fertilisation to trilaminar

Question 1

how does the sperm fertilise the egg?

Answer 1

1- the sperm will secrete hyluronidase which will penetrate through the corona radiata.
2- the sperm will come into contact with the ZP3 which will cause the acrosome to digest the zona pellucida.
3- membrane fusion
4- cortical granules from the egg will break down the ZP3 to prevent secondary penetration and there will be a negative charge increse

Question 2

cleavage, compaction and morula?

Answer 2

cleavage = 4 cells
compaction = 8 cells
morulla = 16 cells
all the cells are still contained within the zona pellucida except when it becomes a morulla, it will dissapear. attached by gap junctions.

Question 3

around what day will the egg start to bind to the uterus?

Answer 3

day 5/6

Question 4

how will the egg bind to the uterus?

Answer 4

there will be downregulation of of anti-adhesion molecule muc-1, this will allow selectins to bind to the glyco-components of the epitheluim on the uterus wall.

Question 5

what happens around 6/7/8 when the blastocyte has implantation is begining?

Answer 5

THIS IS THE START OF IMPLANTATION.
- trophoblast will divide into syncitiotrophoblast and cytotrophoblast
- the embryoblast will divide into hypoblast and epiblast
- the amniotic cavity will form within the epiblast.

Question 6

what happens around day 4?

Answer 6

-trophoblasts will form the outer layer
- emmbryoblasts will create the inner cell mass
- these will migrate towards each other creating the blastocyst cavity.

Question 7

what happens around day 9?

Answer 7

• the hypoblast cells will coat the blastocyst cavity to form the primary yold sac
• spaces will develop within the syncitiotrophoblast
• the amniotic cavity has formed a space in the epiblast laer

Question 8

what forms the primary yold sac?

Answer 8

around day 9, the hypoblast layer that is derived from embryoblast will sound the blastocyst cavity which will now be called the yolk sac.

Question 9

what are the spaces that develop within the syncitiotrophoblast for?

Answer 9

they are connections for the maternal blood supply.

Question 10

what happens around day 11/12?

Answer 10

• the embryonic disc will form 2 layers
• blastocyst burrown completely into the endimetrium
• syncitiotrophoblasts will errode through the walls of maternal capilaries creative a primitive placental curculation.
• A space will form between cytotrophoblast and the yolk sac.

Question 11

the space that forms between the cytotrophoblast and the tolk sac, what does it do?

Answer 11

it will fude to form the chorionic cavity.

embryonic mesoderm

Question 11

at the end of week 2, when the women expects her period, what are the 2 layers in the trophoblast called?

Answer 11

syncytiotrophoblast and cytotrophoblast

Question 11

where does the embryonic disc form?

Answer 11

the embryonic disc will form at the connection between the epiblast and hypoblast

Question 11

at the end of week 2, when the women expects her period, what are the 2 layers in the inner cell mass called?

Answer 11

epiblast - ectoderm
hypoblast - endoderm

Question 12

at the end of week 2, when the women expects her period, what are the 2 cavities called?

Answer 12

amniotic cavity - within epiblast layer
chorionoic cavity - between yolk sac and cytotrophoblast

Question 12

At approx 36 hours after fertilisation, what happens?

Answer 12

The egg splits into 2 blastomeres

Question 13

At which point is the egg called a blastocyst.

Answer 13

When the blastocyst cavity forms in the ambryoblast layer