The Amazing World Of Embryonic Tissue
In general terms, embryonic tissue is a tissue consisting of a loose, gelatinous mass of cells. A more specific definition, and the one commonly accepted is it is a tissue of the embryo.
Usually when we speak of embryonic tissue we're referring to human tissue, but in fact embryonic tissue is present in all animal life forms, and research done on embryonic tissue of animals has in the past been useful in understanding and treating various conditions in the human body.
Given that a tissue consists of a group of cells, there are three major types of embryonic tissue, often referred to as germ layers, where the term germ in this instance has nothing to do with the nasty little guys that make us ill. All the higher animals have all three germ layers or tissue types, but jellyfish have only two, and sponges only one. The presence of the different types of embryonic tissue in a human begins to become evident not long after the fertilized egg begins to evolve into an identifiable organism. It is then that the three germ layers begin to go about their business of building different parts and pieces of what will eventually become an adult human being.
The Endoderm Layer - The three types of embryonic tissue or germ layers are called the ectoderm, the mesoderm, and the endoderm. The endoderm forms first, about 14 days after the egg's fertilization. The endoderm is the tissue layer which forms most of our internal organs. In fact, at about the 5th week of pregnancy the endoderm has defined all of our major internal organs, though they are not yet in any way fully developed. It is the endoderm which is responsible for the development of our respiratory system, with the tissue forming the airways in the lungs, the tiny alveoli, as well as the trachea and bronchi. The endoderm tissue, besides giving us the capability to breathe, also gives us the capability to hear, forming the Eustachian tube and the tympanic cavity of the ear. Its role in developing the bladder and urethra is also greatly appreciated.
The Mesoderm Layer - Whereas the endoderm is the embryonic tissue that builds our organs, the mesoderm is the next layer to spring into action, building the structure around which the internal organs will be arranged. The mesoderm is made up of a number of sub layers, each devoted to the development of a specific body part or organ. Some of the cell types of the mesoderm layer go into further building of internal organs including the urinary and reproductive organs, the vertebrae and other parts of the spine, facial and skeletal muscles, the lining of the abdominal cavity, and the dermal layer of the skin.
The Ectoderm Layer - The third germ layer, the ectoderm, is responsible for the development of our nervous system, our external sensory organisms, the hair and the skin, tooth enamel, and the membranes on the inside of our mouth. A precursor to the spinal column, called the neural tube, is also a product of ectoderm development and expansion, as are bones, cartilage, various connective tissue, and portions of the brain.
A Complex And Miraculous Feat - The different kinds of embryonic tissue therefore perform a myriad of different and complex tasks, and in going about their work, the action of the cells in the various tissues is often dictated by the action of other cells. The creation of the human body and the development of that body from a single fertilized egg, is indeed a wonder to behold. If it were not for the presence of the embryonic tissue, the fertilized egg would forever remain a fertilized egg, and nothing more.