development of urogenital system

1. Development of
Urogenital System
Dr Vinay Kumar VeerannaShetty
MBBS, MD, PGCD, PGDBEME.

3.  Two embryonic structures that play an important role in the development
of the urogenital system are:
1. Intermediate mesoderm
2. Cloaca
INTRODUCTION

5.  The intermediate mesoderm is between paraxial mesoderm and coelomic
cavity in lateral plate mesoderm.
 After the folding of the embryonic disc and the formation of the peritoneal
cavity, the intermediate mesoderm forms a bulging on the posterior
abdominal wall lateral to the attachment of the dorsal mesentery of the gut.
It is known as urogenital ridge. Its surface is covered by the epithelium lining
the peritoneal cavity (coelomic epithelium)
FORMATION OF UROGENITAL RIDGE

6.  The urogenital ridge is divided into two parts. The medial part is called
genital ridge that gives rise to the genital system and a lateral part the
nephrogenic cord that forms the urinary system
 At varying stages of development, number of important structures are formed
in relation to the nephrogenic cord on each side. These are:
Excretory renal tubules
Nephric duct
Mesonephric duct
Paramesonephric duct
Gonad (testis or ovary)
SUBDIVISIONS OF UROGENITAL
RIDGE

8.  Subdivisions of Cloaca
 The part of hindgut caudal to allantois is called cloaca.
 It is divided by the urorectal septum (in the angle between allantois and
cloaca) into dorsal primitive rectum and ventral primitive urogenital sinus.
 Primitive urogenital sinus is subdivided into a cranial part, called the
vesicourethral canal, and a caudal part, called the definitive urogenital sinus.
The openings of the mesonephric ducts (see below) lie at the junction of these
two subdivisions
 Subdivisions of Definitive Urogenital Sinus : The definitive urogenital sinus
shows a division into a cranial, pelvic part, and a caudal phallic part
CLOACA

10.  Definitive human kidney arises from two distinct parts
1. Secretory part, i.e., excretory tubules (or nephrons) are derived from the
lowest part of the nephrogenic cord. This part is the metanephros, the cells
of which form the metanephric blastema.
2. Collecting part of the kidney is derived from a diverticulum called the
ureteric bud which arises from the lower part of the mesonephric (Wolffian)
duct.
DEVELOPMENT OF KIDNEYS

11. DEVELOPMENT OF KIDNEYS

12. DEVELOPMENT OF KIDNEYS

13.  Ductogenesis
Formation of ureteric bud from mesonephric duct.
Contact of ureteric bud with metanephric blastema
DEVELOPMENT OF KIDNEYS

14.  Nephrogenesis
DEVELOPMENT OF KIDNEYS

15.  During ascent, the kidneys pass through the fork, such as interval between
the right and left umbilical arteries. If the arteries come in the way of ascent,
the kidney may remain in the sacral region.
ASCENT OF KIDNEY

16.  The hilum of the kidney, at first, faces anteriorly. The organ gradually rotates
so that the hilum comes to face medially
ROTATION OF KIDNEY

17.  The ureteric buds arise from the mesonephric ducts, a little cranial to the
cloaca.
 The parts of the mesonephric ducts, caudal to the origin of the ureteric buds,
are absorbed into the vesicourethral canal; with the result the mesonephric
ducts and the ureteric buds now have separate openings into the cloaca.
 These openings are at first close together. However, the openings of the
ureteric buds move cranially and laterally due to continued absorption of the
buds.
 The triangular area (on the dorsal wall of the vesicourethral canal) between
the openings of the ureteric buds and those of the mesonephric ducts is
derived from the absorbed ducts and is, therefore, of mesodermal origin.
ABSORPTION OF LOWER PARTS OF MESONEPHRIC
DUCTS INTO CLOACA

19.  The ureter is derived from the part of the ureteric bud that lies between the
pelvis of the kidney, and the vesicourethral canal.
DEVELOPMENT OF URETER

20. DEVELOPMENT OF URINARY BLADDER

22. DEVELOPMENT OF URETHRA

24. This gland develops from a large number of buds that arise from the epithelium of
the prostatic urethra, i.e., from the caudal part of the vesicourethral canal, and from
the pelvic part of the definitive urogenital sinus. These buds form the secretory
epithelium of the gland.
The buds that arise from the mesodermal part of the prostatic urethra (i.e., posterior
wall, above the openings of the ejaculatory ducts) form the inner glandular zone of
the prostate.
Buds arising from the rest of the prostatic urethra (endoderm) form the outer
glandular zone
DEVELOPMENT OF PROSTATE

25. Female Homologues of Prostate
• Endodermal buds, similarto those that form the prostate in the male, are
also seen in the female.
• The buds that arise from the caudal part of the vesicourethral canal give
rise to the urethral glands, whereas the buds arising from the urogenital
sinus form the paraurethral glands of Skene.
DEVELOPMENT OF PROSTATE

