Transcript 07. male genital s..ppt

GENITAL SYSTEM
The development of the genital 
system comprises the development
of:
(1) Gonads (primitive sex cells). 
(2) Genital ducts. 
(3) External genitalia. 
All three components pass through an
indifferent stage in which they may
develop into either a male or a
female.

GENITAL SYSTEM
The Y chromosome causes 
differentiation of the gonad into
testis.
The indifferent duct system and 
external genitalia develop under the
influence of hormones.
Male and Female morphologic 
characteristic do not begin to develop
until the 7TH week
. INDIFFERENT STAGE OF
GONADS
Gonads are derived from 
three sources :
(a) Mesothelium 
(mesodermal epithelium )
lining the posterior
abdominal wall.
(b) Mesenchyme 
(embryonic connective
tissue).
C) Primordial germ cells. 

GENITAL RIDGE
It appears during the fifth
week as a pair of
longitudinal ridges, the
genital (gonadal ridges)
on the medial side of the
mesonephros.
They are formed by 
proliferation of
epithelium
(mesothelium)and
condensation of
underlying mesenchyme.

PRIMITIVE SEX CORDS
They are formed from 
epithelial cells which
penetrate the underlying
mesenchyme and form a
number of irregularly
shaped cords.
In both male and female
embryos these cords are
connected to the surface
epithelium.

PRIMORDIAL GERM CELLS
These primitive sex 
cells appear early in
the fourth week among
the endodermal cells in
the wall of the yolk sac
close to the allantois.
PRIMORDIAL GERM CELLS
They migrate along 
the dorsal mesentery
of the hind gut to the
gonadal ridges.
They invade the 
underlying
mesenchyme of the
genital ridges in the
six week and are
incorporated in the
primary sex cords.
PRIMORDIAL GERM CELLS
If they fail to reach
the ridges, the
gonad remain
indifferent or is
absent.
So they have an 
inductive influence
on development of
the gonad into
ovary or testis.

INDIFFERENT GONAD
The indifferent gonad 
consists of an external
cortex and internal
medulla.
In embryos with XX sex 
chromosomes, the
cortex differentiates
into the ovary and the
medulla regresses.
In embryos with an XY 
sex chromosomes, the
medulla differentiates
into a testis and the
SEX DETERMINATION
1. The sex of the embryo is 
determined genetically at the time of
fertilization depending upon the
sperm (X or Y ) fertilizing the X ovum.
2. Gonads acquire male or female 
morphological characteristics about
the seventh week of development.
SEX DETERMINATION
The key to this sexual differentiation 
is the Y chromosome.
The short arm of this chromosome 
contains SRY (sex determining region
on y ) gene.
The protein product of this gene is the 
TDF (testis determining factor ) that
acts on the medulla of the indifferent
gonad.
TDF
It causes: 
(a) development of the
testis (medullary )
cords.
(b) formation of tunica
albuginea.
C) failure of the 
cortical cords (ovary)
to develop.
in its absence female 
development is
established.


SEX DIFFERENTIATION
(3) The differentiated gonad will 
determine the type of sexual
differentiation in the genital ducts
and external genitalia through the
secretion of hormones.
TUNICA ALBUGINEA
It is a dense layer of 
fibrous tissue which
separates the testis
(seminiferous cords)
from the surface
epithelium.
Its development is the
characteristic and
diagnostic feature of
testicular development
in the fetus.

MEDULLARY (TESTIS) CORDS
They are the primary
sex cords which
condense and extend
into the medulla.

TESTIS CORDS
(SEMINIFEROUS CORDS)
They become horse shoe
shaped in the fourth
month.
The seminiferous cords 
develop into :
Seminiferous tubules. 
Tubuli recti. 
Rete testis. 

RETE TESTIS
They are a network
of tiny strands that
result from the
break up of the
seminiferous cords
at the hilum of the
gonad.
Their extremities 
become continuous
with those of the
cords.

SEMINIFEROUS TUBULES
The wall of the tubules 
contain :
(1) Sustentacular cells of 
Sertoli
They are derived from the 
surface epithelium of the
gonad.They secrete Anti ’
Mullerian Hormone (AMH)
which suppresses the
development of
paramesonephric (mullerian)
ducts.The hormone decreases
SEMINIFEROUS TUBULES
(2) 
Spermatogonia :
primordial sperm
cells derived
from the
primordial germ
cells.
INTERSTITIAL CELLS OF
LEYDIG
These cells are derived
from the original
mesenchyme of the
genital ridge .
They lie between the 
seminiferous cords.
They produce 
testosterone and
androstendione
(androgenic hormones)
by the eight week.

INTERSTITIAL CELLS OF
LEYDIG
The testis becomes
able to influence
sexual
differentiation of
the genital ducts
and external
genitalia.
Testosterone is 
stimulated by
(HCG) which
reaches a peak
between (8th –12th
weeks.

MATURATION OF THE TESTIS
The seminiferous tubules
join the rete testis.
The rete testis are joined
to 15 –20 efferent
ductules (mesonephric
tubules).
These ductules are 
connected to the
mesonephric duct(
ductus deferens) =
ductus epididymis.


