Fertilisation to Trilaminar Flashcards
fertilisation:
union of gametes - fusion of sperm and oocyte to form a zygote
where does fertilisation take place
in the ampulla of the uterine tube
in the firsts stage of fertilisation the Sperm binds to the
zona pellucida glycoprotein (ZP3)
Acrosomal enzymes released from sperm head;
sperm digests its way into egg
Egg and sperm plasma membranes fuse and
sperm contents enters the egg
Sperm entry triggers completion of meiosis 2 and release of
cortical granules by oocyte (make ZP impenetrable to other sperm)
what does one cell embryo undergo
a series ofcleavage divisions
what’s a mitotic division
dividing into identical cells
what else happens during cleavage and why
Rapid mitotic division without increase in size
because cells are confined within the ZP the embryo will change shape(compaction)
what does cleavage form
morula(16+ cells) blastocyst(200-300 cells)
name one type of cell in a blastocyst and explain
Outer cell mass (trophoblast):contacts with the endometrium of the uterus to facilitate implantation and the formation of the placenta
name another type of cell in a blastocyst and explain
Inner cell mass (embryoblast):responsible for the formation of the embryo itself
how to cells maximise available space
by coming into closer contact with each other
Inner cells form
cell junctions
outer cells form
gap junctions