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Structure and Function of
the Renal and Urologic
Systems
Chapter 28
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Structures of the Kidney

Kidneys
 Retroperitoneal
 Renal
capsule
 Renal fascia
 Hilum
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Structures of the Kidney
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Structures of the Kidney
Cortex
 Medullary
 Pyramids
 Calyces

 Minor
and major
Renal pelvis
 Lobe

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Structures of the Kidney
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Nephron

1.2 million nephrons per kidney

Functional unit of the kidney
 Cortical
nephrons
 Juxtamedullary nephrons
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Nephron

Renal corpuscle
Glomerulus
 Bowman capsule
 Mesangial cells

Bowman space
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Nephron
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Glomerulus
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Nephron

Glomerular filtration
membrane
 Inner
capillary endothelium
 Basement membrane
 Outer capillary epithelium
• Also referred to as podocytes or visceral
epithelium
• Filtration slits
 Filtrate
passes through the three
layers and forms the primary urine
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Nephron

Juxtaglomerular apparatus
Juxtaglomerular
Macula
cells
densa
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Juxtaglomerular Apparatus
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Nephron

Renal tubules
 Proximal
tubule
 Loop of Henle
 Distal tubule
 Collecting duct
 Principal cells : water & ECV…reabsorb
NA+
 Intercalated cells : acid-base…reabsorb
K+ & HCO3-,secrete H+
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Structures of the Kidney
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Nephron Tubule
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Blood Vessels







Renal arteries
Interlobar arteries
Arcuate arteries
Glomerular capillaries
Peritubular capillaries and vasa recta
Vasa recta
Renal veins
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Structures of the Kidney
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Structures of the Kidney

Ureters
 30
cm long
 Long, intertwining muscle bundles
 Pass obliquely though posterior
aspect of bladder
 Peristaltic activity
 Micturition compresses the lower
end of the ureter to avoid urine reflux
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Structures of the Kidney

Bladder




Detrusor muscle
Trigone
Micturition reflex
Urethra

Internal and external sphincters
 3 to 4 cm in females
 18 to 20 cm in males
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Bladder and Urethra
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Renal Blood Flow

Receive 1000 to 1200 mL of blood per
minute

Glomerular filtration rate (GFR)

Autoregulation ( MAP 80-180mmHg)

Tubuloglomerular feedback
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Renal
Autoregulation
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Renal Blood Flow

Neural regulation


Celiac ganglion and splanchnic nerve
Hormones
 Renin-angiotensin
system
 Aldosterone
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
RAAS
“Must understand”
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Nephron Function


Filters plasma
Reabsorbs and secretes



Tubular reabsorption and secretion
Forms a filtrate of protein-free fluid
Regulates the filtrate to maintain fluid
volume, electrolytes, and pH
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Nephron Function

Glomerular filtration
 Net filtration pressure (Table 28-1)
• Glomerular capillary oncotic/hydrostatic
pressure
• Bowman capsule oncotic/hydrostatic
pressure
 Filtration
rate
• 180 L/day
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Glomerular Filtration
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Nephron Function

Tubular transport (Box 28-1)
 Proximal
tubule
• Active reabsorption of sodium
 Loop
of Henle and distal tubule
• Concentration or dilution of urine
 Glomerulotubular
balance
• Adjustment of reabsorption of sodium and
water
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Nephron Function
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Concentration and
Dilution of Urine

Countercurrent exchange system




Contributes to production of concentrated
urine
Fluid flows in opposite direction through
parallel tubes
Fluid moves up and down the parallel limbs
of the loop of Henle
The longer the loop, the greater the
concentration gradient
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Countercurrent Exchange
System
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Concentration and
Dilution of Urine





Urea
Aldosterone
Antidiuretic hormone (ADH)
Atrial natriuretic peptide
Diuretics
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Acidification of urine

Hydrogen
excretion
Ammonia
excretion
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Renal Hormones

Urodilatin (natriuretic peptide)


Vitamin D


Inhibits sodium and water reabsorption
Necessary for the absorption of calcium
and phosphate
Erythropoietin

Released when decreased oxygen to the
kidney
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Tests of Renal Function

Clearance and glomerular filtration rate




Inulin
Creatinine
Clearance and renal blood flow
Blood tests
Plasma
creatinine
concentration
Blood urea nitrogen (BUN)
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Tests of Renal Function

Urodynamic tests


Cystometry, uroflowmetry, postvoid residual,
electromyography, video urodynamics
Direct visualization tests

Cystoscopy, ureteroscopy
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Pediatric Renal Function




Decreased ability to remove excess water
and solutes
Decreased concentrating ability
Narrow margin for fluid and electrolyte
balance
Increased risk of drug toxicity
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Aging and Renal Function

Decrease in renal blood flow and GFR





Altered sodium and water balance
Number of nephrons decrease due to
renal vascular and perfusion changes
Response to acid-base changes
delayed
Increased risk for drug toxicity
Alterations in thirst and water intake
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