Fertilization and Gastrulation Flashcards
Obstetrical calendar (gestational calendar)
start date is based on when the LNMP was
- includes weeks -2, -1
Ovulatory calendar
start date based on when fertilization occurred
corona radiata
outermost layer of cells from the ovum; made of follicular cells that radiate out
zona pellucida
glycoprotein mesh work outside the ovum; important in process of fertilization
perivitelline space
the space between the zona pellucida and the cell membrane of an oocyte or fertilized ovum
acrosome
part of sperm in the head; contains enzymes that are needed to get through the different layers outside the ovum
why does the sperm have mitochondria in the tail
to produce ATP in order to propel the flagella of the sperm
5 important events in week 1 of fertilization
- fertilization
- cleavage
- formation of blastocyst
- formation of inner cell mass (embryoblast)
- implantation
where does fertilization occur
in the ampulla of the uterine tube (fallopian tube)
capacitation
the glycoprotein coat and seminal plasma proteins are removed from the plasma membrane of the sperm to allow the acrosome reaction; occurs int he uterus and uterine tubes; takes about 7 hours
what enzyme is released by the sperm to get through the corona radiata
hyaluronidase
what three enzymes does the sperm release to get through the zona pellucida
esterases, acrosin, neuraminidase
what is the significance of the zona reaction
blocks polyspermy
features of the zona reaction
- conformation change in the zona pellucinda
- mesh work becomes rigid
- blocks any more sperm to enter
True or False: the sperm mitochondria enter the oocyte
false
5 key results from fertilization
- completion of second meiotic division
- restoration of diploid # chromosomes
- determination of chromosomal sex of embryo
- metabolic activation of oocyte
- initiation of cleavage
Morula
develops at around day 3; consists of 12-32 cells; when it enters the body of the uterus fluid begins to diffuse in which forms the blastocyst cavity forming the blastocyst (at around day 5)
what day does the blastocyst develop
day 5
when does cleavage start
30 hours after fertilization
when does the morula enter the uterus
day 3 or 4
what does the inner cell mass give rise to
the epiblast
when does the zona pellucida start to degenerate
day 5 (is gone by day 7)
what does the trophoblast give rise to
the placenta
what form is the embryo in at one week
one cell layer
3 types of assisted reproductive strategies
- in vitro fertilization and embryo transfer
- cryopreservation of embryos
- intracytoplasmic sperm injection
in vitro fertilization and embryo transfer
- stimulate mother’s ovaries and collect eggs
- collect sperm from dad
- capacitate the sperm
- implant 1-3 embryos
Cryopreservation of embryos
freezing embryos in liquid nitrogen; viable for up to 21 days
intracytoplasmic sperm injection
- when is it used
- what is it
used when sperm count is low; inject the egg cell with the sperm cell so that it will become fertilized
where do we get embryonic stem cells
cryopreserved embryos
somatic cell nuclear transfer
taking the nucleus out of an adult cell and putting it in an oocyte without a nucleus
–> therapeutic cloning
the trophoblast gives rise to the
cytotrophoblast
the cytotrophoblast gives rise to the
synctiotrophoblast
cytotrophoblast
stem cell layer that is mitotically active; keeps multiplying and gives rise to the synctiotrophoblast
synctiotrophoblast
multinucleated cells that contain proteolytic enzymes that are responsible for implantation; release chorionic gonadotrophin (HCG); don’t have plasma membranes
what releases human chorionic gonadotrophin (HCG)
the synctiotrophoblast
hydatidiform mole
abnormal trophoblast proliferation with excessive amounts of HCG produced
two ways in which a complete hydatidiform mole can occur
- fertilization of an empty oocyte followed by duplication of the sperm (zona reaction occurred)
- fertilization of an empty oocyte by two sperm (zona reaction did not occur)
how can a partial hydatidiform mole form
fertilization of a normal oocyte by two sperm
clinical features of a hydatidiform mole
positive pregnancy test vaginal bleeding pelvic pressure/pain enlarged uterus hyperemesis gravidarum (morning sickness)
choriocarcinomas
malignant tumor that develops from hydatidiform mole; spread to liver, lungs, vagina, intestines, bone, and brain
when does implantation start and finish
day 6 - day 10
what three things does the epiblast give rise to
ectoderm
amnion
amnion cavity
what does the hypoblast give rise to
extraembryonic endoderm
endoderm gives rise to:
prechordal plate
primary and secondary yolk sacs
extraembryonic mesoderm
prechordal plate
large group of cells that fuse to cells of the epiblast which is the location of the future mouth; the organization center for the formation of the head
what does the hypoblast act as a placeholder for
the bilaminar disc
extraembryonic coelom
hollow cavity outside the embryo
what does extraembryonic somatic mesoderm line
lines the trophoblast and covers the amnion
what does extraembryonic splanchnic mesoderm line
lines the yolk sac
connecting stalk
- origin
- what does it become
part of the extraembyronic somatic mesoderm; forms at the embryonic pole; becomes the umbilical cord
primitive blood
- origin
- where does it form
part of the extraembryonic splanchnic mesoderm; forms in the wall of the yolk sac
chorion
- origin
- what’s it made of
- what does it become
part of the extraembryonic somatic mesoderm; one of the layers of the placenta; made up of cytotrophoblast and synctiotrophoblast
placenta previa
vaginal bleeding beyond 20 weeks of gestation
marginal placenta previa
placenta is right on the margin of the internal cervical os, causing vaginal bleeding
partial placenta previa
placenta is covering half of the internal cervical os, causing vaginal bleeding
total placenta previa
placenta is completely covering the internal cervical os, causing vaginal bleeding
why must you do a US instead of a digital vaginal exam with placenta previa
palpation of the placenta can cause severe hemorrhage
when does gastrulation occur
week 3
gastrulation
the formation of the three primary germ layers
the mesoderm gives rise to
- connective tissue layers of the body
- muscle
- bone
- blood
- heart
- spleen
the ectoderm gives rise to
- skin
- hair
- nails
CNS (brain and spinal cord)
the endoderm gives rise to
- lungs
- GI tract organs
- bladder
- most of the glands (thyroid, parathyroid, etc.)
primitive streak
marks the start of gastrulation, the process in which the inner cell mass in converted into the trilaminar embryonic disc, which is comprised of the three germ layers
- forms in the caudal region
the septum transversum develops into the
diaphragm
the cardiogenic area develops into the
heart
the cloacal membrane develops into the
urogenital system
cleavage
increase in cell number and decrease in cell size; embryo size is unchanged; morula develops
