Development Of The Reproductive Tracts Flashcards
Which subdivision of mesoderm are the reproductive tracts formed from?
Intermediate mesoderm
What does the Hindgut give rise to, that then becomes the urogenital sinus? (Common opening for reproductive and urinary systems)
The Cloaca
What determines the chromosomal sex of an embryo at fertilisation?
In what week do male/ female morphological characteristics begin to develop
Whether the sperm is X or Y
Week 7
What is the Urogenital ridge?
An area of intermediate mesoderm in posterior abdominal wall that gives rise to the embryonic kidney and gonad
What are Primordial Germ Cells?
What determines their karyotpe?
Specialised population of cells that arise from yolk sac and will eventually produce sperm/ ova once sexual maturation has occurred
Karyotype of fertilised oocyte
What are the Gonads?
What are they derived from?
The organs (testes or ovaries) that produce sex cells.
- Underlying Mesenchyme (Embryonic CT)
- Mesothelium lining the posterior abdominal wall
- PGCs (Primordal Germ Cells, earliest undifferentiated sex cells)
Explain how the PGCs affect the developmental pathway of the gonads
- PGCs migrate along retroperitoneum to gonads (which are currently Indifferent/ neither male or female)
- Their karyotype determines whether the gonad differentiates to become male or female
Compare the development of the Gonad with and without the Y chromosome which contains a SRY gene
With SRY Gene:
- Gonad becomes testis
- Seminiferous tubules form
- PGCs remain, begin gametogenesis at puberty
Without:
- Gonad becomes ovary
- No Seminiferous tubules
- PGCs remain, develop into oocytes at puberty
Both male and female embryos have a pair of ducts used in developing the urinary system.
Name the pair of ducts
(2 ducts on each side)
- Mesonephric/ Wolffian duct (More straight)
- Paramesonephic/ Mullerian duct (more curved)
Describe how the presence of testes affects the development of Internal Genitalia/ Duct System
What would happen if the male hormones are not present anymore?
- Androgens (Testosterone) produced
- Mesonephric/ Wolffian duct maintained
- Development of Epidydimis and Vas Deferens
- Absence of male hormones/ androgens-> Degeneration of Mesonephric Duct (Duct needs to be stimulated in order to remain)
Describe how the absence of testes affects the development of Internal Genitalia/ Duct System
- Mesonephric/ Wolffian duct regresses
- Paramesonephric/ Müllerian duct remains
- Formation of Uterus, Fallopian Tubes and part of Vagina
(Needs no stimulation, unlike Mesonephric duct)
What do the testes produce to prevent Paramesonephric/ Mullerian Duct from developing in males?
Mullerian Inhibitory Substance (MIH)
Describe the Mullerian and Wolffian ducts’ connection to gonad (ovary/ testes)
Mullerian Duct: Doesn’t fuse with gonad
Wolffian Duct: Does fuse with gonad, so is continuous and not open in the peritoneum
What are the 3 common elements of undifferentiated External Genitalia?
- Genital tubercle
- Genital folds
- Genital swellings
Describe how presence of testes affects external genitalia development of;
- Penis
- Scrotum
- Spongy urethra and Glans Penis
- Development of penis via Elongation and Fusion of Genital Folds
- Development of scrotum via Fusion of Genital Swellings
- Genital Tubercle elonagtes and Genital Folds fuse-> Spongy Urethra
- GT develops into Glans Penis
