Renal Physiology Mock Test.pdf

- NEW CHAPTER - Renal Physiology - Internal Anatomy - Three major regions (frontal section) - Renal Cortex - Renal medulla - Cone - shaped tissue “renal pyramids” (or “medullary”) - Pyramids -...

- NEW CHAPTER - Renal Physiology - Internal Anatomy - Three major regions (frontal section) - Renal Cortex - Renal medulla - Cone - shaped tissue “renal pyramids” (or “medullary”) - Pyramids - urine-collecting tubules - Renal Pelvis - Funnel shaped tube - continuous with the “ureter” leaving the hilus - Pelvis branches inward forms “calyces” - Major calyces - Minor calyces - Calyces drain urine from papilla into ureter - ultimately - bladder - Blood Supply - Kidneys cleanse blood - rich blood supply - Renal arteries primary source - Delivers ¼ of cardiac output to kidney per min - The medulla-cortex junction (border) - Interlobar arteries branch - Arcuate arteries - over base of pyramids - Sympathetic NS - Regulates vasomotor fibers - Regulates renal blood flow by adjusting diameter of renal arterioles - Also influences urine formation by nephrons - Neprhones (= renal tubules) - > 1 million nephrons/kidney - Functional structure - forms the urine - Collecting ducts - Collect urine from nephron - 9/18 - Nephron - Glomerulus - Capillaries associated with renal tubule - Glomerular Capsule (= Bowman’s capsule) - cup shaped - Bind end (start) of renal tubule = nephron - Glomerulus surrounds the capsule - *Urine comes from the blood through the capillaries - The Filtrate - “Renal corpuscle” consists of… - Glomerular capsule - Enclosed glomerulus  - Glomerular endothelium of capillaries is “fenestrated” - Small pores - Solute/fluid pass through pores (blocks proteins) - Termed the “filtrate” = forming urine - Visceral Layer - Podocytes - Visceral layer - with “podocytes” - Epithelial cells “podocytes” assoc. w/ fenestrated endothelium - OPenings between podocytes termed “filtration slits” - Blocks large components - Filtrate pass to interior of the glomerular capsule - *This is how fluid in the body is filtered out! - Direction of Filtrate - Arterioles ender glomerulus - Endothelium lining vessels fenestrated - Solute/fluid (not proteins) through pores (under pressure) - Cross visceral layer (epithelial layer) between podocytes (filtration slits) - Enters interior of glomerular capsule - Three parts to the nephron - Proximal convoluted tubule - After glomerular capsule - Coiled tube - Loop of Henle - hairpin loop - Distal convoluted tubule - Empties into collecting duct - Juxtamedullary Nephrons - Cortical Nephrons - Represent 85% of all nephrons - Within the cortex - Part of loop of Henle enters outer medulla - Juxtamedullary nephrons - At the cortex-medulla junction - Loop of Henle - enters deep into medulla - Role producing concentrated urine - Nephron - Microvasculature - Two capillary beds supply the nephron - Glomerulus - Peritubular capillaries (= vasa recta) - Glomerular Capillaries - Glomerular capillary beds - Generates higher pressure then most capillary beds (to force filtrate out) how? - Arterioles high resistance vessels - ****Afferent (Entering) arterioles larger diameter than efferent (leaving) arterioles (builds pressure)  - Extra pressure forces fluid/solutes out of blood into glomerular capsule - Most filtrate reabsorbed by renal tubules (99%) - Peritubular Capillaries - From efferent arterioles draining the glomeruli - Close contact with the renal tubules - Porous capillaries absorb solutes/water from tubule cells - All substances secreted from blood by nephrons are from peritubular capillaries - Juxtamedullary nephron - tubule extends into medulla - Efferent arterioles (peritubular capillaries) form “vasa recta” - Bundles of long straight vessels in close contact with loop of Henle - Walls of the vasa recta thin and important in forming concentrated urine - Microcirculation - High resistance afferent to efferent arterioles (high pressure) - Pressure declines through system - High resistance at glomerular protects it from BP changes - systemic BP - Practice Exam Questions - Answers - #1, I was thinking in the right direction, however I had both arterioles mixed up! *Higher pressure = bigger flow - Juxtaglomerular Apparatus - Granular juxtaglomerular cells (JG) - Mechanoreceptors - sense blood pressure in afferent arterioles - Have secretory cells with “renin” - Mecula desna - Tall distal tubule cells - close to “JG” cells - Osmoreceptors - sense changes in solute in filtrate - Both cells - regulation of filtrate formation/BP - Filtration Membrane - Filter membrane between the - Blood and the glomerular capsule - Porous membrane - Water and small solute from blood to glomerular - Three layers - Fenestrated endothelium of glomerular capillaries - Visceral membrane of glomerular capsule - Podocytes - Basement membrane - fused basal laminas - 9/20 - Functional Filtration - Capillary Pores - no RBCs pass through - Basement membrane - Small proteins fixed to membrane - anionic charged - Repels most plasma proteins (“-” charged) - More to this… - NOT on exam - Facts - urine production - 1000-2000 ml blood to glomeruli/minute - Filtering full body plasma volume > 60 times/day - Filtrate (defined) - Similar