Early Embryonic Development (Figure 1) Begins with a (A) zygote (fertilized egg), goes through…. Cleavage- Series of mitotic cell divisions resulting in many cells, becomes…. (B) 2 cell stage, (C) 4 cell stage.... (D) Morula- solid ball of approximately 50 cells, develops into…. (E) Blastula- hollow structure, fluid filled mass of cells, followed by….

Early Embryonic Development Gastrulation- indentation of the blastula to form a 3 layered structure called…. The gastrula (3 layers) (Figure 2) A. Ectoderm- outer layer- becomes epidermis, tooth enamel, nervous system, lining of mouth and nose B. Mesoderm- middle layer- becomes skeleton, muscles, excretory system, circulatory system, & gonads C. Endoderm- inner layer- becomes digestive tract, respiratory tract, liver, and pancreas

Later Development Placenta- Umbilical cord- Exchange structure between the mother and developing fetus Exchanges of materials between the blood of the mother & the blood of the fetus. Blood does not mix Umbilical cord- Contains blood vessels Connects the fetus to the placenta