A&PII Lab 18: Embryonic Development Flashcards
Fertilization
successful union between a spermatocyte and oocyte
Embryonic development
1st series of changes during prenatal development follow a series of cell divisions beginning with the 1st division and continuing for about 8 weeks
Zygote
fertilized egg
Cleavage
process of the zygote dividing by mitosis
Morula
small of ball of cells (“little mulberry”); what the zygote is referred to as by the time it reaches the uterus (~3 days)
Differentiation
cell division and change; includes the movement of fluid into the intercellular spaces of the morula, which gradually enlarges the space and separates the cells into 2 portions
Trophoblast
outer layer of cells of the differentiated morula; later contributes to the placenta
Inner cell mass
inner layer of cells of the differentiated morula; later becomes the embryo
Embryo
“a swelling”; develops from the inner cell mass
Blastocyst cavity
the intercellular spaces join to form 1 large cavity; AKA blastocele
Blastocyst
once the intercellular spaces have joined to form 1 large cavity, the morula has become this cell
Implantation
when the trophoblast contacts the inner wall of the uterus (endometrium), this process begins
Germ layers
the cells on 1 side of the disc (ventral side) forms these layers; early cells that will eventually differentiate into the tissues and organs of the body
Endoderm
1st layer formed from germ cells
Ectoderm
2nd germ layer; from the dorsal side of the disc
Mesoderm
middle germ layer; forms after the ectoderm
Amniotic cavity
as small spaces begin to appear between the embryo and the trophoblast, this cavity begins to form
Chorion
trophoblast differentiates to form this “membrane” in the 3rd week of implantation; membrane later associated with the fetus
Placenta
the chorion will eventually form the embryonic portion of this “flat cake”
Amnion
2nd membrane begins developing during the 3rd week; “little membrane of the fetus”; expands the fluid-filled amniotic cavity until it envelops the embryo
Yolk sac
during the latter part of this developmental period, this 3rd membrane arises from the endoderm to form this cavity
Primitive streak
thickening of the ectoderm layer along the midline of the embryo; gives rise to the 3rd germ layer (mesoderm) by folding inward (invaginates)
Gastrulation
process of the primitive streak folding inward to form the mesoderm
Gastrula
what the embryo is called during gastrulation; “little stomach”
Notochord
during gastrulation, this rod-like structure begins to form as an outgrowth of mesodermal cells from the primitive streak
Neural tube
once the notochord has formed, portions of the ectoderm invaginate to form this structure immediately dorsal to it; eventually gives rise to the CNS
Neurulation
process of ectodermal growth
Neurula
what the embryo is called during neurulation
Foregut
head cavity of an embryo
Hindgut
tail cavity of an embryo
Midgut
part of the embryo formed earlier by the endoderm; develops further to become the GI tract
Allantois
yolk sac + ____ = umbilical cord
Umbilical cord
formed from the yolk sac and the allantois (membrane)
Amniotic fluid
fluid within the saclike amnion that bathes the embryo until birth
Organogenesis
process of development of the major organs of the body during the 1st 8 weeks of life
