A Neurula is an embryo

Embryo

An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

 at the early stage of development in which neurulation

Neurulation

Neurulation is the stage of organogenesis in vertebrate embryos, during which the neural tube is transformed into the primitive structures that will later develop into the central nervous system....

 occurs.

Neurulation is the development of the nervous system in the vertebrates, at the thickened area above the notochord

Notochord

The notochord is a flexible, rod-shaped body found in embryos of all chordates. It is composed of cells derived from the mesoderm and defines the primitive axis of the embryo. In some chordates, it persists throughout life as the main axial support of the body, while in most vertebrates it becomes...

 in ectoderms. The neural plate will fold to produce the neural tube

Neural tube

In the developing vertebrate, the neural tube is the embryo's precursor to the central nervous system, which comprises the brain and spinal cord...

 which will develop into the brain

Brain

The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

. Remaining tissue will develop into the spinal cord

Spinal cord

The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...

. Neurula involves the formation of an internal neural tube from an external sheet of cells. The first signs of neurulation are flattening and thickening of the ectoderm overlying the notochord; this thickened area forms a neural plate. The edges of the neural plate that run in an anterior-posterior direction continue to thicken, forming ridges or folds. Between these neural folds, a groove forms and deepens as the fold roll over it to converge on the midline. The fold fuses, forming a cylinder--the neural tube--and a continuous overlying layer of epidermal ectoderm. The neural tube develops bulges at the anterior end, which become the major divisions of the brain. The remaining sections of the tube becomes the spinal cord.

Health

In humans, failure of the neural tube to develop normally can result in serious birth defects. If the neural folds fail to fuse in a posterior region, the result is a condition known as spina bifida. If they fail to fuse at the anterior end of an infant can develop without a forebrain- a condition called anencephaly. There are genetic as well as dietary factors that cause neural tube defects. The incidence of neural tube defects used to be about 1 in 300 live births, but we now know that this incidence can be cut in half if pregnant women have an adequate amount of folic acid in their diets.