<h2>Events In Early Pregnancy</h2>

Formation of Blastocyst 

• Fertilization of the ovum by sperm occurs in the fallopian tube. The fertilized ovum is called the zygote. 
• The zygote divides rapidly by mitosis. The rapidly dividing cells of the fertilized ovum resemble a mulberry and this stage is referred to as morula (12-16 cell stage).
• Around the 5th to 8th day of fertilization, the morula is propelled into the uterine cavity by peristalsis and by the cilia that line the inner surface of the fallopian tube. 
• Once in the uterine cavity, secretions of the endometrial glands diffuse through the membrane of the zygote and accumulate in the morula resulting in tiny fluid filled cavities.
• At the same time, the cells of the morula differentiate into a central mass and a peripheral layer (trophoblast)

• The fluid filled cavities in the morula join together to form a single large cavity (blastocele).
• The inner mass of cells is pushed to the periphery and becomes attached to the peripheral trophoblast layer of cells at one place
• This stage of the embryo is referred to as the blastula or blastocyst