Understanding developmental anatomy of reproductive systems.

1. DEVELOPMENT OF THEDEVELOPMENT OF THE
REPRODUCTIVE (GENITAL)REPRODUCTIVE (GENITAL)
SYSTEMSYSTEM
DrDr
Shittu-LAJShittu-LAJ

2. OBJECTIVE:OBJECTIVE:
• Explain sex determination in human embryos
and the meaning of the terms chromosomal
sex, genetic sex and the phenotypic sex.
• Describe the development of the ovaries,
testes, genital ducts and external genitalia.
• Describe the congenital abnormalities
associated with the development of the genital
system.

3. Development ofDevelopment of
GonadsGonads
• The gonads develop from intermediate
mesoderm.

4. The Indifferent orThe Indifferent or
Undifferentiated GonadsUndifferentiated Gonads
• 5th
week
• Mesodermal epithelium medial to mesonephros
• Gonadal ridge
• Primary sex cords
• (ex) cortex and (in) medulla

5. Primordial Germ CellsPrimordial Germ Cells
• Spherical sex cells
• Endodermal cells of yolk sac
• The gonads develop as primordial germ
cells that form in the wall of the yolk sac
,close to the allantois
• migrate along the dorsal mesentery of the
hindgut to invade the genital ridges.
• Species: Day Gestation: Approx. Human Age:

6. Primordial Germ CellsPrimordial Germ Cells

7. Sex DeterminationSex Determination
• Chromosomal and genetics
• Testis determining factor (TDF)
• Sex determining region of the Y (SRY)
• Absence of Y (XX) results in ovary formation
• Although genetic sex (XX or XY) is determined at
fertilization,
• The embryo’s gender is not distinguishable for the first
six weeks of development; this is known as the
indifferent period of development.
• Characteristics of either male or female genitalia can
often be recognized by week twelve of development

8. mesentery is shown on this micrograph
Species: Mouse Day Gestation: 11 Approx. Human Age:
6 weeks View: Transverse Cut

9. Development of the TestesDevelopment of the Testes
• 1. TDF
• 2. 8th
week Testosterone
• 3. Müllerian - inhibitory factor (MIF)
• The primordial germ cells become surrounded
by cells of the primitive sex cords.
• At this stage the gonad is "indifferent," as one
cannot morphologically distinguish between the
male and female.

10. Male Development
• testis determining factor (TDF) gene (on Y ch.) causes
sex cords to form seminiferous tubules
• TDF induces primary sex cords to become prominent
and convoluted; they then separate from the
epithelium
• a fibrous thick capsule forms around the cords (Tunica
albuginea); they become known as the seminiferous
cords
• enlarged testes separate from the degenerating
mesonephros and become suspended by mesentery
(mesorchium)
• by week 8, interstitial cells of Leydig develop and
produce testosterone that induces masculine
differentiation

11. • Sertoli cells produce Mullarian Inhibiting Factor (MIF),
which suppresses development of the
paramesonephric duct
• seminiferous cords derived from the primary sex cords
develop into seminiferous tubules, tubuli recti and rete
testes
• rete testes becomes continuous with 15-20
mesonephric tubules that become the efferent
ductules, which are connected to the part of the
mesonephric duct near the testis that becomes the
ductus epididymis

12. • the remainder of the mesonephric duct
develops into the ductus deferens, seminal
vesicle and ejaculatory duct . the prostate
arises from urethral endodermal outgrowths
• the bulbourethral glands arise from spongy
tissue of the urethra just inferior to the
prostate

13. Development of the OvariesDevelopment of the Ovaries
• Primary sex cords
• Rudimentary rete ovarii
• Secondary sex cords - cortical cords
• primordial follicles

14. Female Development
• absence of TDF causes gonads to develop
into ovaries
• in absense of TDF, primary sex cords
degenerate and disappear
• during weeks 10-12, secondary sex cords
(cortical cords) develop and extend into the
medullary mesenchyme
• by week 16, cortical cords break into
isolated cell cultures called primordial
follicles

