Key concepts: Fertilisation and implantation Flashcards
conditions associated
ectopic pregnancy
spontaneous aboriton
label the fallopian tube from proximal to distal in relation to the ovaries
fimbriae
infundibulum
ampulla
isthmus
cumulus oophorus
cells on the outside of the oocyte that were pulled away from the inside of the follicle when it burst
label an oocyte outside to inside
corona radiata
zona pellucida
cortical granules
nucleus
cytoplasm
oocyte ploidy
haploid
spermatozoa ploidy
haploid
corona radiata
outer layer of cumulus cells
zona pellucida
outer glycoprotein coat that surrounds the plasma membrane
cortical granules
enzyme packets within the cell
label sperm from head to tail
head containing the acrosome then nucleus
middle containing mitochondria in a spiral shape tail/ flagellum
tail/flagellum
propels sperm towards the egg
mitochondria in sperm
for energy
acrosome
contains enzymes in the head of the sperm
what are the 6 stages of fertilisation
sperm transport
sperm capacitation
sperm-oocyte interaction
sperm-oocyte fusion
completion of meiosis 2
zygote formation and implantation
3 stages of sperm transport
vaginal
cervix
uterus
vaginal sperm transport
where ejaculate is deposited
coagulates to form an alkaline loose gel
protects against the acidic environment of the vagina and immunological response
cervix sperm transport
cervical mucus and high levels of oestrogen cause sperm to change microstructure of the mucus
allowing easy passage
uterus sperm transport
uterine contractions to propel the sperm to the uterus
sperm capacitation
epithelial interactions between the sperm ad uterine wall will destabilise the plasma membrane of the sperm
acrosomal reaction occurs
what happens in the acrosomal reaction
glycoprotein coat covering the acrosome is removed
sperm plasma and acrosomal membrane will fuse
enzyme release from acrosome (across, hyaluronidase and hexosaminidase)
increase in CatSper channels on the flagellum
causing Ca2+ influx and sperm motility is hyper activated
components of the sperm oocyte interactions
corona radiata
zona pellucida
what occurs in the sperm interaction with the corona radiata
capacitated sperm pass through
hyaluronidase dissolves hyaluronic acid that cements the corona radiata cells
what occurs in the sperm interaction with the zona pellucida
sperm penetrates here
due to the acorn released from acrosome
made up of 4 main glycoproteins ZP1,2,3,4
ZP3 proteins only binds to the receptors on the surface of human sperm
sperm oocyte fusion
cortical reaction occurs
sperm fuses with the cell membrane of the oocyte
causes fast block to polyspermy: Na+ channels allow influx into cells, causes depolarisation, repels sperm
triggers SER to increase Ca2+ in the eggs cytosol
causes release of lysosomal enzymes in cortical granules
initiating the zona reaction, slow polyspermy block as cortical granules harden the oocyte membrane
release of hydrolytic enzymes further degrade the zona pellucida
stimulates exocytosis of cortical granules to harden oocyte membrane
impenetrable to further sper m
completion of meiosis 2
oocyte completes meiosis 2
forms a definitive ovum and a polar body
polar body is degraded
when is the zygote formed
when the pronucleus of ovum and sperm fuse
zygote division
by mitosis in the fallopian tubes
morula, 16 cells day 3-4
blastocyst day 5
implantation then occurs day 7-8
blastocyst burrows into the uterine lining
cleavage definition
cell division by mitosis in absence of cell growth
until the 16 cell stage
how many cells in morula
16
morula to blastocyst
when morula becomes leaky and fluid filled cavity
the zona pellucida disintegrates
blastocyst then swept by the cilia and contractions
layers of the blastocyst
trophoblast
embryo blast
inner cell mass
embryoblast
becomes the bilaminar disc
outer cell mass
cytotrophoblast and synchiotrophoblast
implantation
thickening of the endometrium
blastocyst rests on the endometrium
trophoblast extends finger like projections that burrow into the endometrium
implantation has occurred
