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Germ layer; List of distinct cell types in the adult human body; References This page was last edited on 30 December 2024, at 15:41 (UTC). Text ...
A germ layer is a primary layer of cells that forms during embryonic development. [1] The three germ layers in vertebrates are particularly pronounced; however, all eumetazoans ( animals that are sister taxa to the sponges ) produce two or three primary germ layers.
The ectoderm is one of the three primary germ layers formed in early embryonic development. It is the outermost layer, and is superficial to the mesoderm (the middle layer) and endoderm (the innermost layer). [1] It emerges and originates from the outer layer of germ cells.
A germ cell is any cell that gives rise to the gametes of an organism that reproduces sexually. In many animals, the germ cells originate in the primitive streak and migrate via the gut of an embryo to the developing gonads. There, they undergo meiosis, followed by cellular differentiation into mature gametes, either eggs or sperm.
A germ layer is a collection of cells, formed during animal and mammalian embryogenesis. Germ layers are typically pronounced within vertebrate organisms; however, animals or mammals more complex than sponges ( eumetazoans and agnotozoans ) produce two or three primary tissue layers.
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The other two layers are the ectoderm (outside layer) and mesoderm (middle layer). [1] Cells migrating inward along the archenteron form the inner layer of the gastrula, which develops into the endoderm. [2] The endoderm consists at first of flattened cells, which subsequently become columnar. It forms the epithelial lining of multiple systems.
Germ cells are specified early in development [4] and can only differentiate into gametes. [5] The segregation of germ cells is often determined by the species, with some undergoing preformation, where the germ cells are determined by maternally inherited factors before or immediately after fertilisation, and others undergoing epigenesis, where the germ cell lineage is determined from ...