BIOL40C Ch.26 Urinary System

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  1. 4 components of the urinary system
    • 1) kidney (2)
    • 2) ureter (2)
    • 3) bladder (1)
    • 4) urethra (1)
  2. nephrology
    study of the anatomy/physiology/pathology of kidneys
  3. urology
    study of the anatomy/physiology/pathology of male/female urinary systems, and male reproductive system
  4. 8 functions of the urinary system
    • 1) blood ionic composition regulation
    • 2) blood pH regulation
    • 3) blood volume regulation
    • 4) blood pressure regulation
    • 5) blood osmolarity maintenance (300 mOsm/L)
    • 6) hormone production (calcitriol, erythropoietin)
    • 7) blood glucose level regulation
    • 8) excretion on wastes/foreign substances
  5. osmole
    unit of osmotic pressure equivalent to amount of solute substances dissociated in solution to form 1mol of particles
  6. osmolarity
    concentration of a solution in terms of osmoles of solutes per liter of solution
  7. location of kidneys with respect to spinal column
    between T10 and L3
  8. location of kidneys with respect to ribs
    partially protected by 11th & 12th (floating) ribs
  9. Which kidney is higher? Why?
    left, bc of larger size of right liver lobe
  10. kidney dimensions
    4-5in long, 2-3in wide
  11. 3 coverings of the kidney
    • 1) renal capsule (dense irregular CT)
    • 2) adipose capsule
    • 3) renal fascia (dense irregular CT, anchors kidney to peritoneum)
  12. internal components of kidneys
    • 1) renal cortex (outer portion)
    • 2) renal medulla (inner portion)
  13. 3 components of renal cortex
    • 1) cortical zone
    • 2) juxtamedullary zone
    • 3) renal columns (extend into medulla)
  14. renal papillae
    narrower end of renal pyramids facing hilum
  15. Through what vessel does blood enter the kidney?
    renal arteries
  16. Through what vessel does blood enter the glomerulus?
    afferent arterioles
  17. Through what vessel does blood leave the glomerulus?
    efferent arterioles
  18. peritubular capillaries
    • - formed from divided efferent arterioles
    • - surround tubular parts of nephron in cortex
  19. approx number of nephrons present in each kidney
  20. cortical nephrons
    • - renal corpuscles lie in outer portion of renal cortex
    • - short loops of Henle (mostly in cortex)
    • - receive blood from peritubular capillaries
  21. juxtamedullary nephrons
    • - renal corpuscles deep in cortex, close to medulla
    • - long loop of Henle (extends into medulla)
    • - receive blood from peritubular capillaries and vasa recta
  22. proximal
    attached to glomerular capsule
  23. distal
    further away from glomerular capsule
  24. convoluted
    tightly coiled
  25. 3 parts of renal tubule
    • 1) proximal convoluted tubule
    • 2) loop of Henle
    • 3) distal convoluted tubule
  26. 2 major components of a renal corpuscle
    • 1) glomerular (Bowman's) capsule
    • 2) glomerulus
  27. visceral layer of Bowman's capsule
    • -modified squamous epithelial cells (podocytes)
    • -foot-like projections of podocytes wrap around endothelium of glomerular capillaries forming inner wall of capsule
  28. parietal layer of Bowman's capsule
    simple squamous epithelium
  29. epithelial wall in proximal convoluted tubule
    microvilla for increased absorption
  30. epithelial wall in descending loop of Henle
    simple squamous for easy exchange
  31. epithelial wall in ascending loop of Henle
    cuboidal then columnar
  32. macula densa
    crowded epithelial cells in thick ascending loop making contact with afferent arterioles of renal corpuscle
  33. juxtaglomerular apparatus
    macula densa in contact with modified smooth muscle fibers of the arteriole wall
  34. 2 cell types of distal convoluted tubule
    • 1) principal cells
    • 2) intercalated cells
  35. principal cells
    have receptors for ADH and aldosterone
  36. intercalated cells
    role in homeostatic control of blood pH
  37. glomerular filtration
    water and solutes in blood -> glomerular capillaries into glomerular capsule -> renal tubule
