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Introduction to excretory system

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Introduction to excretory system

  1. 1. INTRODUCTION TO EXCRETORY SYSTEM Dr.U.Rathnakumari MBBS., MD Physiology I yr PG
  2. 2. Gross Anatomy of the Kidney
  3. 3. Major Functions of the Kidneys <ul><li>1. Regulation of HOMEOSTASIS: </li></ul><ul><li>body fluid osmolarity and volume </li></ul><ul><li>electrolyte balance </li></ul><ul><li>acid-base balance </li></ul><ul><li>blood pressure </li></ul><ul><li>2. EXCRETION of </li></ul><ul><li>metabolic products </li></ul><ul><li>toxic substances (drugs,pesticides, etc.) </li></ul><ul><li>excess substance (water, etc) </li></ul>
  4. 4. <ul><li>3. SECRETION of : </li></ul><ul><li>Erythropoietin </li></ul><ul><li>1,25-dihydroxy cholecalciferol </li></ul><ul><li>vitamin D3 (vitamin D activation) </li></ul><ul><li>Renin </li></ul><ul><li>prostaglandin </li></ul>
  5. 5. Physiological Anatomy of the Kidney
  6. 6. Nephron <ul><li>The functional unit of the kidney </li></ul><ul><li>Each kidney is made up of about 1 million nephrons </li></ul><ul><li>Each nephron has two major components: </li></ul><ul><li>A glomerulus ( a tuft of capillaries ) </li></ul><ul><li>A long tube (tubule) </li></ul>
  7. 10. The juxtaglomerular apparatus
  8. 11. <ul><li>Where the distal tubule lies against the afferent (sometimes efferent) arteriole </li></ul><ul><li>Arteriole walls have juxtaglomerular (JG) cells </li></ul><ul><ul><li>Enlarged, smooth muscle cells </li></ul></ul><ul><ul><li>Have secretory granules containing RENIN </li></ul></ul><ul><ul><li>Act as mechanoreceptors </li></ul></ul>
  9. 12. <ul><li>Macula densa </li></ul><ul><ul><li>Tall, closely packed distal tubule cells </li></ul></ul><ul><ul><li>Lie adjacent to JG cells </li></ul></ul><ul><ul><li>Function as chemoreceptors or osmoreceptors </li></ul></ul><ul><li>Mesanglial cells: </li></ul><ul><ul><li>Have phagocytic and contractile properties </li></ul></ul><ul><ul><li>Influence capillary filtration </li></ul></ul>
  10. 14. Renin Angiotensin system
  11. 15. Renal Tubule <ul><li>Proximal convoluted tubule (PCT) </li></ul><ul><li>cuboidal cells with numerous microvilli and mitochondria </li></ul><ul><li>Reabsorbs water and solutes from filtrate and secretes substances into it </li></ul><ul><li>Loop of Henle – a hairpin-shaped loop of the renal tubule </li></ul><ul><ul><li>Proximal part is similar to the proximal convoluted tubule </li></ul></ul><ul><ul><li>followed by the thin segment (simple squamous cells) and the thick segment (cuboidal to columnar cells) </li></ul></ul>
  12. 17. <ul><li>Distal convoluted tubule (DCT) </li></ul><ul><li>cuboidal cells without microvilli that function more in secretion than reabsorption </li></ul><ul><li>Collecting Tubules </li></ul><ul><li>Two important cell types are found here </li></ul><ul><ul><li>Intercalated cells </li></ul></ul><ul><ul><ul><li>Cuboidal cells with microvilli </li></ul></ul></ul><ul><ul><ul><li>Maintainin acid-base balance of the body </li></ul></ul></ul><ul><ul><li>Principal cells </li></ul></ul><ul><ul><ul><li>Cuboidal cells without microvilli </li></ul></ul></ul><ul><ul><ul><li>maintain the body’s water and salt balance </li></ul></ul></ul>
  13. 18. Types of nephrons <ul><li>Cortical nephrons – 85% of nephrons; located in the cortex </li></ul><ul><li>Juxtamedullary nephrons: </li></ul><ul><ul><li>Are located at the cortex-medulla junction </li></ul></ul><ul><ul><li>Have loops of Henle that deeply invade the medulla </li></ul></ul><ul><ul><li>Have extensive thin segments </li></ul></ul><ul><ul><li>Are involved in the production of concentrated urine </li></ul></ul>
  14. 20. renal blood flow
