DEVELOPMENT OF MALE & FEMALE GENITAL SYSTEM

1. DEVELOPMENT OF MALE & FEMALE GENITAL SYSTEM By Dr Samina Anjum

2. DEVELOPMENT OF GONADS Sex of the embryo is determined genetically at the time of fertilization. Type of gonads present then determines the type of sexual differentiation that occurs in the genital ducts and external genitalia. Gonads do not acquire male or female morphological characteristics until the 7th week of development.

3. Gonadal / Genital ridge The gonads (testes and ovaries) are derived from three sources : 1.Mesothelial lining the posterior abdominal wall. 2. Condensation of underlying mesenchyme (embryonic connective tissue) 3. Primordial germ cells

4. Migration of primordial germ cells into developing gonad • .

5. Primordial germ cells • Arrive at the beginning of 5th week

6. Invade the genital ridges in the 6th week. Inductive influence

7. Indifferent Gonads • Finger like primitive sex cords appear, grow into underlying mesenchyme, but remained connected to surface epithelium. Consist of: • External cortex • Internal medulla.

9. Development of the Testis • SRY gene & TDF • Primitive sex cords proliferate, penetrate deep into Medulla to form the testis / Medullary cords • Towards the hilum, the cords break up into tubules of rete testis. • The gonadal cords –looses connection with the surface epithelium when thick fibrous capsule develops, tunica albuginea.

10. 4th month testis cords become horse shoe shaped and connect with rete testis. • Spermatogonia -primordial germ cells • Sertoli cells- the surface epithelium. • Interstitial cells of Leydig- mesenchyme • -Testosterone By 8th week

11. Cont…. • Testis cords remain solid till puberty. • Acquire lumen forming seminiferrous tubules. • Once canalized join rete testis which enter ductuli efferentes ---mesonephric duct

12. Derivatives The testis cords develop into: • the seminiferous tubules • rete testis. Mesenchyme between the seminiferous tubules provide • the interstitial cells of Leydig.

13. DEVELOPMENT OF OVARY

14. DEVELOPMENT OF OVARY Degeneration of Primitive/ medullary sex cords Formation of cortical cords, dissociate into irregular cellclusters which occupy the medullary part of the ovary. Later, they disappear & replaced by a vascular stromathat forms the ovarian medulla.

15. 7th week, surface epithelium proliferate Formation of second generation of cords, cortical cords, which remain close to the surface. 4th month, cords split into isolated cell clusters, which surrounds PGCs. Formation of oogonia & the follicular cells.

16. Development of ovaries in absence of TDF

19. DEVELOPMENT OF GENITAL DUCTS INDIFFERENT STAGE Initially; both male & female embryos have two pairs of genital ducts: Mesonephric (wolffian) ducts Paramesonephric (müllerian) ducts

21. Paramesonephric ductsarise as a longitudinal invagination of the epithelium on the anterolateral surface of the urogenital ridge. Cranially, the ducts open into the abdominal cavity with a funnel-like structure. Caudally, it first runs lateral to the mesonephric duct, then crosses it ventrally to grow caudomedially.

22. Close contact with the duct of opposite side. Separated by a septum, later forms the uterine canal. The caudal tip of the combined duct projects into the posterior wall of the urogenital sinus, the paramesonephric or müllerian tubercle. Mesonephric ducts open on each side of urogenital sinus

23. Development of Male Genital Ducts Ejaculatory duct At 4th month After descent of testis

24. GENITAL DUCTS IN THE FEMALES End of 2nd month After descent of ovary

25. When the 2nd part moves mediocaudally, the urogenital ridges come tolie in the transverse plane creating a horizontal fold the broad ligament of the uterus.

26. DERIVATIVES Fused paramesonephric ducts give rise to: • Body of uterus • Cervix • Upper part of vagina Surrounded by: • Mesenchyme ---- Myometrium • Peritoneum ---- Parametrium

27. DEVELOPMENT OF VAGINA Shortly after the solid tip of the paramesonephric duct reaches the urogenital sinus, two solid evaginations grow out from the pelvic part of the sinus. These sinovaginal bulbs proliferate to form a solid vaginal plate.

