BSC 2086 1st Edition Final Exam Study Guide 1 What are the components of the nephron What are the different regions of the renal tubule Where does filtration occur Where does reabsorption occur what gets reabsorbed Where does secretion occur what gets secreted a The nephron is made up of i Renal corpuscle 1 Spherical structure made of a Bowman s capsule glomerular capsule b Cup shaped chamber c Glomerulus capillary network ii Renal tubule 1 Long tubular passageway that begins at the renal corpuscle 2 Located in cortex 3 Made up of a Proximal convoluted tubule PCT b Nephron loop loop of Henle c Distal convoluted tubule DCT b Filtration i Blood pressure pushes water and small solutes across the membrane into capsular space 1 Larger solutes not found in filtrate because they aren t filtered out of the plasma a Includes plasma proteins 2 No energy required passive process 3 Solutes that enter capsular space include a Glucose b Fatty acids c Amino acids d Vitamins e Metabolic wastes f Excess ions c Reabsorption i Useful materials are captured before the filtrate leaves the kidneys ii Takes place in proximal convoluted tube loop of Henle and distal convoluted tube d Secretion i Material that was undesirable and not filtered out is transported from the peritubular fluid into the tubular fluid 1 Peritubular fluid originates from the peritubular capillaries 2 Secretion happens in proximal convoluted tubule distal convoluted tubule and collecting duct 2 What processes occur at the proximal convoluted tubule loop of Henle distal convoluted tubule and collecting duct What type of cells do you find lining the proximal convoluted tubule What is this important Which regions of the renal tubule and collecting duct are affected by ADH a Proximal convoluted tubule PCT i Epithelial lining is simple cuboidal has microvilli on apical surfaces ii Functions in reabsorption of 1 Organic nutrients a 99 of glucose amino acids etc b Not all glucose is reabsorbed if glucose in blood is more than 180 mg dL i Glycosuria glucose in urine c After a protein rich meal amino acid common in urine Aminoaciduria 2 Ions Na K HCO3 3 H2O a By osmosis follows when solutes are reabsorbed 4 These reabsorbed substances enter the peritubular fluid IF around renal tubule and diffuse into the surrounding peritubular capillaries a PCT cells usually reabsorb 60 70 of the filtrate made in the renal corpuscle 5 There is some secretion of substances into tubular lumen a Active transport secretion of H ammonium ions drugs and toxins b Nephron loop Loop of Henle i Reabsorbs about of H2O and 2 3 of Na and Cl ions in tubular fluid ii Very close parallel segments that are separated only by peritubular fluid 1 Very different permeability characteristics iii Descending limb H2O reabsorption 1 Thin permeable to water but impermeable to solutes 2 As tubular fluid flows through osmosis moves water into peritubular fluid leaving solutes behind 3 Osmotic concentration of tubular fluid increases iv Ascending limb Na and Cl reabsorption 1 Thick highly effective pump 2 2 3 of Na and Cl are pumped out of tubular fluid before reaching DCT 3 solute concentration declines 4 In juxtamedullary nephrons the ascending limb will create high solute concentrations in the surrounding peritubular fluid a Concentrates urine c Distal convoluted tubule DCT i Epithelial cells lack microvilli ii Three processes 1 Selective reabsorption of water depending on ADH a Concentrate the tubular fluid which eventually becomes urine 2 Selective reabsorption of sodium depending on aldosterone and calcium depending on PTH and calcitriol from tubular fluid 3 Active secretion of ions including H K and ammonium drugs and toxins d Collecting duct i Collecting ducts receive the fluid from many nephrons ii Each collecting duct starts in the cortex and descends into the medulla 1 Carries fluid to the papillary ducts 2 Papillary ducts drains into minor calyx iii Found at the opening of DCT iv Individual nephrons drain into nearby collecting duct 1 Adjustment of fluid composition a Determines final osmotic concentration and urine volume 2 Na reabsorbed in exchange for K secreted a Controlled by aldosterone 3 HCO3 reabsorbed in exchange for Cl4 H2O reabsorbed controlled by ADH a Urea reabsorbed 5 H secreted in exchange for HCO3 if the peritubular fluid is too acidic 3 Which are affected by aldosterone What is the effect of these two hormones on filtrate tubular fluid composition a Their secretion increases urine osmolarity b Aldosterone i Increases the number of Na K exchange pump at DCT and collecting ducts ii Promotes the reabsorption of Na in exchange for K iii Water is reabsorbed by osmosis c ADH i Increases the aquaporins or water channels in apical cell membranes of DCT and collecting duct ii Concentrates 100 mOsm L tubular fluid arriving at DCT to be concentrated to 1200 mOsm L when it reaches the minor calyx d Absence of ADH i All fluid arriving at DCT is lost in urine since water is not reabsorbed ii As seen in diabetes insipidus large amounts of dilute 20 400 mOsm L urine 24 L day iii Posterior pituitary normally is continuously secreting low levels of ADH 1 DCT and collecting system are both always permeable to water 2 Collecting system reabsorbs 16 8 L day 9 3 of filtrate 3 produces 1200 mL per day 0 6 of filtrate of urine 800 1000 mOsm L e 4 How does filtration occur at the glomerulus What properties of the glomerulus allows for filtration Is everything filtered out during filtration What substances are filtered and what substances are not filtered out a Filtration i Blood pressure pushes water and small solutes across the membrane of the glomerulus and into capsular space 1 Larger solutes not found in filtrate because they aren t filtered out of the plasma a Includes plasma proteins 2 No energy required passive process 3 Solutes that enter capsular space include a Glucose b Fatty acids c Amino acids d Vitamins e Metabolic wastes f Excess ions ii The glomerulus is a capillary network which is governed by the balance between hydrostatic pressure and colloid osmotic pressure 5 How are cortical nephrons different from juxtamedullary nephrons Why are these differences important in urine formation Where is the vasa recta located and what role does it play a Cortical nephrons i 85 of all nephrons ii Efferent arteriole delivers blood to a network of peritubular capillaries iii Found mostly in superficial cortex of kidney iv Nephron loop loop of henle is relatively short b
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