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23-1
Urinary System
23-2
The Urinary System
• Functions of urinary system
• Anatomy of kidney
• Urine formation
– glomerular filtration
– tubular reabsorption
– tubular secretion
• Urine and renal function tests
• Urine storage and elimination
23-3
Urinary System
• What is missing from the following
illustration?
23-4
Urinary System
Two kidneys
Two ureters Urethra
23-5
Kidney Location
23-6
Kidney Functions
• Filters blood plasma
– returns useful substances to blood
– eliminates waste
• Regulates
– osmolarity of body fluids, blood volume, BP
– acid base balance
• Secretes
– renin and erythropoietin
• Detoxifies free radicals and drugs
• Gluconeogenesis
23-7
Nitrogenous Wastes
• Urea
– by product of protein metabolism
– proteins→amino acids →NH2 removed
→forms ammonia, liver converts to
urea
• Uric acid
– nucleic acid catabolism
• Creatinine
– creatine phosphate catabolism
• Renal failure
– azotemia: ↑BUN (blood urea nitrogen),
nitrogenous wastes in blood
– uremia: toxic effects as wastes
accumulate
• Hemodialysis: removes nitrogenous
wastes
23-8
Excretion
• Separation of wastes from body fluids and
eliminating them; by four systems
– respiratory: CO2
– integumentary: water, salts, lactic acid, urea
– digestive: water, salts, CO2, lipids, bile
pigments, cholesterol
– urinary: many metabolic wastes, toxins,
drugs, hormones, salts, H+
and water
23-9
Anatomy of Kidney
• Position, weight and size
– retroperitoneal, level of T12 to L3
– about 160 g each
– about size of a bar of soap (12x6x3 cm)
• Shape
– lateral surface - convex; medial - concave
• CT coverings (3 layers protect kidney)
– renal fascia: binds kidney to abdominal wall
– adipose capsule: cushions and supports kidney;
holds it in place
– renal capsule: encloses kidney like cellophane wrap;
protects from trauma and infection
23-10
Anatomy of Kidney
• Renal cortex: outer 1 cm
• Renal medulla: renal columns, pyramids - papilla
• Lobe of kidney: pyramid and it’s overlying cortex
23-11
Wedge-Shaped Lobe of Kidney
• Glomerular filtrate collects in capsular space, flows into renal tubule
23-12
Renal Corpusle
23-13
The NephronRenal Corpusle
Proximal convoluted
tubule (PCT)
– longest, most coiled,
simple cuboidal with
brush border
• Nephron loop - U
shaped; descending
and ascending limbs
– thick segment
(simple cuboidal)
initial part of
descending limb and
part or all of
ascending limb,
active transport of
salts
– thin segment (simple
squamous) very
water permeable
23-14
The Nephron - Continued
• Distal
convoluted
tubule (DCT)
– cuboidal,
microvilli
– minimal
• Collecting duct
– several DCT’s
join
23-15
Fluid Flow
• Flow of glomerular filtrate: from filtrate to
exit from the body
– glomerular capsule → PCT → nephron loop →
– DCT → collecting duct → papillary duct →
– minor calyx → major calyx → renal pelvis →
– ureter → urinary bladder → urethra
23-16
Nephrons
• True proportions of nephron
loops to convoluted tubules
shown
• Cortical nephrons (85%)
– short nephron loops
– efferent arterioles branch off
peritubular capillaries
• Juxtamedullary nephrons
(15%) – most responsible for
salt gradient
– very long nephron loops,
__________________________
Whether short or long nephron
loops they maintain salt
gradient, helps conserve water
23-17
Nephron Diagram
• Peritubular capillaries shown only on right of nephron
23-18
Path of Blood Through Kidney
• Renal artery
→ interlobar arteries (up renal columns, between lobes)
→ arcuate arteries (over pyramids)
→ interlobular arteries (up into cortex)
→ afferent arterioles
→ glomerulus (cluster of capillaries)
→ efferent arterioles (near medulla → vasa recta)