15. • the developing ovary separates from the
regressing mesonephros and becomes
suspended by mesentery (mesovarium)
• mesonephric ducts regress (due to lack of
testosterone) and the paramesonephric
ducts develop (due to lack of MIF)
• inferior, fused paramesonephric ducts form
uterovaginal (canal) primordium – becomes
uterus and superior vagina

16. • superior, unfused paramesonephric ducts
become fallopian tubes (oviducts); superior
openings become infundibula
• fusion of the uterovaginal primordium with the
urogenital sinus brings together two folds of the
peritoneum and forms the broad ligament; this
creates the vesicouterine pouch and the
rectouterine pouch

17. • contact of uterovaginal primordium with
urogenital sinus induces paired endodermal
outgrowths –forms vaginal plate
• central vaginal cells eventually break down
forming the vaginal cavity; a membrane
(hymen) persists at the inferior end
• urethral and paraurethral glands develop
from urethra
• vestibular glands develop as outgrowths
from the urogenital sinus

18. Indifferent- gonad

19. Adult persistence of embryonic
ducts in the genitourinary system

20. Species: Human Day Gestation: 8; 10 wks
Approx. Human Age: View: Caudal

21. Species: Human Day Gestation: 10 wks
Approx. Human Age: View: Caudal

22. • In both sexes about the fourth week
of development,
• an indifferent genital tubercle
develops near the cloaca and
elongates to form a phallus.
• The external genital organs are not
fully differentiated until about the
twelfth week of development.

23. Development of Male ExternalDevelopment of Male External
GenitaliaGenitalia
• Genital Tubercule and Urethral
folds - Phallus
• Urogenital folds - urethral groove -
penile urethra
• Glandular plate

24. • Genital /labioscrotal swelling -
scrotum
• In a male embryo, androgens secreted
by the testes cause
• the phallus to elongate into the penis
and
• the urogenital folds to fuse and form
the spongy urethra.

25. Male
• phallus elongates and enlarges; urogenital
folds form the urethral groove along the
ventral surface of the penis
• groove is lined by endoderm of the urethral
plate
• urogenital folds fuse to form spongy urethra,
which is enclosed by penile raphe (fusion of
surface ectoderm in midline)

26. • ectodermal glandular plate forms at tip of
penis and grows caudally until it meets the
spongy urethra; this then canalizes
• circular in growth of ectoderm occurs at the
periphery of the glans during week 12;
breaks down and forms prepuce
• corpora cavernosa and corpus spongiosum
develop from mesenchyme within the penis
• labial scrotal swellings fuse to form the
scrotum; line of fusion ⇒ scrotal raphe

27. Development of Female ExternalDevelopment of Female External
GenitaliaGenitalia
• Urethral folds forms labia majora
• Genital tubercule forms Clitoris
• UG Groove forms vestible
• Without influence of androgens,
• the phallus becomes the clitoris,
• the urogenital folds become the labia
minora, and

28. • the labioscrotal swellings become the labia
majora.
• urogenital folds do not fuse except for small
portion that forms the frenulum of the labia
minora
• unfused urogenital folds become labia minora
• labioscrotal folds fuse and form poster. labial
commissure posteriorly, anter.labial
commisure and mons pubis anteriorly
• middle portion of the folds remains unfused and
forms labia majora

29. Development of the Inguinal CanalsDevelopment of the Inguinal Canals
• Forms pathway for the testes.
• - Mesonephrose degeneration
• - Gubernaculum (ligament)
• - Attaches to the labioscrotal swelling in
both sexes
• gubernaculum ligament is attached to the
gonads and descents on each side of the
abdomen
• this passes through anterior wall and attaches
to inferior surface of the labioscrotal swelling

30. • process vaginalis, an invagination of the
peritoneum, develops ventral to the
gubernaculum and pushes through the
• abdominal wall along path formed by the
gubernaculum
• process vaginalis pulls all layers of the
abdominal wall with it; layers cover testes in
males
• opening in transversalis fascia - deep
inguinal ring; opening in external oblique
aponeurosis - superficial inguinal ring

31. • Descent of the Testes
• Descent of the Ovaries
• Fate of embryonic Urogenital
Structure

32. Descent of the Ovaries and Testes
• The ovaries and testes develop in the
abdomen and descend to their adult
anatomical positions before birth.
• In the male the testes descend from
the abdomen into the scrotum about
the twenty-eighth week of
development.

