?Human development can be divided into three phases, growth, embryonic period, and fetal period. Growth includes cell division and the expansion of cell products. The embryonic period, is where cells begin to take on different functions (Moore, K., Persaud, T. & Torchia, M. 2013a). Finally, the fetal period is when growth and maturing of the developing organs occurs (Baddock, S. 2015). Events in the embryonic and fetal period will be covered within this synopsis. During the embryonic period, which includes the fourth to the end of the eighth week after fertilization, most of the organ systems are established (Moore 2013c). This occurs through cell division, movement, separation and planned cell death (Stables, D. 2010). All the major organ systems and structures form from the three germ layers of trilaminar flat disc, ectoderm, mesoderm and endoderm (Stables 2010). This period is the most vulnerable time for the embryo, in relation to deformities due to the amount of activity occurring (Moore 2013a). Within this week, the caudal end of the neural tube is open, and the embryo develops a curved shape due to the head and tail folds (Marieb, E. 2013). The fourth week includes: development of the early heart, which has the ability to pump blood; the anterior of the three primary regions of the brain, giving the prominent structure of the head, and the caudal tail like structure. By day twenty-six, the upper limb buds are visible, as are the internal ears. The skin thickens on the side of the head to indicate the future lenses of the eyes. Also noticeable are the buds for legs, and the establishment of many organ systems, especially the cardiovascular systems (Moore 2013c). Within the fifth week there are minor changes, in comparison to the fourth week. The most significant is the head size. Due to the rapid development of the brain and facial distinctions, the head is considerably larger than the rest of the embryo. The hand plates are p