Q.Trace the sequence of events from fertilisation to the formation and implantation of the blastocyst.

[!TLDR]

Fertilisation in the fallopian tube gives a zygote that undergoes cleavage to a morula, then a blastocyst (trophoblast + inner cell mass), which sheds its zona pellucida and implants into the endometrium about a week later. …

Fertilisation, the fusion of sperm and secondary oocyte to form a diploid zygote, takes place in the ampullary-isthmic junction of the fallopian tube. The zygote then begins cleavage, a series of rapid mitotic divisions -- 2-cell, 4-cell, 8-cell stages -- as it is carried toward the uterus, with the individual blastomeres growing smaller each division so overall size stays roughly constant, the whole structure still enclosed within the zona pellucida. By around the time it enters the uterine cavity, it has become a solid ball of cells, the morula, which continues dividing and develops a fluid-filled cavity, the blastocoel; the structure, now a blastocyst, differentiates into an outer trophoblast layer and an inner cell mass attached to one side. Around day six to seven after fertilisation, the blastocyst sheds its zona pellucida and comes into contact with the endometrium, which by this stage of the luteal phase has been made thick and receptive by progesterone; trophoblast cells adjacent to the inner cell mass adhere to the endometrial surface and then progressively invade and embed thems …

Lay out the sequence as a timeline from fertilisation through to implantation, naming each intermediate stage (zygote, cleaving embryo, morula, blastocyst) and t …

Saying the blastocyst implants while still enclosed in the zona pellucida -- the zona pellucida must first be shed before the trophoblast …