URINARY TRACT

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URINARY TRACT I The kidney Maria M. Picken
MD, PhD mpicken_at_lumc.edu
Renes latin kidneys nephros greek kidney
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Outline I the kidney development gross
structure vasculature glomerulus II the
structure and function of the tubules renal
pelvis ureter urinary bladder urethra
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Objectives General objectives - to identify the
kidneys structures, function and location - to
analyze the relationship between microscopic
structure and function Specific objectives 1.
To identify elements of the gross and microscopic
structure of the kidney and analyze the
relationship between them 2. To list the special
features of renal vasculature and correlate these
with function 3. To describe and analyze the
structure and function of the glomerulus as a
whole 4. To describe and analyze the structure
and function of the glomerular filtration
barrier 5. To identify elements of the nephron
and the collecting system 7. To contrast and
compare the structure and function of different
segments of the nephron 8. To evaluate the
relationship between the vasculature and the
nephron 9. To identify the elements of the
juxtaglomerular apparatus and define their
relationship to each other 10. To identify the
general structural features of the ureters, the
urinary bladder and the urethra 11. To contrast
and compare the male versus the female urethra
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• Retroperitoneum,
• Thoracic vertebra12-Lumbar vertebra3
• 115-170 g (MgtF)
• 11-12 x 5-7.5 x 2.5-3 cm
• Kidneys paired, bean shaped
• Ureters paired
• urinary bladder
• Urethra, male versus female

• Renes latin kidneys
• Nephros greek kidney (Nephrology)
• Function
• Filter blood reabsorb nutrients
• Control water, ion, and salt balance of the body
• Maintain acid-base balance of the blood
• Excrete metabolic wastes (urea and uric acid),
  toxins, drug components
• Secrete hormones (renin, erythropoietin)
• Produce calcitriol (active form of vitamin D
  absorption of dietary calcium into the blood)

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• Kidney development through a series of successive
  phases
• the pronephros (most immature)
• mesonephros
• metanephros (most developed) which persists as
  the definitive adult kidney
• The final stage of kidney development,
  metanephros, arises caudal to the mesonephros at
  5 weeks of development.
• As the kidney develops in the elongating fetus,
  it 'ascends' from its original location (adjacent
  to the developing bladder)
• to its mature location in the retroperitoneum,
  just caudal to the diaphragm.
• As the kidney moves cephalad (towards the head)
  relative to the bladder, it takes new arterial
  supply from the aorta and
• new venous drainage into the vena cava.
• Kidney development is complex and developmental
  abnormalities are relatively common. They
  constitute an
• important consideration in pediatric nephrology.
• http//www.meddean.luc.edu/lumen/MedEd/urology/nlr
  endev.htm

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• Kidney structure bean shaped
• - capsule
• - cortex (outer)
• - medulla (inner)
• - hilum (pelvis, ureter, renal artery, vein)
• Cortex, renal columns (septa) of Bertin
• (cortical tissue on either side of the medullary
  pyramids)
• Medulla divided into several (8-18) conical
  pyramids
• Papillae at apex of medullary pyramid

Glossary capsule - a structure enclosing an
organ, usually composed of dense connective
tissue cortex - the outer portion of an organ,
distinguished from its inner, medullary
portion hilus or hilum - a depression or pit at
that part of an organ where the vessels and
nerves enter medulla - the inner portion of an
organ, usually in the center. See also
http//www.bu.edu/histology/m/glossary.htm
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on either side of medullary pyramid
Posterior division of
renal artery
Interlobular arteries

• Kidney blood supply
• 0.5 of total body weight, 25 of the cardiac
  output
• renal artery, anterior posterior divisions,
  segmental arteries (do not anastomose, end
  arteries)
• interlobar arteries on either side of medullary
  pyramid
• - arcuate artery (Latin curved) between cortex
  and medulla, parallel to kidney surface),
  interlobular arteries

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juxtamedullary glomerulus
Posterior segment

• interlobular arteries ? afferent arteriole ?
  glomerulus ? efferent arterioles
• efferent arterioles in the cortex form
  peritubular capillary plexus
• - efferent arterioles of juxtamedullary nephrons
  (juxta Latin close to)
• go into medulla and loop back vasa recta
  (straight vessels Latin)

Afferent, from afferre Latin to bring
toward Efferent, from efferre Latin to bring
out

• Correlation with pathology
• - cortex 90 of blood supply
• - medulla is relatively a-vascular (10, low
  oxygenation)
• tubular capillary beds derived from the efferent
  arterioles
• acute tubular necrosis (injury), papillary
  necrosis

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vascular pole
Bc

tubular pole
Glomerulus in paraffin section Bowmans capsule
(Bc) glomerular tuft
Afferent arterioles arise from interlobular
vessels and supply the glomeruli Efferent
arterioles arise from glomerular capillaries
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Glomerulus
Paraffin section

• network of capillaries
• - mesangium cells matrix
• (mes angium in the middle of vessels)
• contractile
• phagocytic
• proliferation
• - endothelium
• - basement membrane
• - 2 layers of epithelium
• visceral (aka podocytes) anchored on
  glomerular basement membrane
• parietal line Bowmans capsule

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Urinary space
podocyte foot process (pedicel) slit diaphragm
pedicellus Latin small foot)
lamina rara externa
glomerular basement membrane lamina densa
lamina rara interna
blood
fenestrated endothelium without diaphragms

• Electron microscopy of the glomerular capillary
  wall (aka glomerular filtration barrier)
• - fenestrated endothelium (fenestra Latin
  window)
• - glomerular basement membrane lamina rara
  interna externa, lamina densa
• visceral epithelial cells (podocytes) foot
  processes, filtration slits with thin diaphragm
• Note other capillaries in the kidney are
  fenestrated with diaphragms

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Foot process
Schematic drawing of the slit membrane -
disruption of the slit diaphragms or destruction
of the podocytes can lead to proteinuria where
large amounts of protein are lost from the blood
into urine - effacement of slit diaphragms with
fusion of the foot processes may be transient
and treatable or permanent Examples minimal
change disease, reversible Congenital disorder
Finnish-type nephrosis - neonatal proteinuria
leading to end-stage kidney failure, caused by a
mutation in the nephrin gene.
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Glomerular filtration barrier glomerular
basement membrane

• Glomerular basement membrane combined basal
  lamina of glomerular endothelium pedicels
• High permeability to water small solutes
• Impermeability to proteins
• - size barrier (lt70,000 MW and lt10 nm in
  diameter proteins pass easily)
• - charge dependent restriction
• Pathology
• Proteinuria, loss of charge, slit membrane
• Hematuria - loss of integrity, structural
  damage

Lamina rara externa interna heparan sulphate
(-) Lamina densa collagen type IV, laminin
(size)
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Glomerular filtrate primary urine 125
ml/min 180 L/24 hr 124 ml/min
reabsorbed Daily urinary output 1.5 L End of
the urinary tract part I
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Questions? mpicken_at_lumc.edu