HISTOLOGY OF PREGNANCY Flashcards
What is the operational definition of fertile vs. infertile?
Fertile: conception in < 1 year of unprotected sex
Infertile: no conceptions in > 1 year of unprotected sex
What is the cumulus-oocyte complex?
Metaphase 2 arrested secondary oocyte, surrounded by granulosa cells (aka cumulus cells); this is what is ovulated from the follicle during the ovulatory phase of the menstrual cycle
Describe the path of the cumulus-oocyte complex once its ovulated from the follicle?
Picked up by oviduct fimbria cilia → transported into infundibulum and to lower ampulla (site of fertilization) by ciliary sweeping and smooth muscle peristalsis
What else is dependent on ciliary sweeping/peristalsis?
Transport of preimplantation embryo to uterus
Ectopic pregnancies comprise of what percentage of total pregnancies in the U.S.? What is a major risk factor and why?
1 – 2%
Cigarette smoking – affects motile cilia function
What is continine and what are the effects?
Nicotine metabolite → reduces smooth muscle contractility
What is epididymal maturation?
Sperm gain the capacity for motility and interaction with eggs but they remain latent in the epididymis
What is capacitation?
Process by which sperm express latent fertility; occurs within the female reproductive tract; completed within Fallopian tube
so the sperm fertility is activated in the female reproductive tract
What are the 2 consequences of capacitation?
Novel flagellar motility only seen in Fallopian tube
Express fertility – bind/fuse with eggs
Describe the sperm-egg interaction
Small numbers of sperm reach the egg → sperm acrosome reacts → penetrates zona pellucida (egg coat) → fuses with egg
What is IVF/describe it
Retrieve oocyte from pre-ovulatory follicle in a natural non-stimulated cycle; sperm fertilize the oocyte in vitro → embryo is then transferred into the uterus
What is ICSI (intracytoplasmic sperm injection)?
Single sperm injected directly into oocyte cytoplasm → bypass capacitation, sperm-egg interaction
What are the 4 steps of egg response to sperm fusion?
- Drive egg cortical granule release to block polyspermic fertilization
- Triggers release of 2nd polar body and completion of meiosis II
- Initiate mitotic cell cycle
- Recruit stored maternal mRNA and activate embryonic genome
Sperm induce an increase of what mineral and what does this activate?
Calcium → development!
How does the fertilized egg coordinate the proper events of activation?
By counting calcium spikes (spike = increase in calcium) – the number of spikes determines the event
How does the sperm fusion start the calcium activation? (what do they release)
Phospholipase C – expressed ONLY in sperm; initiates the calcium oscillations
What does implantation require?
Hormonally primed endometrium and appropriately aged blastocyst
When does the endometrium “implantation window” open and for how long does it remain open?
Opens ~4 – 5 days after post-ovulatory progesterone surge
Remains open 2 – 4 days
What is the decidual response?
Set of changes in the endometrium of the uterus that prepare it for implantation of an embryo
- Post-ovulatory remodeling
When does the decidual reponse occur and under the influence of what hormone?
Occurs spontaneously during luteal phase of the cycle under the influence of progesterone
What are the 3 main reactions that occur during the decidual response?
- Transformation of stromal cells into secretory decidual cells
- Influx of immune cells
- Vascular remodeling
What starts the process of implantation?
Initial contact of the trophoblast layer with the columnar epithelium of the wall of the uterus
What is the cytotrophoblast?
Inner layer of the trophoblast; cuboidal cells; embryonic cells at the base
What is the syncytiotrophoblast?
Outer layer, multinucleated, no cell boundaries, syncytium
This is the leading edge that’s pushing through the wall of the uterus
What are the trophoblastic lacunae? What drains into these?
Approximately when do these form?
Spaces in syncytium that increase in size
- Break down of decidual (maternal) blood vessels/maternal blood drains into these
- 9 days after fertilization
What forms the primary stem villus?
Syncytial layer followed by some cytotrophoblast that push into the maternal blood space
What additional component is in the secondary stem villus?
Fetal mesoderm
What is the tertiary stem villus?
Fetal blood vessels now enter the mesoderm core → this system is now where maternal and fetal blood are very close to one another
When does uterine vascular remodeling begin? What’s the major event that happens and what does this ensure?
Begins in the first trimester
Trophoblast cells invade decidua and its spiral arteries → ensures adequate delivery of blood to placenta and fetus
Characteristics of uterine spiral artery before remodeling
Low flow and high resistance
Remodeling makes it high flow and low resistance (which is more ideal for placenta)
What is preeclampsia? Characteristics?
Failure of remodeling during late pregnancy
Poor fetal growth, maternal and fetal mortality, placental ischemia, oxidative stress, elevated syncytial shedding
