Embryology Flashcards
Gestation
The time required for for development of a fetus in uterus
What is a pre-embryonic period
The first two weeks
When is the embryonic period
3 to 8 weeks
When is a foetus formed
9+ weeks
What happens during fertilisation
Female reproductive tract deliver sperm to ampulla of uterine wall
How many hours after ovulation do you sperm and ovum meet
12 to 24 hours in uterine tube
What makes the ovum impermeable to other sperm
Acrosomal reaction- capacitation shedding of acrosomal cap of sperm
Penetration of Corona radiata and Zona pellucide
Without capacitation sperm are incapable
Of penetrating the oocyte
The zygote and its associated membranes- conceptus
Projected Towards uterus by peristalsis and Celia of uterine tubes
What happens during cleavage
Zygote undergoes 5 to 6 rapid mitotic cell divisions
The cavity forms blastocysts
What happens in twins
In non-identical twins the over them splits so is dizygotic, and identical twins the zygote splits and they share a placenta
Formation of blastocyst
16 cell stage – solid sphere of cells called a morula
Differentiation of blastocyst – cavity enlarges, pressure builds and increases number of cells
Changes in uterus in week one
Conceptus floats freely, cells divide, uterine wall thickens, uterine milk secreted, start of implantation signals end of pre-embryonic stage of development
Where does implantation usually takes place
On fundus or posterior wall of body of uterus
Implantation what does trophoblast do
Interact with uterine epithelium
Trophoblasts differentiate into
Cytotrophoblast and syncytiotrophoblast
Implantation defects involve
An ectopic pregnancy as a result of the implantation occurring low down in the opening of the uterus, abdomen or in Fallopian tubes
During implantation trophoblast attach to
Epithelium at embryonic pole of blastocyte
What happens during week 2
Embryoblast organise into epiblast and hypoblast which form bilaminar disc And the amniotic cavity secrete amniotic fluid
What happens during week 3
Third germ layer and cavity formed, trilaminar germ disc forms three distinct layers- the ectoderm (outer most disc), mesoderm and endoderm
What happens during week 4
Folding of embryo both laterally and longitudinally, development – growth, morphogenesis, differentiation and three cavities are formed – blastocoele, amniotic sac, primitive yolk sac
How long does an oocyte stay viable for
A day
How long does sperm stay viable for
Up to 3 days
