K12 Week 2
In the second week of development the dividing zygote forms a solid ball of cells and is now called a blastocyst.
This movie shows human development between day 3 and day 6 after fertilization.
- The cells on the surface of the ball will not form part of the embryo and will go on to make the placenta and membranes that surround the embryo.
- The cells on the inside form a small clump beside a fluid filled space. This small clump of cells (embryoblast) will form all the parts of the embryo.
|This movie shows implantation that occurs during week 2 of human development.
The uterus wall is shown by the white cells (left) and the space where the blastocyst was floating is to the right.
By the end of the second week the embryo is completely within the mother's uterus wall.
The green cells will then form part of the placenta.
Question: You start as a single cell, how many cells are you now?
|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|
blastocyst - the name given to all the new cells formed from the first cell (the zygote).
implanting - this means to burrow into the uterus wall.
placenta - the structure formed by both the mother and baby to allow growth. Egg-laying animals like birds, fish, frogs do not have placentas.
Cite this page: Hill, M.A. (2020, May 25) Embryology K12 Week 2. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/K12_Week_2
- © Dr Mark Hill 2020, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G