33. Descent of the Testes
• through deep inguinal ring and inguinal canal –
enter scrotum with ductus deferens and
testicular vesicles
o abdominal fascia follows testis:
o transversalis fascia - internal spermatic fascia
o internal oblique - cremaster muscle
o external oblique aponeurosis - external
spermatic fascia

34. Descent of the Ovaries
• It starts from posterior abdominal wall to
just below the pelvic brim
• gubernaculum attaches to uterus near
entrance to uterine tube – proximal is
ligament of ovary and distal- round
ligament
• round ligament passes through inguinal
canal and ends in the labium majus

35. Remnants of the Genital Ducts in
Males
• mesonephros becomes:
• appendix of epididymis – blind cranial end of
duct
• paradidymis – tubules caudal to efferent
ductules
• paramesonephros becomes:
• appendix testis – cranial end of duct
• prostatic utrical – corresponds to vagina
• seminal colliculus – corresponds to hymen

36. Remnants of the Genital Ducts in
Females
• mesonephros becomes:
• appendix vesiculosa – cranial end of duct
• epoophoron – correspond to efferent
ductules, epididymis
• paroophron – blind tubules near uterus
• ducts of Gartner – correspond to ductus
deferens and ejaculatory duct (in broad
ligament)
• paramesonephros becomes:

37. Congenital AbnormalitiesCongenital Abnormalities
• Inter sexuality
• True Hermaphroditism
• Female Pseudohermaphroditism
• Male Pseudohermaphroditism
• Testicular Feminization Syndrome
• Hypospadias

38. • Epispadias
• Double Uterus, Uterus Didelphys,
Bicornuate Uterus
• Absence of Vagina and Uterus
• Cryptorchidism or Undescended Testes
• Ectopic Testis
• Congenital Inguinal Hernia
• Hydrocele

39. Hypospadias
• Incomplete fusion of the urogenital folds
creates abnormal openings of the urethra
on the ventral aspect of the penis.
• This malformation occurs in about 1/300
infants.

40. Intersexuality
• Rare true hermaphrodites have both
ovarian and testicular tissues,
• usually possessing a 46,XX karyotype.
• The internal and external genitalia are
variable.
• Female pseudohermaphrodites are
more common, possessing a 46, XX
karyotype, and

41. • typically result from exposure to excess
androgens during embryologic development
(as in congenital virilizing adrenal
hyperplasia).
• Male pseudohermaphrodites have testes
and
• 46, XY karyotype. This condition results from
an inadequate production of androgens by the
testes, or when embryonic genital tissues lack
a specific receptor needed to respond to
normal levels of the hormone

42. Cyrptorchidism
• Failure of the testes to descend into the
scrotum
• is the most common malformation of the
male genital system, resulting in infertility,
• an increased risk of testicular cancer. The
testes may remain anywhere between the
abdomen and the scrotum.

43. Malformations of the Uterus and
Vagina
• If the two paramesonephric ducts fail to fuse correctly
it can result in duplication of the uterus and vagina
(double uterus and double vagina).
• If one paramesonephric duct fails to develop it results
in formation of a single uterine tube and single horn of
the uterus (unicornuate uterus).
• (1) double uterus and vagina (normal condition in
marsupials)
• (2) doubles uterus and single vagina (non-fusion of
paramesonephric ducts)
• (3) incomplete lumen formation of paramesonephric
duct

44. Congenital Inguinal Hernia
• A large patency of the tunica vaginalis can
allow a loop of intestine to herniate into
the scrotum.
• This must typically be corrected surgically.