Phis 206 1nd Edition Exam 3 Study Guide Lectures 20 28 Renal System Renal System 1 Kidney we have 2 of them 2 Urine bladder Kidneys Major function to regulate 1 Total fluid volume 2 H concentration in extracellular fluid 3 Regulate salt balance 4 Elimination of wastes Have 2 kidneys with outer capsule Beneath capsule is cortex o Reddish in color o Vigorous blood supply Beneath that is medulla o Gray in color o Sparse blood supply Kidneys get about 25 of blood flow goes to the nephrons Blood came in through renal artery Blood leaves through renal vein Some fluid leave blood in kidneys This fluid then leaves through ureter Afferent arteriole breaks into capillary bed in cup then glomerulus capillaries They empty into efferent arteriole it breaks up into another bed of capillaries Peritublar Capillaries blood supply for most of nephron drain into a venule which carries blood off Portal System You have arteriole drain into capillaries bed to another arteriole to another capillary bed to venule Collecting duct gathers from many nephrons Collecting ducts eventually flows to ureters 2 Kinds of Nephrons 1 80 are Cortical Nephrons it is entirely located in the renal cortex 2 20 are Juxtamedullary Nephrons Bowan s convoluted tubule in cortex but the Loop of Henle is in the medulla Loop of Henle is very long a next to the medulla Only about 15 of blood flow gets into the Renal Medulla The medulla is bigger so blood flows 20x faster in cortex Three Major happenings in Kidneys 1 Glomerular Filtration just as in other capillaries does not let out proteins occurs in the glomerulus Hydrostatic pressure is higher so more fluid goes out The pressure in glomerulus is higher than most capillaries due to a resistance vessel 20 of plasma volume filtered out known as glomerular filtrate plasma without the protein Average everyday filters out 180 Liters or 50 gallon a day Urinate about a liter a day reabsorb 179 Liters out of every 180 liters produced Kidneys will reabsorb about 99 of solute as well During the movement through the Nephron 1 will reabsorb some stuff out of lumen into ECF 99 5 different solutes will be reabsorbed at different rates 2 Reabsorption secretion and Glomerular Filtration are 3 processes that account for most of the functions of kidneys Because of 2nd Arteriole Pressure in capillary is higher than in most systemic capillaries so little fluid gets reabsorbed 20 of plasma volume gets pushed into Bowman s Capsule Then after moves through second arteriole into another capillary bed has lower pressure due to lower volume so when it gets into peritubular capillaries it has lower volume so it makes it closer to systemic capillaries 99 leaves instead of 100 this is a 2 step process Glomerular Filtration Rate GFR Rate 125mL min this can vary due to the hydrostatic pressure driving force Higher pressure higher rate Anatomically this is set up to be easy if you constrict efferent you increase pressure upstream which increases GFR Constrict afferent reduce GFR Most of physiological control comes from sympathetic stimulation and the sympathetic nerves supply is much denser to afferent than to efferent so afferent constricts so reduces GFR GF protein is free plasma in out urine add to secreted 2 Reabsorption o tends to be active useful reabsorbed o sluggish toxious 2 classes for 1 Active Transportation moves uphill against gradient needs energy ATP 2 Passive Transportation facilitated diffusion carrier molecules mostly protein High Concentration Low Concentration Simple Diffusion across cell membrane Huge amount of sodium reabsorbed Responsible for osmotic pressure Drives passive reabsorption of negative ion Most other active transport systems only work with sodium reabsorption Sodium Reabsorption o Control of body sodium level is controlled by kidney by varying the amount we lose All of the control is done in the distal tube The amount that gets reabsorbed in the distal tube determines the amount of sodium in the body o Sodium goes from the lumen of the nephron to the bloodstream Gets pumped out of the nephron cells into the ECF active transport Allows for sodium in the lumen of the nephron to then move into the cell Then diffuses into the capillaries from ECF o Amount of Sodium Reabsorbed 80 reabsorbed in Proximal 12 in the Loop of Henle 7 5 in the distal tube o Tubular Load Amount of compound entering tubule For glucose 1 mg mL x 125 mL min 125 mg min Amount of glucose that enters your nephron per minute average o Tm of glucose 400 mg min Nephrons can absorb up to that amount if it is present Means that glucose does not wind up in the urine o Water follows concentration of glucose osmotically Causes an overall increase in blood plasma Diabetics cannot control glucose levels Have high urine levels Have sweet pee o Chloride is reabsorbed passively due to being attracted by the positive charge of sodium o Reabsorbing 99 5 of water in nephron Means that everything left behind is in higher concentration than before Anything left behind that can diffuse across nephron membrane WILL diffuse Na enters Bowman s capsule 100 Not subject to control proximal tubule 100 enters 80 reabsorbed Loop of Henle 20 enters 10 12 All control excerted here Distal tubule 8 enters collecting duct urine 1 or less Glucose Amino Acids Active Transport Transport Maximum maximum amount of glucose being reabsorbed in nephrons 400mg min Diabetes Mellitus urine volume goes up with high volumes of glucose When actively reabsorb sodium passively reabsorb chloride Also reabsorb water due to reabsorption of chloride 3 Secretion a Our of capillaries and into tubular fluid Some secretions are added to tubule Hydrogen Ion H actively secreted most important for fine tuning of the pH Potassium Ion H Organics Drugs actively secreted Plasma Clearance volume of plasma containing amount or x that appears in the urine in 1 minute o This is use because the larger the amount of volume that is cleared the more efficient the removal is Typically produce 1 2L a day 1mL a min That amount is the difference of the plasma that is filtered and the plasma that is reabsorbed One useful way to look at amount it is from what volume of plasma would you have to completely remove this compound to get it to show in the mL min Compound named Inulin Garlic Onions one interesting characteristic is that it is filtered as any small compound in kidney but it is not reabsorbed nor secreted at all what that means is that the amount of inulin that got into lumen