Urinary system

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Urinary system

• 2 Kidneys.
• 2 ureters.
• Urinary bladder.
• Urethera.

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A hemisected vew of the kidney
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Kidney

• Cortex---Dark brown and granular.
• Medulla---6-12 pyramid-shape regions (renal
  pyramids)
• The base of pyramid is toward the cortex
  (corticomedullary border)
• The apex (renal papilla) toward the hilum that
  perforated by 12 openings of the ducts of Bellini
  in region called area cribrosa . The apex is
  surrounded by minor calyx.
• Pyramids are separated by cortical columns of
  Bertin
• 3or4 minor calyces join to form 3or 4 major
  calyces that form renal pelvis.

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Cortical arch

• Is formed of
• Renal corpuscles (red dots).
• Convoluted tubules
• (cortical labyrinth).
• Medullary rays
• (cortical continuation of pyramids).
• NB. Lobe of the kidney is formed of
• a- Renal pyramid.
• b-Cortical columns.
• c-Cortical arch
• Each medullary ray with part of the cortical
  labyrinth surrounding it form kidney lobule.

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Uriniferous tubule

• Is the functional unit of the kidney.
• Is formed of
• 1- Nephron.
• 2-Collecting tubule.
• They are densely packed.
• They are separated
• by thin stroma
• and basal lamina.

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Nephron

• There are 2 types
• a-Cortical nephrons.
• b-Juxtamedullary nephrons.
• It is formed of
• 1-Renal corpuscle.
• 2-Proximal tubule.
• 3-Thin limbs of Henles loop.
• 4-Distal tubule

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Renal corpuscle

• Glomerulus (tuft of fenestrated capillaries)
• Bowmans capsule (Parietal layer, urinary or
  glomerular space and visceral layer or
  podocytes).
• Mesangial cells (intraglomerular
  extraglomerular).

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Renal cortex
Renal corpuscle
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Blood-Renal Barrier
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Filtration barrier

• Endothelial wall of the capillaries.
• The basal lamina (inner and outer laminae rarae
  and middle lamina densa).
• Visceral layer of Bowmans capsule (podocytes)
• Podocytes have primary (major) processes and
  secondary (minor) processes (pedicles).
• Between pedicles (on the surface of capillaries)
  there are filtration slits that
• have slit diaphragm

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Proximal tubule

• It has 2 regions
• 1-Pars convoluta (Proximal convoluted tubule).
• 2-Pars recta (descending thick limb of Henles
  loop).
• It is composed of simple
• cuboidal epith.with acidophilic
• cytoplasm. The cells have striated
• or brush border and lateral
• interdigitations. They have
• well-defined basal lamina.

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Cell of proximal tubule
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Thin limb of Henles loop

• It has 3 regions
• 1-Descending thin limb.
• 2-Henles loop.
• 3-Ascending thin limb.
• NB. It is longer in juxtamedullary
• nephron than in cortical nephron.
• It is composed of simple
• squamous epith.

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Renal medulla
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Distal tubule

• It has 3 regions
• 1-Ascending limb of Henles loop (low cuboidal
  epith.).
• 2-macula densa (tall narrow cells).
• 3-Pars convoluta (distal convoluted tubule)
  formed of low cuboidal epith.
• NB. Because distal convoluted are much shorter
  than proximal convoluted tubules, any section of
  renal cortex presents many more sections of
  proximal convoluted tubules.
• Distal tubules drain into collecting tubules.
• Aldosterone hormone increase the active
  rebsorbtion of sodium from the lumen of tubule
  into interstitium.

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Distal tubule cells.
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Juxtaglomerular apparatus
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Juxtaglomerular apparatus

• It has 3 components
• A-The macula densa of distal tubule.
• B-Juxtaglomerular cells of afferent glomerular
  arteriole (modified smooth muscle of tunica
  media). They secrete renin,angiotensin-converting
  enzyme and angiotensin.
• C-The extraglomerular mesangial cells.

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Juxtaglomerular apparatus
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Collecting tubules

• Are composed of simple cuboidal epithelium.
• They arent part of nephron.
• They have 3 regions
• 1-Cortical.
• 2-Medullary.
• 3-Papillary (ducts of Bellini) they open in area
  of cribrosa.
• They are formed of a-principle cells.
• and b-intercalated cells.
• They are impermeable to water except in presence
  of antidiuretic hormone.

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Cells of collecting tubule
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Renal interstitium

• It is a very flimsy, scant amount of CT contains.
• 1-Fibroblasts.
• 2-Macrophages.
• 3-Interstitial cells (their nuclei are elongated
  and they contain lipid droplets). They secrete
  medullipin I, which is converted in the liver
  into medullipin II, that lowers blood pressure.

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Calyces

• Each calyx accepts urine
• from the renal papilla of
• a renal pyramid.
• They are lined with
• transitional epith., lamina propria
• and smooth muscle.
• Minor calyces merge to form major calyces (with
  same lining tissue as minor calyces).
• Major calyces open into renal pelvis.

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Renal papilla and minor calyx.
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Ureter

• 1.Mucosa is formed of transitional
• epith. And lamina propria.
• 2.Muscularis (muscular coat)
• is formed of 2 layers of smooth muscle
• A-Inner longitudinal.
• B-Outer circular.
• 3.Adventitia (fibrous CT covering).

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Urinary bladder

• It has the same structure as the ureter EXCEPT
• The dome-shaped cells have plaques (rigid,
  thickened regions of plasmalemma)
• Between plaques there are normal cell membrane
  (interplaque regions).
• It has 3 layers of smooth muscle,
• inner and outer longitudinal and
• middle circular.
• Its outer covering is serosa.

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Urinary bladder
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Female Urethra

• Female urethra is short and lined by
• 1-Transitional epith. Near the bladder.
• 2-Pseudostratified columnar epith. And stratified
  squamous non-keratinized epith.
• 3-Subepth.fibroelastic CT that contains glands of
  Littre (mucus secreting glands).
• 4-Smooth muscle (inner longitudinal and outer
  circular layer).

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Male Urethra

• It is long and is divided into 3 regions
• 1-The prostatic urethralined with transitional
  epith.
• 2-Membranous urethra---lined with
  pseudustratified columnar and stratified columnar
  epith.
• 3-Penile (spongy) urethra---lined with
  pseudostratified columnar, stratified columnar
  and stratified squamous non-keratinized epith.
• Its lamina propria contains mucus secreting
  glands of Littre.

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Kidney-Cortex Medulla
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Ureter
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Urinary bladder