MATURATION OF THE TESTIS
The surface 
epithelium is
flattened and forms
the mesothelium on
the external surface
of the adult testis.
The seminiferous 
cords remain solid
until puberty when
they acquire a lumen
and become tubules.
INDIFFERENT STAGE OF
GENITAL DUCTS
Between(4th and 5th ) 
weeks, both male and
female embryos have two
pair of genital ducts :
1. Mesonephric (Wolffian) 
ducts.
They play an important role 
in the development of male
genital system.
2. Paramesonephric 
(Mullerian) ducts.
They are important in the 
MESONEPHRIC DUCTS
Under the influence of 
testosterone the
mesonephric duct will
form:
1. Epidydimis: 
It is the proximal highly
convoluted part of the
duct.
2. Ductus Deferens : 
It is the part of the duct
distal to the epididymis.
It acquires a thick
investment of smooth


MESONEPHRIC DUCTS
3. Seminal Vesicles 
They are lateral 
outgrowth from the
caudal end of each
mesonephric duct.
Their secretion
nourish the sperms.
MESONEPHRIC DUCTS
4. Ejaculatory Duct: 
It is the part of the 
mesonephric duct that
lies between the duct of
seminal vesicle and the
urethra.
MESONEPHRIC DUCTS
Efferent 
Ductules of the
testis :
Formed from the
persisting
excretory
mesonephric
tubules.

REMMNANT OF MESONEPHRIC
DUCTS
1. Appendix of 
epididymis.
The most cranial 
part of the duct.
2. Paraydidymis 
Remnants of tubules
at the caudal pole of
the testis which do
not join the cords of
the rete testis.

PARAMESONEPHRIC DUCTS
MIS produced by 
Sertoli cells of the
testes causes the
paramesonephric ducts
to disappear by
epithelial mesenchymal
transformation.
Their remnant is the 
appendix of testis.
PROSTSTE GLAND
It is multiple 
endodermal
outgrowths from
the prostatic
urethra.
It grows into the 
surrounding
mesenchyme that
will form the dense
stroma and the
smooth muscle of
the gland.
BULBOURETHRAL GLANDS
They are pea 
sized structures
that develop from
the spongy part of
the urethra.
The adjacent 
mesenchyme will
form the stroma
and smooth
muscles of the
glands.
INGUINAL CANAL
It is the pathway 
for the descend of
the testis from the
intra abdominal
position to the
scrotum.
It develops in both
sexes because of
the indifferent
stage of the sexual
development.

INGUINAL CANAL
A band of mesenchyme
(Gubernaculum)
extends from the
inferior pole of the
gonad to the
labioscrotal swelling.
This ligament passes 
obliquely on each side
of the abdomen through
the developing anterior
abdominal wall at the
site of the future
inguinal canal.

DESCENT OF THE TESTIS
The descent of the 
testes through the
inguinal canals into
the scrotum begins
during the 26th week.
It takes (2 -3) days. 
About (97%) of full 
term new born boys
have both testes in
the scrotum.
DESCENT OF THE TESTIS
It is due to: 
(1) Enlargement
of the testes and
atrophy of the
mesonephric
kidney.
(2) Atrophy of 
the
paramesonephric
ducts.

(3) PROCESSUS VAGINALIS
It is an evagination of
peritoneum that
develop ventral to the
gubernaculum.
It herniates through 
the abdominal wall
along the path formed
by the
gubernaculum.

PROCESSUS VAGINALIS
It carries extensions of 
the layers of the
abdominal wall before it
which forms the layers of
the inguinal canal.
It produces an opening in
the fascia transversalis
that becomes the deep
inguinal ring.
The opening formed in 
the external oblique
aponeurosis becomes the

DESCENT OF THE TESTES
By (26th ) weeks, the 
testes have descended
retroperitoneally to
the deep inguinal ring.
It is a relative 
movement because of
the growth of the
cranial part of the
abdominal cavity away
from the caudal part.
FACTORS CONTROLLING
DESCENT OF TESTES
1. Androgens (e.g. 
testosterone) produced
by the fetal testes.
2. Gubernaculum : 
Its role is uncertain. 
It can guide the 
descent .
The increase of the 
abdominal pressure can
produces passage
through the inguinal
DESCENT OF TESTES
The descended 
testes carry their
ductus deferens and
vessels with them .
Both the testes and
ductus deferens
become ensheathed
by the fascial
extensions of the
abdominal wall.

TESTIS WITHIN SCROTUM
Within the scrotum, the
testis projects into the
distal end of the
processus vaginalis.
During the intrauterine
life the connecting stalk
of the process is
obliterated normally, so
it isolates the tunica
vaginalis.
The inguinal canal 
contracts around the
spermatic cord.


CRYPTORCHIDISM
It occurs in up to 30% of
premature males and in
3 to 4 % of full term
males.
It can be unilateral or 
bilateral.
The cause is not well 
known but a deficiency
of androgen production
by the fetal testes is an
important factor.

COMMON SITES
It can be in the 
abdominal cavity or
along the path of
the testes in the
inguinal canal.
The Undescended 
testes are
histologically
normal at birth but
failure of
development and
atrophy are
detected by the end
of the first year.
COMPLICATIONS
1. Sterility if 
both testes are
undescended.
2. Increase in 
the risk of
testicular cancer
(20-44%).