Physical Development of Human Beings

Human physical development refers to the process by which the body of a human develops from a zygote formed when sperm fertilize an ovum. The zygote develops from one cell to billions by birth. Prenatal development ends with birth, but the physical growth and development of the human being continues through childhood and adolescence and generally terminates in early adulthood.

Germinal Period

• Lasting from conception until the end of the second week, the germinal period encompasses fertilization and growth of the zygote, as well as it's attachment to the mother's uterine wall. Once the zygote is attached to the uterine wall it becomes implanted and embedded there. The organism is the size of the head of a pin at this point.

Embryonic Period

• The zygote is now referred to as an embryo. During this stage of development, chief organs begin to appear and the placenta establishes a connection from the embryo to mother. The connection is made possible through a structure called the umbilical cord. The placenta is an organ responsible for delivering nourishment and oxygen to the developing embryo, filtering out waste. While all organs begin to develop at this point, the sex organs will come later. The embryonic period extends until the end of the eighth week.

Fetal Period

• The embryo is now called a fetus. Major organ systems further develop as the fetus looks like a complete human being. It has arms, legs, fingers and toes. Sex organs differentiate the fetus as male or female. The face is also developed. The fetal period ends at birth.

Infancy

• Infancy starts at birth and ends at two years of age, according to the National Institute of Child Health and Human Development. Birth is the transitional stage from uterine life to living as an individual organism separate from dependence upon uterine support. Physical development continues with the nervous system, namely the brain, developing much quicker in the newborn than all other systems.