28. By the 5th month, the vaginal outgrowth is entirely canalized. The wing-like expansions of the vagina around the end of the uterus, the vaginal fornices, are of paramesonephric origin.

30. Vagina has dual origin

31. REMANENTS OF MESONEPHRIC DUCT • Cranial excretory tubules--- epoophoron • Cuadal excretory tubules--- paroophoron • Persistent portion of mesonephric duct in uterus or vagina--- Gartner’s cyst

32. Scrotum, prostate

33. UTERINE & VAGINAL DEFECTS

34. a: NORMAL c: UTERUS DIDELPHYS WITH DOUBLE VAGINA b: UTERUS BICORNIS

37. DEVELOPMENT OF GLANDS IN MALE GENITAL SYSTEM

38. DEVELOPMENT OF PROSTATE GLAND • Endodermal outgrowths from prostatic urethra • Smooth m and stroma derived from surrounding mesenchyme • Prostatic utricle is a sac like structure that opens into prostatic urethra, is homologous to vagina • The lining of Prostatic utricle is derived from epithelium of urogenital sinus.

39. DEVELOPMENT OF FEMALE GENITAL GLANDS (Outgrowths of urogenital sinus)

40. Development of External Genitalia Undifferentiated External Genitalia (3rd to 6th Week) Female External Genitalia Male External Genitalia

41. External GenitaliaIndifferent stage

42. Development of Male External Geniatlia 1.The indifferent external genitalia are masculinized by the testosterone. 2. The rapid elongation of genital tubercle into phallus. 3. The phallus pulls the urethral folds forward so that they form the lateral walls of urethral groove. 4. The urethral groove extends along the caudal aspect of the elongated phallus but does not reach the most distal part, the glans. The groove is lined by endodermal epithelium and forms the urethral plate.

43. Development of Male External Geniatlia

44. 5. At the end of 3rd month, the two urethral folds close over the uretheral plate, forming the penile urethra. 6. The most distal portion of urethra is formed during the 4th month, when ectodermal cells from tip of glans penetrate inward and form a short epithelial cord. This cord later forms lumen thus forming external urethtral meatus. 7. The labioscrotal swellings fuse to form the scrotum. 8. The line of fusion form the scrotal septum.

45. EXTERNAL GENITALIA IN FEMALES Estrogens stimulate the development of external genitalia in females. • Genital tubercle ---- Clitoris • Urethral folds do not fuse ---- labia minora • Genital swellings enlarge ---- labia majora • Urogenital groove is open ---- vestibule

46. DESCENT OF TESTIS • Towards the end of 2nd month urogenital mesentery attaches the testis and mesonephros to the posterior abdominal wall. Thus testis begin as retroperitoneal structures in the posterior abdominal wall • With degeneration of Mesonephros the attachment serves as mesentery for the gonads.

47. Caudally urogenital mesentery becomes ligamentous and forms caudal genital ligament. • Also extends from the caudal pole of testis is a mesenchymal condensation, the gubernaculum. Caudal genital ligament and

48. Two parts of gubernaculum can be seen: • Intraabdominal portion: grows prior to descent of testis and terminates in inguinal region • Extraabdominal portion: grows as testis begins to descend from inguinal region towards the scrotal swelling. When testis pass through inguinal canal this part contacts the scrotal floor

49. As the gubernaculum "pulls" the testes into the pelvis and developing inguinal canal, it is preceded by theprocessus vaginalis, evagination derived from the peritoneum which lies anterior to the testes. Once testis are in scrotum the gubernaculum persist as scrotal ligament.

50. Formation of inguinal canal • The processus vaginalis accompanied by muscular and facial layers of anterior abdominal wall evaginates into scrotal swellings forming inguinal canal. • Testis are then covered by a reflected fold of processus vaginalis having parietal and visceral layers. The narrow canal connecting the lumen of the vaginal process with the peritoneal cavity is obliterated at birth.