→ peritubular capillaries
→ interlobular veins → arcuate veins → interlobar veins
• Renal vein
23-19
Blood Supply Diagram
23-20
Urine Formation Preview
23-21
Filtration Membrane Diagram
23-22
Filtration Membrane
• Fenestrated endothelium
– 70-90nm pores exclude blood
cells
• Basement membrane
– proteoglycan gel, negative
charge excludes molecules >
8nm
– blood plasma 7% protein,
glomerular filtrate 0.03%
• Filtration slits
– podocyte arms have pedicels
with negatively charged filtration
slits, allow particles < 3nm to
pass
23-23
Filtration = Diffusion dependent on -Pressure
23-24
Glomerular Filtration Rate (GFR)
• Filtrate formed per minute
• GFR = NFP x Kf ≈125 ml/min or 180 L/day, male
• GFR = NFP x Kf ≈105 ml/min or 150 L/day, female
– filtration coefficient (Kf) depends on permeability and
surface area of filtration barrier
• 99% of filtrate reabsorbed, 1 to 2 L urine
excreted
23-25
Effects of GFR Abnormalities
∀↑GFR, urine output rises → dehydration,
electrolyte depletion
∀↓GFR → wastes reabsorbed (azotemia
possible)
• GFR controlled by adjusting glomerular
blood pressure
– autoregulation
– sympathetic control
– hormonal mechanism: renin and angiotensin
23-26
Juxtaglomerular Apparatus
- vasomotion
- monitor salinity
23-27
Renal Autoregulation of GFR
∀↑ BP → constrict
afferent arteriole, dilate
efferent
• ↓ BP → dilate afferent
arteriole, constrict
efferent
• Stable for BP range of
80 to 170 mmHg
(systolic)
• Cannot compensate for
extreme BP
23-28
Renal Autoregulation of GFR
• Myogenic mechanism
↑ BP → stretches afferent arteriole → afferent
arteriole constricts → restores GFR
• Tubuloglomerular feedback
– Macula densa on DCT monitors tubular fluid
and signals juxtaglomerular cells (smooth muscle,
surrounds afferent arteriole) to constrict afferent
arteriole to ↓ GFR
23-29
Negative Feedback Control of GFR
23-30
Sympathetic Control of GFR
• Strenuous exercise or acute conditions
(circulatory shock) stimulate afferent
arterioles to constrict
∀↓ GFR and urine production, redirecting
blood flow to heart, brain and skeletal
muscles
• BP drop causes JG cells to secrete Renin
which acts on angiotensinogen >
angiotensin I
23-31
Renin-Angiotensin-Aldosterone
23-32
Effects of Angiotensin II
23-33
Effects of Angiotensin II - continued
• Stimulates Adrenal Cortex to secrete
aldosterone > Na+
and water retention by
DCT
• Stimulates ADH secretion > water
retention
• Stimulates Hypothalmus thirst center
23-34
Tubular Reabsorption and Secretion
23-35
Peritubular Capillaries
• Blood has unusually high COP (colloid osmotic
pressure) here, and BHP (blood hydrostatic pressure) is
only 8 mm Hg (or lower when constricted by
angiotensin II); this favors reabsorption
• Water absorbed by osmosis and carries
other solutes with it (solvent drag)
23-36
Proximal Convoluted Tubules (PCT)
• Reabsorbs 65% of GF
• Great length, prominent microvilli and abundant
mitochondria for active transport
• Reabsorbs greater variety of chemicals than
other parts of nephron
– transcellular route - through epithelial cells of PCT
– paracellular route - between epithelial cells of PCT
• Transport maximum: when transport proteins of cell
membrane are saturated; blood glucose > 220 mg/dL
some remains in urine (glycosuria); glucose Tm = 320
mg/min
23-37
Mechanisms of Reabsorption in the Proximal Convoluted Tubule
23-38
Tubular Secretion of PCT
and Nephron Loop
• Waste removal
– urea, uric acid, bile salts, ammonia,
catecholamines, many drugs
• Acid-base balance
– secretion of hydrogen and bicarbonate ions
regulates pH of body fluids
• Primary function of nephron loop
– water conservation -2/3 reabsorbed by PCT
– generates salinity gradient, allows CD to conc.
