Week 3 Development Movie

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Embryology - 19 Mar 2024    Facebook link Pinterest link Twitter link  Expand to Translate  
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<html5media height="540" width="390">File:Week3_folding.mp4</html5media>

Click Here to play on mobile device

Week3 folding icon.jpg

Embryo Folding

This animation shows a mid-sagittal section of the folding of the embryonic disc beginning week 3 of development.

Embryo (midline section) shown to the left and early placenta to the right. The embryonic disc dorsal (ectoderm) top and ventral (endoderm) bottom. Cranial end of disc to the left and caudal end of disc to the right.

Note also the early cardiac region shown at the cranial end of disc and the allantois at the caudal end of disc extending into the connecting stalk.

Folding of the embryonic disc

  1. brings the cardiac region and allantois ventrally
  2. brings the buccopharyngeal membrane, cloacal membrane and connecting stalk ventrally
  3. encloses the embryo in amniotic cavity
  4. narrows the connection between yolk sac and midgut of the gastrointestinal tract to a channel, the yolk stalk or vitelline duct


  • blue - ectoderm layer of embryo and amniotic cavity
  • yellow - endoderm layer of the yolk sac and gastrointestinal tract
  • red - mesoderm layer of embryo and extra-embryonic mesoderm outside of embryo.


Links: MP4 version | Week 3 | Movies
Amnion 001 icon.jpg
 ‎‎Amniotic Cavity
Page | Play

Compare this sectional view of folding with the Amniotic Cavity view, filling the amnion and yolk cavities.

Week 3 Links: stage 7 | stage 8 | stage 9 | Gastrulation | Endoderm | Mesoderm | Ectoderm | Placenta | Coelomic Cavity | Lecture | Category:Week 3 | GA week 5


Glossary Links: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Movies


Cite this page: Hill, M.A. (2024, March 19) Embryology Week 3 Development Movie. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Week_3_Development_Movie

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G