  38. tubular reabsorption
    • - return of substances to blood
    • - 99% of water reabsorbed
  39. tubular secretion
    kidney removes substances that are not wanted for disposal in urine
  40. How much water is filtered through the glomerular capsules of both kidneys each day?
  41. NFP
    • - net filtration pressure
    • - total pressure that promotes filtration
  42. GBHP
    • - glomerular blood hydrostatic pressure
    • - amount of fluid formed in all the renal corpuscles of both kidneys each minute
  43. CHP
    capsular hydrostatic pressure
  44. BCOP
    blood colloid osmotic pressure
  45. NFP equation
  46. approx GFR in healthy adults
    • 125mL/min (males)
    • 105mL/min (females)
  47. if GFR too high...
    needed substances may pass out of body too quickly
  48. if GFR too low...
    everything may be reabsorbed, including some waste products
  49. 2 mechanisms of GFR regulation
    • 1) adjusting blood flow into/out of glomerulus
    • 2) altering glomerular surface area available for filtration
  50. 2 mechanisms of renal autoregulation
    • 1) myogenic mechanisms
    • 2) tubuloglomerular feedback
  51. myogenic mechanism
    stretch in walls of afferent arterioles causes smooth muscle to respond by contracting or relaxing
  52. tubuloglomerular feedback
    macula densa provides feedback to glomerulus

    leads to decreased NO secretion (stops vasodilation) if there is an increase in blood flow
  53. paracellular reabsorption
    between adjacent tubules
  54. transcellular reabsorption
    through an individual tubular cell

    substance has 2 membranes to cross
  55. apical membrane
    side in contact with tubular fluid
  56. basolateral membrane
    side in contact with interstitial fluid
  57. 2 major hormones in regulation of electrolyte balance
    • 1) angiotensin II
    • 2) atrial natriuretic hormone (inhibits reabsorption)
  58. major hormone in regulation of water reabsorption
    antidiuretic hormone
  59. flow of urine from the collecting duct
    • 1) collecting duct
    • 2) papillary duct in renal pyramid
    • 3) minor calyx
    • 4) major calyx
    • 5) renal pelvis
    • 6) ureter
    • 7) urinary bladder
    • 8) urethra
  60. epithelium of parietal layer of glomerular capsule
    simple squamous
  61. epithelium of visceral layer of glomerular capsule
    modified simple squamous epithelial cells - podocytes
  62. fluid in capsular space
    glomerular filtrate
  63. filtration fraction
    fraction of blood plasma in the afferent arterioles of the kidneys that becomes glomerular filtrate
  64. typical filtration fraction in a healthy individual
  65. components of the filtration membrane
    • 1) endothelial cells of glomerular capillaries
    • 2) podocytes
  66. How do glomerular endothelial cells differ?
    • leaky
    • have fenestrations that measure .07-.1um in diameter
  67. mesangial cells
    • contractile cells that help regulate glomerular filtration
    • located amound glomerular capillaries and in the cleft between afferent and efferent arterioles
  68. function of basal lamina in glomerulus
    prevents filtration of larger plasma proteins
  69. tissue makeup of basal lamina
    • collagen and proteoglycans in a glycoprotein matrix
    • acellular
  70. pedicels
    • footlike processes of podocytes
    • wrap around glomerular capillaries
  71. filtration slits
    • spaces between pedicels
    • permits passage of molecules smaller than .006-.007 (water, glucose, vitamins, amino acids, very small plasma proteins, ammonia, urea, ions)
  72. How do mesangial cells contribute to the ability of the glomerular capillaries to filter large volumes of liquid?
    they regulate how much of the glomerular capillary surface area is available for filtration by contraction/relaxation
  73. Why are glomerular endothelial cells leaky?
    permits all solutes in blood plasma to exit glomerular capillaries, but prevents filtration of blood cells and platelets
