Fertilization and Gastrulation Flashcards
What allows sperm to pass through the corona radiata?
hyaluronidase
mucosal proteins
mvmt of tail
What stage of development is only present during week 2?
hypoblast
What is the corona radiata?
layer of follicular cells from mom that surround the oocyte; the most superficial layer of ovum
What does primitive blood come from and where is it formed?
from extraembryonic splanchnic mesoderm
forms in wall of yolk sac
What is the prechordal plate?
part of hypoblast that eventually becomes the mouth and organizational center for the head
What are the basic steps of egg penetration?
capacitation
passage of sperm through corona radiata
penetration of zona pellucida
Where is the mitochondrial sheath on a sperm?
on middle piece of tail
What forms the male pronucleus?
What degrades from sperm?
cytoplasmic contents form pronucleus
tail and mitochondria degrade (mito dna only from mom)
In the obstetrical/gestational view, when does the calendar start?
Last menstrual period
What happens to the primary yolk sac?
splits into 2: secondary goes up against epiblast primary goes to opposite side (remnant of primary umbilical vesicle?)
What is the chorion?
3 layers:
extraembryonic somatic mesoderm
cytotrophoblast
syncytiotrophoblast
What are the 3 parts of the sperm tail?
middle piece (with mitochondrial sheath)
principal piece
end piece
What is the extraembryonic somatic mesoderm?
cells that line the trophoblast and cover the amnion
What happens in week 1 of gestation?
Fertilization Cleavage Blastocyst Inner cell mass Implantation
What can hydatidiform moles turn into?
What percentage of them do this?
choriocarcinomas = malignant tumor
3-5%
When does the acrosomal reaction occur?
when the sperm touches the zona pellucida
What is a complete mole from?
fertilization of empty oocyte –> duplication of sperm
or: fertilization of empty oocyte by 2 sperm
What is the trophoblast? When does it occur?
Cells surrounding inner cell mass
day 5 –> degrades day 7
When does cleavage occur?
~30 hours after fertilization
What is the zona pellucida
meshwork of glycoproteins that surround the oocyte; just deep of corona radiata
What is the bilaminar disc and when does it form?
2 discs are of epiblast and primary yolk sac formed of hypoblast
forms in week 2
When is implantation?
day 6
What is a blastomere?
One of first few cells after fertilization
what are the 2 types of extraembryonic mesoderm?
somatic and splanchnic
What is the extraembryonic splanchnic mesoderm?
cells that line the yolk sac
What is a hydatidiform mole?
benign, giant thing of trophoblast that causes excessive amounts of hCG
can be partial or complete
Where do choriocarcinomas have a high likelihood to spread to? (6)
vagina lungs bone brain liver intestines
What is the very basic structure of a sperm?
head
neck
tail
What does the trophoblast differentiate into?
cytotrophoblast
cyncytiotrophoblast
What is placenta previa?
When placenta implants over cervical os
can be marginal, partial, or total
What is capacitation?
glycoprotein coat and seminal PM proteins removed from PM of sperm
allow acrosomal reaction to occur
What is the extraembryonic coelom?
hollow cavity outside of the embryo
Where does fertilization occur?
ampulla of fallopian tube
In the ovulatory calendar, when is day 1?
Fertilization
What are the derivatives of extraembryonic mesoderm?
connecting stalk
primitive blood
chorion
What is the syncytiotrophoblast and what does it do?
multibucleated cells above embryoblast
responsible for implantation
releases hCG –> signals to body that you are pregnant
What is the cortical reaction?
release of lysosomal enzymes from granules near oocyte pm –> change membrane potential –> inactivates sperm receptors on zona pellucida
Where does extaembryonic mesoderm come from?
Where does it go?
cells pull off from hypoblast –> go and coat trophoblast
What happens right after the sperm reaches the pm of the oocyte? (step 3)
plasma membranes fuse
head and tail of sperm ender oocyte
When is the blastocyst stage?
What is it formed from?
day 5 - 7
morula cells –> fluid from uterus enters and makes cavity
What is the acrosome and its importance?
on head of mature sperm
contains enzymes to penetrate egg
What is the connecting stalk and what does it come from?
from extraembryonic somatic mesoderm
forms at embryonic pole and connects embryo to trophoblast
What do you do with fertilized embryos that you don’t use in IVF?
cryopreserve
good for 21 yrs
What is the female pronucleus? what does it fuse with?
nucleus of ovum after it completes meiosis II –> fuses w/ male pronucleus
What happens in cleavage?
increase in cell number
decrease in cell size
embryo size unchanged
morula development
What are the basic clinical features of a hydatidiform mole? (5)
high hCG vaginal bleeding pelvic pressure or pain enlarged uterus morning sickness
What are the layers surrounding the ovum from outside in?
corona radiata
zona pellucida
perivitelline space
What makes up the epiblast?
ectoderm
amnion
amniotic cavity
What is the cytotrophoblast?
mitotically active stem cell layer surrounding embryoblast and blastocystic cavity
When is the morula stage? What does it look like?
day 3
looks like a bunch of grapes = 16-32 cells
What is the zona reaction and when does it occur?
block to polyspermy
occurs once 1 sperm passes through zona pellucida to prevent other sperms to enter
What is a partial mole from?
fertilization of normal oocyte by 2 sperms
What is the perivitelline space?
layer just superficial of plasma membrane of the oocyte
What must degrade for implantation?
At what stage does this occur?
zona pellucida blastocyst stage (day 5-7)
When does gastrulation occur?
week 3
What does the primitive streak form from?
epiblast
What are the 3 germ layers that form in gastrulation?
ectoderm
mesoderm
endoderm
In what half of the embryo does the primitive streak form?
caudal half
What types of tissues are in the cloacal membrane and the prechordal plate?
Why is this significant?
only endoderm and ectoderm
There is no blood supply, so membrane ruptures and opens, which is what you want
What is a sacrococcygeal teratoma?
benign tumor that is a remnant of the primitive - contains all different types of tissues
What is an orapharyngeal teratoma?
huge gross looking tumor coming out of the head of a fetus
we think it is either abnormal germ cell migration or remnant of primitive streak
What is the primitive streak and what does it do?
fold in epiblast (which becomes ectoderm) where cells migrate down; ones at the bottom are endoderm, ones in the middle are mesoderm
What is the fate of ectoderm?
skin
CNS
hair
nails
What is the fate of mesoderm?
connective tissue: blood, muscle, bones
heart
spleen
What is the fate of endoderm?
lungs
GI organs
bladder
glands
Where is the notochord?
extends from primitive node anterior to prechordal plate (head/mouth)
What is the notochord important for?
template for vertebral column (does not become spinal cord)
induces ectoderm above it to become neural tissue
What tissue is the notochord made of?
where does it lie
mesoderm
in between endoderm and ectoderm
When the notochord canal closes, what does it fuse with to form?
fuses with endoderm
forms notochordal plate
What are chordomas?
What are they from?
Rare, slow-growing, yet aggressive tumors in skeleton; usually in skull and sacral regions
arise from remnants of notochord
What is the allantois?
loop of endoderm formed from wall of yolk sac
at posterior midline
template for umbilical arteries and vein
What does the allantois become that is important for the bladder?
urachus
What are the 3 types of mesoderm?
Paraxial
Intermediate
Lateral plate
What is the fate of paraxial mesoderm?
somites: muscle, skeleton, dermis
What is the fate of intermediate mesoderm?
urogenital: kidneys and gonads
What is the fate of lateral plate mesoderm?
connective tissue: blood, lymph, mesenteries, cardiovascular
What is the intraembryonic coelom?
space in intermediate mesoderm that becomes body cavities
