1. The document describes the development of the male and female genital systems from early embryonic stages through formation of the internal and external genitalia. 2. Key events include formation of the genital ridges which develop into testes in males and ovaries in females, descent of the testes into the scrotum, development of the duct systems including the vas deferens and epididymis in males and Mullerian duct regression leading to formation of the uterus and vagina in females. 3. External genitalia develop from the genital tubercle and swellings, with the penis and scrotum forming in males and clitoris, labia, and vagina developing in females.

1. Development of the Genital
System
Mohammed Alhaji Buba B.Sc., M.Sc., MCIPDM

2. Development of the ovaries
Early developmental stages of the ovary are exactly the same
as the testis
1. The coelomic epithelium on the medial side of the
mesonephros becomes thickened to form the genital ridges
2. Cords of cells proliferate to germinal epithelium and
grows into the underlying mesoderm
3. Primordial germ cells that are formed in relation to the
yolk sac migrate to the region of the developing ovary and
give rise to the oocytes
4. The sex cords become broken into small masses. The cells
of each mass surrounds one primordial germ cell or oocyte
to form aprimordial follicle.

3. Descends of the ovary
Ovary descend from the lumber region where it is
formed to the pelvis. There is formation of
gubernaculum as in male and extends from the
ovary to the labia majus.
It becomes attached to the uterus at its junction with
the uterine tube the part of the gubernaculum that
persist between the ovary and uterus becomes the
round ligament of ovary. The between the uterus
and the labia majus becomes the round ligament of
the uterus.

4. Anomalies of the ovary
1.Absence of the ovary on one or both sides
2.Duplication of the ovary
3.Descend of the ovary into the inguinal canal or
labium majus
4.adrenal or thyroid tissue may be present in the
ovary. the sometimes contain cells that are capable
of differenciating into various tissues like bone,
cartilage, hair e.t.c and growth of the rest of the cells
can give rise to perculiar tumour called teratoma,

5. Paramesonephric duct
This structure remains
rudimentary in males, the greater
part of it disappears however, the
cranial end of it persist as a small
rounded body attached to the
testis (appendix of the testis).
It has generally been considered
that the prostate utricle represents
the utero-vaginal canal in male,
therefore a homologue of the
uterus however, it is now believed
that it corresponds mainly to the
vagina.

6. DEVELOPMENT OF THE UTERUS
The uterus develops from
two major sources;
a. Uterovaginal canal:
develops the epithelium of
the body of the uterus.
b. Mesoderm sorrounding
the uterovaginal canal:
develops muscles of the
uterus (myometrium).
c. Unfused part of the
paramesonephric duct:
develops the fundus of the
uterus.

7. Development of the External Genitilia
Following formation of the
Uro-rectal septum, the cloacal
membrane is therefore
subdivided into:
Ventral, urogenital membrane
Caudal, Anal membrane
Urogenital membrane becomes
elongated in a cranio-caudal
direction and the mesoderm on
either side of it is soon heaped
up to form longitudinal
elevation called primitive
urethral folds.

8. External genitilia in Females
• The genital tubercle becomes cylindrical and
forms the clitoris
• The genital swellings enlarge to form the
Labia majus their posterior end fuse across the
midline to form the posterior commissure.
• The urogenital membrane breaks down so that
continuity is established between the
urogenital sinus and the exterior.

9. External genitilia in Females
• The primitive urethral folds forms the labia
minora.
• Note: labia minora is lined on the outside by
ectoderm and on the inside by the endoderm.

10. Development of the vagina

11. Development of the testis
• It develops from coelomic
epithelium that covers the
medial side of the
mesonephros of the
corresponding side.
• Genital ridge is formed on
the region where the testis is
to develop to thickening of
the germinal epithelium.
Proliferation of the germinal
epithelium results in in the
formation of number of slid
sex cords which grow into
the under lying
messenchyme and reach
deep into the gonad and are
called medullary cords

12. Development of the testis cont.
• The sex cords soon
canalised to form
seminiferous tubules.
• The primary primordial
germ cells migrate to the
region of the underlying
testis and get incorporated
into the seminiferous
tubules.
• Interstitial cells are derived
from
1. Sex cords that are not
canalised
2. Sorounding messenchyme

