Fertilization and Gastrulation and Neurulation Flashcards
What is the difference between the obstetrical (clinical) calendar and the ovulatory calendar?
The ovulatory calendar ignores the first two weeks, where as the obstetrical calendar starts at the last menstrual period (LMP)
How long does fertilization (embryonic stage) last?
8 weeks
What is the corona radiata?
follicular cells around the ovum
What is the zona pellucida and whats it important for?
it is the glycoprotein mesh work between the perivitelline space and corona radiata, important for fertilization
What does the nucleus of an ovum contain?
The DNA egg cell, containing 23X (haploid)
What are included in the head of a sperm and what do the components do?
acrosome: has enzymes to get through layers of egg acrosome-covered nucleus: Contains 23X haploid DNA
What is important of the neck in sperm?
It joins the head and tail
What does the tail of sperm do ?
middle piece: contains mitochondria sheath which gives sperm ATP to move
Flagella like- allows for movement
Week 1 is the ovulatory stage, what important events occur during this?
Fertilization, Cleavage, Blastocyst formation, Inner cell mass (embryoblast), and implantation
Where does fertilization occur?
In the ampulla
Where does capacitation (step 1) occur and what happens?
it occurs in the uterus and uterine tube (takes 7 hours) glycoprotein coat and plasma proteins removed from sperm membrane allowing acrosome to react and release enzymes
What does hyaluronidase do?
Released from acrosome, helps move sperm through corona radiata
How do sperm penetrate the zona pellucida (step 2)?
Using esterases, acrosin, and neuraminidase
What happens during the zona reaction?
Once one sperm gets into zona pellucida, a conformational change in gylcop occurs, trapping and blocking sperm from getting in (preventing polyspermy
What happens when the sperm meets the plasma membrane of an oocyte (step 3)?
Sperm fuses with membrane, the head and tail enter, ***however the mitochondrial sheath does not!!
What happens during step 4 of fertilization (3 things) ?
Second meiotic division complete male pronucleus forms male and femal pronuclei fuse (Zygote)
What are the main results of fertilization (4) ?
1 restores diploid chromosomes (46)
2 know sex of embryo
3 activates oocyte
4 starts cleavage
What is cleavage and when and where does it occur?
Cleavage increases cell #, decreases cell size, makes 2 cells to 4, to 8, forming morula occurs 30 hours after fertilization in uterine (fallopian) tube and uterus
what is made by day 3 of cleavage and where does it go?
a morula with cells inside is formed, goes into uterus
What happens on day 5 of cleavage?
fluid is brought into the morula, some degeneration zona pellucida to form the (early) blastocyst in the uterus
what occurs on day 6/7 of cleavage?
(late) blastocyst; zona pellucida is gone, inner cell mass more defined, contained inside trophoblast, implantation to uterine wall
What does the trophoblast become?
The palcenta
Why is fertilization the most important process?
because assisted reporductive technologies can be used
What occurs in vitro fertilization and embryo transfer?
stimulate moms ovaries, collect sperm, add to eggs, watch fertlization under microscope and then transfer 1-3 fertilized eggs and implant into mom.
What is cryopreservation of embryos?
take fertilized eggs and freeze them in liquid nitrogen, last for 21 years
What is intracytoplasmic sperm injection?
take egg cell and sperm, and inject into egg and watch in petri dish and then implant once eggs are fertilized
Where are embryonic stem cells retreived from and what can they become?
Retreived from the inner cell mass and can become any cell or tissue type
What does the trophoblast (day 7) produce to protect the embryo?
Early pregnancy factor, which is an immunosupressant produced in the first 10 days (early preg tests)
What does the trophoblast become and what does that do?
Becomes the cytotrophoblast, which is a stem cell layer that is mitotically active
What does the cytotrophoblast become and what does that do (2) ?
becomes the syncytiotrophoblast 1. releases proteolytic enzymes, responsible for implantation 2. releases chorionic gonadotropin (hCG): signal for pregnancy
What is a hydatidiform mole?
abnormal trophoblastic proliferation causing excessive hCG
How does a complete hydatidiform mole form (2)?
- fert of an empty oocyte, duplication of the sperm 2. fert of an empty oocyte by two sperm
How does a partial hydatidiform mole form?
fertilization of a normal oocyte by two sperm (polyspermy block didnt work)
What are the clincal presentations for hydatidiform mole(4)?
Vaginal bleeding pelvic pain enlarged uterus hyperemesis gravidarum (morning sickness)
What is a choriocarcinoma and where can it metastasize to?
A malignant tumor which develops from hydatidiform mole (3-5% of the time), metastasizes to liver, lung, intestine, bone and brain
What occurs (2) during week two of development?
Bilaminar disk is formed, implantation continues (end week 2: late missed period)
What are the two cell types that are formed by the inner cell mass?
- Epiblast
- Hypoblast
What does the epiblast give rise to (4)?
Gives rise to the embryo, as well as ectoderm, amnion (roof) and amnion cavity
What does the hypoblast give rise to and what does it do? (only present during week 2!)
gives rise to extraembryonic endoderm (outside), and serves as a place holder for bilaminar disk
What does the hypoblast give rise to (2) and what do they do?
- Prechordal plate: fuse to cells of epiblast, future site of the mouth (help organize head)
- Primary and secondary yoke sac (umbilical vessicle)
How does the hypoblast become the primary yolk sac (umbilical vessile) and eventually the secondary yolk sac?
Hypoblast goes down and around, lining cytotrophoblast creating a loop (primary) and extraembryonic mesoderm
What is the difference between the primary and secondary yoke sac?
Primary yoke sac will pinch off, leading to secondary yoke sac attached to epiblast
When is extraembryonic mesoderm made and where is it located?
During week two, located lining the cytotrophoblast and yoke sace (different types)