urine
– also involved in electrolyte reabsorption
23-39
DCT and Collecting Duct
• Principal cells – receptors for hormones;
involved in salt/water balance
• Intercalated cells – involved in acid/base
balance
• Function
– fluid reabsorption here is variable, regulated
by hormonal action
23-40
DCT and Collecting Duct
• Aldosterone effects
↓ BP → renin release → angiotensin II
formation
– angiotensin II stimulates adrenal cortex
– adrenal cortex secretes aldosterone
• promotes Na+
reabsorption → promotes water
reabsorption → ↓ urine volume → maintains BP
23-41
DCT and Collecting Duct
• Effect of ADH
– dehydration stimulates hypothalamus
– hypothalamus stimulates posterior pituitary
– posterior pituitary releases ADH
– ADH ↑ water reabsorption
↓ urine volume
23-42
DCT and Collecting Duct
• Atrial natriuretic peptide (ANP)
– atria secrete ANP in response to ↑ BP
– has four actions:
1. dilates afferent arteriole, constricts efferent
arteriole - ↑ GFR
2. inhibits renin/angiotensin/aldosterone
pathway
3. inhibits secretion and action of ADH
4. inhibits NaCl reabsorption
• Promotes Na+
and water excretion, ↑ urine
volume, ↓ blood volume and BP
23-43
DCT and Collecting Duct
• Effect of PTH
↑ calcium reabsorption in DCT - ↑ blood Ca2+
↑ phosphate excretion in PCT, ↓ new bone
formation
– stimulates kidney production of calcitriol
23-44
Collecting Duct Concentrates
Urine
• Osmolarity 4x as concentrated
deep in medulla
• Medullary portion of CD is more
permeable to water than to NaCl
23-45
Control of Water Loss
• Producing hypotonic urine
– NaCl reabsorbed by cortical CD
– water remains in urine
• Producing hypertonic urine
– dehydration → ↑ ADH → ↑ aquaporin
channels, ↑ CD’s water permeability
– more water is reabsorbed
– urine is more concentrated
23-46
Countercurrent Multiplier
• Recaptures NaCl and returns it to renal medulla
• Descending limb
– reabsorbs water but not salt
– concentrates tubular fluid
• Ascending limb
– reabsorbs Na+
, K+
, and Cl-
– maintains high osmolarity of renal medulla
– impermeable to water
– tubular fluid becomes hypotonic
• Recycling of urea: collecting duct-medulla
– urea accounts for 40% of high osmolarity of medulla
23-47
Countercurrent Multiplier
of Nephron Loop Diagram
23-48
Countercurrent Exchange System
• Formed by vasa recta
– provide blood supply to medulla
– do not remove NaCl from medulla
• Descending capillaries
– water diffuses out of blood
– NaCl diffuses into blood
• Ascending capillaries
– water diffuses into blood
– NaCl diffuses out of blood
23-49
Maintenance of Osmolarity
in Renal Medulla
23-50
Summary of Tubular
Reabsorption and Secretion
23-51
23-52
Composition and Properties of Urine
• Appearance
– almost colorless to deep amber; yellow color due to
urochrome, from breakdown of hemoglobin (RBC’s)
• Odor - as it stands bacteria degrade urea to ammonia
• Specific gravity
– density of urine ranges from 1.001 -1.028
• Osmolarity - (blood - 300 mOsm/L) ranges from
50 mOsm/L to 1,200 mOsm/L in dehydrated person
• pH - range: 4.5 - 8.2, usually 6.0
• Chemical composition: 95% water, 5% solutes
– urea, NaCl, KCl, creatinine, uric acid
23-53
23-54
Urine Volume
• Normal volume - 1 to 2 L/day
• Polyuria > 2L/day
• Oliguria < 500 mL/day
• Anuria - 0 to 100 mL/day
23-55
Diabetes
• Chronic polyuria of metabolic origin
• With hyperglycemia and glycosuria
– diabetes mellitus I and II, insulin
hyposecretion/insensitivity
– gestational diabetes, 1 to 3% of pregnancies
• ADH hyposecretion
– diabetes insipidus; CD ↓ water reabsorption
23-56
Diuretics
• Effects
↑ urine output
↓ blood volume
• Uses
– hypertension and congestive heart failure
• Mechanisms of action
↑ GFR
↓ tubular reabsorption
23-57
Renal Function Tests
• Renal clearance: volume of plasma cleared of a
waste in 1 minute
• Determine renal clearance (C) by assessing
blood and urine samples: C = UV/P
