Neurulation, or the formation and development of the neural tube, can be divided into primary and secondary neurulation. During primary neurulation, the neural tube forms from the neural plate. During secondary neurulation, the neural tube develops from the caudal end of the embryo. Eventually both neural tubes connect.

Neurulation is induced in embryos through secreted growth factors and inhibitory factors from the notochord. The notochord is a rod-shaped structure located below the neural tube of chordate embryos. Notochords are important in signaling neurulation and organogenesis in embryos. The notochord secretes both growth and inhibitory factors in the regulation of neurulation.

Neural crest cells are a group of multipotent migratory cells. Prior to neurulation, neural crest cells are located between the neural plate and the ectoderm. During neurulation and the infolding of the neural plate, neural crest cells are located on the top of the neural tube. Afterwards, the cells migrate to the area between the neural tube and the ectoderm, where they differentiate into various cell types.

Miscarriage is the death and subsequent abortion of an embryo before it is able to survive outside of the mother. Miscarriage is more common early in pregnancy and common symptoms include vaginal bleeding and cramping. There are many risk factors associated with miscarriage including advanced maternal age, tobacco use, and obesity. In order to prevent miscarriage, expecting mothers are advised to avoid risk factors and practice good prenatal care.

Hemolytic disease of the newborn is a condition during pregnancy in which maternal antibodies pass to the fetus through the placenta. These antibodies attack fetal cells, specifically red blood cells, causing developmental and structural problems in the fetus. Treatment includes blood transfusion into the fetus or early induction of labor.

Hox genes are a class of genes that control body plan development during embryogenesis. The Hox gene DNA sequence is called a “homeobox” and codes for transcription factors.

Fetal alcohol syndrome (FAS) is a disease that occurs when the individual’s mother drank alcohol during the pregnancy in which they were conceived. There are many symptoms including brain damage, intellectual disabilities, and heart disease. These symptoms come from the passage of ethanol to the fetus from the placenta. The ethanol impairs nervous system development and negative impacts on other organ and developmental systems.

During the 1950’s, thalidomide was an over-the-counter drug advertised and used to treat morning sickness in pregnant women. Thalidomide was later found to cause limb and skeletal deformities in resulting fetuses. Subsequently, the sale and use of the drug has ended.

The blastocoel is a fluid-fill cavity region of the blastocyst. The blastocoel is formed through cell polarization, when trophoblasts and embryoblasts differentiate. The trophoblasts are the outer layer of cells that compact to become watertight. Embryoblasts polarize to one end of the cell and form gap junctions for cell-cell communication and developmental coordination. The trophoblasts then secrete fluid into the cavity, which forms the blastocoel.

The blastocoel is a fluid-filled cavity that is a part of the blastocyst. A compacted trophoblast cell layer surrounds the cavity, making it watertight. Trophoblast cells then secret fluid into the cavity.