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A. Morula and B. cross section of a blastula displaying the blastocoel and blastoderm of early animal embryonic development. Blastulation is the stage in early animal embryonic development that produces the blastula. In mammalian development, the blastula develops into the blastocyst with a differentiated inner cell mass and an outer trophectoderm.
Coregonus is a diverse genus of fish in the salmon family ().The Coregonus species are known as whitefishes.The genus contains at least 68 described extant taxa, but the true number of species is a matter of debate.
The blastocoel further expands and the inner cell mass becomes positioned on one side of the trophoblast cells forming a mammalian blastula, called a blastocyst. The axis formed by the inner cell mass and the blastocoel is the first axis of symmetry of mammalian embryo and determines its attachment point to the uterus.
Coregonus albula, known as the vendace or as the European cisco, [1] is a species of freshwater whitefish in the family Salmonidae.It is found in lakes in northern Europe, especially Finland, Latvia, [2] Lithuania, Sweden, Russia and Estonia, and in some lakes of Norway, the United Kingdom, northern Germany, and Poland.
Fish embryos go through a process called mid-blastula transition which is observed around the tenth cell division in some fish species. Once zygotic gene transcription starts, slow cell division begins and cell movements are observable. [4] During this time three cell populations become distinguished. The first population is the yolk syncytial ...
Even at this depth, there is an underwater current, with a velocity of 0.5–1 m/s (1.6–3.3 ft/s), that disperses some of the deposited eggs downstream in the tributary system. Fertilized eggs are 3.1–3.25 mm (0.12–0.13 in) in diameter and are held in spaces between rocks as well as in the ice crystals of the slushy, tributary floor. [ 8 ]
The internal cells become the inner cell mass, and the outer cells become the trophoblast. [2] Before cell differentiation takes place there are two transcription factors , Oct-4 and nanog that are uniformly expressed on all of the cells, but both of these transcription factors are turned off in the trophoblast once it has formed.
The blastocyst has a diameter of about 0.1–0.2 mm and comprises 100-200 cells following 7-8 rounds of cleavage (cell division without cell growth). About seven days after fertilization, [ 6 ] the blastocyst undergoes implantation , embedding into the endometrium of the uterine wall where it will undergo further developmental processes ...