Cleavage Flashcards
Cleavage
cell division that occurs without overall growth of embryo. Cells get smaller in size, divide quickly (once per day)
Blastomere
one cell of the embryo during the cleavage stage
when does cleavage occur?
from fertilization to implantation (in womb)
stages of cleavage
2/4/8 cell, Morula
2,4,8 Cell stage
division occurs in ~1 day. Corona radiata is no longer present. 3, 5 cell stage can exist. releases early pregnancy factor.
early pregnancy factor
molecule used to test for pregnancy. protects conceptus from mother’s immune system. Circulates mother’s blood. Different from what home pregnancy test detects
morula
stage of embryo with 8-16 cells. latin for mulberry
blastocyst
embryo after blastulation
trophoblast
outer layer of cells. forms part of placenta
inner cell mass (of blastocyst)
inner ball of cells. forms conceptus proper, amnion, and umbilical cord
Hatching
release of the blastocyst from the zona pellucida. allows embryo to implant to womb, because zona pellucida isn’t sticky, but embryo is.
How does the embryo know when to hatch?
it hatches after 5 days
Parental Imprinting
functions that always come from the father only or from the mother only
paternal parental imprinting
causes placental development
maternal parental imprinting
embryo proper development
parthenote
oocyte activated without sperm. only has maternal dna. develops similar to blastocyst, but with no inner cell mass
hydatidiform moles
activated oocyte without dna from oocyte nucleus. maternal dna lost in polar body. only sperm dna is present. creates a tumor. does not mature into an organism.
x chromosome inactivation
the “turning off” of one x chromosome. Only occurs in females. Prevents double dose of X products. Chromosome turned off occurs randomly, but permanently
x,y chromosome
determines genter. Male: XY, Female:XX. Y chromosome has fewer genes.
