BIOL204 Lecture 25 Section C (Final)

What is gastrulation?

the process by which the bilaminar embryonic disk is converted into a trilaminar embryonic disk

During which week does gastrulation occur?

week 3

What is the significance of gastrulation?

marks the beginning of the process where the three primary germ layers that give rise to all the tissues and organs of the developing embryo

What marks the beginning of gastrulation in the bilaminar embryonic disc?

appearance of the primitive streak and primitive node in the epiblast of the bilaminar embryonic disc

What are the three germinal layers?

ectoderm, mesoderm, and endoderm

What is the primitive streak?

a structure that forms on the surface of the epiblast in the embryonic disc

What is the primitive node?

the region at the end of the longitudinal groove of the primitive streak

What are the functions of the primitive streak?

establishes the body basic axes and initiates the migration of cells to form the different germ layers

What are the functions of the primitive node?

emits signals that guide cell migration and differentiation

Which cells of the bilaminar disc migrate during the process of gastrulation?

epiblast

To what do the terms primitive streak, primitive groove, primitive node, and primitive pit refer?

early embryonic development in vertebrates during gastrulation

Define primitive streak

a groove-like structure that appears on the surface of the embryo during gastrulation that acts as a gateway for cells to migrate inward and form new layers within the embryo

Define primitive groove

the linear depression/gap within the primitive streak

Define primitive node

a thickened region located at the cranial end of the primitive streak that signals and guides cell migration/differentiation

Define primitive pit

a small depression located within the center of the primitive node that acts as the initial opening for cells to move inward and form the notochord

How do epiblastic cells change during migration and what role does this transformation play in the formation of the mesoderm and endoderm germ layers?

epiblastic cells change shape and become mesenchymal cells which detach from the primitive streak and migrate into the space below the epiblast and give rise to the mesoderm and endoderm layers

Where do the migrating epiblast cells relocate to during gastrulation? What is the pathway through which the epiblast migrates?

relocate to primitive streak, invaginate through it, and migrate to different locations in the embryo

How do the endoderm and mesoderm layers originate?

through the migration and differentiation of mesenchymal cells originating from the epiblast during gastrulation

How is the ectoderm formed?

during gastrulation through the differentiation and organization of cells from the outermost layer of the embryo

Between which two germinal layers does the mesoderm emerge?

ectoderm and endoderm

What role does the epithelial to mesenchymal transformation of epiblast cells, occuring during involution at the primitive streak, play in the process of gastrulation?

facilitates their migration and subsequent differentiation into various cell types which contributes to formation of mesoderm and endoderm germ layers during gastrulation