What Is Human Development
Humans are the most complex beings in the universe, but that much you already know. But did you also know that this complexity actually begins early on after fertilization? It’s a time sensitive process, with every milestone in development being expected at a specified time. Human development has been closely monitored and analyzed by many biologist. A thread like structure in DNA known as Chromosomes are responsible for human development especially it decides the sex.
Early Human Development
Reiterating on an aforementioned point, development begins immediately after fertilization. It’s the first major event that occurs in the very first week. Basically, it’s characterized by the fusion of the sperm and the ova. What follows is multiplication where there’s a rapid increase in the cellular structure of the zygote as it migrates to the endometrium for fertilization.
The embryo is the second stage in this early development, and it’s characterized by cell differentiation. From the third week, a process called gastrulation occurs, and it results in the formation of three germ layers. It is from these three that the organs of the body arise from. The differentiation of the germ layers is actually quite sophisticated, and the resultant systems such as the CNS (central nervous system) and the CVS (cardiovascular system) are formed.
The fetal stage marks the last stage of early development. It commences in the third week and lasts up to about the 40th week of pregnancy. During this stage, there’s continued differentiation, as well as growth in size of the fetus.
Human Development after birth
While there’s no actual development after birth, in the sense that differentiation has ceased, there is growth in size, which is described as follows. There’s childhood, which starts after birth to a period of about 12 years. Neonate, infant and toddler are terms used in this stage, basically describing a child less than 30 days old, between 1 and 12 months old, and between 1-3 years respectively. Prepubescent is sometimes used to describe a child that’s between 4-12 years of age. Adolescence follows, which is the period between ages 13 and 19. Adulthood is the final stage of human development, and it starts at 20 onwards.
This is basically the framework of the whole process. The complexity of human developmental biology is actually fascinating. Though the process is programmed to go on without fault, there are ‘accidents’ that happen. These are described as mutations, and most frequently occur during the embryonic stage where most of the differentiation takes place. Some mutations are mild, such as cleft lip but there are some which are fatal such as acrania (absence of a cranium).