Fertilization and Gastrulation Flashcards
Process by which the glycoprotein coat and seminal plasma proteins are removed from the plasma membrane of sperm.
Capacitation
Reaction by which sperm move through the corona radiata of an egg.
Acrosome Reaction
What reaction of the egg blocks polyspermy?
Zona reaction
Penetration of the zona pellucida is done by what enzymes and what motive force?
The Arcrosome reaction - Esterases, acrosin, neuraminidase.
It is also done with tail movement.
How does the sperm enter the oocyte after passing through the zona pelucida?
What key organelle does sperm not bring in?
Fusion of tail and head enter the plasma membrane.
Sperm does not bring in it’s mitochondria.
What happens after the sperm has entered an oocyte’s nucleus?
The egg will undergo it’s second mitotic division, a male pronucleus will form, and fushion of the male and female pronuclei will occur.
What is significant about the size of the embryo during cleavage?
What CAM is used during this?
It maintains it’s size
Cadherin
When does a morula develop? What about an early blastocyst?
Day 3 and Day 5
Upon what stage and day does an embryo enter the uterus and the zona pellucida begins to degenerate?
What day does it attach to the wall?
As a Blastocyst around Day 5
Day 6
Where is sperm usually capacitated?
Sperm is capacitated 7 hours after ejaculation, and is done so by enzymes in the uterus and uteren tubes.
What steps are neccasary for successful implementation of in vitro fertilization?
How long can sperm be stored for?
- Hormonal stimulaiton of oocyte formation and collection of them with aspirator during laparascopy.
- Placement on pitri dish with capacitated sperms.
- Cleavage of zygotes with 4 to eight cell stage reached.
- Plasmit of embryos back into uterine canal by way of cathetar.
What does early pregnacy factor do?
Immunosupressent that protects embryo during implantation.
Day 5 to Day 7 what significant events occur?
Zona pellucida degenerates, embryo structure changes from early to late blastocyst.
Late in week one what enzymes are realeased and what new structures form?
Early pregnacy factor (immunosuppresant), hCG, and proteolytic enzymes are released.
Cytotrophoblast create a stem cell layer of mitotically active Syncytiotrophoblasts
A hypoblast is present as well.
Cell type of week 2 that releases proteolytic enzymes and chorionic gonadotropin.
Primarily responsible for implantation.
Syncytiotrophoblasts
Caused by fertilization of an empty oocyte and duplication of sperm, or can have a partial pheonotype from fertilization of two sperm (zona block failure).
BENIGN
Hydratidiform Mole
Malignant tumor developing from hydratidiform mole
Choriocarcinomas (3-5% of moles)
Can spread to liver lungs, vagina, intestines, bone, and brain.
Clinical features of Hydratidiform Moles
Vaginal Bleeding
Pelvic pressure or pain
Enlarged Uterus
Hyperemesis gravidarum (Morning sickness)
What is the aspect of an embryo only present during week 2?
The hypoblast
What does the epiblast give rise to during week 2?
The ectoderm, amnion, and amniotic cavity.
What is the prechordial plate?
The prechordial plate is formed from the epiblast and secondary yolk sac. This is where babies are made.
What does the hypoblast give rise to during the second week of gastrulation?
The hypoblast expands around the embryo forming a primary yolk sac. This yolk sac forms the extraembryonic mesoderm. The primary yolk sac pinches off forming the secondary yolk sac.
The top of the secondary yolk sac, and bottom of the amniotic membrane (really its the epiblast) form the embryo.
The Extraembryonic Mersoderm of week 2 consists of what?
The extraembryonic coelem (hollow cavity outside of embryo)
The extraembryonc somatic mesoderm (around trophoblasts and covering the amnion)
Texthe raembryonic splanchnic mesoderm (lining the yolk sac)
What are the derivatives of the extraembryonic somatic mesoderm?
Gives rise to the body
(Gives rise to the placental layers)
Forms connecting stalk (umbilical cord)
Creates an embryonic pole that changes position during development
Extraembryonic splanchnic mesoderm gives rise to what?
Primitive blood
Forms in the wall of yolk sac
Where does implantation occur?
What potentially deadly pregnancy is associated with some incorrect implantations?
Hopefully in the posterior uterus (most of the time)
If not, eptopic pregnancy may occur.
This raises hCG yet no embryo is found on ultrasound.
What are the three types of placenta previa
Marginal - just a bit over cervical os
Partial placental - about half way over
Total placental - completely over
Symptoms and treatment of placental previa
Vaginal bleeding beyond 20 weeks gestation
Sonograph before digital vaginal examination with antepartum bleeding
Palpation can cause severe hemmorage
Many times the placenta will move.
What replaces the hypoblasts in week three, during formation of the germ layers.
Mesoblasts form the definitive endoderm
Label
Describe expansion of the intraembryonic layer of the germ layers.
Forms in caudal end and moves up with the notochord towards the cranial end of the germ layers.
What doe the ectoderm, mesoderm, and endoderm give rise to?
Ectoderm - skin, hair, nails, CNS
Mesoderm - connective tissue of body, heart, blood, spleen
Endoderm - lungs, GI Tract, bladder, glands
The primitive pit becomes what?
After fusing with the Endoderm it forms a canal which will become the neural canal.
The alantois becomes what?
The alantois is an outgrowth of the yolk sac (umbillical vesical) which will become surrounded by the mesoderm of the body stalk, it becomes the urachus (fetal bladder).
