2014 Group Project 4
| 2014 Student Projects | ||||
|---|---|---|---|---|
| 2014 Student Projects: Group 1 | Group 2 | Group 3 | Group 4 | Group 5 | Group 6 | Group 7 | Group 8 | ||||
| The Group assessment for 2014 will be an online project on Fetal Development of a specific System.
This page is an undergraduate science embryology student and may contain inaccuracies in either description or acknowledgements. | ||||
Genital
System Development
[NB: having formatting issues trying to put the following information into a table, an attempt at the table is included below]
- the initial stages of genital development are indifferent, both males and females are anatomically identical until morphological changes occur beginning at week 7
- males and female changes are determined by the chromosomal sexual differentiation which occurs at fertilisation
- initial stages of gonadal development begins during the fifth week of development. First change is a thickened area of mesothelium on the medial side of the mesonephros [primitive kidney]
- this proliferation + underlying mesenchyme produces a bulge known as the GONADAL RIDGE
- finger like epithelial chords [gonadal chords] grow into underlying mesenchyme
- This who structure is referred to as an indifferent gonad
- indifferent gonad consists of an external cortex and internal medulla
- in embryos with an XX sex chromosome, the cortex of the indifferent gonad progresses to developing into an ovary
- Conversely, embryos with an XY chromosome, the medulla of the indifferent gonad progresses into a testes
- CHROMOSOMAL SEX DETERMINATION - the indifferent gonads differ after the seventh week by the presence the SRY gene which produces the TESTES DTEREMINING FACTOR on the short arm of the Y Chromosome. Under this influence, the gonadal chords differentiate to somniferous cords expression of Sox9 and Fgf9
- once the gonad that develops [ovary or testes] then determines the type of sexual and genital differentiation which occurs
- fetal testes produce testosterone, dihydrotestosterone and anti mullerian hormone
- TESTES DEVELOPMENT -- insert picture here
- seminferous chords --> rete testes - development of dense tunica albiguinea- enlarging testes separate from the degenerating mesonephros to form the somniferous tubules, tubuli, recti and rate testis - seminferous tubules --> interstitial cells [leydig cells] which produce androgens - insert diagram showing the production of androgens (testosterone, dihydrotestosterone and antimullerian hormones (sertoli cells) )
- DEVELOPMENT OF OVARIES
- ovary not identifiable until 10th week - gonadal chords aren't prominent in developing ovary but extend to medulla and form the rate ovary OOGENESIS DIAGRAM
- DEVELOPMENT OF GENITAL DUCTS
- fifth and sixth weeks - mesonephric ducts (wolfing duct) and paramesonephric ducts (mullein ducts)
| Weeks | M A L E | F E M A L E | |
|---|---|---|---|
| FERTILIZATION | both male and female are same at this point- only difference is presence of XY or XX chromosome | ||
| WEEKS 1-7 | GENITAL DEVELOPMENT IS UNDIFFERENTIATED. gonads derived from:
* mesothelium lining posterior abdominal wall * underlying mesenchyme * primordial germ cells. | ||
| WEEK 5 | development of indifferent gonads
| ||
| WEEK 8 | seminiferous tubules begin to release androgens | ||
| WEEK 10 | rudimental rete ovarii forms from indifferent gonads | ||
| WEEK 12 |
| ||
| WEEK 16 | primordial follicles begin to develop |
Genital system development is an extremely interesting area of embryology as it is not until the later stages of embryogenesis (around week 4-6) that sexual differentiation occurs in the fetus, and the sexual organs actually look very similar up until this point, and the formation of the correct sex organs depend really on whether the genital ridge releases Testosterone or oestrogen
<pubmed>24240231</pubmed> <pubmed>24928207</pubmed> <pubmed>24741072</pubmed>
