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• 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.

• 10 days

• 30-34 somites present. The embryo is 3.1-3.9mm.

• Systemic development continues.

• The lens plate is slightly indented and the olfactory placode is visibly indented.

• The posterior neuropore is beginning to close.

• Placental development continues.

• Hind limb bud and Tail limb bud formation occurs.

• 10 ½ days

• 35-30 somites present and the embryo is now 3.5-4.9mm.

• Development of the systems continues .

• Appendages and tail are developing rapidly.

• Olfactory discs are more developed, with a noticeable marginal lip forming.

• The lens vesicles are also progressing in development.

• 11 Days

• 40-44 somites present and the embryo has reached 5-6mm in length.

• Closure of the lens vesicle occurs. Systemic development continues.

• Vertebral column development begins.

• 11 ½ Days

• over 45 somites present and the length of the embryo has reached 6-7mm.

• external features are becoming more defined.

• Systemic development is progressing.

• Limb development is continuing.

• 12 Days

• the embryo is now 7-9mm in length measured from crown to rump.

• Development of fingers begins.

• Development of all systems continues.

• 13 days

• the embryo is 9-11mm in length.

• External features continue to grow whiskers and hair follicle have begun to form.

• The handplate is indented and the footplate is starting to indent.

• Systemic development continues as skeletal system development commences.