Pregnancy and Development of the Embryo

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• Embryonic development begins while the fertilized egg is still in the oviduct. 

• It takes two to three days for the embryo to travel from the oviduct to the uterus. 

• In the uterus, it undergoes several mitotic divisions. 

• Resulting in hundreds of spherical cells called blastocysts. Cells forming the outer layer of a blastocyst are called trophoblasts.

• Blastocysts attach themselves to the thickened wall of the uterus for about one week. 

• The process is called implantationImplantation is the embedding of the blastocyst into the endometrium of the uterus. Implantation begins about the 7th day after fertilisation of ovum and it takes about 3 days for the... More. 

• As the embryo grows, it absorbs nutrients from the walls of the uterus for its development. The uterus becomes bigger to contain it. 

• The embryonic membranes , amnionThis is a membrane in reptiles, birds and mammals, forming a fluid-filled cavity (the amniotic sac) that encloses the embryo. The amniotic sac and the fluid it contains are sometimes referred... More, chorionThe chorion is a membrane that surrounds a developing fetus in conjunction with the amnion. The chorion eventually forms the fetal placenta. The placenta provides nourishment and protection for the developing... More, yolk sac, and allantois develop, for protection, nutrient exchange, and waste storage.

• The yolk sac is the first fetal membrane to be formed in all mammals. The function of the yolk sac is to provide nutrition and oxygen to the developing embryo for the first 12 weeks of gestationGestation is the period of time between conception and birth. During this time, the baby grows and develops inside the mother's womb. More until the placenta takes over.

• Amnion forms a fluid-filled sac ( amniotic fluid ) that encloses the embryo and protects it from injury and temperature changes. It also allows for