During the three to four day passage through the fallopian tube following fertilization, three of the days floating in the intrauterine fluid, the zygote undergoes a series of divisions giving rise to a ball of cells with the beginnings of structure. This ball of cells is called the blastocyst, consisting of an outer layer of cells, the trophoblast, and an inner cell mass as well as a fluid filled cavity. The inner cell mass gives rise to the embryo. Upon implantation, the trophoblast develops into structures involved in secretory and nutritive support of the developing embryo/fetus. The outer layer of the trophoblast is called the chorion, which gives rise to chorionic villi, which integrate with maternal endometrial tissue in the placenta. Although there is extensive exchange of materials, there is no actual mingling of fetal and maternal blood. Further structures that form include the amniotic cavity, which forms between the inner cell mass and the trophoblast. The amniotic cavity is lined with the amnion, which eventually fuses with the chorion.

The WikiPremed MCAT Course is a comprehensive course in the undergraduate level general sciences. Undergraduate level physics, chemistry, organic chemistry and biology are presented by this course as a unified whole within a spiraling curriculum. Please read our policies on Privacy and Shipping & Returns.  Contact Us. MCAT is a registered trademark of the Association of American Medical Colleges, which does not endorse the WikiPremed Course. WikiPremed offers the customers of our publications or our teaching services no guarantees regarding eventual performance on the MCAT.

Creative Commons License
WikiPremed is a trademark of Wisebridge Learning Systems LLC. The work of WikiPremed is published under a Creative Commons Attribution NonCommercial ShareAlike License. There are elements of work here, such as a subset of the images in the archive from WikiPedia, that originated as GNU General Public License works, so take care to follow the unique stipulations of that license in printed reproductions.