  74. How much more leaky are glomerular endothelial cells?
  75. What makes the glomerular blood pressure higher than mean arterial pressure?
    the efferent arteriole is smaller in diameter than the afferent arteriole, so resistance to the outflow of blood from the glomerulus is high
  76. Is GFR increased or decreased by sympathetic NS activation?
    • decreases
    • vasoconstriction of the afferent arterioles predominates -> blood flow into glomerular capillaries is decreased
  77. What NT is released by sympathetic ANS fibers supplying the kidney?
  78. What receptors are activated in the kidney by norepinephrine?
    • Image Upload 11 receptors
    • plentiful in smooth muscle fibers of afferent arterioles
  79. ANP
    • atrial natriuretic peptide
    • secreted by cells in the atria of the heart
  80. How does ANP influence GFR?
    blood volume increases -> atria stretch -> secrete ANP -> relaxation of glomerular mesangial cells -> increase capillary surface area available for filtration -> GFR rises
  81. angiotensin II
    • vasoconstrictor that narrows both afferent and efferent arterioles
    • reduces renal blood flow
    • decreases GFR when blood volume and blood pressure decrease
    • enhances reabsorption of Na+, Cl-, and water in PCT
  82. How is glucose transported out of the PCT?
    • enters cell by Na+/glucose symporter (2 Na+, 1 glucose)
    • leaves cell by facilitated diffusion
  83. How are sodium ions transported out of the PCT?
    • enters cell by Na+ symporters
    • leaves cell by active transport
  84. urinalysis
    evaluation of the volume and physical, chemical, and microscopic properties of urine
  85. specific gravity
    ratio of the weight of a substance to the weight of an equal volume of water
  86. What causes the color in urine?
    bile breakdown products (urochrome)
  87. normal pH range of urine
  88. effect of high protein diet on urine pH
    more acidic
  89. effect of vegetarian diet on urine pH
    more alkaline
  90. BUN
    • blood urea nitrogen test
    • measures blood nitrogen that is part of urea
  91. plasma creatinine
    • urine test
    • creatinine occurs in plasma from breakdown of creatine phosphate in skeletal muscle
    • high values indicate poor renal function
  92. renal plasma clearance
    volume of blood that is cleared of a particular substance each minute in mL/min
  93. 3 factors renal plasma clearance is dependent on
    • 1) glomerular filtration
    • 2) tubular reabsorption
    • 3) tubular secretion
  94. dialysis
    artificial cleansing of blood when kidneys fail
  95. hemodialysis
    • directly filters the blood and then returns cleansed blood
    • uses an artificial membrane in a machine (hemodialyzer)
  96. peritoneal dialysis
    uses the peritoneal membrane of the abdominal cavity as the dialysis membrane
  97. urinary tract infection
    any infection of part of the urinary system resulting in microbes in the urine
  98. glomerulonephritis
    • inflammation of the kidneys that involves the glomerulus
    • glomeruli become swollen and fail as a filtration membrane
    • often caused by allergy to toxins produced by streptococcal bacteria
  99. acute renal failure
    • glomerular filtration abruptly stops working
    • common in major trauma/blood loss
    • may be reversible
  100. chronic renal failure
    • progressive decrease/cessation of glomerular filtration
    • irreversible
  101. polycystic kidney disease
    • kidney tubules become full of cysts
    • non-cystic tubules die by apoptosis
    • inherited disorder
  102. diabetic kidney disease
    • diabetics often suffer glomerular damage
    • proteins leak into urine
  103. azotemia
    presence of urea/other nitrogen-containing substances in blood
  104. dysuria
    painful urination
  105. polyuria
    excessive urination
  106. uremia
    toxic levels of urea in blood
  107. urinary retention
    failure to urinate
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BIOL40C Ch.26 Urinary System
Urinary System
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