ectoderm

(noun)

Outermost of the three tissue layers in the embryo of a metazoan animal. Through development, it will produce the epidermis (skin) and nervous system of the adult.

Related Terms

Examples of ectoderm in the following topics:

  • Development of the Integumentary System

    • The integumentary system develops from all embryonic layers (ectoderm, mesoderm and neural crest cells).
    • Fetal skin forms from three layers: ectoderm, mesoderm, and neural crest cells.
    • At four weeks gestation, simple ectoderm epithelium forms.
    • Ectoderm thickens into finger and toe nails.
    • Other regions of the ectoderm form into epithelial columns called cords which will become hair follocles and sebaceous and sweat glands.

  • Gastrulation

    • During gastrulation, the embryo develops three germ layers (endoderm, mesoderm, and ectoderm), which differentiate into distinct tissues.
    • These three germ layers are known as the ectoderm, mesoderm, and endoderm.
    • In amniotes such as humans, gastrulation occurs in the following sequence: (1) the embryo becomes asymmetric, (2) the primitive streak forms, and (3) cells from the epiblast at the primitive streak undergo an epithelial to mesenchymal transition and ingress at the primitive streak to form the germ layers.The ectoderm gives rise to epidermis, and also to the neural crest and other tissues that will later form the nervous system.
    • The mesoderm is found between the ectoderm and the endoderm, giving rise to somites.
    • However, some common features of gastrulation across triploblastic organisms include: (1) A change in the topological structure of the embryo, from a simply connected surface (sphere-like), to a non-simply connected surface (torus-like); (2) the differentiation of cells into one of three types (endodermal, mesodermal, or ectodermal); and (3) the digestive function of a large number of endodermal cells.

  • Neurulation

    • Following gastrulation, the neurulation process develops the neural tube in the ectoderm, above the notochord of the mesoderm.
    • Neurulation is the formation of the neural tube from the ectoderm of the embryo.
    • During gastrulation cells migrate to the interior of the embryo, forming the three germ layers the endoderm (the deepest layer), mesoderm (the middle layer), and ectoderm (the surface layer) from which all tissues and organs will arise.
    • In a simplified way, it can be said that the ectoderm gives rise to skin and nervous system, the endoderm to the intestinal organs, and the mesoderm to the rest of the organs.
    • During the third week of gestation, the notochord sends signals to the overlying ectoderm, inducing it to become neuroectoderm.

  • Amnion Development

    • This cavity is roofed in by a single stratum of flattened, ectodermal cells called the amniotic ectoderm.
    • Its floor consists of the prismatic ectoderm of the embryonic disk.
    • Outside the amniotic ectoderm is a thin layer of mesoderm (continuous with that of the somatopleure), which is connected by the body-stalk with the mesodermal lining of the chorion.

  • Tissue Development

    • During embryogenesis, the three germ layers (endoderm, mesoderm, and ectoderm) are formed from which all body tissues will later develop.
    • The top layer is now called the ectoderm.
    • The ectoderm is the start of a tissue that covers the body surfaces.
    • This image illustrates the types of cells produced by the ectoderm (external germ layer) of the developing embryo.
    • Compare the three embryonic germ layers (endoderm, mesoderm, and ectoderm) from which all body tissues develop

  • Blastocyst Formation

    • As already stated, the cells of the trophoblast do not contribute to the formation of the embryo proper; they form the ectoderm of the chorion and play an important part in the development of the placenta.
    • The floor of this cavity is formed by the embryonic disk, which is composed of a layer of prismatic cells, the embryonic ectoderm.

  • Embryonic Development of the Brain

    • Neurulation is the formation of the neural tube from the ectoderm of the embryo.
    • During gastrulation cells migrate to the interior of embryo, forming three germ layers— the endoderm (the deepest layer), mesoderm, and ectoderm (the surface layer)—from which all tissues and organs will arise.
    • In a simplified way, it can be said that the ectoderm gives rise to skin and nervous system, the endoderm to the guts and the mesoderm to the rest of the organs.
    • During the third week of gestation, the notochord sends signals to the overlying ectoderm, inducing it to become neuroectoderm.

  • Development of Vision

    • The optic visicle will then induce the ectoderm that thickens (lens placode) and further invaginates to a point that detaches from the ectoderm and forms a neurogenic placode by itself.

  • Trophoblast Development

    • This layer of trophoblasts is also collectively referred to as "the trophoblast," or, after gastrulation, the trophectoderm, as it is then contiguous with the ectoderm of the embryo.
    • Body stalk., etc Embryonic ectoderm, ent.

  • Bilaminar Embryonic Disc Development

    • The floor of the amniotic cavity is formed by the embryonic disc, which is composed of a layer of prismatic cells and the embryonic ectoderm.