K12 Week 3

Week 3

In the third week of development the blastocyst has now burrowed into the wall of the uterus and cells on the outside are beginning to form early parts of the placenta.

<html5media height="540" width="390">File:Week3_folding.mp4</html5media>

This movie shows folding of the embryonic disc beginning week 3 of development.

(blue) The embryo has been cut in the middle from head to tail to show the growth and folding.

(yellow) The gastrointestinal tract.

(red right) The connecting stalk that will form the future placental cord.

(red left with white "8" shaped cavity) The early heart.

A week 3 Human Embryo

The clump of cells inside the blastocyst has also begun to change and now looks like 2 discs of cells. It looks like 2 dinner plates stacked on top of each other. The picture shows looks at this stack from the top. Cell from the top plate move down to form a new layer.

The embryo now looks like stacked 3 dinner plates.

We use stages as a way of measuring changes in the embryo. Stages are like different years at school: each year something new will occur, each stage something new will happen. Stages are also a way of comparing changes that occur in different animals.

Cite this page: Hill, M.A. (2023, December 11) Embryology K12 Week 3. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/K12_Week_3

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