ch25

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Author:
swasdo
ID:
277083
Filename:
ch25
Updated:
2014-06-17 22:44:44
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bio242
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Description:
urinary system
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  1. kidney functions
    • regulating total water volume and total solute concentration in water
    • regulating ECF ion concentrations
    • ensuring long term acid base balance
    • removal of matabolic wastes, toxins, drugs
  2. kidney endocrine functions
    • renin: regualtion of blood pressure
    • erythropoietin: regulation of rBC production
    • acitvation of vitamin D
    • gluconeogensis druing prolonged fasting
  3. urinary system organs
    • kidneys
    • ureters
    • urinary bladder
    • urethra
  4. layers of surrounding supportive tissue of kidneys
    • renal fascia: anchoring outer layer of dense fibrous connective tissue
    • perirenal fat capsule: fatty cushion
    • fibrous capsule: prevents spread of infection to kidney
  5. renal cortex of kidney
    grandular appearing superficial region
  6. renal medulla of kidney
    • composed of cone shaped medullary pyramids
    • pyramids separated by renal columns
  7. papilla
    tip of pyramid; releases urine into minor calyx
  8. lobe of kidney
    • medullary pyramid and its surrounding cortical tissue
    • 8 per kidney
  9. renal pelvis
    funnel shaped tube continuous with ureter
  10. minor calyces
    drains pyramids at papillae
  11. major calyces
    • collect urine from minor calyces
    • empty urine into renal pelvis
  12. nephrons
    • structural and functional units that form urine
    • more than 1 million per kidney
    • two main parts: renal copuscle and renal tubule
  13. two parts of the renal copruscle
    • glomerulus: tuft of capillaries; allows filtrate formation
    • bowman's capsule: cup shaped hollow structure surrounding glomerulus
  14. bowman's capsule
    parietal layer: simple squamousvisceral layer: branching epithelial podocytes
  15. three parts of the renal tubule
    • prixmal convoluted tubule
    • nephron loop (loop of henle)
    • distal convoluted tubule
  16. proximal convoluted tubule
    • cuboidal cells with dense microvillie to increase surface area
    • functions in reabsorption and secretion
    • confined to cortex
  17. nephron loop
    • descending and ascending limbs
    • descending: simple squamous epithelium
    • ascending limb: cuboidal to columnar cells
  18. distal convoluted tubule
    • cuboidal cells with very few microvilli
    • function more in secretion than reabsorption
    • confined to cortex
  19. two types of cells of the collecting ducts
    principle and intercalated cells
  20. principle cells
    • sparse, short microvilli
    • maintain water and Na+ balance
  21. intercalated cells
    • cuboidal cells
    • abundant microvilli
    • 2 types; a and B; both maintain acid base balance of blood
  22. collecting ducts
    • reeive filtrate from many nephrons
    • run through medullary pyramids
    • fuse together to deliver urine through papillae into minor calyces
  23. classes of nephrons
    cortical nephrons and juxtamedullary nephrons
  24. cortical nephrons
    • 85% of nephrons
    • almost entirely in cortex
  25. juxtamedullary nephrons
    • long nephron loops deeply invade medulla
    • ascending limbs have thick and thin segments
    • important in production of concentrated urine
  26. is blood pressure in glomerulus high or low
    • high because afferent artieroles are larger in diamter than efferent artierioles
    • arterioles are high resistance vessels
  27. how is the glomerulus drained
    afferent arteriole > glomerulus > efferent arteriole
  28. peritubular capillaries
    • low pressure, porous capillaries adapted for absorption of water and solutes
    • arise form efferent arterioles
    • cling to adjacent renal tubules in cortex
    • empty into venules
  29. vasa recta
    • long thin walled vessels parallel to long nephron loops of jutamedullary nephrons
    • arise fomr efferent arterioles serving juxtamedullary nephrons
    • function in formation of concentrated urine
  30. JGC
    • juxtaglomerular complex
    • one per nephron
    • involved modified portions of distal portion of ascending limb, and afferent arteriole
    • important in regulation of rate of filtrate formation and blood pressure
  31. what are the three cell populations of the JGC
    • macula dense
    • granular cells
