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  2. 2. Human Urinary System kidney ureter urinary bladder urethra
  3. 3. Human Urinary System aorta renal artery ureters urinary bladder left kidney renal vein right kidney sphincter muscle urethra inferior vena cava
  4. 4. Structure of Mammalian Kidney <ul><li>made up of three parts: - cortex - a light outer region </li></ul><ul><li>- medulla - a dark inner region </li></ul><ul><li>- pelvis - a whitish central region leads to ureter </li></ul><ul><li>contains numerous tiny tubules called nephrons </li></ul>
  5. 5. Structure of Mammalian Kidney cortex medulla renal artery renal vein ureter pelvis nephron
  6. 6. Structure of Nephron Bowman’s capsule (with glomerulus) afferent arteriole efferent arteriole loop of Henle collecting duct first & second convolution venule
  7. 7. Nephron renal artery renal vein proximal convoluted tubule (first convolution) capillaries around nephron Loop of Henle afferent arteriole glomerulus efferent arteriole collecting duct distal convoluted tubule (second convolution)
  8. 8. How does a nephron work ? By two ways, one is ultrafiltration and the other is reabsorption
  9. 9. Ultrafiltration <ul><li>diameter of tiny artery leading to the glomerulus is larger than the one leaving, so a pressure is set up as blood tries to force its way out of the smaller tube </li></ul><ul><li>the high hydrostatic pressure forces small molecules through the walls of capillaries and Bowman’s capsule into the capsular space </li></ul>
  10. 10. <ul><li>fluid which filtered into the nephron is called glomerular filtrate </li></ul><ul><li>glomerular filtrate has the same composition as that of blood except that it does not contain blood cells, blood proteins & blood platelets </li></ul>
  11. 11. Reabsorption <ul><li>reabsorption is the process of absorbing useful substances into capillaries which wrapped around tubule </li></ul><ul><li>as in glomerular filtrate, some substances like glucose and amino acid are useful to human so they are absorbed back while fluid travels along the tubule </li></ul>
  12. 12. <ul><li>those urea which remains in the fluid pass the whole nephron and finally drains into collecting duct which leads to pelvis and form urine </li></ul><ul><li>urine contains mostly water, with urea and excess mineral salts </li></ul>
  13. 13. <ul><li>reabsorption of all the glucose and amino acids and some salts begins in the first convolution and finished when the fluid reaches loop of Henle </li></ul>
  14. 14. <ul><li>useful substances are reabsorbed by diffusion down the concentration gradient and active transport against concentration gradient </li></ul><ul><li>in collecting duct, water is mainly reabsorbed by osmosis but the first convolution actually reabsorbs the largest amount of water </li></ul>
  15. 15. Functions of Kidney <ul><li>kidney mainly has three functions: </li></ul><ul><li>osmoregulation </li></ul><ul><li>removal of excess salt </li></ul><ul><li>excretion </li></ul>
  16. 16. Functions of Kidney - Osmoregulation drink a lot of water Amount of water in blood: CONSTANT blood becomes diluted dilute urine is formed small proportion of water is reabsorbed
  17. 17. after sweating Amount of water in blood: CONSTANT Functions of Kidney - Osmoregulation blood becomes concentrated large proportion of water is reabsorbed concentrated urine is formed
  18. 18. Functions of Kidney - Removal of Excess Salt after eating a salty meal salt enters blood, concentration of salt in blood increases volume of urine increases concentration of urine is higher man feels thirsty drink water
  19. 19. Functions of Kidney - Excretion <ul><li>amino acids are broken down in liver to form urea by deamination </li></ul><ul><li>Urea is carried by blood to the kidneys which excrete them from the body in the form of urine </li></ul>
  20. 20. Kidney Failure and Artificial Kidney <ul><li>some kidney diseases can lead to kidney failure and the kidneys can no longer function properly </li></ul><ul><li>toxic substances will accumulate in blood and patient will die </li></ul>
  21. 21. KIDNEY FAILURE <ul><li>Caused by </li></ul><ul><li>Bacterial infection </li></ul><ul><li>External mechanical damage </li></ul><ul><li>High blood pressure </li></ul>
  22. 22. Air trap Air trap pump Dialysis fluid in Dialysis fluid out ‘ Blood carrying waste ‘ clean’ blood
  23. 23. <ul><li>artificial kidney is a bulky machine attached to patient which is used to filter and clean patient’s blood </li></ul><ul><li>artificial kidney make use of the principle of dialysis. It has a filter made of cellophane which acts as a selectively permeable membrane </li></ul>
  24. 24. <ul><li>along one side of the membrane is the patient’s blood while the other side is dialysis fluid which has the same contain as plasma except urea </li></ul><ul><li>only urea diffuses from patient’s blood into dialysis fluid through cellophane filter </li></ul><ul><li>blood without urea will return to patient through his vein </li></ul>
  25. 25. <ul><li>dialysis fluid flows in direction opposite to that of blood flow to increase the efficiency of diffusion of urea into dialysis fluid </li></ul><ul><li>other than using artificial kidney, kidney transplant is another possible method but only few people are willing to donate their kidneys after death </li></ul>
  27. 28. ~ End ~