The Developing Person
Developmental Psychology
study of physical, cognitive, and social changes across the life span
In the woman’s body, hormones are causing a follicle (egg container) in one of her ovaries to ovulate – that is, to rupture and release an egg cell, or ovum. When released, the ovum begins a slow voyage down a 4-inch long Fallopian tube to the uterus. It is within this tube that one of millions of sperm cells will fertilize the ovum. The fertilized ovum, or zygote, is 1/175th of an inch across.
Within nine months, the newly conceived organism develops from a nearly microscopic cell to a neonate (newborn) about 20 inches long. The zygote divides repeatedly as it proceeds on its three to four-day voyage to the uterus. The ball like mass of multiplying cells wanders about the uterus for another three to four days before being implanted in the uterine wall. Implantation takes another week or so.
Germinal stage – the period from conception to implantation – or the period of the ovum. Embryonic stage – lasts from implantation until about the eighth week of development. During this stage, the major body systems take form. The growth of the head is followed by the growth of the organs (heart, lungs, etc.) and finally the extremities. The relatively early maturation of the brain and organ systems allows them to participate in the nourishment and further development of the embryo.
Fourth week – a primitive heart begins to pump blood in an organism that is 1/5 of an inch long. End of second month – the head becomes rounded and facial features distinct – all in an embryo that is about 1 inch long and weighs 1/30th of an ounce. The nervous system also begins to transmit messages By five to six weeks, nondescript sex organs have formed. By about the seventh week, the genetic code (XX or