The Urinary System

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The Urinary System

• Chapter 26

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Functions figure 26.1

• ___________-
• Excrete waste in urine
• Regulate blood volume composition (ions, pH)
• Help regulate blood pressure
• Synthesize glucose
• Release erythropoietin
• Participate in vitamin D synthesis
• ___________ transport urine from kidneys to
  urinary bladder
• Urinary bladder stores urine, capacity
  700-800mL
• ____________ discharges urine from the body

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Kidney

• Regulates ___________________ composition
• Na, K, Ca2 , Cl-, and HPO4 2-
• Regulate _______________
• Excrete H
• Conserve HCO3
• Reg. __________________ conserve or elim water
• ? blood volume? ? bp, ? blood vol ? ? bp
• Regulating ___________
• Secrete renin ? ? bp, or adjust blood volume
• Maintaining blood osmolarity- reg water solute
  loss
• Hormones calcitrol (active Vit D),
  ________________________
• Regulate blood glucose- use glutamine in
  gluconeogenesis
• Excreting waste and foreign substances

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Kidney anatomy figure 26.3

• Retroperitoneal
• 3 layers surrounding
• Renal capsule deepest
• Adipose capsule
• Renal fascia superficial, anchors to ab wall
• _______________- fissure where following emerge
• Renal aretery
• Renal vein
• Ureter
• Internally, 2 distinct regions
• Renal _________ superficial
• Renal _________ deep, arranged in renal pyramids

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Nephron figure 26.5 a b

• Functional unit of the kidney, 2 parts
• _________________ where blood plasma is
  filtered
• Glomerulus capillary network
• Glomerular (Bowmans) capsule epithelial cup
• _________________ into which the filtrate is
  passed
• Proximal convoluted tubule (PCT)
• Loop of Henle (LOH)
• Distal convoluted tubule (DCT)
• Types
• __________ nephron- short LOH, blood from
  peritubular cap
• __________________ nephron- close to medulla,
  long LOH
• Long loops enable excretion of very dilute or
  very

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Renal corpuscle fig 26.6

• __________________- capillary network
• Glomerular (Bowmans) capsule- double walled
  epithelial cup that surrounds the capillaries
• Blood plasma is filtered collected in capsule
• Filtered fluid then passes thru renal tubule
• _____________- visceral, modified simple squamous
  cells, wrap around glomerular capillaries form
  inner wall of capsule
• Outer wall (parietal) is simple squamous

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Renal physiology, 3 processes

• _______________________
• Water most solutes capillary ? renal capsule
• _______________________
• Filtered fluid move thru tubule
• Cells reabsorb 99 of water useful solutes
• Returns to blood via
• Peritubular capillaries
• Vasa recta
• ________________________
• Removes substances from blood
• Urine contains these excreted substances
  wastes, drugs, excess ions

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Glomerular filtration fig 26.8

• Filtration fraction- amt of plasma in
  ______________ that becomes glomerular filtrate
  16-20 of plasma
• Daily volume of glomerular filtrate
• 150L female,180L male
• gt99 returned to blood, ? 1-2 L urine/day
• Substances pass _________________
• Glomerular endothelial cells fenestrated
• Between capillaries mesangial cells regulate GF
• Basal lamina
• Podocytes w/ pedicel create filtration slits
• ____________ ______________________
• Most plasma proteins, blood cells platelets DO
  NOT

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The filtration membrane, fig 26.8
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Net filtration pressure, figure 26.9

• Glomerular filtration dependent on these 3
• Glomerular blood hydrostatic pressure
• Blood pressure in glomerular capillaries
• Promotes filtration
• Capsular hydrostatic pressure
• Hydrostatic P exert by fluid in capsular space
• Opposes filtration
• Blood colloid osmotic pressure
• Presence of proteins in blood plasma
• Opposes filtration

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Glomerular filtration rate (GFR)

• Filtrate formed in renal corpuscles of both
  kidneys each minute
• 125 mL/min male, 105 mL/min female
• Homeostasis req it to be constant
• If too ?, substance not reabsorbed, lost in urine
• If too ?, not enough waste excreted
• Directly related to P determining NFP
• Regulation
• Adjusting _______________ to glomerulus
• Alter glomerular capillary __________- filtration

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Regulation of GFR, table 26.2

• 1. _____________________
• Myogenic mechanism- smooth muscle contraction
  wall of afferent arteriole
• ? bp, stretch wall, ? smooth mus contracts,
  narrow lumen? renal blood flow ? ? ? GFR
• Tubuloglomerular feedback- macula densa provide
  feedback to glomerulus
• If GFR ? due to ? bp, filtered fluid flows
  faster, less time for reabsorption ? nitric oxide
  not released ________________ constricted

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Regulation of GFR (2)

• 2. _____ regulation- kidney bv supplied by
  SympNS
• Release NE ? vasoconstrict (exercise,
  hemhorrrage)
• Blood flow ?, GFR ?
• ? urine output, conserve blood volume
• ? blood flow to other body tissues
• At rest, bv dilated autoregulation occurring
• 3. ___________ regulation-
• Angiotensin II- ? GFR by vasoconstriction
• Atrial natriuretic peptide (ANP) secreted when ?
  blood vol ? relax mesangial cells ? SA ? ? GFR

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Tubular reabsorption

• PCT
• ______ _______ reabsorbed in large quantities
• 65 of filtered water reabsorbed
• Na/glucose (phosphate, sulfate, aa) symporters
• Na/H antiporter
• _________ (HCO3-) reabsorbed- fac diffusion
• _________ of water
• Concentrates remaining solutes in PCT
• Passive reabsorption of other solutes
• Cl-, K, Ca2, Mg2, urea
• Urea and ammonia ____________ by PCT

