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The mesoderm germ layer forms in the embryos of triploblastic animals. During gastrulation, some of the cells migrating inward contribute to the mesoderm, an additional layer between the endoderm and the ectoderm. [9] The formation of a mesoderm leads to the development of a coelom. Organs formed inside a coelom can freely move, grow, and ...
The germ layers are referred to as the ectoderm, mesoderm and endoderm. In diploblastic animals only the ectoderm and the endoderm are present. [8] * Among different animals, different combinations of the following processes occur to place the cells in the interior of the embryo: Epiboly – expansion of one cell sheet over other cells [9]
The position of the ectoderm relative to the other germ layers of the embryo is governed by "selective affinity", meaning that the inner surface of the ectoderm has a strong (positive) affinity for the mesoderm, and a weak (negative) affinity for the endoderm layer. [6] This selective affinity changes during different stages of development.
The endoderm of vertebrates produces tissue within the lungs, thyroid, and pancreas. The mesoderm aids in the production of cardiac muscle, skeletal muscle, smooth muscle, tissues within the kidneys, and red blood cells. The ectoderm produces tissues within the epidermis and aids in the formation of neurons within the brain, and melanocytes.
Endoderm is the innermost of the three primary germ layers in the very early embryo. 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.
Triploblasty is a condition of the gastrula in which there are three primary germ layers: the ectoderm, mesoderm, and endoderm. Germ cells are set aside in the embryo at the blastula stage, and are incorporated into the gonads during organogenesis. The germ layers form during the gastrulation of the blastula.
Bilaterians constitute one of the five main metazoan lineages, the other four being Porifera (sponges), Cnidaria (jellyfish, hydrozoans, sea anemones and corals), Ctenophora (comb jellies) and Placozoa (tiny "flat animals"). For the most part, bilateral embryos are triploblastic, having three germ layers: endoderm, mesoderm and ectoderm.
The mesoderm germ layer forms in the embryos of animals and mammals more complex than cnidarians, making them triploblastic. During gastrulation , some of the cells migrating inward to form the endoderm form an additional layer between the endoderm and the ectoderm .