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5094 excretion 2014


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Sec 4 Excretion

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5094 excretion 2014

  1. 1. Prepared by, Ms Wong Fui Yen Chapter 11 Excretion
  2. 2. Prepared by, Ms Wong Fui Yen Learning Objectives: (a) define excretion and explain the importance of removing nitrogenous and other compounds from the body (b) outline the function of kidney tubules with reference to ultra- filtration and selective reabsorption in the production of urine (c) outline the role of anti-diuretic hormone (ADH) in the regulation of osmotic concentration (d) outline the mechanism of dialysis in the case of kidney failure
  3. 3. Prepared by, Ms Wong Fui Yen Excretion is the removal of toxic materials and the waste products of metabolism from the body. Egestion is the removal of undigested food matter which have never been involved in the metabolic activities of cells, from the alimentary canal. Faeces is NOT a product of metabolism!
  4. 4. Prepared by, Ms Wong Fui Yen Metabolic Waste Products: Excretory product Organ Mode of excretion Carbon dioxide Lungs Exhalation Urea and excess mineral salts Kidneys Skin Urine Sweat Excess water Kidneys Skin Lungs Urine Sweat Expired Air Bile pigments (from breakdown of haemoglobin) Liver Faeces
  5. 5. Prepared by, Ms Wong Fui Yen Excretory Organs in Man Lungs: CO2, water vapour Kidneys: excess water, excess salt, Nitrogenous waste products (urea) Liver: Bile pigmentsSkin: Urea, excess water, excess salt
  6. 6. Prepared by, Ms Wong Fui Yen Ureter: thin tube carries urine from kidneys to bladder Urinary bladder: elastic, muscular bag to store urine temporarily. Sphincter muscle voluntarily relaxes to release urine from bladder Urethra: passage of urine out of body. The Urinary System
  7. 7. Prepared by, Ms Wong Fui Yen
  8. 8. Prepared by, Ms Wong Fui Yen Blood reaches the kidney via the renal artery, which branches into arterioles Blood from each arteriole flows into a network of capillaries (glomerulus) in the Bowman's capsule Blood leaving the glomerulus flows through the capillaries that run along the kidney tubules Blood from the capillaries enter the venules, which lead to the renal vein
  9. 9. Blood vessels Renal artery Renal vein Ureter
  10. 10. Nephron- smallest unit of kidney Prepared by, Ms Wong Fui Yen
  11. 11. Urine formation Prepared by, Ms Wong Fui Yen •Nitrogeneous wastes and excess mineral salts are removed from the body via the urine •The renal artery carries oxygenated blood, nutrients, and wastes to the kidney while the renal vein carries filtered blood away from the kidney. •The pathway of blood flow in the kidney is shown below:
  12. 12. Prepared by, Ms Wong Fui Yen Urine Formation Two stages: 1. Ultrafiltration 2. Selective Reabsorption 1. Ultrafiltration: • Occurs in the Renal/Bowman's capsule. • Blood enters kidney via the renal artery • Renal artery divides to form a mass of arterioles, and then capillaries which form a knot (glomerulus) in the Bowman’s capsule • Afferent arteriole leading into the glomerulus is wider than the efferent arteriole that leads out, so creates a high blood pressure
  13. 13. Prepared by, Ms Wong Fui Yen Urine Formation •This pressure forces plasma containing small molecules to be filtered out of the blood. • Red and white blood cells, large plasma proteins remain in the blood capillaries and continue into the proximal convoluted tubule. •Glomerular filtrate: liquid that is filtered out contains  glucose,  amino acids,  mineral salts,  excess water  nitrogenous waste (urea).
  14. 14. Prepared by, Ms Wong Fui Yen 2. Selective re-absorption: Starts at the proximal convoluted tubule. This is the longest and widest part of the nephron. Over 80% of the filtrate is reabsorbed into the blood. Filtrate flows down the nephron, all useful materials are reabsorbed back into network of capillaries. Examples such as glucose, amino acids, salts, water are reabsorbed. Excess water and salts, and metabolic waste products pass from the tubules into the collecting ducts and then into the renal pelvis as urine. Urine Formation
  15. 15. Prepared by, Ms Wong Fui Yen Loop of Henle: mainly water (by osmosis). Distal tubule: remaining fluid with more urea, excess useless substances e.g. sodium chloride, uric acid, ammonia, creatinine, water. Collecting duct: Urine collected, passed into renal pelvis, leads to ureter. Urine Formation