– U (waste concentration in urine)
– V (rate of urine output)
– P (waste concentration in plasma)
• Determine GFR: inulin is neither reabsorbed or
secreted so its GFR = renal clearance GFR =
UV/P
• Clinical GFR estimated from creatinine excretion
23-58
Urine Storage and Elimination
• Ureters (about 25 cm long)
– from renal pelvis passes dorsal to bladder and
enters it from below, with a small flap of
mucosa that acts as a valve into bladder
– 3 layers
• adventitia - CT
• muscularis - 2 layers of smooth muscle with
3rd
layer in lower ureter
– urine enters, it stretches and contracts in
peristaltic wave
• mucosa - transitional epithelium
– lumen very narrow, easily obstructed
23-59
Urinary Bladder and Urethra -
Female
23-60
Urinary Bladder
• Located in pelvic cavity, posterior to pubic
symphysis
• 3 layers
– parietal peritoneum, superiorly; fibrous adventitia rest
– muscularis: detrusor muscle, 3 layers of smooth
muscle
– mucosa: transitional epithelium
• trigone: openings of ureters and urethra,
triangular
• rugae: relaxed bladder wrinkled, highly
distensible
• capacity: moderately full - 500 ml, max. - 800 ml
23-61
Female Urethra
• 3 to 4 cm long
• External urethral orifice
– between vaginal orifice and
clitoris
• Internal urethral sphincter
– detrusor muscle thickened,
smooth muscle, involuntary
control
External urethral sphincter
skeletal muscle, voluntary
control
23-62
Male Bladder and Urethra
• 18 cm long
• Internal urethral sphincter
• External urethral sphincter
3 regions
prostatic urethra
during orgasm receives semen
membranous urethra
passes through pelvic cavity
spongy urethra
23-63
Voiding Urine - Micturition
• 200 ml urine in bladder, stretch receptors send
signal to sacral spinal cord
• Signals ascend to
– inhibitory synapses on sympathetic neurons
– micturition center (integrates info from amygdala, cortex)
• Signals descend to
– further inhibit sympathetic neurons
– stimulate parasympathetic neurons
• Result
– urinary bladder contraction
– relaxation of internal urethral sphincter
• External urethral sphincter - corticospinal tracts to
sacral spinal cord inhibit somatic neurons - relaxes
23-64
Neural Control of Micturition
23-65
Hemodialysis
23-66

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Urinary system

  • 2. 23-2 The Urinary System • Functions of urinary system • Anatomy of kidney • Urine formation – glomerular filtration – tubular reabsorption – tubular secretion • Urine and renal function tests • Urine storage and elimination
  • 3. 23-3 Urinary System • What is missing from the following illustration?
  • 6. 23-6 Kidney Functions • Filters blood plasma – returns useful substances to blood – eliminates waste • Regulates – osmolarity of body fluids, blood volume, BP – acid base balance • Secretes – renin and erythropoietin • Detoxifies free radicals and drugs • Gluconeogenesis
  • 7. 23-7 Nitrogenous Wastes • Urea – by product of protein metabolism – proteins→amino acids →NH2 removed →forms ammonia, liver converts to urea • Uric acid – nucleic acid catabolism • Creatinine – creatine phosphate catabolism • Renal failure – azotemia: ↑BUN (blood urea nitrogen), nitrogenous wastes in blood – uremia: toxic effects as wastes accumulate • Hemodialysis: removes nitrogenous wastes
  • 8. 23-8 Excretion • Separation of wastes from body fluids and eliminating them; by four systems – respiratory: CO2 – integumentary: water, salts, lactic acid, urea – digestive: water, salts, CO2, lipids, bile pigments, cholesterol – urinary: many metabolic wastes, toxins, drugs, hormones, salts, H+ and water
  • 9. 23-9 Anatomy of Kidney • Position, weight and size – retroperitoneal, level of T12 to L3 – about 160 g each – about size of a bar of soap (12x6x3 cm) • Shape – lateral surface - convex; medial - concave • CT coverings (3 layers protect kidney) – renal fascia: binds kidney to abdominal wall – adipose capsule: cushions and supports kidney; holds it in place – renal capsule: encloses kidney like cellophane wrap; protects from trauma and infection
