Neural tube

Neural tube
Transverse section of half of a chick embryo of forty-five hours' incubation. The dorsal (back) surface of the embryo is toward the top of this page, while the ventral (front) surface is toward the bottom. (Neural tube is in green.)
Chick embryo of thirty-three hours' incubation, viewed from the dorsal aspect (30x magnification).
Details
Carnegie stage	10
Precursor	Neural groove
Gives rise to	Central nervous system (brain and spinal cord)
Identifiers
Latin	tubus neuralis, tuba neuralis
Code	TE E5.14.1.0.0.0.1
Anatomical terminology []

In the developing chordate (including vertebrates), the neural tube is the embryo's precursor to the central nervous system, which comprises the brain and spinal cord. The neural groove gradually deepens as the neural folds become elevated, and ultimately the folds meet and coalesce in the middle line and convert the groove into the closed neural tube. The ectodermal wall of the tube forms the rudiment of the nervous system. The centre of the tube is the neural canal.

The neural tube develops in two ways: primary neurulation and secondary neurulation.

Primary neurulation divides the ectoderm into three cell types:

Primary neurulation begins after the neural plate forms. The edges of the neural plate start to thicken and lift upward, forming the neural folds. The center of the neural plate remains grounded, allowing a U-shaped neural groove to form. This neural groove sets the boundary between the right and left sides of the embryo. The neural folds pinch in towards the midline of the embryo and fuse together to form the neural tube.

Each organism uses primary and secondary neurulation to varying degrees.

Mammalian neural tubes close in the head in the opposite order that they close in the trunk.

Four neural tube subdivisions each eventually develop into distinct regions of the central nervous system by the division of neuroepithelial cells: The prosencephalon, the mesencephalon, the rhombencephalon and the spinal cord.

For a short time, the neural tube is open both cranially and caudally. These openings, called neuropores, close during the fourth week in humans. Improper closure of the neuropores can result in neural tube defects such as anencephaly or spina bifida.