1. Development of male genital system
Dr. Lubna Nazli

2. Objectives Development of testis, epidydimis, vas deferens.
Prostate, seminal vesicle, penis and scrotum developments.
Congenital anomalies of internal & external genitalia.

3. The primordial germ cells arise from the yolk sac/endoderm and migrate into the intermediate mesoderm

4. Genital System Sexual dimorphism is due to Y chromosome.
Y chromosome contains the SRY (sex-determining region on short arm of Y) gene.
The SRY protein is the testis-determining factor; its presence influences the male development, while its absence establishes the female development.

5. Gonads
The sex of the embryo is determined genetically at the time of fertilization.
The gonads do not acquire male or female morphological features until the 7th week of development.
A pair of longitudinal ridges lie ventro-medial to the mesonephric kidney. These are called genital or gonadal ridges.
Germ cells start appearing in these ridges after 5th week.

6. Primordial germ cells appear in the endoderm of the yolk sac
Primordial germ cells appear in the endoderm of the yolk sac. They migrate by ameboid movements, via dorsal mesentery, reach the genital ridges during 5th week & invading the genital ridges in the 6th week. If they fail to reach the ridges, the gonads do not develop.
The primitive sex cords arise from the epithelium, penetrate the underlying mesenchyme & still keep contact with the surface epithelium in both sexes. It is impossible to differentiate between the male and the female gonad. Hence the gonad is known as the indifferent gonad.

7. Primordial Germ Cells Placenta Yolk sac
Umbilical cord
Mesonephric kidney
Gonad
Placenta
Embryo in amniotic sac
Yolk sac
Primordial germ cells
Migrating primordial germ cells
Inside the embryo
Uterus

8. Indifferent Gonads Ovary Testis Mesenchyme ? Celoemic epithelium
Primordial germ cells
Primary sex cords
MedullaCortex
No TDF
TDF
Primary sex cords
Secondary sex cords
Tunica albuginea
Seminiferous tubules
Pre-Sertoli cells
Germ cells
Follicles
Ovary
Testis

9. Genital ridge Covered by coelomic epithelium
Primary sex cords
Grow into underlying mesenchyme
Inner mass is composed of mesenchyme
Outer layer called cortex
Inner layer called medulla
Males- medulla differentiates, cortex regresses
Females-cortex develops, medulla regresses

10. Development of testes
Primary sex cords of testes containing the primordial germ cells = testes cords
Well defined cords within the medulla
Contain two types of cells
Epithelial cells  Sertoli cells
Primordial germ cells  spermatoblasts
Testes cords remain solid until puberty
Canalize to form seminiferous tubules (ST), tubuli recti, rete testis
ST separated from each other by mesenchyme that gives rise to interstitial cells (Cells of Leydig)

11. Y Chromosome Influence
44 + XY XX
Y Influence Absence of Y
Indifferent Sex
Testis Ovary
Medullary cords develop Medullary cords degenerate
No cortical cords Cortical cords develop
Thick tunica albuginea No tunica albuginea
SRY Gene (TDF)

13. In the Developing Human Male:
Testis take over the mesonephric duct for itself, and it winds up becoming the spermatic duct, or DUCTUS DEFERENS.

14. DESCENT OF THE TESTES:
Recall from the previous lecture that the male testes descend from their initially intraperitoneal position, through the body wall, into a pouch protruding from the body wall called the SCROTUM.
Everything gets drug along in this descent: ductus deferens, nerves, blood vessels.
All of these together form a connection (“leash”) of testicular connections called the SPERMATIC CORD.

