A cellular mass that forms early in the process of embryo development in mammals.
At this stage, the embryo is called a blastocyst and has undergone the 1st step in differentiation; it separates into two tissue types, the trophectoderm and the inner cell mass. The trophectoderm is what is destined to become the placenta, while the inner cell mass eventually forms the fetus. A blastocyst is an embryo that has been developed in the laboratory for five or six days after insemination, in contrast to conventional IVF which involves transferring embryos to the womb two to three days after egg collection and insemination (this is referred to as a Day 2 or 3 transfer). The outer layer of the blastocyst consists of cells collectively called the trophoblast. This layer surrounds the inner cell mass and a fluid-filled cavity known as the blastocoele. Blastocyst: A thin-walled hollow structure in early embryonic development that contains a cluster of cells called the inner cell mass from which the embryo arises. From Fertilization to Blastocyst. This time-lapse video shows a human embryo from the time of fertilization, when it is a single cell, until it reaches the blastocyst stage (around five days after fertilization). The blastocyst is a sphere of about 150 cells, with an outer layer (the trophoblast), a fluid-filled cavity (the blastocoel), and a cluster of cells on the interior (the inner cell mass). The blastocyst consists of an outer layer (trophoblast) which is attached to the inner cell mast. A pre-implantation embryo consisting of a thin-walled hollow sphere of 16–40 cells, which appears in early mammalian development, the wall of which is the trophoblast. A blastocyst is a cellular mass that forms early in the process of embryo development in mammals. In humans, this stage of embryogenesis occurs five days after fertilization, when there are fewer than 100 cells in the mass. At this stage of development, the embryo has not yet implanted in the uterus. Within the blastocyst, there are two types of cells. In the interior is the inner cell mass, a portion of which will begin to divide at a very rapid pace and become the developing fetus. It is surrounded by a fluid-filled cavity called the blastocoele.
http://www.givf.com/aboutgivf/library/blastocyst.shtml http://www.carefertility.com/fertility-treatments-sc1/fertility-treatments-sj2/page-11/ https://en.wikipedia.org/wiki/Blastocyst http://www.medicinenet.com/script/main/art.asp?articlekey=18258 http://stemcells.nih.gov/info/pages/cellmovie.aspx http://stemcells.nih.gov/info/pages/cellmovie.aspx http://medical-dictionary.thefreedictionary.com/blastocyst http://www.wisegeek.org/what-is-a-blastocyst.htm http://www.wisegeek.org/what-is-a-blastocyst.htm
what is a blastocyst