Alcohol on Embryonic Tissue Development

Alcohol consumption can affect the developing embryo/fetus all throughout pregnancy. Different anomalies arise depending on the time of alcohol exposure. To understand how alcohol affects development, an understanding of the normal progression of the developmental process is required. For our purposes, we will describe the normal progression of development starting with the formation of the bilaminar germ disc. Alcohol consumption during and/or prior to forming the bilaminar germ disc causes devastating disruptions in normal developmental progression.

The epiblast normally forms when the inner cell mass of the morula delaminates into the bilaminar germ disc. The bilaminar germ disc consists of both the epiblast and the hypoblast cell layers. The primitive streak forms on the surface of the epiblast. Cells normally migrate through the primitive streak of the epiblast to form the centrally located mesodermal layer during the process of gastrulation. After gastrulation takes place, a trilaminar germ disc has formed which contains the three germ layers. The three germ layers are the ectoderm, mesoderm, and endoderm. The ectoderm and mesoderm germ layers are derived from the epiblast cells, while the endodermal germ layer is derived from both the epiblast and hypoblast cells.

After the three germ layers are established, the development of the various organ systems takes place. Normally, the ectodermal germ layer gives rise to the nervous system, inner eye structures, as well as the epidermis layer of the skin. The mesodermal layer normally gives rise to the muscular, skeletal, and urinary systems. The cardiovascular system is derived from the mesenchymal cells of the mesodermal germ layer as well. The endodermal germ layer gives rise to the gastrointestinal system as well as internal linings of other organ systems.

Alcohol has been shown to affect the normal development of the epiblast cell layer, which has the potential to affect development of all of the major organ systems. Alcohol has also been shown to inhibit the migration of cells through the primitive streak. Even though alcohol can disrupt the normal formation of potentially every organ system, it appears as if the brain and heart are more affected than any other system. The reasons behind this have yet to be determined. Previous studies have also revealed that mesodermal derived structures are affected by prenatal alcohol exposure. It is thought that either the damage done to the epiblast or the inhibition of proper gastrulation migrations may be responsible. Both effects can be responsible for the malformations and it likely depends on when the developing embryo/fetus is exposed to alcohol.

Thank you so much for your answer! That was so helpful and clear! 

NP