Development Vocabulary

fusion of sperm head acrosome with zona pellucida releasing enzymes that cause Ca2+ mediated release of cortical granules to make the egg impenetrable to subsequent sperm

pluripotent stem cells which will form the syncytiotrophoblast and cytotrophoblast that form the placenta

migration of inner cell mass to one pole of the embryo to form a fluid filled centre (blastocoel)

emergence of the embryo from the zona pellucida before implantation

first penetrating cells of the placenta which also secrete HCG for the maintenance of the corpus luteum in the first trimester for progesterone secretion

placental tissue penetrating into the endometrial stroma consisting of two layers: syncytiotrophoblast and cytotrophoblast

placental tissue penetrating into the endometrial stroma consisting of three layers: syncytiotrophoblast, cytotrophoblast and extraembryonic mesoderm

differentiation of uterine endometrium to form layered structure that supports embryo

outermost layer of endometrium (during pregnancy known as decidua) that surrounds the implanting embryo forming a strong cellular matrix that allows for controlled invasion; in contact with trophoblast cells

arrangement of chorion on maternal side

maternal side of placenta

fetal side of placenta, formed from migration of epiblast cells outwards

formed by migration of hypoblast outwards

placental tissue penetrating into the endometrial stroma consisting of syncytiotrophoblast, cytotrophoblast, extraembryonic mesoderm and fetal capillaries (formed from extraembryonic mesoderm)

part of trophoblast that remains in contact with uterine wall forming the placenta proper

part of trophoblast that fuses with the amniotic sac and decidua to form the outer covering of the amniotic cavity

migration of epiblast cells during the third week into the primitive streak to form the mesoderm, forming a trilaminar disc of ectoderm (epiblast), mesoderm (migrated cells) and endoderm (hypoblast)

GIT, respiratory tract

CNS, skin

genitourinary tract, skeletal muscle, bone, connective tissue

looping of the trimlaminar disc, amnion and yolk sac to form a tubular structure at the end of the third week