Early Embryonic Development

Flashcards covering the specific stages and structures of early human embryonic development from Day 1 to Day 23.

Day 1

The stage of fertilisation, which involves the polar body and pronuclei.

Day 2

The stage of cleavage, involving blastomeres.

Day 3

The stage of compaction, characterized by the formation of tight cell junctions.

Day 4

The stage of differentiation where the embryo develops into the trophoblast and inner cell mass.

Day 5

The stage of cavitation, featuring the blastocoelic cavity and the zona.

Day 6

The stage characterized by zona hatching.

Day 7

The stage of implantation into the uterine epithelium.

Day 9

The stage involving cell mass differentiation.

Day 12: Bilaminar disc formation

The stage where the bilaminar disc forms, consisting of the epiblast and hypoblast.

Day 12: Mesoderm formation

The stage involving the primitive streak and the development of the ectoderm, mesoderm, and endoderm.

Day 18

The stage characterized by mesoderm spreading.

Day 23

The stage of development involving amniotic sac enlargement.

Trophoblast

An outer layer of cells in the embryo that develops during Day 4 differentiation.

Inner cell mass

The internal cluster of cells in the embryo that forms during Day 4 differentiation.

Blastocoelic cavity

A fluid-filled cavity that develops during the Day 5 cavitation stage.

Primitive streak

A structure that forms during the Day 12 mesoderm formation stage.

Bilaminar disc

A two-layered structure formed on Day 12 composed of the epiblast and hypoblast.

Extraembryonic structures

Includes the amniotic sac, trophoectoderm, umbilical cord, exocoelom, chorion, amnion, and yolk sac.