The stages of human development from a single cell to a whole being are very interesting. It has been widely studied and today the stages of human development are well documented. The development stages are divided into four. These are: germinal period, embryonic period, fetal period and full term or delivery (Kail and Cavanaugh 53). There is a wide variability in the features of the baby-to-be at the various stages of development.. The normal gestation period takes about 40 weeks (Charlesworth 169). After this a mature baby can be delivered.
The germinal period, also known as the zygotic stage is the first period in the fetal development (Charlesworth 170). It begins with the fusion of the sperm and the ovum. Pregnancy is believed to begin in the first day of the woman’s last menstrual period. Conception marks the start of the germinal period and it takes about two weeks. During this stage, there is rapid cell division (Kail and Cavanaugh 55). A single cell divides rapidly into multiple cells. This stage ends with the implantation of the zygote into the uterine wall and marks the beginning of the embryonic period (Greene 171).
The embryonic period is the second stage in fetal development. It begins with the implantation of the zygote onto the uterine wall and last up to week 8 of pregnancy (Charlesworth 171). The embryonic stage develops the foundations for maturity into a baby. There is continued rapidly differentiation of cells into placental cells and the cells that form the baby (Charlesworth 171). The placenta, which is important for transport of food and nutrients to the fetus, is formed. It is also a channel for excretion of wastes from the fetus (Kail and Cavanaugh 56). Three layers of cells are formed through a process called gastrulation: ectoderm, mesoderm and endoderm. The ectoderm acts as a precursor for the skin, hair and the brain. The mesoderm forms the lungs, heart, muscles and bones. The endoderm forms the gastrointestinal system, the bladder and other internal organs (Charlesworth 171). The organs start functioning at this stage.
The third stage of fetal development is the fetal period. It marks the end of the embryonic period. Fetal period is the longest period and takes place between weeks 9 and week 38 of pregnancy (Charlesworth 172). At the end of the fetal period, the baby can be delivered and is capable of surviving outside the mother’s womb. This stage is characterized by a rapid increase in the size of the fetus. Early in the fetal period the fetus weighs below an ounce. After 4 weeks the fetus weighs 4-8 ounces and the mother can even feel the fetus’ movements in the uterus. During the last phase of the fetal period, the fetus adds 7-8 pounds more (Kail and Cavanaugh 56). There is also improvement in the development of major organs that prepares the fetus for the outside environment. The respiratory system, digestion system and ocular system of the fetus are improved (Charlesworth 57). The fetus is ready for delivery at this stage although an additional 2 weeks may be needed to attain full term. The three periods of fetal development are the major stages that lead to the development of a full term baby. The cells differentiate into a mature system. The development of the baby continues even after birth.
Works Cited
Charlesworth, Rosalind. “Understanding Child Development.” 8th Edition, Wadsworth Cengage Learning, 2010. Print
Greene, Elliot, and Barbara Goodrich-Dunn. The Psychology of the Body. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins, 2014. Print.
Kail, Robert V. and Cavanaugh, John C. “Human Development: A Life-Span View.” 7th Edition, Cengage Learning, 2016. Print
