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Posts: 24515
5 years ago
Describe the events of embryonic development from conception until the fetal stage, including development of the primary germ layers.
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Sunshine ☀ ☼
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Staff Member
Educator
5 years ago
A fertilized egg ( zygote) undergoes rapid mitotic cell division in a stage called cleavage. Cleavage provides the building blocks for constructing the embryo, which develops until it has about 100 cells and then hollows out to form a blastocyst. The blastocyst has two areas: the trophoblast and the inner cell mass. The inner cell mass forms the primary germ layers, which are the ectoderm, the endoderm, and the mesoderm. The ectoderm gives rise to the nervous system, the epidermis, and the skin. The endoderm forms the mucosae and associated glands. The mesoderm gives rise to everything else. The trophoblast develops projections called chorionic villi which form the placenta along with tissues from the mother's uterus. By the eighth week, all the organ systems have been laid down and the embryo looks distinctly human. Beginning in the ninth week, the embryo is referred to as a fetus.
Mastering in Nutritional Biology
Tralalalala Slight Smile
wrote...
5 years ago
thank u Slight Smile
wrote...
Staff Member
Educator
5 years ago
thank u Slight Smile

Slight Smile
Mastering in Nutritional Biology
Tralalalala Slight Smile
Answer accepted by topic starter
wrote...
Valued Member
Top Poster
Posts: 24515
5 years ago
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Answered my question perfectly!! Thanks so much Smiling Face with Open Mouth
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Sunshine ☀ ☼
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