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PCT
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PCT
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PCT, 2nd half
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Tubular reabsorption (2)

• Loop of Henle
• Descending limb
• ___________ is reabsorbed (15 of filtered water)
• Ascending limb
• Na, K, 2Cl- symporters
• most K leaks back into tubule thru channels
• Ca2, HCO3-,
• ____________- ascending LOH virtually impermeable
  to water
• not automatically coupled to reabsorption of
  other solutes like in PCT
• Filtrate osmolarity ? as ascend (ions, not water
  reabsorb)

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Ascending LOH
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Tubular reabsorption (3)

• DCT
• Na Cl- symporter ? reabsorption
• PTH causes reabsorption of Ca2
• Water 10-15, (at this point 80 already ab)
• by time fluid reaches end of DCT 90-95 of
  filtered solutes water have been returned to
  bloodstream
• Collecting duct
• ______ reabsorb thru leak channel?
  Na/Kpump?blood
• ______ reabsorbed by intercalated cells, secreted
  in variable amounts thru leak channels of
  principal cells

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DCT collecting duct
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Tubular secretion

• Secretion of H helps control ___________
• Secretion of others for ____________ from body
• PCT
• H and NH4 ions, urea
• DCT
• H ions, (K by principal cells at end of DCT)
• Collecting duct
• K/ H /NH4 ions (depending on salt, pH balance)

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Hormonal effects table 26.4

• Angiotensin II-(released when? blood volume, ?
  bp)
• ? GFR
• Stim antiporter reabsorb Na, Cl-, H2O in PCT
• Stim release aldosterone
• Aldosterone (? plasma K)
• K secretion, Na, Cl-, H20 reabsorbed
• ADH- (? osm of ECF or ? blood volume)
• water reabsorption ? in DCT
• ANP- (stim by atria stretch, ? blood volume)
• ? secretion of Na (natriuresis)
• Suppress reabsorption at PCT
• ? urine output (diuresis)
• ANP suppresses ADH aldosterone secretion

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Figure 26.17
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Dilute concentrated, fig 26.18

• Body __________ depends largely on kidney
• Large volume, dilute urine when fluid intake ?
• Asc LOH DCT rel impermeable to water
• End of DCT collecting duct impermeable to water
  when ADH ________
• Small volume, concentrated fluid intake ?
• ADH enabled by osmotic gradient
• Differences in solute water permeability along
  LOH collecting duct
• Countercurrent flow in Des Asc LOH

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Dilute urineformation
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Countercurrent mechanism

• Hairpin shape of LOH- countercurrent flow
• Descending limb one direction
• Very permeable to water
• I.F. osmolarity gt than inside tube ? water? out
• As fluid moves down- gradient, osmolarity ?
• Impermeable to solutes except urea
• Ascending limb opposite direction
• Impermeable to water
• Symporters reabsorb Na, Cl-
• Fluid osmolarity ? as ascending

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Countercurrent mechanism (2)

• ____________ loops working similar to LOH
• Descending- renal medulla I.F. more
• More Na, Cl-, urea diffuse into blood
• Blood osmolarity ?
• Ascending- I.F. increasingly less
• Ions diffuse out of Asc vasa recta
• Reabsorbed water diffuses from I.F. ? vasa recta
• Osmolarity of blood leaving vasa recta only
  slightly higher than what entered
• O2 nutrients dropped off w/out ? gradient

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Constituents of urine (lab, p60)

• ORGANIC
• Urea
• Creatinine
• Uric acid

• INORGANIC
• Chloride
• Sodium
• Potassium
• Sulfates
• Phosphates
• Ammonia
• Calcium
• Magnesium

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Diuretics

• ______________ elevated urine flow rate
• Substances slow renal reabsorption of water
• Often prescribed for _________________
• Lower blood volume ? lower bp
• Most interfere w/mechanism for Na reabsorption
• Naturally occurring
• Caffeine- inhibits Na reabsorption
• Alcohol- inhibits ADH secretion

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Dialysis- to separate

• _________ of large solutes from smaller ones by
  diffusion thru selectively permeable mem
• Kidneys so impaired that unable to function
• __________dialysis- filter patients blood by
  removing wastes, excess electrolytes fluids and
  return blood to patient
• Hemodialyzer, dialysis membrane
• Dialysate- solution formed to maintain diffusion
  gradients add needed substances
• Peritoneal dialysis- catheter dialysate

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Flow from nephron to urethra

• (Nephron Bowmans capsule?PCT?LOH?DCT?)
• Collecting duct ?
• Papillary duct ?
• Minor calyx ?
• Major calyx ?
• Renal pelvis ?
• Ureter ?
• Urinary bladder ?
• Urethra

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Micturition

• Urination or voiding
• Discharge of urine from urinary bladder
• Voluntary (SNS) involuntary (ANS) muscle
  contractions
• When 200-400mL ? stretch receptors trigger
  ________________- S2-S3 ? spinal reflex
• Contraction of detrusor
• Relaxation- internal urethral sphincter muscle
• Filling causes sensation before reflex occurs
• _______________- lack of voluntary control

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Clinical connections

• Diabetes insipidus- nephrogenic- kidneys do not
  respond to __________
• ADH receptors may be damaged
• Or kidneys may be damaged
• UTIs- infection of urinary system or presence of
  large of microbes in the urine
• Urethritis- inflammed urethra
• Cystitis- inflammed urinary bladder
• Pyelonephritis- inflammed kidneys, if chronic-
  scar tissue forms

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Medical terminology

• Polyuria- excessive urine formation- maybe due to
  D.M. and ___________________-
• Inflammation of kidney involving glomeruli often
  from allergic rxns to toxin produced by
  streptococcus
• Anuria- absence of urine formation
• Oliguria- abnormally slight or infrequent
  urination