12.2.13 kin 272 class notes- Process of urine formationo 3 basic principles 1. Filtration- 2 forceso 1. Oncotic and hydrostatic force (pressure) 2. Reabsorption - the movement of substances (ions, solutes, pieces) out of renal tubules into peritubular fluid and then into peritubular capillaries- reabsorbing items (ions, substances) out of what we caught in nephron, putting it back into system 3.secretion - opposite of resabsorption- movement of items out of peritubular capillaries, into peritubular fluid and back into the renal tubes-- in-- picture of nephron… on screen- …- …- …- PCT- Loop of henle- DCT- Collecting duct- Bomens capsule- Collecting duct spits into minor calyx- Filtrationo Only occurs in capsule (glemarular capsule)o Occurs because of hydrostatic pressureo High hydrostatic force o Pushed into bomen’s capsule, pulling water & solutes towards capsule- Proximal convoluted tubuleo 99% of what enters is reabsorbed into peritubular capillarieso what remains is waste products we don’t want to get rid of uric acid, hydrogen ions sodium, potassium, magnesium are reabsorbed (some water aswell) this is because of how high the hydrostatic pressure iso selective secretion will happen hereo diffusing- loop of henleo sodiumo counter current multiplicationo maintain sodium balance- DCTo secretiono anything that needs to be removed o only thing reabsorbed is water and handful of ions (potassium, little sodium)o selective reabsorption- don’t have enough ions to maintain balance, selectively put back into peritubular capillarieso filters a bunch of stuff out, then picks & chooses- filtration o how does it happen?o Hydrostatic pressureo Oncotic pressure- Reabsorption/secretion o DCT & PCT rely on these to get correct ion balanceo Diffusiono Carrier mediated transportation Facilitated diffusion- Using carrier protein to move substance across membrane, follows concentration gradient Active transport- Using atp to move substance across membrane against concentration gradient Cotransport- 2 substances travelling together through same tube using 1 substances concentration gradient “hitching a ride” countertransport- same as the last one except substance hitching a ride is going in the opposite direction- GFR – glomerular filtration rateo Each nephron responsible for producting filtrate/urineo Ureter bladdero Should produce a certain amount every dayo Filtration rate can give information about How well nephrons are working How well is blood volume doing How well is metabolism doingo Filtration altered by Blood pressure- If it increases, GFR increases Reverse is also true- Blood pressure decreases, GFR decreases- Things you shouldn’t see in nephron:o Job is to filter metabolic wastes o (H2O, sodium, potassium, magnesium, hydrogen ions)o CO2 (some of it)o Uric acido Difference between protein and amino acid? Yes! Amino acids, yes! We don’t store them Eat excess protein and if you don’t use it, you get rid of it here! They are small Can be filtered out (good thing)o Creatinine Byproduct of metabolismo Couple of things you don’t want to see in here: Protein- Very big- Bomens capsule doesn’t have big enough holes to fit typically Blood- Stay inside arteriole- Hydrostatic pressure never pushes out Bacteria- Not in nephron unless it came from outside in- UTI(?) Glucoseo High blood pressure for long period of time, glomerulas keeps filtration high for long period of time Size of fenestrations in capsule get bigger Over a long period of time it increases what gets forced through the capsule Glucose, protein get forced through fenestrations See them in urine The longer blood pressure is elevated, nephrons can get destroyed- Kidney function decreases over time- Best ways to analyze this is to look at levels of creatinine determine filtration
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