Embryology 1 Flashcards
name of cell division process in spermatogenesis/oogenesis?
meiosis
2 step process
produces haploid gametes
what is produced through oogenesis?
1 ovum and 3 polar bodies (follicles formed at same time as egg but they cannot be fertilised)
what is produced through spermatogenesis?
4 sperms
define zygote
a diploid sex cell- it is the first cell of a human being
genetically unique as it has 23 c from mum and dad
what does a zygote divide to form in pre embryonic phase?
blastocyst
where do the mitochondria and organelles come from?
the mum as the sperm leaves them all behind and only the pro-nucleus of the sperm fuses with the egg at fertilisation
what is a morula?
a solid ball of cells formed when a zygote divides a number of times
zygote- morula- blastocyst
blastocyst structure
trophoblast
inner cell mass
blastocyst cavity
what is a trophoblast
the outer lining of cells of the blastocyst
what is inner cell mass
accumulation of cells at one end of blastocyst that forms the baby
how does the fertilised egg move down uterine tube?
cilia beat egg down, mucous secretion helps reduce friction
ectopic pregnancy
if it occurs anywhere outwith uterine cavity
could occur if cilia function is abnormal
when is the pre-embryonic phase
0-3 weeks
when is the embryonic phase
4-8 weeks
when is the foetal phase
9-40 weeks
fertilisation
pronucleus of sperm enters pronucleus of ovum to give a diploid zygote
define pronucleus
pronucleus is either of a pair of gametic nuclei, in the stage following meiosis but before their fusion leads to the formation of the nucleus of the zygote.
pre-embyronic phase: week 1
zygote is formed and it then divides to form a blastocyst
it moves through uterine tube, to reach uterine cavity
which is the first cell in the body
zygote
it is diploid- 46 chromosomes
how does a zygote divide
by mitosis forming 2 then 4 then 8
what is a solid ball of cells called that is formed from zygote division
morula
what goes on to form the baby from the blastocyst
the inner cell mass
what is the lining of the blastocyst called
trophoblast
what is the lining/ wall of the uterus called
endometrium- smooth muscle where embryo wants to be embedded
how does the egg move down the Fallopian tube?
cilia on epithelium beating it through
what is an ectopic pregnancy
egg implanting in uterine tube itself may be due to cilia function is abnormal
week 2 of pre-embryonic phase
implantation occurs and placenta begins to develop
cells that later form the embryo form a bilaminar disc
sacs, membranes and cord to nourish the human conceptus (baby) start to form
does the ovum divide as it moves through fallopian tube
yes it does and it becomes a blastocyst just as it reaches the uterine cavity normally
where does implantation occur
in the endometrium- lining of the uterus
what does the chorion do
Implantation process (chorionic villi)
Forms part of the placenta in due course
Secretes human Chorionic gonadotropin (HCG)
what does a trophoblast form
a chorion
what can HCG hormone be used to detect in women
pregnancy, hormone can be detected in urine
what does the chorion have on it’s surface and why is this helpful
it has chorional villi that enable it to penetrate into the endometrium and implant into the uterine cavity lining.
what is the endometrium called after implantation
decidua
what do the cells of the inner cell mass form
a 2- layered flat disc called the bilaminar disc
what 2 cavities form either side of the bilaminar disc
amniotic cavity
yolk sac
which cavity is formed on top of the bilaminar disc?
amniotic cavity
what are the 2 layers of cells called in the bilaminar disc
epiblast
hypoblast (below the epipblast)
where does waste accumulate in the embryo
allantoic sac
what is the main source of nutrition for an embryo
placenta but also a little from yolk sac
main functions of the placenta
Foetal nutrition
Transport of waste and gases
Immune etc