15. SERIAL HOMOLOGUES OF SCROTAL STRUCTURES
As testes push through body wall, they carry with them all layers and a bit of coelomic space. The equivalents are:
Skin: SCROTAL SAC
Superficial fascia: DARTOS MUSCLE
External oblique: EXTERNAL SPERMATIC FASCIA
Internal oblique: CREMASTER MUSCLE
Transversus abdominus: INTERNAL SPERMATIC FASCIA
Coelom + peritoneum: TUNICA VAGINALIS

16. Indifferent Stage
Both male and female embryos start with two pairs of genital ducts: the mesonephric ducts and paramesonephric ducts.
Paramesonephric duct originates as longitudinal invagination of the coelomic epithelium lateral to the mesonephric duct. Cranially it stays open into the abdominal cavity as a funnel shaped structure. Caudally it runs lateral to the mesonephric duct, then crosses it ventrally to take a medial position & come in close contact with the paramesonephric duct from the opposite side.
The caudal tips of these ducts project into the wall of the urogenital sinus, where it causes a small swelling, the paramesonephric or mullerian tubercle. Mesonephric ducts are opening into the urogenital sinus on either side of the mullerian tubercle.

17. Indifferent Stage
Sinus tubercle

18. Primitive urogenital sinus
Mesonephros
Ureteric bud
Urorectal septum
Hind gut
Cloaca
Urogenital sinus
Metanephros
Urinary bladder
Ureter
Rectum
Cloacal membrane
Urogenital membrane
Urogenital tubercle
Anus
Division of Cloaca
Into
&
Allantois
Paramesonephric duct

19. Uterine tube
Kidney
Ovary
Uterus
Vagina
Clitoris
Anus
Testis
Ureter
Ductus deferens
Penis
Urethra
Urinary bladder
Female
Male

20. Male sex determination is controlled by the SRY gene, the testis determining factor on the Y chromosome.
SRY gene leads to production of Mullerian inhibiting substance (MIS), and testosterone . MIS, produced by Sertoli cells, causes regression of the paramesonephric ducts. Testosterone produced by the Leydig cells influences the differentiation of the mesonephric ducts into male genital ducts and modulates the differentiation of the male external genitalia.
The female produces no MIS and its absence causes paramesonephric ducts to stay & develop into the uterine tubes and uterus.
Since testosterone is absent, the mesonephric duct system regresses.
In the absence of androgens, the indifferent external genitalia differentiate into labia majora, labia minora, clitoris, and part of the vagina.

21. The mesonephric duct
It forms the epidydimis, vas deferens, Seminal vesicles,& ejaculatory ducts. (1,2,3).
On epidydimis it remains as appendix of epidydimis (5).
Where as the appendix of testis is the remains of paramesonephric duct (4).

22. Prostate & bulbourethral glands
These glands are derived from the sinovaginal bulb.
The penis and scrotum develops from the median genital tubercle and labioscrotal swellings.

23. Development of external genitalia
Indifferent stage
Genital tubercle
Develops at upper end of cloacal membrane
Elongates to form the Phallus
Labioscrotal swellings appear
Urogenital folds appear
Cloacal membrane divided into two
Development of urorectal septum
Upper urogenital membrane
Lower anal membrane
These membranes rupture around week 7 forming urogenital and anal openings

24. Development of external genitalia
Male genitalia
Phallus elongates to form the penis
Enlongation pulls the urogenital folds together
When folds start to fuse they enclose the urethra
Urethral opening moves progressively towards end of penis
Labioscrotal swellings fuse forming scrotum
Female genitalia
Phallus becomes clitoris (relatively small)
Urogenital folds do not fuse  labia minora
Labioscrotal fuse only at ends  labia majora

25. Accessory sex glands Male Female Highly developed Minimal
Seminal vesicles
Prostate
Bulbourethral glands
Female
Minimal
Major vestibular glands (homologous to bulbouretharal glands in male)

26. Development of the external genitalia

28. EMBRYONIC DERIVATIVES
Genital tubercle = Penis
Labioscrotal swellings = Scrotum
Urethral groove closure = spongy urethra
Mesonephric duct = epidydimis+vas deferens+seminal vesicle
Sinovaginal bulb=prostate+bulbourethral glands, membranous urethra
Paramesonephric duct= prostatic utricle+appendix of testis

29. Congenital anomalies Ectopic testis/undescended testis Hypospadias
Epispadias

30. Epispadias

31. Hypospadias

32. Bifid scrotum

33. 2 months-------3 months of IUL. DESCENT OF TESTIS

34. Descent of testis
7 month
9 month
Gubernaculum testis

35. Ectopic testis/undescended testis