What happens in 3rd week of development?

During the third week of gestation the notochord sends signals to the overlying ectoderm, inducing it to become neuroectoderm. This results in a strip of neuronal stem cells that runs along the back of the fetus. This strip is called the neural plate, and it is the origin of the entire nervous system.

Which week of development does gastrulation happen?

week 3
Gastrulation occurs during week 3 of human development. The process of gastrulation generates the three primary germ layers (ectoderm, endoderm, mesoderm), which primes the system for organogenesis and is one of the most critical steps of development.

Which process in the third week of development converts the embryonic disc into primary germ layer?

Gastrulation
Gastrulation. Gastrulation is the conversion of the epiblast from a bilaminar disc into a trilaminar embryonic disc consisting of ectoderm, mesoderm, and endoderm.

Which germ layers are present at the end of week 3 of development?

During week 3 of development, the process of gastrulation, which establishes the three primary germ layers (ectoderm, intraembryonic mesoderm, and endoderm), occurs. The origin of all tissues and organs of the adult can be traced to one of these germ layers because these are whence they “germinate.”

What happens during gastrulation quizlet?

During gastrulation, cell movements result in a massive reorganization of the embryo from a simple spherical ball of cells, the blastula, into a multi-layered organism. During gastrulation, many of the cells at or near the surface of the embryo move to a new, more interior location.

What is the first indication of gastrulation in the embryo?

The formation of the primitive streak on the dorsal surface of the bilaminar embryonic disk is the first indication of gastrulation.

What happens in the fourth week of embryonic development?

In the fourth week the embryo (the embryonic disc) will grow from about 2 to about 6 mm. The processes of the third week (neural tube formation, development of blood circulation) continue in the fourth week. At the same time, the amnion increases enormously in size, while the yolk sac does not.