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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.
This is a list of cells in humans derived from the three embryonic germ layers – ectoderm, mesoderm, and endoderm. Cells derived from ectoderm. Surface ectoderm
These three germ layers are the ectoderm (outer layer), mesoderm (middle layer), and endoderm (inner layer). [3] [4] In diploblastic organisms, such as Cnidaria and Ctenophora, the gastrula has only ectoderm and endoderm. The two layers are also sometimes referred to as the hypoblast and epiblast. [5] Sponges do not go through the gastrula stage.
The epiblast keeps moving and forms a second layer, the mesoderm. The epiblast has now differentiated into the three germ layers of the embryo, so that the bilaminar disc is now a trilaminar disc, the gastrula. The three germ layers are the ectoderm, mesoderm and endoderm, and are formed as three
The blastoderm now consists of three layers, an outer ectoderm, a middle mesoderm, and an inner endoderm; each has distinctive characteristics and gives rise to certain tissues of the body. For many mammals, it is sometime during formation of the germ layers that implantation of the embryo in the uterus of the mother occurs. [18] [20]
The endoderm is the inner most germ layer of the embryo which gives rise to gastrointestinal and respiratory organs by forming epithelial linings and organs such as the liver, lungs, and pancreas. [5] The mesoderm or middle germ layer of the embryo will form the blood, heart, kidney, muscles, and connective tissues. [5]
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.
The mesoderm is the middle layer of the three germ layers, between the outer ectoderm and inner endoderm. During the third week of embryonic development the lateral plate mesoderm splits into two layers forming the intraembryonic coelom .