26. Paramesonephric (Mullerian) Ducts
• Paramesonephric ducts are present in the intermediate
mesoderm.
• They are formed by invagination of coelomic
epithelium.
• They lie lateral to the mesonephric ducts in the cranial
part of the nephrogenic Cord.
• When traced caudally, they cross to the medial side of
the mesonephric ducts. Here the ducts of the two sides
meet and fuse in the middle line to form the
uterovaginal canal (or uterine canal).
• The caudal end of this canal comes in contact with the
dorsal wall of the definitive urogenital sinus.
• In the female, this part of the sinus gives rise to the
vestibule. In the female, the paramesonephric ducts
give origin to the uterine tubes, the uterus, and part of
the vagina.

27. DEVELOPMENT OF UTERUS AND UTERINE
TUBES

28. DEVELOPMENT OF VAGINA

29. DEVELOPMENT OF EXTERNAL GENITALIA

30. DEVELOPMENT OF EXTERNAL GENITALIA

31. DEVELOPMENT OF EXTERNAL GENITALIA

32. DEVELOPMENT OF FEMALE EXTERNAL
GENITALIA

33.  The cells of the ovaries and the testes, from
which germ cells develop are believed to be
segregated early in the life of the embryo.
 They probably differentiate in the wall of
the yolk sac and migrate to the region of the
developing gonads.
 All spermatozoa and ova that are formed
throughout the life of the individual are
believed to arise from these primordial
germ cells.
 Migration of primordial germ cells into
them is essential for the development of
gonads.
 These cells have an inducing effect on the
gonad
PRIMORDIAL GERM CELLS

34. DEVELOPMENT OF TESTES

35. DUCT SYSTEM OF TESTES

36. The descent of the testes is caused or
assisted by several factors. These
are:
 Differential growth of the body
wall
 Formation of inguinal bursa
The gubernaculum
Processus vaginalis
DESCENT OF TESTES

37.  Appendix of testis (also called hydatid of Morgagni)
 Appendix of epididymis
 Superior aberrant ductules
 Inferior aberrant ductules
 Paradidymis
VESTIGIAL STRUCTURES IN THE REGION
OF THE TESTIS

38.  The early stages in the development of the ovary are exactly the same as in
the testis
 The coelomic epithelium on the medial side of the mesonephros becomes
thickened to form genital ridge.
 Cords of cells (sex cords or medullary cords) proliferate from this germinal
epithelium, and grow into the underlying mesoderm.
DEVELOPMENT OF OVARY

39.  Primordial germ cells that are formed in relation to the yolk sac migrate to the
region of the developing ovary, and give rise to oocytes.
 The sex cords become broken up into small masses. The cells of each mass
surround one primordial germ cell, or oocyte, to form a primordial follicle
 According to some authorities, the original (medullary) sex cords undergo
regression in the ovary, and are replaced by a new set of cortical cords arising
from coelomic epithelium. Follicular cells are derived from these cortical cords.
DEVELOPMENT OF OVARY

40.  Interstitial gland cells differentiate from mesenchyme of the gonad.
 As no tunica albuginea is formed, the germinal epithelium may contribute to
the ovary even in postnatal life
DEVELOPMENT OF OVARY

41.  The ovary descends from the lumbar region, where it is first formed, to the
true pelvis. A gubernaculum forms, as in the male, and extends from the
ovary to the labium majus. It becomes attached to the developing uterus at
its junction with the uterine tube. The part of the gubernaculum that persists
between the ovary and the uterus becomes the (round) ligament of the ovary.
The part between the uterus and the labium majus becomes the round
ligament of the uterus.
DESCENT OF THE OVARY

42. The mesonephric ducts give rise to the following
structures:
• Ureteric buds from which the ureters, pelvis,
calyces and collecting tubules of the kidneys
are derived
• Trigone of the urinary bladder
• Posterior wall of the part of the prostatic
urethra, cranial to the openings of the
ejaculatory ducts
• Epididymis
• Ductus deferens
• Seminal vesicles
• Ejaculatory ducts
• Mesodermal part of prostate
Remnants of Mesonephric
Tubules:
• Superior aberrant ductules
(or epigenital tubules)
• Inferior aberrant ductules
• Paradidymis
FATE OF MESONEPHRIC (WOLFFIAN) DUCT
AND TUBULES IN MALE

43. FATE OF MESONEPHRIC (WOLFFIAN) DUCT
AND TUBULES IN FEMALE

45.  Testis determining factor
 Müllerian inhibiting substance
 Androgen binding factor
CONTROL OF DIFFERENTIATION OF GENITAL
ORGANS