K12 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.
(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.
|K12 Links: Start Here | Week 1 | Week 2 | Week 3 | Week 4 | Week 5 to 8 | Arms and Legs | Heart | Fetus | Brain Growth | Eyes and Ears | Animal Development Times | Humans and Animal Embryology | Comparative Embryology | Thalidomide|
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
- © Dr Mark Hill 2023, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G