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From Embryology
- 0 Days
- Fertilisation
- 1 Day
- Cleavage of cells has begun. Day ends with 4 cells present
- 2 Days
- Formation of Morula
- 3 Days
- Compaction of morula. 16-25 cells within same sized morula.
- 4 Days
- Blastocyst formation
- 4.5 Days
- Implantation and invasion into the uterine epithelium
- 5 Days
- Embryoblast and trophoblast formation.
- Endometrial reaction occurs
- 6 Days
- Embryoblast begins to divide into embryonic and extramembryonic cavities.
- The proamniotic cavity also starts to form.
- Trophoblast cells also begin to differentiate
- 6.5 Days
- Axis of embryonic germ disc is defined.
- Uterine reaction (decidual reaction) occurs.
- 7 Days
- Formulation of amnion occurs.
- Formation of mesoderm, entoderm and endometrium also occur.
- 7 ½ Days
- Closure of the amnion.
- The neural plate is clearly delimited anteriorly and laterally.
- The head process is now developing.
- Foregut development begins.
- Blood islands develop in the wall of the yolk sac.
- 8 Days
- Embryo has 1-7 somites present.
- Progressive deepening of the neural tube.
- Circulatory system development begins.
- Intestinal tract development continues.
- Central nervous system development begins.
- Extraembryonic membranes grow and begin to fuse.
- Yolk sac continues to enlarge.
- 8 ½ Days
- 8-12 somites present.
- rotation of embryo occurs.
- development of the systems continues
- 9 Days
- 13-20 somites present.
- Turning of the embryo has completed.
- Central nervous system circulatory system and intestinal tract development continues.
- The urogenital system development begins.
- Placenta development begins.
- 9 ½ Days
- 21-29 somites present. The embryo is 1.8-3.3 mm.
- Cardiovascular, CNS, Intestinal and urogenital development continue.
- Condensation of forelimb bud occurs.