Embryo

1. ‫اليمنية‬ ‫الجمهورية‬
‫والسكان‬ ‫العامة‬ ‫الصحة‬ ‫وزارة‬
‫البولي‬ ‫المسالك‬ ‫جراحة‬ ‫الختصاص‬ ‫العربي‬ ‫المجلس‬
‫ة‬
‫صنعاء‬ ‫مركز‬
–
‫اليمن‬
‫التعليمي‬ ‫الجمهوري‬ ‫مستشفى‬
Embryology of the Genito-urinary system
Prepared by : Dr. Salah M. AL-towaity.
Supervised : Dr. Abdulsamad Alsanapani

2. Renal systems during intra-uterine life
Pronephros Mesonephros Metanephros
Rudimentary and
nonfunctional
Function for a short
time during early fetal
period
form the permanent
kidney

3. 1- Pronephros:
 1st kidney to appear.
 In the beginning of 4th week.
 Developed from intermediate mesoderm ,
at cervical region of embryo.
 Formed form 7 cell clusters called
nephrotomes.
 Each nephrotome grows laterally and
canalized to form pro-nephric tubules.

4. 1-Pronephros:
The pro-nephric tubules:
 open medially into the intra-embryonic
coelom.
 There lateral ends grow in a caudal
direction and unite with each others to
form the pro-nephric duct that open into
the cloaca.
Fate of pronephros:
All pronephros disappear except pronephric
duct that form mesonephric duct for the
developing mesonephros.

5. 2- Mesonephros:
 2nd kidney to appear in the 4th week.
 Develops in the thoracic and upper lumber
regions of embryo.
 Form 70 mesonephric tubules.

6. 2- Mesonephros:
Each mesonephric tubules grows to form S shaped loop and acquire glomerulus.
Lateral end joins with mesonephric duct ( it is now the Wolffian duct ).

7. In the middle of the 2nd
month:
The mesonephros form ovoid organ
on either sides of the midline , there
is:
1- Genital ridge medially.
2-Wolffian duct laterally.

8. Mesonephros
Male
Tubules Duct
Vasa efferentia.
Head of
epididymis.
Body and tail of
epididymis.
Appendix of epididymis.
Vas deference.
Seminal vesicles.
Ejaculatory duct.

9. Mesonephros
Female
Tubules Duct
Epoophron
Paraophoron
Gartner’s duct

10. Metanephros ( Definitive Kidney).
Ureteric bud Metanephric mesoderm
It arises as an outgrowth
from lower end of
mesonephric duct.
It form the collecting
system of the kidney.
It form the excretory
system of the kidney.

11. Fate of the ureteric bud:
• It grows up forming the ureter.
• Its cranial end:
 bud penetrate the metanephric tissue , which is molded over its
distal end as a cap.
 Then dilate to form the renal pelvis and splits into cranial and
caudal portions.

12. Fate of the metanephric mesoderm:
• Cells of metanephric caps form renal vesicles that elongated to form S shaped loop.
• Proximal end form Bowman’s capsule that acquired glomerulus.
• Distal end connects with one collecting tubule.
• Continuous growth form PCT , loop od Henle and DCT.

13. Final changes of the developing kidney
Shape Position Blood supply Direction
At birth: its lobulated.
The lobulation
disappear during
infancy due to further
growth of nephron.
Its pelvic organ.
It become abdominal
organ
At pelvis : supplied by
median sacral artery.
With its ascent is supplied
form common iliac artery.
Finally supplies form
abdominal Aorta.
At first: Hilum looks
forward, then it
rotate 90 degree , so
the hilum looks
medially.

14. 1- Agenesis: due to
degeneration of ureteric bud.
It may be uni or bilateral.
2- Double kidney:
due to early splitting of
ureteric bud.
1- pelvic kidney:
due to failure of kidney to
ascent , usually caused by
arterial fork formed by
umbilical arteries.
2-Cross fused renal
ectopia.
Congenital anomalies of the kidney
Number Position

15. Aberrant renal artery:
due to persistence of one or more of
transient arteries.
The artery usually enter the kidney at its
pole ( lower).
Horse-shoe kidney:
fusion of lower poles of both kidney.
Low in position and usually hilum faced
forward.
Congenital anomalies of the kidney
Blood supply Shape

16. complete splitting of
the ureteric bud.
partial splitting of the
ureteric bud.
The ureteric orifice
opens into abnormal
site:
In male:
bladder neck , prostatic
urethra or rectum.
In female:
bladder neck , urethra ,
vagina or rectum.
Congenital anomalies of the ureter
Double ureter Bifid ureter Ectopic ureter

17. Development of the UB and urethra
Source of the UB :
Endoderm: see later
Mesoderm: the lower parts of both mesonephric ducts absorbed to form the
trigone.

