BCMB 230 1st Edition Lecture 21 Outline of Last Lecture I Respiration Control II Plasma Glucose Levels and Regulation III Hormones IV Increasing Plasma Glucose Levels V Decreasing Plasma Glucose Levels VI Other Factors Outline of Current Lecture I Urinary System II Structure of Nephron III Flow Path IV Types of Nephrons V Glomerulus and Glomerular Capsule VI Physiological Processes of the Nephron VII Processes of the Kidney Current Lecture I Urinary System Kidney primary organ of the urinary system Three other structures of urinary system ureter bladder urethra these structures handle the weight the urine byproducts of urinary system ureter connects kidney and bladder bladder muscular sac that holds the urine urethra exit out of the bladder Kidney location high in abdominal cavity top of the kidney are above lowest ribs last two ribs come across top of the kidney embedded in fat and held very tightly against abdominal wall very well fixed in place in body Various layers within kidney The two layers we will look at renal cortex outer portion of kidney typically everything looks the same homogenous renal medulla inner portion see different looking things heterogeneous nephron function unit in the kidney where work is going on consist of two kinds of tubes These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute renal tubules blood vessels that are very closely associated with them II Structure of the Nephron Glomerular capsule Bowman s capsule swollen portion that is two layered with space between it parietal layer and visceral layer general anatomical terms parietal means outside visceral means inside Capsular space continuous with the tube Proximal convoluted tubule windy area adjacent to capsular space general anatomical terms proximal means near when talking about along the flow path Descending loop of Henle Ascending loop of Henle Distal Convoluted tubule another windy spaced tube general anatomical term distal means far away when talking about along the flow path Collecting duct leads into the ureter which eventually leads to the bladder III Flow path Afferent arteriole blood coming into the nephron term arteriole small artery Glomerulus capillaries that blood spills into after afferent arteriole called glomerular capillaries efferent arteriole blood comes out of glomerular capillaries efferent arteriole comes out and wraps around peritubular capillaires IV Types of Nephrons Two kinds of nephrons cortical nephron pretty much all within the cortex portion of the kidney outer layer most nephrons are cortical nephron peritubular capillaries in the cortex form a net juxtamedullary nephrons part of these nephrons are in the medulla makes up about 15 of nephrons loop of henle is longer in juxtamedullary nephrons come well down into medulla capillaries are different in juxtamedullary nephrons subset of peritbulular capillaries follow the loop of Henle vasa recta part of the peritubuluar capillaries that does this down in the medulla form big loops V Glomerulus and Glomerular capsule Renal corpuscle term used to talk about glomerulus and glomerular capsule collectively Look at visceral layer very complicated in shape because it wraps around each turn of the capillary within it all capillaries have folds of visceral layer around them visceral layer of glomerular Bowman s capsule fits to it very tightly podocytes specialized cells of the visceral layer have finger like projections that interlace but there are some spaces between these cells called filtration slits this is what covers the capillaries moving material from inside capillary to capsular space have to go through filtration slits VI Physiological Processes of the Nephron 1 Filtration take material from blood plasma and put it into new fluid called filtrate happening between the glomerulus and capsular space push material through filtration slits filtration silts are not empty have basement membrane no plasma membrane present paracellular transport have to go between the cells Filtration slits are so small that proteins and cells are going to stay in blood but smaller solutes and particles will leave Filtrate has water and any small solute in the blood this all happens as long as kidney is acting appropriately 2 Reabsorption renal or tubular once we filter want to reclaim some of it materials go from filtrate back into the blood filtrate is in renal tubules blood is in peritubular capillaries allows to reclaim things that have been filtered about before turning it into urine 3 secretion renal or tubular take material from blood and put it into filtrate blood in peritubuluar capillaries filtrate in renal tubules especially in the distal convoluted tubes 4 tubular metabolism chemical reactions in the renal tubules VII Processes of the Kidney Kidney operates processes blood move components of blood from blood into tube system do this through filtration selectively remove stuff basis of selection on size once in filtrate can selectively reclaim some things reabsorption add stuff to filtrate through secretion get rid of things additionally can also manipulate things by having the appropriate enzymes in the tubules to make new chemicals ex glucose through gluconeogenesis and carbonic anhydrase enzyme that helps with the reaction of water and carbon dioxide helps adjust pH Different substances in the blood are handled differently through these processes some things are filtered some things are not reabsorb things that are needed such as glucose amino acids water etc If something is bound to a protein like a steroid hormone can t get rid of a lot of it through the kidney protected by being bound to that protein kidney not very effective in moving things that are protein bound Reabsorption obligatory reabsorption happen regardless of how much we have reabsorb water if we don t have enough water or if we have too much does not matter there are some places in the kidney that this happens regulated reabsorption can turn reabsorption on and off want this when we don t have enough water want to reclaim as much of it as we can Once we go through nephron and once filtrate leaves the collecting duct filtrate cannot be changed is already urine can t reclaim things or change concentration anymore Make sure we get rid of something in the kidney want it filtered not reabsorbed want it secreted Give drug that s secreted by the kidney to maintain levels