Fertilization Flashcards
fertilization
process by which the male and female gametes unite to form a single celled zygote
sequence of events of sperm/oocyte interaction
oocyte- maturation to metaphase 2/ovulation
sperm- capacitation, acrosome reaction
penetration of cumulus and zona pellucida
ionic changes, cortical granules release-block to polyspermy
meiotic resumption, 2nd polar body extruded
pronuclear formation
DNA synthesis
metabolic exchange
syngamy-merging haploid sets of chromosomes on mitotic spindle
cleavage
ovulated oocyte
surrounded by cumulus oophorus cells and corona radiata
zona pellucida (granulosa cells)
plasma (vitalize membrane) surrounding oocyte
perivitelline space with first polar body
acrosome must release enzyme to dissolve zona pellucida
ovulation
communication between oocyte and granulosa cells
Sperm path
needs to move through uterotubular junction through convoluted oviduct and to the oocyte- cumulus cell complexes in ampulla
Capacitation
sperm capacitation= biochemical and reversible process which enables spermatozoon to penetrate the zona pellucida of the ovum
initated in the uterus and completed in the oviduct (sperm binding) with hyperactive motility
Fallopian tube
haven for sperm
does not respond to insemination with influx of leukocytes like the vagina, ,cervix, and uterus do
convoluted
Sperm in oviduct
bind to the epithelium- sperm reservoir
prolongs sperm viability- stabilizes sperm membranes (preventing capacitation) and prevents hyper activation (low levels of cytoplasmic Ca)
Capacitation completion
in oviduct
induction of ovulation (hormones and follicular fluid)- epithelium secretes factors that trigger sperm capacitation and hyper activation
sperm released from epithelium and move to ampulla (thermotaxis- b/c ampulla warmer than isthmus and chemotaxis)
Capacitation of sperm
occurs in female repro tract, mostly in the isthmus of oviduct
loss of membrane cholesterol and surface proteins increasing membrane fluidity
increase in pH and changes in intracellular Ca
changes in tail- hyper activation
Transfer of cholesterol to albumin
capacitation
necessary for activation of the membrane signal transduction pathway
protein kinase A activation
necessary for phosphorylation of proteins and polymerization to filamentous actin
capacitation
tyrosine phosphorylation of proteins
necessary for hyperactive sperm motility
source of energy cascade of events
polymerization of globular actin to filamentous actin
necessary for sperm penetration into the oocyte and decondensation of sperm DNA
2 sources of energy in sperm
ATP from glycolysis to fuel hyper activated motility in sperm and further broken down in mitochondria
Capactitation- what it is
no change in sperm morphology, motility change= hyper activation- increased cAMP= chaotic movement
step 5- fertilization
acrosome reaction
sperm penetrate oocyte
male and female pronuclei form
steps of sperm binding
hyperactive motility binding zona pellucida (ZBR ZP3 reaction) acrosomal reaction penetration of zona pellucida (motility) sperm-oocyte membrane fashion sperm engulfed decondensation of sperm nucleus formation of male pronucleus
Acrosome reaction
irreversible process, breakdown zona pellucida
fusion of the sperm plasma membrane with the outer acrosomal membrane
vesiculation
release of hydrolytic enzymes- hyluronidase and acrosin
Fusion proteins
post acrosome reaction located in equatorial region
sperm oocyte membrane fushion
cortical granules will close gate behind penetrating sperm
zona will harden- zona block
Block to polyspermy
zona block-cortical granules exocytosis and hardening of zona pellucida (modification of ZP3 and ZP2)
membrane block- vitelline block- changes in oocyte plasma membrane (vitelline membrane) polarization
tail
no attachment to nuclear membrane, typically
Perivitelline space
between oocyte and zona pellucida where polar bodies released and where sperm travels
maturation promoting facotr
pronucleus formation and 2nd polar body forming, during meiosis II
allows Ca2+ to flow into the oocyte and increases Ca which has negative feedback on MPF decreasing it
then 2nd division of meiosis unblocked and second polar body released finishing decondensation of female and pronucleus production in Ootid
Final results of oogenesis
ootid production
pronuclei- male and female
2 polar bodies indicates fertilization
syngamy
fashion of pronuclei to form zygote which is when fertilization is complete
