Exam 2: Fertilization/ Implantation Flashcards
sperm structure
head
mid piece
tail
sperm head
- haploid
- nuc with highly condensed chromatin wrapped around protamines
- protamines= specialized basic histone
sperm acrosome
- ant 1/2 or 1/3 of sperm head
- thin, double layered membrane sac
- hydrolytic enzymes critical for fertilization
sperm tail
- 9+2 axoneme microtubule structure
- distributed on either side for movement, gives tail pattern
**kartagener’s= defective cilia, immotile sperm
normal semen analysis values
vol >1.5ml
concentrations > 15x10^6/ml
motility > 32%
morphology 4%
female fertility eval
to test how many eggs are available: US, blood draw for FSH, E2, AMH
***cannot do with someone on birth control
euploid embryos decrease with maternal age
when does woman have peak # of oocytes?
20 weeks gestation
exponential decay after that
primary oocytes are arrested at _______
prophase I –> after LH surge, become secondary oocyte + 1 polar body
Zona pellucida
- shell like structure that surrounds oocytes
- glycoprotein sheet made up of protein, hexose, sialic acid, sulfate
- GPs: Z1, Z2, Z3
T/F: mutated or inactivated zone proteins is a cause of infertility?
True. They act as the “sperm receptors”.
quick, run through the steps of sperm-oocyte fusion
1) ovulation, collection of oocyte
2) deposition of sufficient # sperm
3) sperm capacitation
4) sperm traverse cumulus oophorus
5) sperm meet ZP
6) acrosomal rxn
7) plasma mem fusion
8) oocyte activation/ cortical reaction
9) male pronuclei formation
sperm capacitation
- “activation” to be able to undergo acrosomal rxn
- acq ability to capacitate in distal genital tract of male
- req Ca, ATP, etc
- capacitated sperm display HYPERMOTILITY—–> go and bind the egg
where on the oocyte do capacitated sperm bind?
Z3 on zona
“sperm receptor”
acrosomal reaction
outer mem of acrosome region fuses with plasma mem of sperm
fusion of membranes –> release hyaluronidase and acrosin –> complete fusion of sperm with oocyte
whats the protein that facilitates fusion of sperm and egg?
fertilin
cortical reaction
occurs as soon as first sperm fuses
- release cortical granules
- changes ZP3, which makes oocyte impenetrable
- prevents polyspermy
male pronuclei formation
- protamine unwinds –> SS bond reduced by oocyte glutathione
- sperm nuclei decondense
- form male/female pronuclei!
day 4 embryo
morula
-it is a morula usu by the time it reaches uterus
day 5 embroy
blastocyst
- trophoectoderm –> becomes placenta
- inner cell mass –> becomes fetus
implantation timeline
- 6-7 days after conception
- req interaction of trophectoderm and primed lining of uterine cavity
where does implantation most commonly occur?
posterior wall, midsagittal plane
but it can implant anywhere
blastocyst hatching
- blasto “escapes” from ZP (day 6-7)
- unfertilized eggs do NOT hatch
can you have implantation without hatching?
NO.
decidualization
- morphological and biochemical differentiation of uterine stromal cells
- critical for:
1) trophoblast invasion
2) placental formation
decidualization is dependent on what signals?
progesterone, estrogen, cAMP
what does decidualization start?
day 23 of cycle
-if implantation occurs, process expands to remaining stromal cells
what is the window of implantation?
SMALL (days 20-24)
- when epithelium lining of utereus is ready to accept
- dependent on progesterone being secreted from corpus luteum
what are the 3 stages of implantation?
apposition - loose, unstable connection of trophoectoderm/endo lining
adhesion- integrins, L selectin, hep sulfate proteoglycans
invasion - buries into endometrium
placenta previa
implantation occurs near cervix
- can be obstructing –> Csection
- vascular–> causes bleeding
placenta accreta
implantation at site of prior uterine scar
- can be traumatic birth
- can req hysterectomy at birth
medical treatment of ectopic pregnancy
methotrexate –> chemotherapy drug that targets rapidly dividing cells
surgical treatment of ectopic pregnancy
if too big for drugs
- salpingectomy –> removal of FT (usu preferred)
- salpingostomy –> surgical unblocking of FT
