Embryology (fertilisation, week 1 -2) Flashcards
How many sperm are allowed to penetrate the ovum
one
What is the products of oogensesis meiosis
1 ovum and 3 polar podies (X)
What is the product of spermogeneis meiosis
4 sperm bodies ( X/Y)
What is the first cell of the body
zygote
What fuses between the egg and the sperm
The pronucleases
What enters the ovum when the sperms pronucleus fuses
the sperms genetic material, everything else is left behind
Is mitochondiral cell organelles inherited by the paternal or maternal
Maternal
what is an example of a maternal mitochondrial inherited condition
Lebers hereditary optic neuropathy - blindness
What are the two processes that occur in week 1
The zygote divides to from a blastocyte
The zygote moves through the uterine tubes to the uterine cavity
The zygote divides by mitotsis forming a ball of cells called what?
morula
The central core of the mass of cells becomes harder forming a cavity through, what is this cavity called
blastolytic cavity
What is the cells that from the outer layer of the morula called
trophoblast
Where is the inner cell mass found in the morula
The cells that are accumulating at one end of the cell
The ovary releases the ovum and fertilisation occurs in the uterine tubes, what feature of the uterine tubes than allows the transport of the zygote to the uterine cavity
They have cillated epithelium to push zygote through uterine tube and into uterine cavity
When and where should the blastocyte be formed by
around 5-6 days when it reaches the uterine cavity
How long is the first division of the zygote to from the balstocyte
36 hours
What happens to the division time as it continues moving through the uterine tubes
Successful division take less time
What should the blastocyte be ready to do when it reaches the uterine cavity
ready for implantation
What hormones prepare the body form implantation
Progesterone and oestrogen produced by the ovary
Due to what circumstance can ectopic pregnancy occur
cilia function is abnormal, so zygote implants in the uterine tubes rather than the uterine cavity, leading to a failure in the pregnancy as the uterine tube cant support it
What is the differences between monozygotic and dizygotic twins
mono = 1 zygote, share placenta, genetically identical Di = 2 zygotes, different placentas, not genetically identical
Where does implantation occur in the uterine cavity
in the endometrium layer
By what day does the blastocyte burrow into the endomtetium
day 7
The trophoblast divides to from 2 layers called what
Chrorion
What does the chorion chronic villi allow the trophoblast to do
Helps the implantation into the endometrium
What does the chronic vili of the trophoblast then go on to become for the embryo
the placenta
What is the part of the endometrium called which hold the burrowed blastocyte
Decidua
When the blastocyes implants in the endometrium these is an increase in blood vessels surrounding the chorion what are these blood vessels called
decidua basalis
What hormone does the chorion secrete and what is its function
secretes hormone human chorionic gonadotrophin HCG
prevents endometrium sheding by infoming ovary to keep producing oestrogen and progesterone
What hormone is used to detect pregnancy
HCG
HCG levels increase until what week
12 weeks gestation
Are the chorion villi in contact with the maternal blood?
No, passage of nutrients occurs by diffusion
What is the main functions of the placenta
Foetal nourishment
inspirit of waste and gas
immune protection
How long does it take the placenta to mature
18 - 20 weeks
Where is the two surfaces of the placenta facing and what are they like?
maternal - desidua basalis (rough)
foetus - amniotic membrane attaching to the end of umbilicus chord (smooth)
What does the inner cell mass go on to from
Bilaminar disc
What two layers are divided by the bilaminar disc
the epiblast and the hypoblast
What cavity sits above the epiblast
the amniotic cavity (where the embryo develops)
What cavity sits below the hypoblast
Yolk sac
