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POWERPOINT® LECTURE SLIDE PRESENTATION by LYNN CIALDELLA, MA, MBA, The University of Texas at Austin Additional text by J Padilla exclusively for Physiology 31 at ECC UNIT 3 19 PART A The Kidneys HUMAN PHYSIOLOGY AN INTEGRATED APPROACH DEE UNGLAUB SILVERTHORN Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings FOURTH EDITION Functions of the Kidneys Regulation of extracellular fluid volume and blood pressure works with CV system to ensure tissues get enough oxygen and BP is within normal values Regulation of osmolarity – blood osmolarity needs to be maintained around 290mOsM Maintenance of ion balance - in response to diet urinary loss helps to maintain proper levels of Na+, K+, Ca 2+ . Homeostatic regulation of pH – they remove either H+ or HCO3- as needed, they don’t correct pH imbalances as effectively as the lungs Excretion of wastes – removes waste molecules dissolved in the plasma like urea (from amino acid breakdown), uric acid (nucleic acid turnover), and creatine (from creatine phosphate breakdown). Production of hormones – erythropoietin (signal RBC production), renin (influence BP and BV), and vitamin D conversion to control Ca 2+ Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings . Anatomy: The Urinary System Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-1a Anatomy: The Urinary System Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Cortico & juxtamedullary nephrons Figure 19-1c Anatomy: The Urinary System Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-1d–e Anatomy: The Urinary System Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-1g–h Anatomy: The Urinary System Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-1f Kidney Function Peritubular capillaries Distal tubule Efferent arteriole Glomerulus F Afferent arteriole Bowman’s capsule KEY F = Filtration: blood to lumen Proximal tubule Loop of Henle Collecting duct Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings To renal vein Figure 19-2 (1 of 4) Kidney Function Peritubular capillaries Distal tubule Efferent arteriole R Glomerulus F R Afferent arteriole Bowman’s capsule Proximal tubule R R KEY F = Filtration: blood to lumen R = Reabsorption: lumen to blood R Loop of Henle Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Collecting duct To renal vein Figure 19-2 (2 of 4) Kidney Function Peritubular capillaries Efferent arteriole Distal tubule S R Glomerulus F R Afferent arteriole Bowman’s capsule S Proximal tubule R S R KEY F = Filtration: blood to lumen R = Reabsorption: lumen to blood S = Secretion: blood to lumen R Loop of Henle Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Collecting duct To renal vein Figure 19-2 (3 of 4) Kidney Function Peritubular capillaries Efferent arteriole Distal tubule S R Glomerulus F R Afferent arteriole Bowman’s capsule S Proximal tubule R S R KEY F = Filtration: blood to lumen R = Reabsorption: lumen to blood S = Secretion: blood to lumen R Loop of Henle To renal vein Collecting duct E E = Excretion: lumen to external environment Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings To bladder and external environment Figure 19-2 (4 of 4) Kidney Function The urinary excretion of substance depends on its filtration, reabsorption, and secretion Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-3 Filtration Fraction Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-5 Filtration at the glomerulus Podocytes wrap around fenestrated capilaries creating filtration slits at the glomerulus . Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Forces that Influence Filtration Hydrostatic pressure (blood pressure) – pressure of flowing blood in glomerular capillaries is 55mmHg, it favors the movement of filtrate into Bowman’ Capsule Colloid osmotic pressure –Plasma proteins that enter the capsule create a gradient the favors movement back into the capillaries Fluid pressure created by fluid in Bowman’s capsule – The fluid build-up in the enclosed capsule creates a gradient that favors movement back into the capillaries The combination of these factors causes filtration to return plasma into the capillaries and allow for only 20% of the filtered plasma to move along the tubules. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Filtration Filtration pressure in the renal corpuscle depends on hydrostatic pressure, colloid osmotic pressure, and fluid pressure Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-6 Filtration Autoregulation of glomerular filtration rate takes place over a wide range of blood pressure Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-7 Glomerular Filtration Rate Changes GFR is controlled by a myogenic response, tubuloglomeru lar feedback, hormones and autonomic neurons Changing resistance in arterioles altes the filtration coefficient Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Juxtaglomerular Apparatus Juxtaglomerular cells and Macula densa monitor blood flow and blood pressure along the arteioles. They send chemical signals needed to restore the proper filtration rate Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-9 Tubuloglomerular Feedback Distal tubule Efferent arteriole Bowman’s capsule Macula densa Glomerulus Proximal tubule 1 GFR increases. 2 Flow through tubule increases. 1 Afferent arteriole Granular cells 2 Collecting duct Loop of Henle Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-10, steps 1–2 Tubuloglomerular Feedback Distal tubule Efferent arteriole Bowman’s capsule Macula densa Granular cells 1 GFR increases. 