glomerulus is the site of filtration◦the filtration mechanism is sieve-like and consists of fenestrated glomerular capillaries, podocytes and a basement membrane that allows free passage of water and solutes smaller than plasma proteinsUnit 1 - Objective 4Location of the GlomerulusLocation of the GlomerulusAfferent ArterioleEfferent ArterioleBowman’s CapsuleProximal Convoluted TubuleGlomerulusGlomerular Filtration Glomerular Filtration MechanismMechanismBowman’s CapsuleGlomerulusFenestrated CapillaryPodocyte with Basement MembraneWhat are PODOCYTES?What are PODOCYTES?Podocytes- (or visceral epithelial cells) are cells of the visceral epithelium in the kidneys and form a crucial component of the glomerular filtration barrier contributing size selectivity and maintaining a massive filtration surface. Look for these in the kidney section slide ; focus on glomerulus.The Juxtaglomerular (JG) The Juxtaglomerular (JG) ApparatusApparatusUsed in maintaining blood pressure continued:◦the macula densa cells monitor the salt content of the blood◦if the blood salt content gets too high, the macula densa cells begin to inhibit the granular cells and suppress renin releaseUnit 1 - Objective 6The Juxtaglomerular ApparatusThe Juxtaglomerular ApparatusDescription◦the juxtaglomerular apparatus consists of specialized macula densa cells that develop in the distal convoluted tubule (DCT) and specialized granular juxtaglomerular (JG) cells that develop mainly in the afferent arteriole. See following diagram.Unit 1 - Objective 6The Juxtaglomerular The Juxtaglomerular Apparatus (JG)Apparatus (JG)Afferent ArterioleEfferent ArterioleDCTMacula Densa CellsGranular Juxtaglomerular (JG) CellsPCTBowman’s CapsuleJuxtaglomerular ApparatusJuxtaglomerular Apparatus- vasomotion- monitor salinityRenin-Angiotensin-AldosteroneRenin-Angiotensin-AldosteroneThe Juxtaglomerular ApparatusThe Juxtaglomerular ApparatusUsed in maintaining blood pressure continued:◦Angiotensin II also stimulates the release of aldosterone hormone from the adrenal cortex◦aldosterone stimulates the DCT to reabsorb salt (NaCl). Continued on next slide.Unit 1 - Objective 6The Juxtaglomerular ApparatusThe Juxtaglomerular ApparatusUsed in maintaining blood pressure continued:◦salt reabsorption attracts water to the blood by osmosis and raises blood volume, as well as, contributing to the increase in blood pressure. Continued on next slide.Unit 1 - Objective 6The Juxtaglomerular ApparatusThe Juxtaglomerular ApparatusUsed in maintaining blood pressure continued:◦suppression of renin acts as a negative feedback mechanism to prevent further increases in angiotensin II, Aldosterone and blood pressure Unit 1 - Objective 6Effects of Angiotensin II Effects of Angiotensin IIMaintaining Water BalanceMaintaining Water BalanceWater intake must equal water outputSources for water intake◦Ingested foods and fluids◦Water produced from metabolic processesSources for water output◦Vaporization out of the lungs◦Lost in perspiration◦Leaves the body in the feces◦Urine productionMaintaining Water BalanceMaintaining Water BalanceDilute urine is produced if water intake is excessiveLess urine (concentrated) is produced if large amounts of water are lostProper concentrations of various electrolytes must be presentRegulation of Water and Regulation of Water and Electrolyte ReabsorptionElectrolyte ReabsorptionRegulation is primarily by hormones◦Antidiuretic hormone (ADH) prevents excessive water loss in urine◦Aldosterone regulates sodium ion content of extracellular fluidTriggered by the rennin-angiotensin mechanismCells in the kidneys and hypothalamus are active monitorsMaintaining Water and Electrolyte Maintaining Water and Electrolyte BalanceBalanceFigure 15.10Maintaining Acid-Base Balance in Maintaining Acid-Base Balance in BloodBloodBlood pH must remain between 7.35 and 7.45 to maintain homeostasis◦Alkalosis – pH above 7.45◦Acidosis – pH below 7.35Most ions originate as byproducts of cellular metabolismMaintaining Acid-Base Balance in Maintaining Acid-Base Balance in BloodBloodMost acid-base balance is maintained by the kidneysOther acid-base controlling systems◦Blood buffers◦RespirationBlood BuffersBlood BuffersMolecules react to prevent dramatic changes in hydrogen ion (H+) concentrations◦Bind to H+ when pH drops◦Release H+ when pH risesThree major chemical buffer systems◦Bicarbonate buffer system◦Phosphate buffer system◦Protein buffer