Around the 14th day of development, the primitive streak begins to develop in the embryo which signals the start of the development of the nervous system.
This develops in an embryo at about day 14 when the cells separate into 2 groups: those that will eventually become a foetus; and those which will form the placenta and umbilical cord.
The initial band of cells from which the embryo begins to develop. The primitive streak establishes and reveals the embryo's head-tail and left-right orientations.
A line running axially along the blastodisc, the site of inward cell migration during formation of the three-layered embryo. Formed in the embryos of birds and fish.
Region visible on the surface of the early epiblast embryonic disc showing the region where gastrulation (cell migration to form endoderm) is occurring. In the human embryo this process occurs from week 3 through week 4. (More? Carnegie Stage 7 | Week 3 Gastrulation)
this develops in an embryo by day 14 when the cells which form the fetus separate from those which form the placenta and umbilical cord.
PRIM-eh-tiv STREEK The pigmented band along the back of a 3-week embryo that develops into the notochord. 226
A line of cells in the center of the embryonic disk of reptiles, birds, and mammals that forms the future axis of the embryo.
A marking which appears on an blastocyst about 14 days after fertilization, at about the time that it is implanted in the wall of the uterus. Division into identical twins is very rate after this point. (See "Twinning"). The streak will eventually develop into the fetus' spinal column. This essay continues below. Click below to visit one of our sponsors
A collection of cells which appears at about 14 days after fertilisation from which the central nervous system eventually develops.
A faint white trace at the caudal end of the embryonic disc, formed by the movement of cells at the beginning of the mesoderm formation. It provides the earliest indication of the embryonic axis.
A vertical, opaque line where the embryo begins to grow and develop.
primitus - at first]. Longitudinal cleft formed on surface of amniote blastodisc by a convergence of cells. Gastrulation begins as epiblast cells migrate towards and into the streak.
The initial band of cells from which the embryo begins to develop. The primitive streak is present at about 15 days after fertilization.
The development of a nervous system in an embryo
The primitive streak is a structure that forms during the early stages of avian, reptilian and mammalian embryonic development. The formation of the primitive streak is one of the first signs of gastrulation. It is characterized as a furrow in the midline of the embryonic disk at the future caudal end of the embryo.
