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EXCRETORY SYSTEM

EXCRETORY SYSTEM. Function. Disposes of wastes & excess ions Regulates volume & chemical makeup of blood by maintaining proper balance between water & salts, acids & bases. UREA. Produces renin to regulate blood pressure & kidney function

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EXCRETORY SYSTEM

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  1. EXCRETORY SYSTEM

  2. Function • Disposes of wastes & excess ions • Regulates volume & chemical makeup of blood by maintaining proper balance between water & salts, acids & bases UREA

  3. Produces renin to regulate blood pressure & kidney function • Produces erythropoietin to stimulate RBC production in bone marrow • Metabolizes vitamin D to its active form

  4. Organs • Kidneys • Ureters • Urinary Bladder • Urethra

  5. Anatomy of Kidney • Bean-shaped • Located between 12th thoracic vertebra and 3rd lumbar vertebra (partial protection) • Rt. kidney lies lower than left • Concave cleft on medial surface called- hilus which leads to the renalsinus

  6. Adrenal Glands lie on top of each kidney

  7. External anatomy • surrounded by renal capsule (protects from surrounding infection and trauma), • adipose capsule (holds kidneys in place and protects from trauma), • renal fascia (anchors).

  8. Internal anatomy • renal cortex - outer region • renal medulla - inner region with cone shaped renal pyramids • renal columns separate pyramids • renal pelvis - continuous with the ureter leaving the hilus • major and minor calyces

  9. Renal column Renal pyramid Renal calyx

  10. Blood and Nerve Supply • renal arteries - deliver 1/4 total cardiac output to kidneys per minute • lobar arteries • interlobar arteries • arcuate arteries • Interlobular arteries

  11. Nephron (this is where the action is!) • Interlobar, Interlobular, Arcuate, Lobar, Renal veins • Renal Plexus – sympathetic nerve fibers

  12. Nephron • over 1 million/ kidney; filtering unit of kidney; results in production of urine

  13. renal corpuscle - consisting of glomerulus, Bowman's capsule • proximal convoluted tubule (PCT) • loop of Henle

  14. distal convoluted tubule (DCT) • collecting tubule (urine collecting duct) • papillary ducts (collection of all collecting tubules)

  15. Nephron

  16. Bowman’s Capsule • PCT • DCT • Loop of Henle • Collecting Tubule • Renal artery

  17. 7. Renal vein 8. Interlobular artery 9. Afferent artery 10. Glomerulus 11. Efferent artery 12. Peritubule capillaries

  18. Kidney Physiology • 3 Steps involved in kidney filtration • Glomerular Filtration • Passive • Mechanical

  19. based on hydrostatic pressure • enhanced by permeability of filtration membrane • filtration membrane consists of 3 layers

  20. porous endothelium - prevents passage of cells & large proteins • thin basement membrane– charged to repel charged proteins

  21. visceral membrane with slit-like openings; prevents passage of large plasma proteins • Net Filtration Pressure– Glomerular hydrostatic pressure + Bowman's hydrostatic pressure (opposing forces)

  22. Filtration Rate: rate at which fluid is forced from blood into Bowman's capsule; dependent upon: - surface area - filtration membrane permeability - Net filtration pressure

  23. Glomerular filtration rate • is proportional to Net filtration pressure • anything changing pressure at the membrane also changes the GFR, therefore higher blood pressure = higher GFR; dehydration = lower GFR

  24. Tubular Reabsorption - reclamation of tubule contents • difference b/t filtrate & urine • filtrate - everything in blood plasma except proteins & cells • urine - wastes & unneeded substances

  25. reclamation begins in PCT (both active/passive transport) • active - glucose; a.a., vit, Na, Ca, Cl, K, P,; most require a carrier molecule. When all carrier molecules are bound, excess are excreted into urine

  26. passive - (diffusion, osmosis) • usually tied to active transport of Na • other anions move with Na to balance charges in the blood. • The anions that move depend on the blood pH • H2O moves passively (osmosis) due to its linkage to Na+

  27. solvent drag occurs when filtrate becomes concentrated & solvent follows the concentration gradient back into the body • Explains why some drugs & toxins are not excreted easily

  28. Nonreabsorbed substances • Urea (40% reabsorbed) • Creatine • uric acid • Tubule absorption capabilities • PCT most reabsorption occurs here Uric Acid

  29. DCT • permeable to Na but not H2O • urine concentration determined here • dependent on blood pressure or volume • dependent on hormone release:

  30. aldosterone - increases Na reabsorption & therefore H2O • ANF - opposes this • sex hormones • glucocorticoids

  31. Tubular Secretion– Reabsorption in reverse • ammonia (secreted into the collecting tubule from the blood) • Active process • Some drugs (penicillin)

  32. Pathology • Suppression- holding back • Pyuria- tract infection • Ptosis (hydronephrosis)- kinked ureter • Pyelonephritis– kidney inflammation

  33. Pyelitis- inflammation of pelvis • Anuria- no output due to low pressure • Urethritis- inflammation of urethra • Cystitis- inflammation of bladder

  34. Dysuria- painful urination • Incontinence- sphincter control • Retention- involuntary suppression • Diabetes insipidus– lack of ADH • Addison's Disease– not enough aldosterone • Excess Cl– indicate stone formation

  35. Excess phosphates- alkaline urine • Cushing's Disease - hyperaldosteronism • Dehydration– low GFR • Hypotonic hydration–“water intoxication”; Hyponatremia, too much ADH • Renal calculi– kidney stones

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