18. The ventral part.
Its closed by uro-genital membrane.
Its connected to both mesonephric
duct and allantois.
The dorsal part.
Its closed by anal membrane.
Division of the coloaca (endoderm).
Primitive uro-genital sinus Ano-rectal canal

19. The superior expanded part
Its apex connected to
allantois.
The middle narrow part. The caudal flattened
part.
The mesonephric ducts are
attached to the sinus
between the vesical and
pelvic portions.
The uro-genital sinus
Vesical portion Pelvic portion Phallic portion

20. Epithelium of most of UB
except trigone.
In male:
pre-prostatic + upper ½ of
prostatic urethra.
In female:
the whole urethra.
In male:
lower ½ of prostatic
urethra + membranous
urethra.
In male:
most of spongy (penile)
urethra except at glans
of penis.
The pelvic and phallic
portions in female gives
vestibule and lower 2/3 of
the vagina.
Fate of uro-genital sinus
vesical portion Pelvic portion Phallic portion

21. due to failure of the lateral
body wall folds to close in
the midline in the pelvic
region.
These anomaly is rare ,
occurring in 2/10,000 live
births.
Urachal fistula.
Urachal cyst.
Urachal sinus.
Urachal diverticulum
Anomalies of the urinary bladder
Ectopia vesicae Patent urachus

22. Anomalies of the urinary bladder
Recto-vesical fistula:
Due to incomplete uro-rectal
septum.

23. Vesical portion of
uro-genital sinus.
Upper ½ : vesical
portion.
Lower ½: pelvic portion.
From pelvic portion. Major part: form
phallic portion.
Distal part (in glans):
Ectodermal ingrowth.
Source of the urethra
Pre-prostatic part Prostatic part Membranous part Spongy (penile) part

24. Urethral meatus on under
surface of penis.
Due to incomplete fusion
of urethral folds.
Urethral meatus on
dorsal surface of penis
Anomalies of the urethra
Hypospadias Epispadias

25. Development of the gonads
The development of the testis or ovary passes in 2 stages:
1. Indifferent gonads ( before the 7th week )
2. Stage of differentiation which includes development of the testis or development of
the ovary ( starts from 7th week) .
Each of the testis or ovary develops from :
1. Genital ridge : it is the medial part of the mesonephros , it gives capsule , stroma
( connective tissue of the gonad )
2. Coelomic epithelium. Which covers the genital ridge ( gives the six cords , sertoli or
follicular cells )
3. Primordial germ cells , which migrate from wall of the yolk sac ( which give
spermatogonia or ogonia which lies in between the cells of the sex cords

26. Development of the testis
The Y chromosome have a specific gene called SRY-SEX determining
region on Y gene that determines the formation of the testis and male
internal organs.
Anti-Mullerian hormone :
AMH production by the sertoli cells of the testis.
In male mammals, AMH prevents the development of the mullerian
duct into the uterus and other Müllerian structures

27. Give tunica albuginea ,
connective tissue stroma
and septate of the testis.
cover genital ridge.
Give testis cord which become
seminiferous tubules at puberty and join
the rete testis which entre the ductuli
efferentes (ductus deferens).
Migration form the wall of yolk
sac , give spermatogonia which
lie in between the cells of the sex
cord.
Development of the testis
Genital ridge (mesoderm) Coelomic epithelium (mesoderm) Primordial germ cells (endoderm)

28. Descent of the testis
It develops in the abdomen then descend reaching
the deep inguinal ring at 7th month.
It migrates in the inguinal canal at the 8th month.
It reach the scrotum just before birth.
Cause of descent:
1- Internal descent.
2- Rise of intra-abdominal pressure.
3- Shortness of gubernaculum.

29. In abdomen.
In the inguinal canal.
In superficial inguinal ring.
Descent in abnormal
position:
perineum , root of penis or
femoral triangle.
due to failure of obliteration
of processes vaginalis.
Anomalies of the testis
Undescending
testis(cryptorchism)
Maldescending testis (ectopic) Congenital inguinal hernia

30. Development of male external genitalia
Development of the external genitalia in male is under
the influence of androgen secreted by the fetal testis
and is characterized by rapid elongation of the phallus
that will form the penis.
The 2 genital folds are pulled by the elongated phallus
, They will form the edge of a groove called urethral
groove.
The endoderm of the bottom of the urethral groove
will form the urethral palate.
Fusion of the urethral folds from backward forward
will close over the urethral plate which form the
urethral canal.

31. The genital swelling, known in the male as the scrotal swelling, arise in the inguinal region.
They move caudally and each swelling then makes up of the scrotum.
They separated by the scrotal septum.

32. Development of the prostate
Prostate development results from complex interaction between urogenital sinus
epithelium and mesenchyme in the presence of androgen.
The prostate develops as multiple solid outgrowths of the urethral epithelium both
above and below the entrance of the mesonephric duct.

33. These simple tubular outgrowths begin to develop in five distinct groups at the end of the 11th
week .
Mesenchymal cells start to develop around the tubules by the 16th week and become denser
at the periphery to form the prostatic capsule.
By the 22 weeks , the muscular stroma is considerably developed, and it continues to increase
progressively until birth.
There is five groups of epithelial buds , which form five lobes: anterior , posterior , median and
two lateral lobes.
They meet, with no definite septa dividing them.
Development of the prostate

34. Thank
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