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**Embryonic stage (WEEKS 3-8)**
After the zygote divides for about 7-10 days and has 150 cells, it travels down the fallopian tubes and implants itself in the lining of the uterus. Upon implantation, this multi-cellular organism is called an embryo. Now blood vessels grow, forming the placenta. The placenta is a structure connected to the uterus that provides nourishment and oxygen from the mother to the developing embryo via the umbilical cord. Basic structures of the embryo start to develop into areas that will become the head, chest, and abdomen. During the embryonic stage, the heart begins to beat and organs form and begin to function. The neural tube forms along the back of the embryo, developing into the spinal cord and brain.
*LICENSES AND ATTRIBUTIONS
CC licensed content, Shared previously, CNX Psychology, Stages of Development, Authored by: OpenStax College.
License: CC BY: Attribution. License Terms: Download for free at http://cnx.org/contents/Sr8Ev5Og@4.100:b7opmCF3@3/Stages-of-Development*
