The migration of the embryo through the fallopian tube
While the fertilized oocyte develops into a morula and blastocyst and then hatches from the pellucid zone, it wanders from the ampulla through the fallopian tube into the uterine cavity, where it embeds itself in the endometrium at the end of the sixth day. The fertilized oocyte / embryo is transported via the movement of the cilia of the tubal epithelium and the contractions of its muscular layer.
In summary, the temporal course of the preimplantation stages follows this scheme.
- 1
- Ovary
- 2
- Fallopian tube
- 3
- Endometrium
- 4
- Myometrium
- 5
- Uterine cavity
- A
- Spermatozoon penetrates into the oocyte (conception), day 0
- B
- Two-cell stage, day 1
- C
- Four-cell stage, day 2
- D
- Eight-cell stage, day 3
- E
- Morula (16-32 cells), day 4
- F
- Free blastocyst (following hatching), day 6
Fig. 18
The embryo goes through its cleavage stages while it is migrating along the fallopian tube. As a blastocyst it reaches the uterine cavity at the end of the 5th day. There, the hatching and the embedding into the endometrium occur on the 6th day.
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