Excretion

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Excretion

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Excretion

  1. 1. In this chapter, you should be able to: • Identify and label parts of the urinary system • Describe the functions of parts of the urinary system • Define excretion • Describe dialysis
  2. 2. Excretion is the removal of metabolic waste products from the body of an organism. Excretory organs Lungs Skin Liver Kidney
  3. 3. Bladder Kidney Ureter Urethra Renal artery Renal vein The Urinary system of Human
  4. 4. Medulla Cortex The kidney consists of 2 portions: Outer region known as cortex Inner region known as medulla
  5. 5. Nephron Within the kidney is millions of subunits called nephrons. The nephrons are the site of urine formation.
  6. 6. Glomerulus Blood enters the kidney by the renal artery. The renal artery branches into a mass of blood capillaries called glomerulus.
  7. 7. Ultrafiltration occurs in the glomerulus.
  8. 8. Ultrafiltration occurs in the glomerulus. Large molecules and cells are retained in the blood. i.e. hormones & RBC Blood plasma are filtered into the renal tubule.
  9. 9. Glomerulus Loop of Henlé Renal tubule As the blood plasma moves along the Loop of Henlé, some substances are reabsorbed back into the capillaries. These substances include glucose, amino acids, mineral salts and water. Purified blood moves out of the kidney via the renal vein.
  10. 10. Glomerulus Urea and excess water & mineral salts are retained in the Loop of Henle, and sent to the collecting duct. Loop of Henlé Renal tubule Collecting duct
  11. 11. Bladder Kidney Ureter Urethra Renal artery Renal vein The Urinary system of Human
  12. 12. Normal constituents of urine Average composition of normal human urine in grams / 100 cm³ Water Mineral salts (NaCl) Urea Other nitrogenous substances 96.0 1.8 2.0 0.2 100.0
  13. 13. Kidney Failure – Dialysis When a kidney transplant is not available or not feasible, dialysis can mimic the critical functions of the kidneys and sustain life. Peritoneal dialysisHemodialysis
  14. 14. Hemodialysis Fresh dialysis fluid in Used dialysis fluid out Blood flowtubing
  15. 15. Dialysis machine has the following features: • Tubing of the machine: ⇒ has walls which are partially permeable, ⇒ are highly coiled ∴ allow urea to diffuse out into the dialysis fluid. ∴ More urea can diffuse out in a given time. tubing to ↑ surface area: volume ratio,
  16. 16. Dialysis machine has the following properties: • dialysis fluid has same osmotic concentration as blood plasma ∴No net movements of useful components of blood plasma Fresh dialysis fluid in Used dialysis fluid out • continual flow of dialysis fluid in and out of machine ∴maintains diffusion gradient of urea between blood and dialysis fluid. tubing
  17. 17. http://www.clevelandclinic.org/nephrology/patient/dialysis.htm
  18. 18. Metabolic excretory product Excretory organ Excreted as Carbon dioxide Urea Excess water Bile pigments Lungs Gas in expired air Kidneys Constituent in urine Kidneys Constituent in urine Liver Constituent in faeces

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