Urogenital

1. Development of Hindgut and the
Urogenital system
By : Adish Chundunsing
Roll # 147

2. Contents
– Hindgut development
– Anal canal
– Applied
– Urinary System development
– Kidney systems
– Ureter, urinary bladder, urethra
– Applied
– Genital system
– Gonads
– Ducts
– External Genitalia
– Applied

3. Hindgut
– Left one third of transverse colon
– Descending colon
– Rectum
– Upper part of anal canal
(Blood supply : Inferior mesentric artery)
– Parts of urogenital system formed from hindgut
development
• Urinary bladder
• Urethra

4. Primitive gut

5. • Cloaca divides into broad ventral part and
narrow dorsal part by urorectal septum.
– Ventral part: primitive urogenital sinus
• Urinary bladder and urethra (primarily)
– Dorsal part: anorectal canal
• Urorectal septum fuses with cloacal
membrane to form perineal body.
– Urogenital membrane (urogenital sinus)
– Anal membrane (rectum)

7. • Anal canal development
– The anal membrane disappears between the
Endoderm of primitive rectum and ectoderm of
anal pit (proctodaeum)

8. Clinical
1) Rectal atresia / stenosis - the lumen of the rectum is totally /
partially interrupted.
2) Rectal fistulas

9. Urinary system development
• Intermediate mesoderm Nephrogenic cord
• Primitive Urogenital sinus

10. • Formation of 3 kidney systems
– Pronephros (cervical)
– Mesonephros (upper thoracic to upper lumbar)
– Metanephros (sacral)

11. • Pronephros
– Form vestigial excretory units (nephrotomes) (up
to 4th
week) – degenerates thereafter
• Mesonephros
– Mesonephric duct along Tubules form S shape to
form a bowmans capsule around tuft of capillaries
(4th
to 9th
week)
* Note – mesonephros will develop into epididymis
and ductus deferense

13. • Metanephros – definitive kidney
– Develop from metanephric mesoderm
– Before mesonephric duct enters cloaca, there is an
outgrowth ureteric bud (form the collecting
system)
– Penetrates metanephric tissue

14. • Each collecting tubule at its distal end has
metanephric tissue caps renal vesicles to form
small S shaped tubules with a glomeruli Nephrons
(excretory units)

15. • Ascent of kidneys
– Due to dimunition of body curvature and growth
of body in lumbar and saccral regions. (Blood
supply from higher levels in aorta)
– Rotation of hilum of kidneys from anterior to
medially

16. Development of:
• Ureter
– elongation of ureteric bud
• Urinary Bladder
– visicourethral canal of (upper) urogenital sinus
– Allantois becomes urachus which forms median umbilical
ligament (adults)
*Trigone is formed from mesoderm
• Urethra
– Pelvic and phallic parts of urogenital sinus

18. Clinical
• Renal agenesis - kidneys fail to develop
– Unilateral
– Bilateral –incompatible with post natal life
• Ectopic kidney - pelvic kidney
• Horseshoe kidney – 1 out of 5 births; inferior poles are
fused. Kidneys ascent is blocked by inferior mesentric artery.
• Aberrant renal arteries – may press on reter and cause
hydronephrosis.

19. Genital System
• Begins in 7th
week of development
• Gonadal ridge appears – proliferation of epithelium
and condensation of underlying mesenchyme.
• Sex determined by Y chromosome – SRY gene

20. Testis
development
Ovary
development

21. • Duct system development - male
– Mesonephric duct = Wolffian duct
– Paramesonephric duct = Mullerian duct - degenerates due
to mullerian inhibiting factor

22. • Duct system development – female
– Paramesonephric duct = Mullerian duct

23. • Descent of testis
– By differential growth of body wall
– Inguinal bursa inguinal canal
– Gubernaculum
– Processus vaginalis

24. • External Genitalia development

26. Clinical
• Uterus didelphys – lack of fusion of
paramesonephric ducts causes double uterus
with double vagina. Uterus bicornis -
two uterus with common vagina.
• Hypospadias – urethral folds fail to fuse
(anterior part of the phallus)

27. Summary:
• Hindgut development
– division of the cloaca by the urorectal septum
• Urogenital system develop from mesodermal tissue
– 3 urinary systems develop (cranial to caudal)
• Pronephros
• Mesonephros
• Metanephros
• Genital System
– Sex determined by SRY gene
– Genital ridge develops into gonads(by primordial germ cells)
– Mesonephric (Wolffian duct) - males
– Paramesonephric (Mullerian duct) – females
– External genitalia from genial tubercule, urethral folds and genital
swelling

28. References
• Human Embrology 8th
edition by Indebir Singh
and G K Pal
• Langman’s Medical Embryology by T.W Saddler
Thank you!