Excretory kidney


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Excretory kidney

  1. 1. Excretory System
  2. 2. Outline <ul><li>The Mammalian Kidney </li></ul><ul><li>Transport Processes in Mammalian Nephron </li></ul><ul><li>Ammonia, Urea, and Uric Acid </li></ul><ul><li>Hormones Control Homeostatic Functions </li></ul>
  3. 3. Vertebrate Kidney <ul><li>Kidney is made up of thousands of repeating units ( nephrons ), each with the structure of a bent tube. </li></ul><ul><ul><li>Blood pressure forces the fluid in blood past a filter, glomerulus, at the top of each nephron. </li></ul></ul><ul><ul><ul><li>Water and small molecules pass through filter and into the nephron tube. </li></ul></ul></ul><ul><ul><ul><ul><li>Sugars and ions are removed by active transport. </li></ul></ul></ul></ul>
  4. 4. Vertebrate Nephron Organization
  5. 5. The Mammalian Kidney <ul><li>Each kidney receives blood from a renal artery, and produces urine. </li></ul><ul><ul><li>Urine drains from each kidney through a ureter which carries urine to urinary bladder . </li></ul></ul><ul><ul><li>Within the kidney, mouth of ureter flares to form renal pelvis. </li></ul></ul><ul><ul><ul><li>Divided into renal cortex and renal medulla . </li></ul></ul></ul>
  6. 6. Urinary System of a Human Female
  7. 7. The Mammalian Kidney <ul><li>Nephron structure and function </li></ul><ul><ul><li>Blood is carried by an afferent arteriole to the glomerulus . </li></ul></ul><ul><ul><ul><li>Blood is filtered as it is forced through porous capillary walls. </li></ul></ul></ul><ul><ul><ul><ul><li>Glomerular filtrate enters Bowman’s capsule. </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Moves to the proximal convoluted tubule . </li></ul></ul></ul></ul></ul>
  8. 8. The Mammalian Kidney <ul><li>Fluid then moves down the medulla and back into the cortex in a loop of Henle . </li></ul><ul><ul><li>After leaving the loop, the fluid is delivered to a distal convoluted tubule in the cortex that drains to a collecting duct . </li></ul></ul><ul><ul><ul><li>merges with other collecting ducts to empty its contents into the renal pelvis </li></ul></ul></ul>
  9. 9. Mammalian Kidney Nephron
  10. 10. The Mammalian Kidney <ul><li>Reabsorption and secretion </li></ul><ul><ul><li>Most of the water and dissolved solutes that enter the glomerular filtrate must be returned to the blood. </li></ul></ul><ul><ul><li>Reabsorption of glucose and amino acids, is driven by active transport carriers. </li></ul></ul><ul><ul><li>Secretion of waste products involves transport across capillary membranes and kidney tubules. </li></ul></ul><ul><li>Excretion </li></ul>
  11. 11. Fig. 49.18(TE Art) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Renal tubule Excretion Filtration Reabsorption to blood Secretion from blood Glomerulus Bowman's capsule
  12. 12. Transport Processes in the Mammalian Nephron <ul><li>Some mechanism is needed to create an osmotic gradient between the glomerular filtrate and the blood, allowing reabsorption. </li></ul><ul><li>Proximal convoluted tubule </li></ul><ul><ul><li>Approximately two-thirds of NaCl and water filtered in Bowman’s capsule is immediately reabsorbed across the walls of the proximal convoluted tube. </li></ul></ul>
  13. 13. Transport Processes in the Mammalian Nephron <ul><li>Loop of Henle </li></ul><ul><ul><li>Descending limb is permeable to water, thus water leaves via osmosis. </li></ul></ul><ul><ul><li>Water loss in the descending limb multiples concentration achieved at each loop. </li></ul></ul><ul><ul><li>Ascending limb actively extrudes N + and Cl follows. </li></ul></ul><ul><ul><li>NaCl pumped out of ascending limb is trapped within surrounding interstitial fluid. </li></ul></ul><ul><ul><li>countercurrent multiplier system </li></ul></ul>
  14. 14. Transport Processes in the Mammalian Nephron <ul><li>Distal tubule and collecting duct </li></ul><ul><ul><li>Permeability of the collecting duct to water is adjusted by antidiuretic hormone (ADH - vasopressin ). </li></ul></ul><ul><ul><ul><li>Kidneys also regulate the balance of electrolytes in the blood by reabsorption and secretion. </li></ul></ul></ul>
  15. 15. Reabsorption of Salt and Water
  16. 16. Hormones Control Homeostatic Functions <ul><li>Antidiuretic hormone </li></ul><ul><ul><li>Stimulates reabsorption of water by the kidneys. </li></ul></ul>
  17. 17. Hormones Control Homeostatic Functions <ul><li>Aldosterone </li></ul><ul><ul><li>Promotes reabsorption of NaCl and water across the distal convoluted tubule and the secretion of K + into the tubule. </li></ul></ul><ul><li>Atrial natriuretic hormone </li></ul><ul><ul><li>decreases NaCl reabsorption </li></ul></ul>
  18. 18. Fig. 49.22(TE Art) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Low blood pressure Bowman's capsule Distal convoluted tubule Glomerulus Afferent arteriole Efferent arteriole Loop of Henle Increased NaCl and H 2 O reabsorption Increased blood volume Negative feedback 1 2 8 9 Low blood flow Proximal convoluted tubule Renin Adrenal cortex Angiotensinogen Angiotensin II 3 Juxtaglomerular apparatus Kidney Aldosterone 4 5 6 7