(a) Trace the events from fertilization till implantation of blastocyst in human female. Also mention the site where fertilization takes place.

After the entry of sperm into female gamete, it undergoes meiotic division II, to produce haploid ovum ie ootid, then the nucleus of sperm and ootid fuse together to form zygote, zygote moves through the isthmus of oviduct towards uterus and it undergoes mitotic division or cleavage to form blastomeres, the embryo with $\displaystyle 8$ to $\displaystyle 16$ blastomere is called morula and it further divides and transforms into

Blastocyst, blastocyst have outer layer trophoblast and inner cell mass and the trophoblast layer of blastocyst gets attached to endometrium,

Uterine wall divide rapidly and covers blastocyst and this it gets embedded in the endometrium of uterus this is called implantation.

• The site of fertilization is-

ampullary region of fallopian tube /isthmus ampullary junction of fallopian tube.

Case I

In vitro fertilization followed by zygote intra fallopian transfer or ZIFT /

In vitro fertilization followed by Intra uterine transfer or IUT /

Intra Uterine insemination or IUI / Artificial insemination or AI .

Case II -

Invitro fertilization followed by IUT

Case III -

Intra Cytoplasmic Sperm Injection or ICSI / Artificial insemination or

AI / Intra Uterine insemination or IUI.

The copper releasing IUD’s are CUT, Cu7, Multiload $\displaystyle 375$ (Any two)

Copper releasing IUD’s increases phagocytosis of sperms within the uterus,

Cu ions released suppress sperm motility and the fertilising capacity of sperms.