  • 10. 23-10 Anatomy of Kidney • Renal cortex: outer 1 cm • Renal medulla: renal columns, pyramids - papilla • Lobe of kidney: pyramid and it’s overlying cortex
  • 11. 23-11 Wedge-Shaped Lobe of Kidney • Glomerular filtrate collects in capsular space, flows into renal tubule
  • 13. 23-13 The NephronRenal Corpusle Proximal convoluted tubule (PCT) – longest, most coiled, simple cuboidal with brush border • Nephron loop - U shaped; descending and ascending limbs – thick segment (simple cuboidal) initial part of descending limb and part or all of ascending limb, active transport of salts – thin segment (simple squamous) very water permeable
  • 14. 23-14 The Nephron - Continued • Distal convoluted tubule (DCT) – cuboidal, microvilli – minimal • Collecting duct – several DCT’s join
  • 15. 23-15 Fluid Flow • Flow of glomerular filtrate: from filtrate to exit from the body – glomerular capsule → PCT → nephron loop → – DCT → collecting duct → papillary duct → – minor calyx → major calyx → renal pelvis → – ureter → urinary bladder → urethra
  • 16. 23-16 Nephrons • True proportions of nephron loops to convoluted tubules shown • Cortical nephrons (85%) – short nephron loops – efferent arterioles branch off peritubular capillaries • Juxtamedullary nephrons (15%) – most responsible for salt gradient – very long nephron loops, __________________________ Whether short or long nephron loops they maintain salt gradient, helps conserve water
  • 17. 23-17 Nephron Diagram • Peritubular capillaries shown only on right of nephron
  • 18. 23-18 Path of Blood Through Kidney • Renal artery → interlobar arteries (up renal columns, between lobes) → arcuate arteries (over pyramids) → interlobular arteries (up into cortex) → afferent arterioles → glomerulus (cluster of capillaries) → efferent arterioles (near medulla → vasa recta) → peritubular capillaries → interlobular veins → arcuate veins → interlobar veins • Renal vein
  • 22. 23-22 Filtration Membrane • Fenestrated endothelium – 70-90nm pores exclude blood cells • Basement membrane – proteoglycan gel, negative charge excludes molecules > 8nm – blood plasma 7% protein, glomerular filtrate 0.03% • Filtration slits – podocyte arms have pedicels with negatively charged filtration slits, allow particles < 3nm to pass
  • 23. 23-23 Filtration = Diffusion dependent on -Pressure
  • 24. 23-24 Glomerular Filtration Rate (GFR) • Filtrate formed per minute • GFR = NFP x Kf ≈125 ml/min or 180 L/day, male • GFR = NFP x Kf ≈105 ml/min or 150 L/day, female – filtration coefficient (Kf) depends on permeability and surface area of filtration barrier • 99% of filtrate reabsorbed, 1 to 2 L urine excreted
  • 25. 23-25 Effects of GFR Abnormalities ∀↑GFR, urine output rises → dehydration, electrolyte depletion ∀↓GFR → wastes reabsorbed (azotemia possible) • GFR controlled by adjusting glomerular blood pressure – autoregulation – sympathetic control – hormonal mechanism: renin and angiotensin
  • 27. 23-27 Renal Autoregulation of GFR ∀↑ BP → constrict afferent arteriole, dilate efferent • ↓ BP → dilate afferent arteriole, constrict efferent • Stable for BP range of 80 to 170 mmHg (systolic) • Cannot compensate for extreme BP
  • 28. 23-28 Renal Autoregulation of GFR • Myogenic mechanism ↑ BP → stretches afferent arteriole → afferent arteriole constricts → restores GFR • Tubuloglomerular feedback – Macula densa on DCT monitors tubular fluid and signals juxtaglomerular cells (smooth muscle, surrounds afferent arteriole) to constrict afferent arteriole to ↓ GFR
