Renal Function

• Kidneys


  Two bean shaped organs located under the diaphragm
• Nephrons


  Functional units of kidneys
• Functions of Kidney


  • Filter blood; clears waste
  • Maintain overall fluid balance
• Divisions of Kidney


  1. Renal Cortex

  2. Renal Medulla
• Divisions of Nephrons


  1. Cortical Nephrons

  2. Juxtamedullary Nephrons
• Renal Corpuscle


  Responsible to maintain Blood Pressure through RAAS (renin-angiotensin)
• Erythropoietin (EPO)


  Hormone produced by kidneys to stimulate bone marrow to produce RBC in response to hypoxia
• Renal Functions


  1. Renal Blood Flow

  2. Glomerular Filtration

  3. Tubular Reabsorption

  4. Tubular Secretion
• Renal Blood Flow


  • Kidneys receive 25% of blood pump at all times
  • Difference between blood flow and urinary filtrate flow
• Glomerular Filtration


  1. Cellular Structure of the Glomerulus

  2. Glomerular Pressure

  3. Renin-Angiotensin-Aldosterone-System (RAAS)
• Glomerular Filtration Barrier


  • Capillary wall membrane
  • Basement membrane
  • Visceral epithelium of the Bowman capsule
• Fenestrated Endothelium


  Responsible for further restriction of large molecules
• Podocytes


  Intertwining foot processes seen in inner layer of Bowman's capsule
• Glomerular Pressure


  Hydrostatic pressure<|>Oncotic pressure
• Renin-Angiotensin-Aldosterone-System (RAAS)


  1. Regulates the flow of blood to and within the glomerulus

  2. The Juxtaglomerular apparatus monitors the system in response to changes in blood pressure and plasma sodium content
• Decreased sodium


  Decreases water retention resulting in decreased overall blood volume and blood pressure
• Tubular Reabsorption


  1. Reabsorption Mechanisms

  2. Tubular Concentration

  3. Collecting Duct Concentration
• Active Transport


  Requires a carrier protein and electrochemical energy
• Passive Transport


  Movement of molecules across a membrane as a result of gradient
• Renal Threshold


  Plasma concentration at which active transport stops (e.g. Glucose: 160-180 mg/dL)
• Substances Reabsorbed


  • Glucose
  • Amino Acids
  • Salts
  • Chloride
  • Sodium
  • Water
  • Urea
• Tubular Concentration


  Begins in the descending and ascending loops of Henle<|>Countercurrent mechanism - selective reabsorption process that serves to maintain the osmotic gradient of the medulla
• Collecting Duct Concentration


  Final concentration of the filtrate through the reabsorption of water begins in the late distal convoluted tubule and continues in the collecting duct<|>Depends on the osmotic gradient in the medulla and the hormone vasopressin released by the posterior pituitary gland
• Tubular Reabsorption


  Substances are removed from the glomerular filtrate and returned to the blood
• Tubular Secretion


  Passage of substances from the blood in the peritubular capillaries to the filtrate
• Functions of Tubular Secretion

  • Eliminating waste products not filtered by glomerulus
  • Regulating the acid-base balance in the body through the secretion of hydrogen ions
• Acid-Base Balance


  Lungs and Kidneys are the two organs involved in maintaining the normal blood pH of 7.4
• Juxtaglomerular Apparatus is made up of juxtaglomerular cells and macula densa
• Total Renal Blood Flow is approximately 1,200 mL/min
• Total Renal Plasma Flow is 400-700 mL/min
• Glomerular Filtration Rate (GFR) is calculated based on the specific gravity of the glomerular filtrate, which is 1.010
• Tubular Secretion


  1. Medications can't be filtered by glomerulus

  2. Peritubular capillaries -> proximal cells - secretion
• Acid-Base Balance


  pH of blood
• Organs involved in acid-base balance

  • Lungs
  • Kidneys
• Juxtaglomerular Apparatus


  • To maintain normal blood pressure
  • Total Renal Blood Flow: approx. 1,200mL/min
  • Total Renal Plasma Flow: 400-700mL/min
  • Juxtaglomerular cells
  • Macula densa - sense changes within RAAS
• Glomerular Filtration Rate (GFR)


  Correction that is calculated if dealing with body sizes that are not average
• Specific Gravity of Glomerular Filtrate


  1.010 - confirms the ultrafiltrate plasma
• Renal Threshold of Glucose


  140-180 mg/dL - for reabsorption
• Renal Blood Flow


  Unfiltrate; subject for REABSORPTION
• Renal Filtrate Flow


  Filtrate; subject for EXCRETION through the urine