Urinary system. General outline

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					Urinary system
             General outline
 component
 urinary organs: kidneys
 micturition organs: ureter, bladder and urethra
 function
 discharge metabolite
 regulate the balance of water and electrolyte
 endocrine function: renin, erythropoietin,
       Renal anatomic structure

 Fibrosa
                         Cortical labyrinth
                         Medullary ray
 Parenchyma
                          Renal pyramids
                          Renal columns
      Renal histological structure
            Renal corpuscles
                               Bowman’s capsule
 nephron
            Renal tubules

 collecting duct

 juxtaglomerular apparatus
Renal cortex   Renal medulla
  Structure of Renal corpuscle:

      afferent arteriole     efferent arteriole
               capillary network
               mesangial cells

            parietal layer: simple squamous Epi.
         capsular cavity: filtrate
            visceral layer: podocytes
     (primary and secondary processes, slit membrane)
Renal corpuscle   Glomerulus
      Functions of Renal corpuscle:

 Produce filtrate (primary urine)

                         fenestrated endothelium
 Filtration membrane basement membrane
    (filtration barrier)
                         slit membrane of podocyte

                                 molecular weight
 relevant factors of filtrate
    Renal tubules:

            convoluted tubule
            straight tubule

thin segment                    Henle’s loops

         straight tubule
         convoluted tubule
               Proximal tubule

 Location: cortical labyrinth

 LM: simple cuboidal or pyramid Epi.
      acidophilic cytoplasm
      no discrete cell margin;
      brush border;
      longitudinal striation
Convoluted segments of proximal
       and distal tubules
EM: apical canaliculi and vesicles
      numerous lysosomes, Mi.
      many lateral interdigitations
      microvilli on the surface
      membrane invaginations
      abundant Na+-K+ATPase
 Function

 reabsorb water, glucose, amino acid,
  protein, vitamin and inorganic salts etc.
 secrete ammonia and some metabolic
                thin segment
 location: medullary ray and renal pyramids
 LM: simple squamous Epi.; pale cytoplasm,
 EM: a few microvilli; less organelles
 Function: water, and ions pass through easily
Thin segment and straight
 segment of distal tubule
               Distal tubule
 location: medullay ray and renal pyramids
 LM: simple cuboidal Epi;
      clear cell boundary;
      pale cytoplasm;
      nuclei near lumen;
      without brush border;
      have longitudinal striation
 EM: a few microvilli;
      many membrane invagination;
      many mitochondria;
      abundant Na+-K+ATPase
 Function: reabsorb Na+ and water;
           excrete K+; secrete NH3
Distal straight tubules and
    collecting tubules
Convoluted segments of proximal
       and distal tubule
  Collecting tubules:
 location: medullary ray and renal pyramids
 components: arched collecting tubules;
               straight collecting tubules;
               papillary ducts
 simple cuboidal Epi simple columnar Epi.,
  papillary ducts line tall columnar Epi;
  pale staining; distinct borders;
  rare microvilli and Mi.
 function: similar to that of distal convoluted
 Straight segment of distal
tubule and collecting tubule
   Juxtaglomerular apparatus:
 located in a triangle area at the vascular pole of
the renal corpuscles
 consist of juxtaglomerular cells, macular densa
 and extraglomerular mesangial (polar cushion)
 function: control water and electrolyte balance;
           regulate blood pressure;
           produce erythropoietin
             Juxtaglomerular cells
 smooth muscle cells of the afferent arteriole
 transform into the epithelial cells
 cytoplasm: a few myofibrils;
    PAS-positive granules contained renin;
    abundant RER, ribosomes and
    well developed Golgi apparatus;
 function: secrete renin and erythropoietin
                Macular densa

 transformed from the cells of distal tubule
 which near the vascular pole of the renal corpuscle
 the cells become taller and narrow, arranged
 compactly; pale cytoplasm; nuclei located at the
 a chemical (Na+ ) sensor
Macular densa
    Extraglomerular mesangial cells

 resemble the intraglomerular mesangial cells
 gap junctions between the component of the
 juxtaglomerular apparatus
 transmit information
   Features of renal blood circulation
 blood flow is large
 two sets of capillary network
 the diameter of afferent arterioles is larger
 than that of efferent, so as to facilitate filtration
 the vasa recta are parallel to the Henle’s loop, so
 aid water reabsorption and urine concentration
Blood vessels
  of kidney
           Micturition organs
              (ureter, bladder,)

            Epi: transitional Epi
 mucosa
            Lamina propria: L.C.T.

 muscle layer: smooth muscle

 adventitia: fibrosa