    • extraglomerular mesangial cells
  32. macula densa cells
    • tall, closely packed cells of ascending limb
    • chemoreceptors; sense NaCl content of filtrate
  33. grandular cells or JG cells
    • enlarged, smooth muscle cells of arteriole
    • secretory granules contain enzyme renin
    • mechanoreceptors; sense blood pressure in afferent arteriole
  34. extraglomerular mesangial cells
    • betwen areriole and tubule cells
    • interconnected with gap junctions
    • pass signals between macula densa and granular cells
  35. how many liters of fluid are processed daily
    180; only 1.5 become urine
  36. what are the three processes in urine formation and adjustment of blood composition
    • glomerular filtration
    • tubular reabsorption
    • tubular secretion
  37. golmerular filtration
    produces cell and protein free filtrate
  38. tubular reabsorption
    selectively returns 99% of substances from filtrate to blood in renal tubules and collecting ducts
  39. tubular secretion
    selectively moves substances from blood to filtrate in renal tubules and collecting ducts
  40. urine
    • <1% of original filtrate
    • contains metabolic wastes and unneeded substances
  41. glomerular filtration
    • passive process
    • no metabolic energy required
    • hydrostatic pressure forces fluids and solutes through filtration membrane
    • no reabsorption into capillaries of glomerulus
  42. filtration membrane
    • porous membrane between blood and interior of glomerular capsule.
    • water, solutes smaller than plasma proteins pass, no cells pass
    • has 3 layers
  43. what are the three layers of the filtration membrane
    • fenestrated endothelium
    • basement membrane
    • foot processes of podocytes
  44. proteins in filtrate indicate what
    a membrane problem
  45. pressures that affect filtration
    • outward pressures promote filtrate formation
    • inward forces inhibiting filtrate formation
  46. net filtration pressure
    pressure responsible for filtrate formation
  47. glomerular filtration rate
    • volume of filtrate formed per minute by both kidneys
    • GFR directly proportional to NFP, total surface area available for filtration, and filtration membrane permeability
  48. what are the two types of renal autoregulation
    myogenic mechanism and tubuloglomerular feedback mechanism
  49. what are the two routes of tubular reabsorption
    transcellular and paracellular
  50. transcellular route
    • apical membrane of tubule cells
    • cytosol of tubule cells
    • basolateral mebmranes of tubule cells
    • endothelium of peritubular capillaries
  51. paracellular route
    • between tubule cells
    • limited by tight junctions, but leaky in proximal nephron
  52. tubular reabsorption of sodium
    • Na+ most abundant cation in filtrate
    • transport across basolateral membrane
    • transport across apical membrane
  53. reabsorption of nutrients, water and ions
    • Na+ reabsorption by rpimary active transport provides energy and means for reabsorbing most other substances
    • creates electrical gradient for passive reabsorption of anions
    • organic nutrients reabsorbed by secondary active transport; cotransported with Na+
  54. obligatory water reabsorption
    aquaporins always present in PCT
  55. fcultative water reabsorption
    aquaporins inserted in collecting ducts only if ADH present
  56. PCT
    • site of more reabsorption
    • all nutrients e.g. glucose and amino acids
    • 65% of Na+ and water
    • many ions
    • all uric acid
  57. nephron loop (absorption)
    • descending limb, water can leave, solutes can't
    • ascending limb, water can't leave but solutes can
  58. DCT and collecting ducts
    • reabsorption hormonally regulated
    • ADH-water
    • aldosterone-Na+ (and water)
    • atrial naturetic peptride - Na+
    • PTH-Ca2+
  59. ADH
    • antidiuretic hormone
    • released by posterior pituitary gland
    • causes principal cells of collecting ducts to insert aqauporins in apical membranes for water reabsorption
  60. aldosterone
    • targets collecting ducts and distal DCT
    • promotes synthesis of luminal Na+ and K+ channels and basolateral Na+-K+ ATPases for Na+ reabsorption; water follows
    • functions are to increase blood pressure and decrease K+ levels
  61. ANP
    • atrial natriuretic peptide
    • reduces blood na+ which decreases blood volume and blood pressure
    • released by cardiac atrial cels if blood volume or pressure elevated
  62. osmolality
    • number of solutes particles in 1 kg of H2O