  • 30. 23-30 Sympathetic Control of GFR • Strenuous exercise or acute conditions (circulatory shock) stimulate afferent arterioles to constrict ∀↓ GFR and urine production, redirecting blood flow to heart, brain and skeletal muscles • BP drop causes JG cells to secrete Renin which acts on angiotensinogen > angiotensin I
  • 33. 23-33 Effects of Angiotensin II - continued • Stimulates Adrenal Cortex to secrete aldosterone > Na+ and water retention by DCT • Stimulates ADH secretion > water retention • Stimulates Hypothalmus thirst center
  • 35. 23-35 Peritubular Capillaries • Blood has unusually high COP (colloid osmotic pressure) here, and BHP (blood hydrostatic pressure) is only 8 mm Hg (or lower when constricted by angiotensin II); this favors reabsorption • Water absorbed by osmosis and carries other solutes with it (solvent drag)
  • 36. 23-36 Proximal Convoluted Tubules (PCT) • Reabsorbs 65% of GF • Great length, prominent microvilli and abundant mitochondria for active transport • Reabsorbs greater variety of chemicals than other parts of nephron – transcellular route - through epithelial cells of PCT – paracellular route - between epithelial cells of PCT • Transport maximum: when transport proteins of cell membrane are saturated; blood glucose > 220 mg/dL some remains in urine (glycosuria); glucose Tm = 320 mg/min
  • 37. 23-37 Mechanisms of Reabsorption in the Proximal Convoluted Tubule
  • 38. 23-38 Tubular Secretion of PCT and Nephron Loop • Waste removal – urea, uric acid, bile salts, ammonia, catecholamines, many drugs • Acid-base balance – secretion of hydrogen and bicarbonate ions regulates pH of body fluids • Primary function of nephron loop – water conservation -2/3 reabsorbed by PCT – generates salinity gradient, allows CD to conc. urine – also involved in electrolyte reabsorption
  • 39. 23-39 DCT and Collecting Duct • Principal cells – receptors for hormones; involved in salt/water balance • Intercalated cells – involved in acid/base balance • Function – fluid reabsorption here is variable, regulated by hormonal action
  • 40. 23-40 DCT and Collecting Duct • Aldosterone effects ↓ BP → renin release → angiotensin II formation – angiotensin II stimulates adrenal cortex – adrenal cortex secretes aldosterone • promotes Na+ reabsorption → promotes water reabsorption → ↓ urine volume → maintains BP
  • 41. 23-41 DCT and Collecting Duct • Effect of ADH – dehydration stimulates hypothalamus – hypothalamus stimulates posterior pituitary – posterior pituitary releases ADH – ADH ↑ water reabsorption ↓ urine volume
  • 42. 23-42 DCT and Collecting Duct • Atrial natriuretic peptide (ANP) – atria secrete ANP in response to ↑ BP – has four actions: 1. dilates afferent arteriole, constricts efferent arteriole - ↑ GFR 2. inhibits renin/angiotensin/aldosterone pathway 3. inhibits secretion and action of ADH 4. inhibits NaCl reabsorption • Promotes Na+ and water excretion, ↑ urine volume, ↓ blood volume and BP
  • 43. 23-43 DCT and Collecting Duct • Effect of PTH ↑ calcium reabsorption in DCT - ↑ blood Ca2+ ↑ phosphate excretion in PCT, ↓ new bone formation – stimulates kidney production of calcitriol
  • 44. 23-44 Collecting Duct Concentrates Urine • Osmolarity 4x as concentrated deep in medulla • Medullary portion of CD is more permeable to water than to NaCl
  • 45. 23-45 Control of Water Loss • Producing hypotonic urine – NaCl reabsorbed by cortical CD – water remains in urine • Producing hypertonic urine – dehydration → ↑ ADH → ↑ aquaporin channels, ↑ CD’s water permeability – more water is reabsorbed – urine is more concentrated
  • 46. 23-46 Countercurrent Multiplier • Recaptures NaCl and returns it to renal medulla • Descending limb – reabsorbs water but not salt – concentrates tubular fluid • Ascending limb – reabsorbs Na+ , K+ , and Cl- – maintains high osmolarity of renal medulla – impermeable to water – tubular fluid becomes hypotonic • Recycling of urea: collecting duct-medulla – urea accounts for 40% of high osmolarity of medulla
