Embryology Flashcards
What happens during fertilisation?
- sperm digest its way through the zona pellucida using enzymes from the acrosome
- once inside, both nuclei fuse forming a zygote - 2n
What happens during the 1st 4 days after fertilisation?
- after fertilisation, there is rapid mitotic divisions which produces smaller daughter cells as there is no increase protoplasmic mass - they are now called blastomeres - this process is called cleavage
- by day 4 there are 16 cells and the zygote is now called a morula
What happens between day 5 and 7?
- by day 5, fluid has entered the the morula when there are 32 cells and it becomes a blastocyst - after that 2 cell masses arise giving an embryoblast and a throphoblast - and the blastocyst hatches from the zona pellucida
- on day 6, the blastocyst loosely attaches to the endometrium
- on day 7 the endometrium becomes more vascularized and the blastocyst releases enzymes which enable it to move further into the endometrium
- the endometrium becomes the deicdua
What happens to the trophoblast in week 2?
the trophoblast is the outer layer of the blastocyst and develops into 2 layers - cytotrophoblast and syncytiotrophoblast
the trophoblast secrets hCG which acts similar to LH
What is the bilaminar germ disc?
The embryoblast differentiates into 2 layers - hypoblast and epiblast
What is and what happens during gastrulation?
gastrulation is when the bilaminar develops into the trilaminar germ disc
- cells from the epiblast invaginate and displace the hypoblast forming the endoderm
- cells remaining form the mesoderm and cells left in the epiblast form the ectoderm
What is neurulation?
mesodermal cells migrate to head end and form a hollow tube
by day 22-24 it becomes a solid cylinder known as a notochord
ectodermal cells cover the notochord to form the neural plate
neural folds convert the plate into a tube
neural tube develops into the brain and spinal cord
What is gametogensis?
process of production of male and female gametes from the primordial germ cells