  16. 16. Blood containing metabolic waste products from renal artery Renal capsule (i) Ultrafiltration (ii) Selective Reabsorption filtrate Blood capillaries • amino acids • glucose • salts • water • •amino acids • glucose • salts • water • urea Excess water, excess mineral salts and urea removed through urine Purified blood to renal vein
  17. 17. Concentration of fluid in different regions of a nephron, with and without presence of ADHPrepared by, Ms Wong Fui Yen
  18. 18. Prepared by, Ms Wong Fui Yen Proximal convoluted reabsorption Tubule All of the glucose and amino acids and most of the mineral salts( by diffusion and active transport ) Water ( by osmosis) Loop of Henle reabsorption •Water (by osmosis) •Sodium ions ( Na+) (by active transport ) Distal convoluted reabsorption tubule •Water (by osmosis) •Sodium ions (Na+) (by active transport) Collecting tubule reabsorption / duct •Water (by osmosis) Glomerular filtrate
  19. 19. Prepared by, Ms Wong Fui Yen
  20. 20. Osmoregulation Prepared by, Ms Wong Fui Yen •Osmoregulation is the control of water and solute levels in the blood to maintain a constant water potential in the body. •The water potential of blood (concentration of water and salts in the plasma) must be maintained at a relatively constant level. The water content is regulated via hormone vasopressin (also known as anti-diuretic hormone, ADH) •ADH is produced by the hypothalamus in the brain and is released by the pituitary gland •ADH increases water reabsorption of the kidneys by increasing permeability of the distal convoluted tubule and collecting duct to water.
  21. 21. Prepared by, Ms Wong Fui Yen Kidney failure refers to the inability of the kidney to function properly, causing accumulation of nitrogenous waste in the blood. Kidney failure may be caused of the following: a) Diabetes b) Hypertension c) Excessive alcohol intake d) Severe injury or bacterial infection When both kidneys fail to function, the person will need to get a kidney transplant, or undergo kidney dialysis to get rid of wastes from patient’s blood. Kidney Failure & Dialysis
  22. 22. Prepared by, Ms Wong Fui Yen Kidney Dialysis Machine
  23. 23. Prepared by, Ms Wong Fui Yen Larger molecules (e.g. plates and blood cells) remain in the tubing The filtered blood is returned to a vein in the patient’s arm artery dialysis tubing pump filtered blood fresh dialysis fluid dialysis machine dialysis fluid vein 1 2 3 6 4 5 23 Blood is drawn from an artery in the patient’s arm 1 Blood is pumped through a tubing to the dialysis machine 2 The tubing is bathed in a special dialysis fluid and the tubing is semi-permeable. 3 Small molecules (e.g. urea) and metabolic waste products diffuse out of the tubing 45 6
  24. 24. Prepared by, Ms Wong Fui Yen
  25. 25. Prepared by, Ms Wong Fui Yen How does the kidney dialysis machine work? 1. Patient’s blood is drawn from the artery and allow to flow through the tubing in the dialysis machine. 2. Tubing which represents the partially permeable membrane is bathed in a specially controlled dialysis fluid. They only allow small molecules, like urea and other waste products, to diffuse out of the tubing.
  26. 26. Prepared by, Ms Wong Fui Yen 3. The direction of blood flow is opposite to the flow of the dialysis fluid. 4. A concentration gradient is set up to allow diffusion of waste products from patient’s blood to the dialysis fluid. 5. The filtered blood is then returned to the patient’s arm vein.
  27. 27. Prepared by, Ms Wong Fui Yen Comparing the Blood Composition & Dialysis Fluid Partially permeable membrane of tubing
  28. 28. Resources Online: The Urinary System: roVY&feature=related Kidney Dialysis: Prepared by, Ms Wong Fui Yen
  29. 29. Prepared by, Ms Wong Fui Yen • Factors affecting composition of urine •Diet: - Protein rich diet more urea being formed as proteins are deaminated in the liver - More water intake more urine formed -Salty foods more salt secreted in urine •Diseases: -Diabetes: Glucose in urea -Kidney Stone: glomerulus becomes fully permeable  Red blood cells able to pass through membrane, hence RBC found in urine -Infection of kidney: White blood cells in urine •Lifestyle: -More exercise less water left in the body less water secreted in urine •Climate: -Cold weather  sweat less  more water left in the body  urine more water
  30. 30. Prepared by, Ms Wong Fui Yen Why you shouldn’t drink the salty sea water? •Drinking sea water will increase the concentration of dissolved mineral salts in the blood, hence causing water to diffuse from all the body cells into the bloodstream. •This causes the cells to shrink and malfunction.