The floor of the amniotic cavity is formed by the embryonic disk (or embryonic disc) composed of a layer of prismatic cells, the embryonic ectoderm, derived from the inner cell-mass and lying in apposition with the endoderm.
In humans, it is the stage of development that occurs after implantation and prior to the embryonic folding (e.g. seen between about day 14 to day 21 post fertilization). It is derived from the epiblast layer, which lies between the hypoblast layer and the amnion. The epiblast layer is derived from the inner cell mass. Through the process of gastrulation, the bilaminar embryonic disc becomes trilaminar. The notochord forms thereafter. Through the process of neurulation, the notochord induces the formation of the neural tube in the embryonic disc.
Famous quotes containing the words embryonic and/or disc:
“Quintilian [educational writer in Rome around A.D. 100] thought that the earliest years of the child’s life were crucial. Education should start earlier than age seven, within the family. It should not be so hard as to give the child an aversion to learning. Rather, these early lessons would take the form of play—that embryonic notion of kindergarten.”
—C. John Sommerville (20th century)
“Perhaps all music, even the newest, is not so much something discovered as something that re-emerges from where it lay buried in the memory, inaudible as a melody cut in a disc of flesh. A composer lets me hear a song that has always been shut up silent within me.”
—Jean Genet (1910–1986)