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Development of the urinary system

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					Dr Mostafa Kandil   1
          Development of the urinary system




Dr Mostafa Kandil                             2
        Development of the urinary
                system




Dr Mostafa Kandil                    3
                    objectives
1. To revise general embryology
2. To understand the 3 kidney system
3. To know the stages of development of
   ureter,urinary bladder and urethera
4. To list the congenital anomalies of the
   urinary system



Dr Mostafa Kandil                            4
Dr Mostafa Kandil   5
   A - Development of the kidney
The kidney is composed of several units
   called the uriniferous tubules.
These tubules arise from the mesoderm of
   the intermediate cell mass or nephrogenic
   cord.
It lies between somites and intraembryonic
   coelum.


Dr Mostafa Kandil                              6
During their development ,vertebrates
have developed three kidneys:

                     1.Pronephros .
                    2.Mesonephros.
                    3.Metanephros.


Dr Mostafa Kandil                       7
                    1-Pronephros
• It is the first kidney to appear.
• It is simple in structure,temporary and has
  no function.
• It lies in the cervical region extending from
  7th to 14th somites.
• Collected to form pronephric duct ending
  in the cloaca.

Dr Mostafa Kandil                                 8
               Fate of the Pronephros
• The pronephros is vestigial
  and has no function.
• Its degeneration is complete in
  5 mm embryo.
• The pronephric duct remains

 Dr Mostafa Kandil                      9
         2-Mesonephros (Wolffian)
•   It is the second kidney to appear
•   In the 4th week
•   In the thoracic and upper lumbar region.
•   The mesonephric tubules end in the
    pronephric duct which is now called
    mesonephric duct (Wolffian duct)



Dr Mostafa Kandil                              10
              Fate of the Mesonephros
• In male
• The upper tubules degenerate forming the
  suspensory ligament of the testis (or ovary in female).
• The middle tubules form efferent ductules of the
  testis
• The mesonephric (Wolffian) duct becomes vas
  deferens and ejaculatory duct in male.
• In female it degenrates leaving few rudimentary
  ducts (ep &par oophoron).


   Dr Mostafa Kandil                                        11
                    3- Metanephros
         • It is the last and permanent
                       kidney.
             • It has a double origin:
          a. Ureteric bud
          b. Metanephric cap

Dr Mostafa Kandil                         12
Dr Mostafa Kandil   13
Ureteric bud
• Arises as a diverticulum from lower part of
  the mesonephric duct near the cloaca.
• Extends dorsally then cranially.
• Its upper end elongates forming pelvis of
  the ureter.
• Divides into cranial ,centeral and caudal
  tubules.

Dr Mostafa Kandil                           14
Ureteric bud (cont.)
• Secondary tubules arise and give further
  tubules and the process repeated.
• In the 5th month about 12 generations are
  formed.
• At birth there are about 20 generations.




Dr Mostafa Kandil                             15
    Differntiation of metanephric cap
• Arises from nephrogenic cord (intermediate cell mass).
• The metanephric tissue surrounds the
  collecting tubules (developed from ureteric bud).
• It divides into numerous masses.
• They divide into smaller masses.
• Each mass forms one of the secretory
  tubules.

Dr Mostafa Kandil                                          16
        Differentiation of Metanephric cap
                        cont.
• The spherical mass converted into hollow vesicle
• Which becomes elongated and S-shaped in
  appearance.
• One end joins the collecting tubule and the other
  blind end forms the Bowman`s capsule.
• Further growth leads to formation of PCT,DCTand loop of
  Henle




 Dr Mostafa Kandil                                          17
                       Cont.
• The formation of tubules stops one month before
  birth when about 1 million tubules have been
  formed in each kidney.
• Any increase in kidney size after birth results from
  enlargment of the tubules already present.
• The human kidney is capable of secretion in the
  third month of fetal life.
• Since the placenta acts as excretory organ,renal
  function is minimal or nil.
• Urine is formed by the kidney and passes in the
  amniotic fluid.

 Dr Mostafa Kandil                                   18
                    Geneva




Dr Mostafa Kandil            19
                    Shape of the kidney
• In early stages the kidney is lobulated
  organ,later these grooves disappear and
  the surface of the kidney is smooth.
• Lobulation is a permanent feature in
  reptiles ,birds, whales and ox.




Dr Mostafa Kandil                           20
                    Migration of the kidney

• In early stages the kidney lies in the
    pelvic region.
• Later it migrates upwards till it lies in the
  upper part of the posterior abdominal wall.




