Embryology Flashcards
how many weeks does the pre-embryonic stage of development last?
0-3 weeks
what weeks does the embryonic stage of development last?
weeks 4-8
in oogenesis what does the oogonium develop into?
1 ovum and 3 polar bodies
what develops into 4 sperm in spermatogenesis?
spermatogonium
what two things fuse in the egg during fertilisation?
the( pro)nuclease of the egg and sperm
apart from the (pro)nucleus what else can be transferred in fertilisation?
the mothers mitochondrial DNA, meaning mitochondrial disease can be passed from parent to child
what does the diploid zygote form?
a morula (solid ball of cells)
what does it nutrition become difficult for the morula and how is this problem overcome?
as the morula increases in size getting nutrition to the core becomes difficult so a cavity develops- blastocystic cavity
in a blastocyst what cells is the outer lining made of?
trophoblasts
where does fertilisation occur in the uterus?
at the distal ends of the uterine tubes
where in the womb does the blastocyst settle?
in the endometrium, an inner lining of blood vessels that grow under the influence of hormones
around what day has the blastula formed and reached the uterine cavity?
day 5 or 6
what is an ectopic pregnancy?
this occurs if the cilia function is abnormal and unable to transport the blastocyst to the uterus so it implants in the uterine tube. this is known as a tubular pregnancy and can often rupture
what do the trophoblasts form during implantation in week 2?
the divide forming two layers that makes up the chorion
what are chorionic villi?
the chorion develops finger like processes that aides in implantation
what does the chorion do?
> implants
forms part of the placenta
secretes human chronic gonadotropin (HCG) which keeps the endometrium in place during pregnancy
what is the decidua basalis?
part of the endometrium deep to the implanted conceptus
what do the inner cell mass form in week two?
the bilaminar disc
in week 2 what two cavities are formed?
the amniotic cavity and yolk sac
what are the main functions of the placenta?
> foetal nutrition
transport of waste and gases
immune protection
describe the maternal surface of the placenta
the decidua basalis is rough and has maternal blood vessels
describe the foetal side of the placenta
it is smooth and contains the end of the umbilical cord
when is the placenta matured?
weeks 18-20
describe the conditions in a dizygote/fraternal multiple birth
2 ova are released and are fertilised by two sperm creating two separate zygotes that have different genetic make up. this can run in families.