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Weeks 1-2
Preimplantation is the time between a woman's ovum being released and when it is joined with a man's sperm known as fertilization. During fertilization the joined sperm and ovum become a blastocyst. At the time of implantation, the blastocyst consists of a trophoblast layer and a embryoblast layer. An increase in cell number through proliferation, differentiation, morphogenesis, helps the blastocyst develop the bilaminar embryonic disc that forms a three dimensional cell formation. -
Weeks 3-4
In the bilaminar embryonic disc, what is call the primitive streak forms down the middle, almost as cutting the disc in half. Along with this the mesoderm, ectoderm and endoderm are formed. Cells form from the ectoderm and create a layer called the neuroectoderm. These cells make up the neural plate which folds to form the neural tube. The embryonic disc has a head end and tail end. Embryonic folding leads to a tube shaped embryo with somites present. -
Weeks 5-6
Embryonic folding also has created the oropharyngeal membrane, cloacal membrane, foregut, midgut, and hindgut. Frontonasal, maxillary, and mandible processes start to form the face and stomodeum. Stomodeum will later be oral cavity proper. Upper and lower lip is also developing. -
Week 7
Primary palate formation is complete and secondary palatal formation is taking place. -
Week 8
Tongue has developed. -
Week 9-10
Four muscles for mastication are formed from the mandibular process. -
Week 11-12
Oral cavity is now separated from the nasal cavity. Facial features fully formed as well as the final palate.