  15. 21. Characteristics of renal blood flow <ul><li>high blood flow . </li></ul><ul><li>1200 ml/min, or 21 percent of the cardiac output. </li></ul><ul><li>94% to the cortex </li></ul><ul><li>Two capillary beds </li></ul><ul><li>High hydrostatic pressure in glomerular capillary (about 60 mmHg) and low hydrostatic pressure in peritubular capillaries (about 13 mmHg) </li></ul>
  16. 22. Capillary Beds <ul><li>Vasa recta – long, straight efferent arterioles of juxtamedullary nephrons </li></ul>
  17. 23. Functions of the Nephron <ul><ul><ul><ul><li>Filtration </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Reabsorbtion </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Secretion </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Excretion </li></ul></ul></ul></ul>
  18. 24. Glomerular filtration <ul><li>First step in urine formation </li></ul><ul><ul><li>Bulk transport of fluid from blood to kidney tubule </li></ul></ul><ul><ul><ul><li>Isosmotic filtrate </li></ul></ul></ul><ul><ul><ul><li>Blood cells and proteins don’t filter </li></ul></ul></ul><ul><ul><li>Result of hydrostatic pressure </li></ul></ul><ul><ul><li>GFR = 180 L/day </li></ul></ul>
  19. 25. filtration membrane
  20. 26. filtration membrane <ul><li>Filter that lies between the blood and the interior of the glomerular capsule </li></ul><ul><li>It is composed of three layers </li></ul><ul><ul><li>Fenestrated endothelium of the glomerular capillaries </li></ul></ul><ul><ul><li>Visceral membrane of the glomerular capsule (podocytes) </li></ul></ul><ul><ul><li>Basement membrane composed of fused basal laminae of the other layers </li></ul></ul>
  21. 27. filtration membrane
  22. 28. Glomerular filtration rate (GFR) <ul><li>Amount of filtrate produced in the kidneys each minute. 125mL/min = 180L/day </li></ul><ul><li>Factors that alter filtration pressure change GFR. These include: </li></ul><ul><ul><li>Increased renal blood flow -- Increased GFR </li></ul></ul><ul><ul><li>Decreased plasma protein -- Increased GFR. Causes edema. </li></ul></ul><ul><ul><li>Hemorrhage -- Decreased capillary BP -- Decreased GFR </li></ul></ul>
  23. 29. Tubular Reabsorbtion <ul><ul><li>Process of returning filtered material to bloodstream </li></ul></ul><ul><ul><li>99% of what is filtered </li></ul></ul><ul><ul><li>May involve transport protein(s) </li></ul></ul><ul><ul><li>Normally glucose is totally reabsorbed </li></ul></ul>
  24. 30. Tubular Secretion <ul><ul><li>Material added to lumen of kidney from blood </li></ul></ul><ul><ul><li>Active transport (usually) of toxins and foreign substances, drugs etc </li></ul></ul><ul><ul><ul><li>Saccharine </li></ul></ul></ul><ul><ul><ul><li>Penicillin </li></ul></ul></ul>
  25. 31. Mechanisms of Urine Formation <ul><li>involves three major processes </li></ul><ul><ul><li>Glomerular filtration </li></ul></ul><ul><ul><li>Tubular reabsorption </li></ul></ul><ul><ul><li>Secretion </li></ul></ul>
  26. 32. QUESTIONS
  27. 33. <ul><li>What are the parts of the excretory system? </li></ul>
  28. 34. <ul><li>2 . name the functions of the kidneys. </li></ul>
  29. 35. <ul><li>3.How is the kidney related to hematopoiesis? </li></ul>
  30. 36. <ul><li>4.How does the kidney regulate blood calcium level? </li></ul>
  31. 37. <ul><li>5.What is the total no .of nephrons in the human body? </li></ul>
  32. 38. <ul><li>6.What are the types of nephrons you know? </li></ul>
  33. 39. <ul><li>7.What is a renal corpuscle? </li></ul><ul><li>name its parts. </li></ul>
  34. 40. <ul><li>8.Describe the epithelium of PCT. </li></ul>
  35. 41. <ul><li>9.Name the parts of JGA- The juxtaglomerular apparatus. </li></ul>
  36. 42. <ul><li>10.Define GFR. what is its normal value? </li></ul>
  37. 43. <ul><li>11.What is the normal volume of urine excreted in one day? </li></ul>
  38. 44. <ul><li>what is ‘POLKISSEN’? </li></ul>

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