Embryology Flashcards
gametogenesis types:
oogenesis (female)
- 2 mil primary oocytes at birth
- 40 000 oocytes by adolescence
spermatogenesis (males)
- after puberty
brief procedure of fertilisation:
- 200-600 mil sperms in cervical os (uterus) after sex
- sperms pass through female reproductive system
- fusion of male and female gamete
- occurs in uterine tube 12-24hrs (after ovulation)
- secondary oocyte viable 24hrs
- sperm 48hrs
oocyte linings:
corona radiata and zona pelucida
zygote
fertilised ovum
dizygotic twins vs monozygotic twins:
dizygotic:
2 secondary oocytes fertilised by 2 sperm
monozygotic:
1 egg, 2 sperm in same placenta but different amniotic sacs
how does conjoined twins occur:
cell separation not within 8 days after fertilisation, may be conjoined
list first week development:
- fertilisation
- cleavage
- morula
- formation of blastocyst
- implantation
when does each occur: first-week development (5)
- fertilisation (12-24 hrs) a.o
- cleavage (30 hrs) a.f
- morula (3-4 days) a.f
- blastocyst (4.5-5 days) a.f
- implantation (6 days) a.f
o-ovulation
f-fertilisation
fertilisation features/ location:
near/ in uterine tube
- muscular uterine contractions help aid sperm
- cervix open during ovulation
- cilia push egg to uterus
define zygote:
fertilised ovum
cleavage features: define morula and name its membrane
- mitotic cell division of zygote, divide every 6 ish hrs
- solid cell mass (morula)
- surrounded by zona pellucida
- doesn’t grow in size
- only increase SA
define/ formation of blastocyst features/ location:
day 4-5:
- morula enter uterine cavity
- uterine milk penetrate morula/ blastomeres and form fluid cavity (blastocyst cavity)
- removes zona pellucida for embedding
hollow sac in cell mass
two layers of blastocyst and brief info:
trophoblast:
- squamous epithelial cells
- nourishes embryo
embryoblast: (inner cell mass)
- shifted to one side, forms the embryo
implantation: features/ location
blastocyst attaches to endometrium of uterus, implants onto posterior wall of uterus
endometrial lining (uterus mucous membrane) after implantation of blastocyst (Decidua)
list second week development:
- trophoblast development
- bilaminar embryonic disc (embryoblast)
trophoblast differentiation:
2 layers:
- syncytiotrophoblast
- cytotrophoblast
syncytiotrophoblast features:
- outer layer, no cell boundary
- secretes enzymes, can deepen in endometrium,
- produce HCG (pregnancy hormone)
placenta: function
- organ of pregnancy (after 28wks)
- exchange of nutrients and waste products btw mother/foetus
- produces hormones to sustain pregnancy
- develops from foetal and maternal sources