Movie - Human Development annotated cartoon
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00:02 - Two blastomere cell stage: enclosed within the zona pellucida (pink ring) with polar bodies (upper right) lying under the zona pellucida.
00:06 - Morula stage: a solid ball of cells, still dividing rapidly.
00:08 - Blastocyst stage: trophoblast cells (at periphery), embryoblast (inner cell mass, right) and blastocoel (fluid-filled cavity, yellow) still within the zona pellucida.
00:09 - Blastocyst hatches from zona pellucida and adplants (attaches, adheres) to the uterine endometrium epithelium (right red structure)
00:10 - Bilaminar embryo stage: Embryoblast has formed two layers, hypoblast layer (yellow) and epiblast layer (blue). Amniotic cavity (fluid-filled space, blue beside the epiblast) forms, implantation continues into the uterine wall and the trophoblast layer now also forms two cellular layers (outer synctiotrophoblast and inner cytotrophoblast).
00:12 - Conceptus is completely implanted in uterine wall, maternal lacunae (blood-filled spaces, right, dark red) provide nutrition and hCG hormone exchange into the maternal blood.
00:14 - Chorionic cavity (extraembryonic coelom, pale blue space) forms and epiblast gastrulation continues.
00:15 - Yolk sac (yellow cavity, left) formed, now 3 cavities lie outside the embryo.
00:23 - Embryo (dark blue vertical) forms in amniotic cavity and connecting stalk (dark brown, bottom) is the region of eventual placental cord vessel development. Trophoblast layers and extraembryonic mesoderm are forming the early placental villi.
00:24 - Embryo folding with the heart bulge and pharyngeal arches.
00:28 - Embryo growth with limb bud development.
00:38 - Amniotic sac expands and fuses with chorionic cavity wall and the yolk sac remnant is also pushed to the periphery.
00:40 - Week 8, end of the embryonic period of development.