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Between the two layers of cells is a liquid-filled interior space, which, except for the immediate zones of contact with the ventral and dorsal sides, is pervaded by a star-shaped fibre syncytium: a fibrous network that consists essentially of a single cell but contains numerous nuclei that, while separated by internal crosswalls , do not have ...
There are at least six different cell types. [32] The upper epithelium is the thinnest portion and essentially comprises flat cells with their cell body hanging underneath the surface, and each cell having a cilium. [33] Crystal cells are sparsely distributed near the marginal edge. A few cells have unusually large number of mitochondria. [32]
Cells migrate to the primitive streak, and as they enter the embryo the cells separate into two layers. The deep layer joins the hypoblast along its midline, displacing the hypoblast cells to the sides. [5] The first cells to migrate through Hensen's node are destined to become the foregut's pharyngeal endoderm. [5]
The different stages of mitosis all together define the M phase of an animal cell cycle—the division of the mother cell into two genetically identical daughter cells. [3] To ensure proper progression through the cell cycle, DNA damage is detected and repaired at various checkpoints throughout the cycle.
During implantation the blastocyst, which contains the inner cell mass, undergoes cellular differentiation into the two layers of the bilaminar embryonic disc. One of which is the epiblast, also known as the primitive ectoderm. The epiblast is the outer layer of the bilaminar embryonic disc and consists of columnar cells.
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 two-domain system is a biological classification by which all organisms in the tree of life are classified into two domains, Bacteria and Archaea. [ 1 ] [ 2 ] [ 3 ] It emerged from development of knowledge of archaea diversity and challenges the widely accepted three-domain system that classifies life into Bacteria, Archaea, and Eukarya . [ 4 ]
The lateral plate mesoderm will split into two layers, the somatopleuric mesenchyme, and the splanchnopleuric mesenchyme. The somatopleuric layer forms the future body wall. The splanchnopleuric layer forms the circulatory system. Spaces within the lateral plate are enclosed and forms the intraembryonic coelom.