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Embryology: From Fertilization to Neural Tube and Somite Formation
Citation:
Hunter, S. Embryology: From Fertilization to Neural Tube and Somite Formation. Pharmceutical and BioScience Society, Virtual, NC, November 03 - 04, 2021.
Impact/Purpose:
Invited presentation to the Pharmceutical and BioScience Society (PBSS), Bay Area conference (virtual) November 2021 for the Reproductive and Juvenile toxicity workshop.
Description:
Embryogenesis progresses from the fusion of the egg and sperm through many critical processes to establish the embryo proper. This lecture will describe and discuss those processes. Fusion of the sperm and egg establishes the one cell zygote. Continued cellular division, initiation of zygotic gene expression and cellular specification occurs during the pre-implantation period with the formation of the blastocyst. The process of implantation occurs with the attachment, penetration, and implantation of the blastocyst into uterine tissues. The blastocyst has two distinct cell types, trophoblasts and the inner cell mass. Trophoblast cells form placental anlagen. Differentiation of the inner cell mass ultimately forms the three “germ cell” lineages and layers in the embryo. The three germ cell layers, ectoderm, mesoderm and endoderm, contribute to establishing the body plan and distinct cell types and structures. This period of gestation is called organogenesis. The neuroectoderm, derived from ectoderm, begins as a sheet of cells that close into a tube giving rise to the neural tube and ultimately, brain and spinal cord. Somites are specialization of the mesoderm that establish block-like structures throughout the body of the embryo and form vertebrae and other segmented structures. Other organ systems, such as the cardiovascular system, are being established during this window of development. With the closure of the neural tube and establishment of somites, the embryo has established its characteristic body plan and awaits further development and histogenesis of tissues and organs. This abstract does not necessarily reflect U.S. EPA policy.