Location of KidneysKidney StructureFunctions of the KidneysRenal Blood VesselsSlide 5Structure of a NephronGlomerular CapsuleNephron and Associated Blood VesselsJuxtaglomerular ApparatusCortical and Juxtamedullary NephronsBlood Supply of NephronPathway of Blood Flow Through Kidney and NephronUrine FormationSlide 14Glomerular FiltrationGlomerular Filtrate and Urine CompositionFiltration Pressure and RateSlide 18Amounts of Glomerular Filtrate and UrineControl of Filtration RateSodium and Water ReabsorptionSodium and Water Filtration, Reabsorption, and ExcretionTubular SecretionRegulation of Urine Concentration and VolumeThe Countercurrent MultiplierRole of ADH in Regulating Urine Concentration and VolumeFunctions of Nephron ComponentsUrea and Uric Acid ExcretionUrine CompositionRenal ClearanceElimination of UrineUretersUrinary BladderSlide 34Cross Section of UrethraUrethraMicturition1Location of KidneysThe kidneys which are positioned retroperitoneally lie on either side of the vertebral column, high on the posterior wall of the abdominal cavity2Kidney Structure3Functions of the Kidneys• removal of metabolic wastes from the blood and excretion to the outside of the body• regulation of red blood cell production, blood pressure, calcium ion absorption, and the volume, composition, and pH of the blood .•Can you list the other functions we mentioned yesterday?4Renal Blood Vessels5Renal Blood Vessels6Structure of a Nephron7Glomerular Capsule8Nephron and Associated Blood Vessels9Juxtaglomerular Apparatus10Cortical and Juxtamedullary Nephrons• cortical nephrons• 80% of nephrons• located close to the surface of the kidney• juxtamedullary nephrons• regulate water balance• located near the renal medulla11Blood Supply of Nephron• The glomerular capillary receives blood from the afferent arteriole and passes it to the efferent arteriole• The efferent arteriole gives rise to the peritubular system, which surrounds the tubule• Capillary loops called vasa recta dip down into the medulla12Pathway of Blood Flow Through Kidney and Nephron13Urine Formation• nephrons remove wastes from the blood and regulate water and electrolyte concentrations• urine is the final product of the processes of:• glomerular filtration• tubular reabsorption• tubular secretion14Urine Formation• Glomerular Filtration• substances move from blood to glomerular capsule• Tubular Reabsorption• substances move from renal tubules into blood of peritubular capillaries• glucose, water, urea, proteins, creatine• amino, lactic, citric, and uric acids• phosphate, sulfate, calcium, potassium, and sodium ions• Tubular Secretion• substances move from blood of peritubular capillaries into renal tubules• drugs and ions15Glomerular Filtration• The first step in urine formation is filtration of substances out of the glomerular capillaries into the glomerular capsule• Glomerular filtrate passes through the fenestrae of the capillary endothelium16Glomerular Filtrate and Urine Composition17Filtration Pressure and RateNet Filtration Pressure = force favoring filtration – forces opposing filtration (glomerular capillary ( capsular hydrostatic pressure hydrostatic pressure) and glomerular capillary osmotic pressure )Glomerular Filtration Rate• directly proportional to the net filtration pressure18Filtration Pressure and Rate• normally the glomerular net filtration pressure is positive causing filtration• the forces responsible include hydrostatic pressure and osmotic pressure of plasma and the hydrostatic pressure of the fluid in the glomerular capsule19Amounts of Glomerular Filtrate and Urineaverage amounts over a 24 hour period20Control of Filtration Rate• Primarily three mechanisms are responsible for keeping the GFR constant• Increased sympathetic impulses decrease GFR by causing afferent arterioles to constrict• Renin-angiotensin system• AutoregulationRenin-Angiotensin system21Sodium and Water Reabsorption• osmosis reabsorbs water in response to active transport reabsorbing sodium and other solutes in the proximal portion of the renal tubule22Sodium and Water Filtration, Reabsorption, and Excretion23Tubular Secretion• transports substances from the blood within the peritubular capillary into the renal tubule24Regulation of Urine Concentration and Volume• the distal convoluted tubule and collecting duct are impermeable to water, so water may be excreted as dilute urine• if ADH is present, these segments become permeable, and water is reabsorbed by osmosis into the hypertonic medullary interstitial fluid25The Countercurrent Multiplier• helps maintain the NaCl concentration gradient in the medullary interstitial fluid26Role of ADH in Regulating Urine Concentration and Volume27Functions of Nephron Components28Urea and Uric Acid ExcretionUrea• by-product of amino acid catabolism• plasma concentration reflects the amount or protein in diet• enters renal tubules through glomerular filtration• contributes to the reabsorption of water from the collecting ductUric Acid• product of nucleic acid metabolism• enters renal tubules through glomerular filtration• most reabsorption occurs by active transport• ~10% secreted and excreted29Urine Composition• about 95% water• usually contains urea, uric acid, and creatinine• may contain trace amounts of amino acids and varying amounts of electrolytes• volume varies with fluid intake and environmental factors30Renal Clearance• the rate at which a chemical is removed from the plasma• tests of renal clearance• inulin clearance test• creatinine clearance test• para-aminohippuric acid (PAH) test• tests of renal clearance used to calculate glomerular filtration rate31Elimination of Urine• nephrons• collecting ducts• renal papillae• minor and major calyces• renal pelvis• ureters• urinary bladder• urethra• outside32Ureters• 25 cm long• extend downward posterior to the parietal peritoneum• parallel to vertebral column• in pelvic cavity, join urinary bladder• wall of ureter • mucous coat• muscular coat• fibrous coat33Urinary Bladder• hollow, distensible, muscular organ located within the pelvic cavity, posterior to the symphysis pubis and inferior to the parietal peritoneum34Urinary Bladder• the internal floor of the bladder includes a triangular area called the trigone which has an opening at each of three angles35Cross Section of