What Is the Ectoderm?

The ectoderm is the outermost layer of the embryo. In the drawing, the ectoderm is traditionally represented in blue. Primitive ectoderm forms mesoderm during the process of neural embryo formation (start of nervous system formation).

Ectoderm

One of the germ layers that arises during the occurrence of metazoans, appears on the outer surface or surface of the embryo. Generally, when the gut is formed, it remains on the surface of the embryo and separates from the endoderm and mesoderm that move into the embryo. Within the amniotic membrane, the predetermined ectoderm and the predetermined mesoderm form the upper layer of the blastoderm. Later, when the original mesoderm is trapped through the original strip (mammal, bird) or the chord mesoderm tube (reptile), it starts to be independent Germ layer while covering the surface of the embryo. The ectoderm line is derived from the cytoplasm near the ovum of the animal, and the yolk concentration in the germ layer is extremely low (because it is mostly the smallest germ layer of the cell). The ectoderm forms the epidermis and nervous system . However, experimental studies on vertebrates, especially amphibians, have proven that parts of mesenchyme , cartilage pigment cells, and somites (back trunk and tail) that were previously thought to be derived from mesoderm are now clear. It is derived from ectoderm. In vertebrates, the initial differentiation of the ectoderm is the formation of neural plates under the influence of the mesoderm of the chordae. On the other hand, the later differentiation of mesoderm tissue also depends on the process of ectodermal tissue, which is also clarified. In vertebrates, the predetermined ectoderm has a wide range of occurrence possibilities under experimental conditions. Tissues belonging to the mesoderm can differentiate into tissues belonging to the endoderm under certain conditions. In addition, in insects, the differentiation of mesoderm tissue depends on ectoderm, which has been shown in experiments.

It develops into thickened ectodermal cells in the upper chordal cord, forming a neural plate-neural groove-neural tube, and finally develops into the brain and spinal cord. The remaining ectoderm differentiates into the epidermis.

The ectoderm of the gastrula embryo is composed of cells at the extreme end of the animal that coats the surface of the embryo. The endoderm is composed of cells trapped in the blastocyst cavity. The mesoderm is located between the endoderm and the ectoderm. These three germ layers continue to develop and undergo tissue differentiation. , Organ formation, and finally a complete larva

1. Vine Chizhong. Anhidrotic ectodermal insufficiency. Nippon Shokai, 1981, 91: 439.

2.Amold MI, Anton I, Amprecht I, et al. Prenatal diagnosis of ectodermal dysplasias. Semin Dermatol, 1984, 3: 247.