Dr Mostafa Kandil                             21
       Change of blood supply of the
                  kidney
• During its migration the kidney changes its
  blood supply.
• At first it receives its blood from the
  median sacral ,the common iliac and then
  from the lower part of abdominal aorta
• Accessory renal arteries may occur



Dr Mostafa Kandil                           22
               Rotation of the kidney
• At first the convex border of the kidney is
  directed posterioly while the hilum lies
  ventrally
• Later the kidney rotates about 90 degrees
  and the dorsal convex border becomes
  lateral.



Dr Mostafa Kandil                           23
Dr Mostafa Kandil   24
Congenital anomalies of the Kidney
1.     Unilateral renal agenesis
2.     Unilateral dwarfed or hypoblastic kidney
3.     Supernumerary kidney ; 3 or more
4.     Horse-shoe kidney
5.     Cake kidney
6.     Double ureter
7.     Persistent lobulation
8.     Congenital cystic kidney
9.     Pelvic kidney

Dr Mostafa Kandil                                 25
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Dr Mostafa Kandil   28
         Variations of kidney anatomy: double kidneys, Cake kidneys




Dr Mostafa Kandil                                               29
Dr Mostafa Kandil   30
                        Cloaca
•   LOWER EXPANDED PART OF THE HIND GUT
•   ENDODERMAL in origin
•   CONTINEOUS ABOVE WITH ALLANTOIS
•   IT ALSO RECEIVES MESONEPHRIC DUCTS.

• Urorectal septum divides the cloaca into:
•   A. a small dorsal part(rectum)
•   B. an anterior part(primitive urogenital sinus)


    Dr Mostafa Kandil                                 31
          Primitive Urogenital sinus
• It is the anterior part of cloaca
• A constriction divides it into 2 parts;
  a.vesico-urethal portion gives the
  bladder and prostatic urethra.
  b.definitive urogenital sinus gives rest
  of prostatic and membranous urethra .
  its lower part gives penile urethra

Dr Mostafa Kandil                        32
   B- Development of the urinary bladder
• It develops from the anterior ventral part of
  the cloaca (vesicourethral ortion){endoderm}
• Early it receives common stem of ureters and
  mesonephric ducts(mesoderm)
• Later on absorbed and open
  separately(trigone).
• Dilated sac connects umblicus called
  urachus ,obliterates after birtth –> median
  umblical ligamnt.
Dr Mostafa Kandil                          33
Dr Mostafa Kandil   34
                     interureteric ridge
 detrusor muscle


                              1″
 sphincter vesicae



Trigone




     Prostatic
     utericle




 Dr Mostafa Kandil                         35
             Abnormalities of Bladder
1. Rarely consisted of 2 or 3 parts
2. Ureter may end in urethra, seminal vesicle,
   rectum, uterus or vagina
3. Persistent urachus: urine flow out of umbilicus
4. Recto-vesical fistula
5. Urachal cyst or sinus
6. Ectopia-vesica:
   absence of anterior abdominal wall and
   anterior wall of bladder
  Dr Mostafa Kandil                           36
Dr Mostafa Kandil   37
          C- Development of urethra
• Female urethra
  is totally derived from vesicourethral portion of th
  cloaca
• Male urethra: upper prostatic from vesicourethal
  ,lower prostatic and membranous from pelvic
  urogenital sinus
• Penile from phallic portion of the sinus
• Glans penis urethra develops from ectoderm

  Dr Mostafa Kandil                              38
                    Male Urethra (20 cm)
  3 regions of urethra
        prostatic urethra, membranous urethra & spongy urethra




Dr Mostafa Kandil                                                39
                    Anomalies of urethra
• Hypospadias :
    external urethral orifice opens in the ventral part
    of the penis,scrotum or perinium


• Epispadias:
    the external urethral orifice is situated on
    the dorsal surface of the penis


Dr Mostafa Kandil                                     40
Hypospadia: Urethral opening on underside of
                   penis
 Dr Mostafa Kandil   www.ammerland-klinik.de/ urologie/hypospadie.jpg   41
Dr Mostafa Kandil   42
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                        summary
1.     The kidney passes three systems during development
       (pronephron,mesonephron and lastly metanephron)
2.     Permanent kidney is pelvic then ascends to its definite
       location
3.     Ureters develop from mesonephric duct then undergo
       20 generations
4.     Urinary bladder and most of urethera develops from
       anterior part of cloaca
5.     Congenital anomalies result from agenesis
       ,malrotation ,no closure ,non union and fragmentation
       of the developing embryonic tissues.


Dr Mostafa Kandil                                            45
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posted:3/28/2013
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