kidney

• Homeostasis


  Maintaining a constant internal environment
• Osmoregulation


  Keeping the water and salt content of the internal body environment constant
• Excretion


  Removal of metabolic waste from the body
• Three organs of excretion


  The kidneys, lungs and skin
• Urine


  Fluid stored in the bladder and discharged through the urethra. Composed of mainly water, salts and nitrogenous waste products.
• Nitrogenous waste


  e.g. ammonia and urea
• Urea


  Waste product of metabolism made by liver from excess protein - must be removed as it is harmful to the body
• Kidney


  A homeostatic and excretory organ that controls the water and salt concentration in the body and helps to eliminate nitrogenous waste.
• Renal artery


  Supplies oxygenated blood to the kidneys
• Renal vein


  Transports deoxygenated blood from the kidneys
• Ureter


  Tube connecting each kidney to the bladder.
• Bladder


  Muscular bag that stores urine
• Urethra


  Tube that takes urine from the bladder out of the body
• Cortex


  Outer layer of the kidney
• Medulla

  Middle layer of the kidney that is roughly divided into pyramids
• Kidney tubule / Nephron


  Filtration unit found in the kidney. Each kidney has millions.
• Pelvis


  Funnel-shaped cavity of the kidney into which urine is emptied before it passes into the ureter
• Bowman's capsule


  Hollow cup of cells that surround the glomerulus. This is where filtrate enters the nephron
• Glomerulus


  A ball of blood capillaries under high pressure, which act as the site of ultrafiltration
• Glomerular filtrate


  Fluid forced from the blood out of the capillaries of the glomerulus into the Bowman's capsule. Composed of water, salts, glucose and urea.
• Ultrafiltration


  The process where small molecules are forced from the blood out of the capillaries of the glomerulus, under high pressure, into the Bowman's capsule.
• Loop of Henlé


  U-shaped loop that runs down into the medulla of the kidney, from which water and salts are resorbed into the blood
• Collecting duct


  The ends of several nephrons join to make this structure. Urine passes down this tube on its way to the ureter.
• Anti-diuretic Hormone (ADH)


  A hormone produced by the pituitary gland when the body is dehydrated. It causes the kidneys to reabsorb more water into the blood making the urine more concentrated.
• Hypothalamus


  A region of the brain that coordinates the activity of the pituitary gland and monitors blood concentration.
• Selective reabsorption


  Process where certain moleules are removed from the nephron and put back into the blood. Occurs in the first coiled tubule of the nephron.