Human Gastrulation Stages: Primitive Streak, Germ Layers, and Notochord

What is the significance of the Primitive Streak in human gastrulation?

It establishes the body's axes: anterior-posterior, dorsal-ventral, and left-right.

What happens during the cell migration and ingression stage of gastrulation?

Epiblast cells migrate toward the primitive streak, invaginate to form new layers, with the first wave forming endoderm, the second wave forming mesoderm, and remaining cells becoming ectoderm.

What are the three germ layers formed during gastrulation and their primary derivatives?

Ectoderm: skin and nervous system; Mesoderm: muscles, bones, cardiovascular system; Endoderm: gut lining, liver, lungs.

What is the role of the notochord in embryonic development?

The notochord, formed from mesodermal cells, induces neural development and defines the embryo's midline.

Where does the Primitive Streak appear during gastrulation?

It appears on the surface of the epiblast, which is the upper layer of the bilaminar disc.

What is the first wave of cell migration during gastrulation responsible for?

It replaces the hypoblast and forms the endoderm.

What do the remaining epiblast cells become after the second wave of migration?

They become the ectoderm.

What structures does the mesoderm give rise to during development?

The mesoderm forms muscles, bones, and the cardiovascular system.