Early Embryonic Stages

Animal Hemisphere

Half region of the egg that contains the animal pole.

Vegetal hemisphere

This pole will become the caudal end of the future embryo.

Blastomere

cell produced by cell division (cleavage) of the zygote after fertilization

type of cell as a product of cell division (cleavage).

Cleavage furrow

Physical indentations between cells that results from cell division

Animal pole

This pole will become the cranial end of the future embryo.

Vegetal pole

This pole will become the caudal end of the future embryo.

Micromere

Blastomeres that are small and many in numbers. Contain little amount of yolk.

At animal pole

Macromere

Blastomeres that are very large and few in numbers. Contain large amount of yolk.

At Vegetal Pole

Blastocoel

Blastomeres that surrounds a cavity (space) is called the blastocoel. It is a fluid filled cavity.

Main structure formed during blastulation

allows for the distribution of nutrients and signaling molecules to the cells of the blastoderm.

Blastoporal lip

A slit-like appearance that marks the opening of the Archenteron.

Archenteron Gastrocoel

A empty cavity that will give rise to the GI Tract.

A primitve gut cavity lined by the endoderm

Yolk Plug

A patch of endodermal cells that is left during the formation of the Blastoporal lip.

Mesoderm

Is the middle germ layer that gives rise to the skeletal system, muscles, and heart.

Ectoderm

The outermost germ layer that will give rise to the skin.

Endoderm

The innermost germ layers that will give rise to internal organs.

Neural plate

A thickened, elongated region along the dorsal midline of the embryo.

A flat sheet of ectodermal cells cells located on the dorsal side of the embryo.

Notochord

A temporary structure that will be replaced by the vertebral column

A rod-like structure that signals the overlying ectoderm to form the neural plate.

Epidermis

outermost part of the ectoderm

Neural Fold

Raised edges of the neural plate that elevates and converge towards midline.

Neural groove

A depression in the neural plate formed by the invagination of cells.

Endoderm

Neural tube

cylindrical structure composed of neuroepithelial cells.

Somites

segmented blocks of mesoderm that form on either side of the neural tube

lateral plate mesoderm

The mesoderm that is found at the periphery of the embryo.

Midgut

region of the embryonic gut tube