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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.
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 ...
The division of blastomeres from the zygote allows a single fertile cell to continue to cleave and differentiate until a blastocyst forms. The differentiation of the blastomere allows for the development of two distinct cell populations: the inner cell mass, which becomes the precursor to the embryo, and the trophectoderm, which becomes the precursor to the placenta.
The blastula is usually a spherical layer of cells (the blastoderm) surrounding a fluid-filled or yolk-filled cavity the blastocoel. [ citation needed ] Mammals at this stage form a structure called the blastocyst , [1] characterized by an inner cell mass that is distinct from the surrounding blastula.
The eukaryotic cell cycle consists of four distinct phases: G 1 phase, S phase (synthesis), G 2 phase (collectively known as interphase) and M phase (mitosis and cytokinesis). M phase is itself composed of two tightly coupled processes: mitosis, in which the cell's nucleus divides, and cytokinesis, in which the cell's cytoplasm and cell membrane divides forming two daughter cells.
The morula then develops by cavitation to become the blastocyst, or in many other animals the blastula. Cell differentiation then further commits the morula's cells into two types: trophectoderm cells that surround the lumen and the inner mass of cells (the embryoblast). The inner cell mass is at the origin of embryonic stem cells. [15]
Cells are thought to time the MBT by measuring the nucleocytoplasmic ratio, which is the ratio between the volume of the nucleus, which contains DNA, to the volume of cytosol. Evidence for this hypothesis comes from experiments showing that the timing of MBT can be sped up by adding extra DNA [ 4 ] to make the nucleus larger, or by halving the ...
The whitefish is part of the salmon family, and the distinctive traits of this subfamily (in comparison to the rest of the salmon family) include larger scales, smaller mouth, weak or no teeth, and other internal characteristics. [6] The round whitefish is a cylindrical fish (hence cylindraceum) and is considered a deep-bodied fish. It is ...