    • reflects ability to cause osmosis
  63. osmolality of body fluids
    • kidneys maintain osmolality of plasma at 300 MOsm by regulating urine concentration and volume
    • kidneys regulate with countercurrent mechanism
  64. countercurrent mechanism
    • occurs when fluid flows in opposite directions in two adjacent segments of same tube with hair pin turn
    • countercurrent multiplier: interaction of filtrate flow in ascending/descneding limbs of nephron loops of juxtamedullary nephrons
    • countercurrent exchanger: blood flow in ascending/descneding limbs of vasa recta
  65. role of countercurrent mechanisms
    • establish and maintain osmotic gradient from renal cortex through medulla
    • allow kidneys to vary urine concentration
  66. descending limb
    • freely permeable to water
    • water passes out of filtrate into hyperosmotic medullary interstitial fluid
    • filtrate osmolality increases to 1200
  67. ascending limb
    • impermeable to water
    • selectively permeable to solutes
    • Na+ and Cl- actively reabsorbed in thick segment, some passively reabsorbed in thin segment
    • filtrate osmolality decreases to 100
  68. countercurrent exchanger
    • vasa recta
    • preserve medullary gradient-prevent rapid removal of salt from interstitial space, remove reabsorbed water
    • water entering ascneding vasa rect either from descending vasa recta or reabsorbed from nephron loop and collecting duct
  69. overhydration
    • large volume dilute urine
    • ADH production decreases
    • if aldosterone present, additional ions are removed
  70. dehydration
    • small volume concentrated urine
    • ADH released
  71. severe dehydration
    99% of water is reabsorbed
  72. urea
    • helps form medullary gradient:
    • enters filtrate in ascending thin limb of nephron loop by facilitated diffusion
    • cortical collectiving duct reabsorbs water and leaves urea
    • in deep medullary region now highly concentrated urea > interstitial fluid of medulla > back to ascending thin limb > high osmolality in medulla
  73. chemicals that enhance urinary ouput
    • ADH inhibitors (e.g. alcohol)
    • Na+ reabsorption inhibitors (caffeine)
    • loop diuretics inhibit medullary gradient formation
    • osmotic diuretics -substance not reabsorbed so water remains in urine
  74. renal clearance
    • volume of palsma kidneys clear of particular substance in given time
    • renal clearance tests used to determine GFR
  75. physical characteristics of urine
    • clear: cloudy may indicate urinary tract infection
    • pale to deep yellow: pigment form hemoglobin breakdown, more concentrated urine>deeper color
    • abnormal color: food ingestion, bile pigment, blood, drugs
  76. odor of urine
    • slightly aromatic when fresh
    • develops ammonia odor upon standing
    • may be altered by some drugs and vegetables
  77. pH of urine
    slightly acidic
  78. normal solutes of urine
    Na+, K+ CA2+, Mg2, HCO3, etc.
  79. what are the three layers of the ureters
    • mucosa: transitional epithelium
    • muscularis: smooth muscle sheets, contracts in response to stretch, propels urine into bladder
    • adventitia: outer fibrous connective tissue
  80. urinary bladder
    • muscular sac for temporary storage of urine
    • retroperitoneal on pelvic floor posterior to pubic symphysis
  81. urethra
    • muscular tube draining urinary bladder
    • lining epithelium: mostly pseudostratified columnar epithelium, except transitional near bladder and stratified squamous near external urethral orifice
  82. sphincters of the urethra
    internal urethral sphincter and external urethral sphincter
  83. internal urethral sphincter
    • involuntary (smooth muscle) at bladder urethra junction
    • contracts to open
  84. external urethral sphincter
    voluntary (skeletal muscle) surrounding ureathra as it passes through pelvic floor
  85. three named regions of male urethra
    • prostatic: within prostate gland
    • intermediate part: passes through urogentical diaphragm from prostate to beginning of penis
    • spongy: passes through penis; opens via external urethral orifice
  86. micturition
    urination
  87. three simultaneous event that occur for urination
    • contraction of detrusor muscle by ANS
    • opening of internal urethral sphincter by ANS
    • opening of external urethral sphincter by somatic nervous system
  88. when do the pontine control centers mature
    between ages 2 and 3

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