ii Kidneys paired organs located in the posterior abdomen either side of the vertebral I Chapter 26 Renal Function a Anatomy i Blood Supply 1 Abdominal Aorta 2 Divides into 2 Renal Arteries 1 in each kidney 3 Nephron afferent arteriole 4 Glomeruli a The glomerulus is the point of blood filtration 5 Efferent Arteriole 6 Peritubular capillaries 7 Peritubular venules 8 Renal Vein 9 Inferior Vena Cava column iii Right Kidney is slightly lower than the left kidney iv Functional unit is the nephron 1 Each nephron has 1 collection duct v Renal Perenchyma has 3 Anatomic Sections 1 Pelvis urinary collecting structures and calyces 2 Medulla the middle portion renal pyramids 3 Cortex outer portion glomeruli and nephron tulubles vi Urine Pathway 1 Bowman s Capsule a 1st part of urine formation 2 Proximal 3 Loop of Henle a Descending concentrating area b Ascending diluting losing NaCl i ADH in aquaporins 4 Distal Convoluted Tubule 5 Collecting Duct 6 Fuse together to form the Renal Calyx 7 Renal Pelvis 8 Ureter 9 Bladder 10 Urethra vii Dirty Blood comes through the afferent arteriole then the glomerulus then Bowman s capsule into filtrate b Main Functions i Urine Formation 1 Normal Urine output 1500 mL day which is about 1 of the overall filtrate 2 Mechanism of toxic waste product removal 3 1000 1500 ml of blood min passes through kidney 1 1 5 L 4 Glomerular Filtration Rate GFR a High hydrostatic pressure in glomerular capillaries filter substances in Bowman s capsule at 130mL min b Glomerular filtrate premature urine is plasma without proteins i Cells large plasma proteins cannot be filtered ii 187000 ml of filtrate produced per day Important clinical assessment of renal function c ii Fluid and electrolyte balance regulation 1 Kidneys filter blood and produce urine 2 Ureter duct from kidney to urinary bladder a Branches and envelops renal pyramids which form medulla The outer layer of medulla is cortex 3 Urethra tube for urine excretion 4 The ureter renal artery and renal vein enter the kidney from its concave side 5 Nephrons a Glomeruli in cortex b Proximal convoluted tubules i Initial twisted renal tubule segments in cortex c Renal tubule descends into medulla to form the Loop of Henle i Urine concentration unit d Tubule then returns to the cortex as the Ascending Loop of Henle and becomes the Distal Convoluted Tubule e Distal Tubules join collecting duct in cortex f Collecting ducts descend through renal pyramids and empty into the renal pelvis 6 Glomerulus a Site of blood filtration b Blood enters via afferent arteriole and leaves efferent arterioles i Think e in efferent for exit c Efferent arterioles become peritubular capillaries surrounding tubule and serving as exchange sites d Renal tubule starts with Bowman s capsule which encloses the glomerulus e Glomerulus produces fluid without cells or large molecules Filtered f High filtration rate due to high pressure and high permeability g The pores of the glomerulus give it its permeability h Pressure due to diameter 7 Pelvic divisions join and leave the kidney as a ureter 8 Renal blood vessel organization parallels nephron organization 9 Glomeruli drained by arterioles become peritubular capillaries 10 Vasa Recta Network of peritubular capillaries parallel to Loops of Henle and 11 All Peritubular capillaries from the nephron join into venules that form the renal the collecting duct vein 12 Proximal Convoluted Tubule a Water and solute reabsorption site b Cells have microvilli to increase surface area c Actively transport Na glucose and amino acids water follows solute 13 Urine concentration is due to countercurrent multiplier mechanism in loops of a Tubule fluid flows in opposite directions in ascending and descending transport Henle limbs 14 Loops increase interstitial fluid osmolarity in a graduated way 15 Loop of Henle Segments a Thin descending limb loses water to adjacent interstitial fluid with high b Thick Ascending limb Actively transports Na Cl follows and raises c Thin ascending limb receives concentrated fluid and allows Na and Cl Na and Cl concentration interstitial fluid concentration diffusion into interstitial fluid 16 Fluid reaching the distal collecting duct is less concentrated a Solutes in medulla create a concentration gradient 17 Concentration gradient is preserved by Vasa Recta 18 Blood Flowing down descending limb loses water and gains solutes Concentrated blood then flows up ascending limb gains water and loses solutes so water is returned to blood 19 Regions of the nephron differ in water permeability 20 Aquaporins membrane proteins abundant in highly water permeable areas such as proximal convoluted tubule and descending loops of Henle 21 Water reabsorption starts in the distal convoluted tubule 22 Fluid that leaves the tubule and flows into collecting duct has the same solute concentration as blood plasma but with a different composition 23 In the collecting duct urea is a major solute in tubular fluid 24 Fluid flows down collecting duct and loses water to interstitial fluid due to the concentration gradient established in the Loops of Henle 25 Some Urea also diffuses and adds to osmotic force Urea recycling contributes to urine concentration 26 Takes out sodium Chloride to maintain sodium gradient blood pressure 27 H2O moves out and solutes become more concentrated iii Acid Base Balance Regulation 1 Bicarb ions a Major buffers in blood b Formed by carbon dioxide hydration followed by carbonic acid dissociation C O2 H 2O H 2C O3 H HC O3 2 Lungs control CO2 levels in blood a Acid portion of reaction because more CO2 means more H ions 3 Kidneys control base portion of reaction by removing H ions and adding bicarbonate iv Nitrogenous Waste Excretion 1 Kidneys eliminate nitrogenous products produced by protein catabolism 2 Nitrogenous products ammonia urea and uric acid 3 Ammonia from amino acid deamination a Toxic converts to non toxic urea in the liver b If it reaches the brain it can cause coma death which is why the liver converts it 4 Urea Assessed as BUN a Normally urea production exceeds renal urea secretion b Urea is filtered at the glomerulus but 40 50 is reabsorbed by proximal tubules c Can indicate renal function but it is not as specific as GFR 5 Uric Acid from purine base metabolism DNA a Plasma levels are higher in males b Filtered by glomerulus c Undergo tubular reabsorption and secretion Increased in advanced chronic renal failure d Increased uric acid is associated with Gout e 6 Creatinine serum