to blood plasma without protein - Most material “rescued” back into blood - What ends up in urine? - Metabolic waste - Non-Essential substances - Major Processes in Urine Formation - Glomerular filtration - Renal tubule reabsorption - Renal tubule secretion - COllecting ducts and nephrons produce dilute or concentrated urine - Glomerular Filtration - Hydrostatic pressure drives process - More efficient process than other capillary beds because… - Filtration membrane more permeable to water and solute - Glomerular capillary pressure is higher than other capillaries - higher net filtration pressure - 180 liters/day other 3-4 liters/day - Net Filtration Pressure - Net Filtration Pressure (NFP) - Calculated by accessing opposing pressures - OPg (colloid osmotic (oncotic) pressure in blood) = Chemical Pressure! - HPc (Capsular hydrostatic pressure) - nephron = Force - HPg (Hydrostatic pressure in blood) = Force - *Should know the name and not just the abbreviation - NFP = HPg - (OPg + HPc) - NFP = 55mm Hg - (30 mm Hg + 15 mm Hg) - *NFP = 10 mm Hg - Glomerular Filtration Rate - Total amount of filtrate formed per minute - Factors influencing filtration rate at the capillary beds - Total surface area for filtration - Filtration membrane permeability - Net filtration pressure - High Level of GFR - Why is GFR so large at such a low NFP(10 mm Hg)? - Glomerular capillaries - highly permeable (leaky) - **Massive surface area - Full surface area of skin on the entire body - NFP and GFR - GFR directly proportional to NFP - CHange in any parameter influences NFP will change GFR proportionally - Increases in NFP = increase in GFR - Decreases in NFP = decreases in GFR - Example - Dehydration - Increases in glomerular osmotic pressure (OPg) inhibits filtrate formation (decreases GFR) - *Less water = less oncotic pressure - Practice Exam Question - Explanation = RIGHT answer was A? - Regulation of Glomerular Filtration - Why regulate GFR *to keep it the same? - ***Rate filtrate flows though tubule determines rate of reabsorptoin of water and solute - Examples - If high GFR = High flow rate in tubule - Massive flow through tubule not allow time for reabsorption (lost with urine) - If low GFR = Low flow rate in tubule - Low flow in tubule most solute reabsorbed including wastes - Renal Autoregulation - Mycogenic Mechanisms - Increases in BP (systemic) - Results - afferent arterioles constricting - Restricts blood to glomerulus - Lower pressure = lower flow - Prevents glomerular VP from rising too high - Protects glomerulus in response to High BP - Decline in BP (systemic) - Dilation of Afferent arterioles - (remember efferent arterioles are constricted) - Increases glomerular pressure - Low Filtrate Flow or Low Osmolarity - Low filtrate flow rate (or low filtate osmolarity) = low Na+ or Cl- - Stimulates vasodilation afferent arterioels = increases pressure - = More blood to flow into glomerulus - Increases NFP and GFR - Increases filtrate flow - less time for filtrate processing (less solute reabsorption) - more Na+ and Cl- remains in filtrate - 9/25 - Absorptive Capabilities - Proximal Confoluated Tubules - Most active reabsorbing cells of renal tubule  - 125 ml of filtrate/min entering tubule - 85… - Hyponatremia = low levels of sodium - Aldosterone and Sodium - Conditions activating aldosterone (adrenal) the renin-angiotensin II pathway - Decreased blood volume (= decrease BP) - Hyponatremia (low Na+) - Direct release aldosterone - “Hyperkalemia” (High K+) - Aldosterone acts at “principle cells” collecting duct - Makes more Na+ channels (apical side) - Makes more Na+/K+ channels (basolateral side) - Little Na+ leaves as urine - W/O aldosterone - Na+ is lost (critical electrolyte) - Na+ is reabsorbed with aldosterone (steroid, released when there is low sodium in blood) - Indirectly water follows Na+ - reabsorbed - “What if you’ve been injected with aldosterone?” - Answer - Filtrate levels will go down, Blood level of sodium will go up. - Pulls the sodium from the filtrate into the blood! - As Na+ is reabsorbed - K+ secreted into filtrate (sodium goes one way, potassium goes the other way.) - Na+ enters cells (lumenal side) and K+ secreted into filtrate - Regulation of Urine - Major function - kidney - keep salute concentration of body fluids within 300 MOsm (milliosmol - Equal to osmotic concentration of blood plasma - Kidney creates dilute or concentrated urine - In other words - Can increase or decrease blood solute concentration - Requires a countercurrent system - *The kidney can either decrease or increase water content - Countercurrent Mechanism - Two mechanisms make this happen - Countercurrent multiplier - Flow of filtrate through the loop of Henle of the Juxtamedullary tubules - Countercurrent exchanger - Flow of blood in the vasa recta - *Interaction allows kidney to regulate urine concentration - Medullary Osmotic Gradient - An osmotic gradient is set up - Interstitial fluid increases in solute concentration - from cortex to medulla  - 300 mOsm - cortex - 1200 mOsm - medulla - Descending Loop of Henle - Impermeable to solutes - permeable to water - Water leaves filtrate due to increasing solute concentration in interstitial fluid - Results - increases in salt concentration of filtrate to a maximum (bottom of loop) - 1200 mOsm - Ascending Limb - Impermeable to water - transports NaCl into interstitial fluid - Thick ascending limb reabsorbs Nacl - From filtrate into cells and then into interstitial fluid - Increases the interstitial NaCl concentration - HIgher NaCl at the start of the ascending limb drives the transport of NaCl from the filtrate to the interstitial fluid - Differences in solute concentration Descending limb Vs Ascending Limb - Descending limb - has a higher solute concentration (by about 200 mOsm) - Ascending limb and the interstitial fluid has lower solute concentration - Descending limb - Higher solute than ascending limb and interstitial fluid - Descending limb - water leaves filtrate - Concentrates filtrate bottom of ascending limb - Allows ascending limb (reabsorbs NaCl) to increase salt in interstitial fluid of medulla - Leads to a positive Feedback mechanism - More salt extruded from the ascending limb more water diffuses out the descending limb and more salt in the filtrate of descending limb - Major effect of countercurrent system - Primary effect is… - Produces high osmolarity of the filtrate at the descending limb and interstitial fluids - Energy that powers this system - Active transport of Na+ at the ascending limb to interstitial fluid - Collecting Duct - Permeable to Urea - Collecting ducts - deep medulla - Urea diffuses from filtrate to interstitial fluid - Adds to high osmotic pressure in deep medulla - Vasa Recta - Countercurrent Exchanger - Permeable to NaCl and water - Vasa recta enters the cortex and extends into medulla  - Loss of water - From teh vasa recta into interstitial fluid - Gains NaCl - From the interstitial fluid into vasa recta - Blood at bottom vasa recta becomes “hypertonic” - Vasa Recta exits - extends from the medulla to the cortex this process is reversed - Picks up water - Interstitial fluid to the vasa recta - Loses NaCl - Vasa recta (maintains the gradient) to hte interstitial fluid - *Loop of Henle creates the gradient - Significance of the Vasa Recta? - System protects the medullary gradient - maintains the gradient - By preventing rapid loss of NaCl from the medullary interstitial fluid - Vasa Recta protects the gradient by preventing the removal of salt - Formation of Dilute Urine - Wihtout ADH (from pituitary) - Collecting ducts - impermeable to water - Little water reabsorbed - Water lost to urine - Na+ (and other ions) removed at distal and collecting tubules (back to blood) - 9/30 - Chronic Renal Disease - 400,000 renal impairment per year require dialysis (or transplant) - $16.7 billion per year spent on patients with impaired kidney function - Stages of Renal Disease - Acute Failure (less common onset) - Trauma - Infections - Metal Poisons - Chronic Failure (more common onset) - Asymptomatic - Gradual reduction in filtrate production (< 60 ml/min) - Nitrogenous wastes increase (blood) - Blood pH becomes acidic - Stages - State 1 GFR - State 2 GFR - State 3 GFR - State 4 GFR - State 5 - Symptoms  - High BP - Frequent urination (difficult or painful urination) - Swollen extremities (ankles and hands for example) - *Symptoms appear after much damage has already been done. - Diagnosis - early sign of disease - Urinalysis useful early marker of disease - Proteinuria - protein in the urine (albumin usually) - Normal levels of albumin = 3 mg/day - > 300 mg/day - Creatinine clearance (urine creatinine compare to blood creatinine) - Breakdown of creatine to creatinine - Breakdown of muscle = creatine - Normal 100-140 ml/min (men) is reduced with poor renal function - Causes - Diabetes mellitus (33% of cases per year) - Hypertension (30%) - Damages renal blood vessels - Reduces circulation to the kidney - Atherosclerosis compounds problem - reduces circulation - Treatment - Control BP and glucose (diabetic patients) - Regulate BP < 130/85 mm Hg - Diet - Reduce proteins (Urea build up) - Reduce Phosphorus (release calcium from bone) - Reduce Sodium (raises BP) - Hemodialysis - Artificial kidney device - Removes wastes from the blood using tubing membrane and solutions - Two types of dialysis - Kidney dialysis - Peritoneal dialysis - infants/children - Kidney Dialysis - Blood is warmed and passes through semi-porous membranes - Surrounding membrane sterile solution - Water and some electrolytes - Blood cells (RBCs, lymphocytes retained) - Components pass through membrane into the solution - Components passing through membrane (removed from blood) - Urea - Salt - Other wastes - Dialysis Membrane  - Membrane semi-permeable - Blood side VS Dialysate side - Counter current flow - “ultrafiltration” - Blood/dialysate opposite flow - Fluid “pulled” from blood - Diffusion - waste products removed - From the dialysate - Electrolytes move back to blood - Returns electrolyte conc. - 3-4 hours (3 times per week) - Transplants - last resort treatment - Immunosuppression is required - Limited kidneys are available for transplant - Stem cells research - Cloned kidney cells from skin cells (bovine model) - Transplanted into animals - Produce urine like fluid - metabolic like wastes - No immunosuppressive drugs were required