13. Development of the testis
Duct system of the testis
• Testis develops in close proximity with the
mesonephros and mesonephric duct
• Mesonehric duct degenerates, however some
persist. The persist ones along with the
mesonephric duct forms the duct system of the
testis

14. Development of the testis cont.
1. Rete testis is formed as a result of
anastomoses between the ends of the
seminiferous tubules.
2. Vasa defferencia is formed when the rete
testis establishes contact with the existing
mesonephric tubules.
3. Epiddedymis is formed when the cranial part
of the mesonephric duct becomes highly
coiled on itself.

15. • Note : seminal vesicle arises on either side as a
diverticulum from the lower end of the
mesonephric duct.
• The part of the mesonephric duct between its
opening into the prostatic urethra and the
origin of this diverticulum forms the
ejaculatory duct.

16. Descend of the testis
• In relation to the posterior
abdominal wall
• Descend to the scrotum and
reach the iliac fossa during
the 3rd month and lie at the
side of the deep inguinal
ring at the 7th month of intra
uterine life.
• They pass through the
inguinal canal in the 7th
month and reach the
scrotum by the eight month.

17. Testis descend due to the
following:
• Differential growth of the
body wall
• Formation of inguinal
bursa
• The gubernaculum
• Processus vaginalis
• Hormones of the pars
anterior of the hypophysis
cerebri

18. Anomalies of the testis
• Absence of the testis on one or both sides
• Testis may be reduplicated
• The two testis may be fused together
• cryptochidisms

19. Anomalies of descend
The testis may failed to descend and may be in
the following position
Lumber region
Inguinal canal
Illiac fossa
Upper part of the scrotum

20. Anomalies of the duct system
1.The seminiferous tubules may fail to establish
connection with the vasa deferencia
2.The ductus deference may absent , in whole or
in part on one or both sides
3.The ductus deference may have no connection
with the epididymis

21. Anomalies of processus vaginalis
Part of the processus vaginalis that extends from
the deep inguinal ring up to the tunica vaginalis
normally disappears, this may persist in whole or
in part. Abdominal content may enter it to
produce various forms of inguinal hernia.
Alternatively fluid may accumulate in it
producing the condition called hydrocoele.

22. Development of the penis

23. • The genital tubercle is now cylindrical called
the Phallus. It undergoes great enlargement to
form the penis. As Phallus grows, the glans
becomes distinguishable by the appearance of
coronary sulcus.
• The prepuce is formed by reduplication of the
ectoderm covering the distal part of the
phallus.

24. We have seen that the urogenital membrane lies
in a linear groove flanked on either side by the
primitive urethral folds.
As phallus grows the groove elongates and
extends on the undersurface. The groove is lined
by ectoderm and is termed as primitive
urethral groove.

25. • It is clear that the phallus is closely related to
the endodermal lining of the phallic part of the
UGS.
• The endodermal cells proliferate and grow into
the phallus in the form of solid plate of cells
called the urethral plate.

26. • The urogenital membrane soon breaks down so
that UGS (Phallic part) opens to the outside in
the caudal part of the primitive urethral
groove.
At the same time the cells forming the core of
the urethral plate degenerate along with the
ectodermal cells lining the primitive urethral
groove.

27. In this way a deeper groove called the definitive
urethral groove lined by endodermal cells is now
formed on the undersurface of the phallus.
At the base of the phallus, this groove is
continuous with the cavity of the UGS. The
margins of this groove is called the primitive
urethral folds.
This folds now approach and fuse with each
other.

28. The fusion begins posteriorly in the regions of
the UGS and extends forward onto the Phallus.
The penile urethra is formed as a result of this
fusion. It will now be apparent that the wall of
the:
1. Original endodermal lining of the phallic part
of the UGS
2. Endodermal cells of the urethral plate.

29. The penile urethra formed in this way extends
only up to the glans penis.
The distal most part of the urethra is ectodermal
in origin and is formed by the canalization of the
solid mass of ectodermal cells
The genital swellings fuse with each other, in the
midline to form the scrotal sac into which testis
later descend.