Download 2- urinary bladder development

Development of the
urinary bladder
and
Urethra
Objectives
Discuss the development of bladder, •
ureter, and urethra.
Describe the congenital anomalies of both •
the urinary bladder and urethra.
• The Cloaca is the
dilatation of hind gut
closed by The cloacal
membrane
• The Cloaca receives
three openings:
- The Alantois ventrally
- 2 Mesonephric ducts one
on each side
Division of the cloaca
-Occurs during 4th to
7th weeks
- Urorectal septum ,
which is a
mesodermal septum,
divides cloaca into:
1-Primitive
urogenital sinus
anteriorly
2- Anorectal canal
posteriorly
After division of the cloaca, the anorectal •
canal becomes continuous with the
hindgut to form the Rectum and Anal canal
Formation of primitive
urogenital sinus & anorectal
canal
Division of cloacal membrane
Urorectal septum divides the
Cloacal
membrane into:
1- The urogenital
membrane
anteriorly
2- The anal
membrane
Cloacal membrane
urogenital membrane
(anteriorly)
anal membrane
(posteriorly)
Urogenital
membrane
Urorectal
septum
Anal
membrane
Division of the primitive
urogenital sinus
The
entrance
of
the
mesonephric ducts into the
primitive urogenital sinus
divides it into:
1- An upper part called the
“vesico-urethral canal (3)”
2- A lower part called the
“definitive urogenital sinus”
which is subdivided into:
A- A pelvic part (6)
B- A phalic part (4) closed by
the urogenital membrane
Urorectal septum
Cloaca
Cloacal
membrane
Vesicouretheral
canal
Definitive
Urogenital
sinus
Primitive
Urogenital
sinus
Anorectal canal
Pelvic part
Phalic part
Formation of the Trigone &
migration of the
Mesonephric ducts
-The caudal parts of the mesonephric ducts are
absorbed into the wall of the urinary bladder
forming the trigone.
- The mesonephric ducts migrate to open into
future prostatic urethra leaving the ureters
opening into lateral angles of the trigone
1- mesonephric duct
2-ureter
3-bladder
trigone
Migration of the
mesonephric
ducts to open
into the
prostatic
urethra
- The greater part of the urinary bladder develops
from the vesico-rethral canal
- The apical part develops from the proximal part of
alantois
- The distal part of the alantois is obliterated to form
the median umbilical ligament ( Urachus)
- The trigone develops from the absorbed caudal
parts of mesonephric ducts
• The mucosa of urinary bladder has double
origin:
1.The trigone is mesodermal in origin
develops from the lower parts of both
mesonephric ducts.
2.The remaining part is endodermal in origin
develops from the vesico-urethral canal
(upper part of the primitive urogenital
sinus).
• The muscle of the urinary bladder is
derived from the splanchnic mesoderm.
Congenital anomalies of
urinary bladder
Urachal fistula, cyst & sinus
-Allantois fails to
obliterate
-urine passes from
the umbilicus
-Localized area of the
allantois persists
-Secretory activity of
epithelium results in
cystic dilatation
-Proximal part of alantois
is obliterated and distal
part persists.
Serous fluid is discharged
through umbilicus
Ectopia vesica
• The posterior wall of the urinary bladder is exposed to the
exterior.
• It is caused by the failure of the anterior abdominal wall
and anterior wall of the bladder to develop.
• It is due to inability of the mesoderm of the primitive
streak to migrate around the cloacal membrane
Development of the urethra in male
-The Upper part of
prostatic
urethra
develops from the vesicourethral canal
-The Lower part of
prostatic urethra and
membranous
urethra
develop from the pelvic
part
of
definitive
urogenital sinus
-The
Penile
urethra
develops from the phalic
part
of
definitive
urogenital sinus
• The Upper part from the
vesicourethral canal
• The Lower part from the
pelvic
part
of
the
definitive
urogenital
sinus
• From the pelvic part of
the definitive urogenital
sinus
• From the phalic part
of
the
definitive
urogenital sinus
• The
surrounding
connective
tissue
and
smooth muscle tissue is
derived from the splanchnic
mesoderm
Development of the urethra in
female
The female urethra develops
from
canal
the
vesicourethral
• The female urethra
develops from the
vesicourethral canal
• The
surrounding
connective tissue and
smooth muscle tissue is
derived
from
the
splanchnic mesoderm
Fate of the primitive urogenital sinus:
A- Vesicouretheral canal:
-1-Forms most of urinary bladder in both sexes.
-2-Female urethera.
-3-Upper ½ of prostatic urethera.
N.B. Absorbed mesonephric ducts form:
1-Trigone of the bladder.
-2-Back of female urethera.
-3-Back of upper ½ of prostatic urethera.
B- Pelvic part of the defenitive urogenital
sinus:
Forms the lower ½ of the prostatic urethera and
the membranous urethera.
C- Phalic part of the definitive urogenital
sinus:
- Forms the uretheral plate which is transformed
into the uretheral canal that forms the penile
urethera except in glans penis which is developed
from cord of ectodermal cells which becomes
canalized and communicates with rest of the
urethera.
CONGENITAL ANOMALIES OF
URETHERA
Epispadius: when the urethera opens into •
the upper surface of penis.
Hypospadius: when the urethera opens •
into the lower surface of penis.
Thank you