Renal system

• The Renal System

  • Anatomy
  • Physiology
  • Pathophysiology
• For thousands of years physicians have known that urine is an indicator of health and disease
• Very little and dark in colour

  • Dehydration
• Lots of it, pale in colour and attracts wasps

  • You're going to die soon (type 1 diabetes)
• Normal amount, dark in colour

  • Possible impending death (serious metabolic/liver disease)
• It's cloudy and frothy (foamy)

  • If it doesn't return to normal soon, you'll die slowly (progressive kidney disease)
• It has fresh blood and tissue debris in it


  • If it hurts to wee you may die soon (urinary infection). If it doesn't hurt to wee you will definitely die soon (bladder cancer)
• Components of the renal system

  • Kidneys
  • Ureters
  • Bladder
  • Urethra
• Kidneys


  • Filter blood, reabsorb most of it, make urine
• Ureters


  • Drain urine to bladder
• Bladder


  • Stores urine
• Urethra


  • Empties bladder
• Kidney Function


  • Large blood supply
  • Filters blood plasma
  • Makes urine
  • Drains urine to bladder
• Liver disease


  Liver fails to break down molecules which are then excreted by the kidneys
• Plasma Filtration


  • Glomerulus capillaries
  • Bowman's Capsule
  • Form a leaky barrier
  • Small substances leave blood
  • Water, ions, glucose
  • Not proteins, fats, cells
• Glomerulonephritis causes inflammation and the filter becomes more porous, leading to proteins in urine (cloudy, frothy)
• Urine Formation


  • Reabsorbs to body: Glucose, ions, water
  • Secretes into urine: Drugs, toxins, acid
  • Reabsorbs more water
• Type 1 diabetes


  Too much glucose in blood and filtrate, glucose in urine
• Water Balance


  • Water intake/creation
  • Obligatory water loss
  • Excess lost in urine (controllable by collecting duct)
• Low intake/high obligatory loss

  Low volume urine
• Urine Collection


  • Collecting duct
  • Renal pelvis
  • Ureter (peristaltic)
  • (Urinary) Bladder
  • Sphincters prevent emptying
  • Periodic relaxation of sphincters and bladder contraction cause micturition via urethra
• Bacterial infection or neoplasm


  Causes epithelial cell sloughing and bleeding
• Composition of Urine


  • Water
  • Excess ions
  • Metabolic wastes
  • Creatinine from muscle
  • Urea from amino acid deamination
  • Exogenous excreted compounds (drugs)
• Yellow colour is urobilin, a product of haemoglobin (red blood cell) breakdown in the liver
• Modern Diagnoses


  • Nephritic/ nephrotic syndrome
  • Type 1 diabetes mellitus
  • Dehydration
  • Liver and/or blood disease
  • Acidosis