2 Flow through tubule increases. 4 Afferent arteriole Glomerulus Proximal tubule 1 3 Flow past macula densa increases. 3 2 4 Paracrine diffuses from macula densa to afferent arteriole. Collecting duct Loop of Henle Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-10, steps 1–4 Tubuloglomerular Feedback Distal tubule Efferent arteriole Bowman’s capsule Macula densa Glomerulus Proximal tubule 1 GFR increases. 2 Flow through tubule increases. 4 1 5 Afferent arteriole Granular cells 3 Flow past macula densa increases. 3 2 4 Paracrine diffuses from macula densa to afferent arteriole. 5 Afferent arteriole constricts. Resistance in afferent arteriole increases. Collecting duct Loop of Henle Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-10, steps 1–5 (2 of 4) Tubuloglomerular Feedback Distal tubule Efferent arteriole Bowman’s capsule Macula densa Glomerulus Proximal tubule 1 GFR increases. 2 Flow through tubule increases. 4 1 5 Afferent arteriole Granular cells 3 Flow past macula densa increases. 3 2 4 Paracrine diffuses from macula densa to afferent arteriole. 5 Afferent arteriole constricts. Resistance in afferent arteriole increases. Collecting duct Loop of Henle Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Hydrostatic pressure in glomerulus decreases. GFR decreases. Figure 19-10, steps 1–5 (4 of 4) Reabsorption Principles governing the tubular reabsorption of solutes and water. Sodium and water always follow each other.Transepithelial transport- (passing through cells)-Substances cross both apical and basolateral membraneParacellular pathway (passing around cells)Substances pass through the junction between two adjacent cells 1 Na+ is reabsorbed by active transport. Filtrate is similar to interstitial fluid. 1 Na+ 2 Electrochemical gradient drives anion reabsorption. 2 Anions 3 Water moves by osmosis, following solute reabsorption. 3 H2O 4 K+, Ca2+, urea Tubule lumen Tubular epithelium Extracellular fluid 4 Concentrations of other solutes increase as fluid volume in lumen decreases. Permeable solutes are reabsorbed by diffusion. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-11 Reabsorption Saturation of mediated transport Transport rate is proportional to plasma concentration until transport saturation=ren al threshold Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-14 Reabsorption Glucose handling by the nephron This graph does not show saturation at Bowman’s capsule Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-15a Reabsorption Saturation is reached within the proximal tubule Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-15b Reabsorption Excretion rate shows that no glucose is excreted with when plasma glucose concentration is low. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-15c Reabsorption Glucose is not secreted When filtration and reabsoption are equal and below threshold there is no secretion. Above that results in glucosuria or glycosuria Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-15d Secretion Transfer of molecules from extracellular fluid into lumen of the nephron - dependent on membrane transport proteins to move organic compounds Active process – move against concentration gradient and use secondary active transport to move into lumen Secretion of K+ and H+ is important in homeostatic regulation Enables the nephron to enhance excretion of a substance – adds to the substances collected during filtration, making excretion more effective Competition decreases penicillin secretion – doctors combined probenecid with penicillin so it would compete for the transporter protein and keep the kidneys from clearing penicillin so quickly. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Excretion Excretion = filtration – reabsorption + secretion Clearance Rate at which a solute disappears from the body by excretion or by metabolism Non-invasive way to measure GFR Inulin and creatinine used to measure GFR Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Inulin Clearance Inulin=polysaccharide; 100% of it is excreted so it is used to measure glomerular filtration rate Clearance is the rate at which a solute disappears from Efferent arteriole Filtration (100 mL/min) Glomerulus Peritubular capillaries 2 Afferent arteriole 1 Inulin molecules Nephron KEY the body = 100 mL of plasma or filtrate 1 Inulin concentration is 4/100 mL 2 GFR = 100 mL /min 3 100 mL plasma is reabsorbed. No inulin is reabsorbed. 4 100% of inulin is excreted so inulin clearance = 100 mL/min Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings 3 100% inulin excreted 100 mL, 0% inulin reabsorbed 4 Inulin clearance = 100 mL/min Figure 19-16 Excretion Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Excretion The relationship between clearance and excretion is that clearance is the rate of excretion. Different substance have difference clearance. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Micturition The storage of urine and the micturition reflex Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-18a Micturition 1 (b) Stretch receptors fire. 2 Parasympathetic neurons fire. Motor neurons stop firing. 3 Smooth muscle contracts. Internal sphincter passively pulled open. External sphincter relaxes. Micturition Stretch receptors Higher CNS input may facilitate or inhibit reflex. Sensory neuron Parasympathetic neuron 1 2 3 + – Motor neuron Internal sphincter 2 3 Tonic discharge inhibited External sphincter Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-18b