  • 48. 23-48 Countercurrent Exchange System • Formed by vasa recta – provide blood supply to medulla – do not remove NaCl from medulla • Descending capillaries – water diffuses out of blood – NaCl diffuses into blood • Ascending capillaries – water diffuses into blood – NaCl diffuses out of blood
  • 51. 23-51
  • 52. 23-52 Composition and Properties of Urine • Appearance – almost colorless to deep amber; yellow color due to urochrome, from breakdown of hemoglobin (RBC’s) • Odor - as it stands bacteria degrade urea to ammonia • Specific gravity – density of urine ranges from 1.001 -1.028 • Osmolarity - (blood - 300 mOsm/L) ranges from 50 mOsm/L to 1,200 mOsm/L in dehydrated person • pH - range: 4.5 - 8.2, usually 6.0 • Chemical composition: 95% water, 5% solutes – urea, NaCl, KCl, creatinine, uric acid
  • 53. 23-53
  • 54. 23-54 Urine Volume • Normal volume - 1 to 2 L/day • Polyuria > 2L/day • Oliguria < 500 mL/day • Anuria - 0 to 100 mL/day
  • 55. 23-55 Diabetes • Chronic polyuria of metabolic origin • With hyperglycemia and glycosuria – diabetes mellitus I and II, insulin hyposecretion/insensitivity – gestational diabetes, 1 to 3% of pregnancies • ADH hyposecretion – diabetes insipidus; CD ↓ water reabsorption
  • 56. 23-56 Diuretics • Effects ↑ urine output ↓ blood volume • Uses – hypertension and congestive heart failure • Mechanisms of action ↑ GFR ↓ tubular reabsorption
  • 57. 23-57 Renal Function Tests • Renal clearance: volume of plasma cleared of a waste in 1 minute • Determine renal clearance (C) by assessing blood and urine samples: C = UV/P – U (waste concentration in urine) – V (rate of urine output) – P (waste concentration in plasma) • Determine GFR: inulin is neither reabsorbed or secreted so its GFR = renal clearance GFR = UV/P • Clinical GFR estimated from creatinine excretion
  • 58. 23-58 Urine Storage and Elimination • Ureters (about 25 cm long) – from renal pelvis passes dorsal to bladder and enters it from below, with a small flap of mucosa that acts as a valve into bladder – 3 layers • adventitia - CT • muscularis - 2 layers of smooth muscle with 3rd layer in lower ureter – urine enters, it stretches and contracts in peristaltic wave • mucosa - transitional epithelium – lumen very narrow, easily obstructed
  • 59. 23-59 Urinary Bladder and Urethra - Female
  • 60. 23-60 Urinary Bladder • Located in pelvic cavity, posterior to pubic symphysis • 3 layers – parietal peritoneum, superiorly; fibrous adventitia rest – muscularis: detrusor muscle, 3 layers of smooth muscle – mucosa: transitional epithelium • trigone: openings of ureters and urethra, triangular • rugae: relaxed bladder wrinkled, highly distensible • capacity: moderately full - 500 ml, max. - 800 ml
  • 61. 23-61 Female Urethra • 3 to 4 cm long • External urethral orifice – between vaginal orifice and clitoris • Internal urethral sphincter – detrusor muscle thickened, smooth muscle, involuntary control External urethral sphincter skeletal muscle, voluntary control
  • 62. 23-62 Male Bladder and Urethra • 18 cm long • Internal urethral sphincter • External urethral sphincter 3 regions prostatic urethra during orgasm receives semen membranous urethra passes through pelvic cavity spongy urethra
  • 63. 23-63 Voiding Urine - Micturition • 200 ml urine in bladder, stretch receptors send signal to sacral spinal cord • Signals ascend to – inhibitory synapses on sympathetic neurons – micturition center (integrates info from amygdala, cortex) • Signals descend to – further inhibit sympathetic neurons – stimulate parasympathetic neurons • Result – urinary bladder contraction – relaxation of internal urethral sphincter • External urethral sphincter - corticospinal tracts to sacral spinal cord inhibit somatic neurons - relaxes
  • 64. 23-64 Neural Control of Micturition
  • 66. 23-66