- Intermediate mesoderm forms duct along length of embryo and tubule that becomes kidney
- 2 duct systems present:
-
- Gonads start as indifferent tissue.
- germ cells formed in midgut (yolk sac) and migrate to gonadal region
- germ cell invasion causes gonads to develop into genital ridges
- mseonephric cells and coelomic epithelium form primitive sex cords. Interaction with
germ cells causes gonad development
- Primarily a sex cord structure is developed
- in the male goes on to form seminiferous tubules
- in the female goes on to form cortical structure of ovary
| Male |
Female |
- Sex determining region of Y chromosome causes production ofof testis determining factor
- SRY causes medullary sex cords to differentiate into Sertoli cells, cortical sex cords
degernerate
- Sertoli cells becomes testis cords
- testis cords fifferentiate into seminiferous tubules and rete testis
- mesonephric ducts become vasa deferentia
- MIH causes regression of paramesonephric ducts
- MIH causes differentiation of Leydig cells in testis
-
|
- cortical sex cords remain, medullary sex cords degenerate
- germ cells become oogonia and undergo first meiotic division
- folicle cell responsible for arrested development of oocytes
- mesonephric ducts degenerate
- paramesonephric ducts ive rise to fallopian tubes, uterus and superior vagina
- vagina opens by membrane breakdown
|
- External genitalia develop from indifferent material: genital tubercle, cloacal fold and
cloacal membrane
- Grow to urogenital membrane, urogenital fold, perineum, anal membrane and fold,
labioscrotal swelling
- urogenital membrane breaks down
|
- labioscrotal and urethral folds fuse in midline surrounding penile urethra.
- genital tubercle elongates
- urethra in glans formed by invagination of epithelium
- gubernaculum pulls testes behind processus vaginalis, through inguinal canal to scrotum Undescended
testicles are infertile and can become malignant
-
|
- gubernaculum causes descent of ovaries
|
13.1.3 Reproductive tract differentiation and development
| Source and migration of germ cells |
|
| Sex chromosomes, SRY gene, sexual differentiation |
|
| Formation of female and male gonads; their migration |
|
| Formation of female and male internal reproductive tracts
from mesonephric and paramesonephric ducts |
Bicornuate uterus, imperforate hymen, recto-vaginal
fistula. |
| Indifferent stages of external genitalia; formation of
female and male external genitalia |
|
| Effects of androgens, Mullerian inhibiting factor on
differentiation of internal and external genitalia. |
|
| Maldescent of testis. Torsion of testis. |
Appendices of testis and epididymis; torsion. Cysts
derived from mesonephric duct in female; torsion of ovary; ovarian cysts. |
| Effects on differentiation of androgen insensitivity,
androgen excess. |
|
|