Fertilisation and development Flashcards
What is syngamy?
Gamete fusion
How does the sperm capacitate in the female reproductive tract?
1) Acrosomal reaction
- Holes in the acrosomal cap
- Allow enzymes which erode the surface of the egg out
2) Motility changes
What makes the male pronucleus?
- The head of the sperm
- Must decondense
What makes the female pronucleus?
When the egg completes meiosis after fertilisation
Where does the zygote attach to?
The endometrium
Why do females mature earlier than males?
Gestation time is one day longer (266 days)
What determines the gender of the embryo?
Y bearing sperm from the male
Where do gonads develop?
In gonal ridges either side of the midline
What are oogonia and how do they divide?
Undifferentiated germ cells of the female which give rise to oocytes
Devide by mitosis
What causes oogonia to derive into oocytes?
MIS (meosis inducing substance) from the mesenepheric ducts
Where are mesenepheric ducts present?
in both males and females but males also produce MPS (meosis preventing substance) from the testes cords in higher amounts
How do spermatogonia divide?
By mitosis`
What gene induces the formation of testes?
SRY gene produced by the sertoli cells
What is AMH?
Anti mullerian hormone, released from the testes
What is the SOX9 gene?
- Gene involved in the long term maintenance of the male development pathway
- Increases a few days after SRY activated in males
- Declines in females
What happens if there is a mutation in SOX9 in females?
Can direct the females down the male pathway
What happens in the absence on Jmj1a in males?
- SRY not expressed
- XY is phenotypically female
What does 5 alpha reductase do and what happens if there is a deficiency in it?
- Converts testosterone into 5-DHT (dihydroxytestosterone) a more active version
- If deficiency, lack male genetalia
What is testicular feminisation syndrome and when does it occur?
- Karyotype 46/XY
- Normal male genotype but female phenotype, due to low levels of cytosolic carrier protein
- Testosterone cant work but normal levels produced
- Female phenotype due to unopposed action of small amounts of oestrogen from the testes and adrenal cortex
What duct is degenerated in the male at 10 weeks?
The mullerian duct
What duct is degenerated in the female at 10 weeks?
The wolffian duct
