5Development and Senescence
Our bodies develop from a single cell—the fertilized egg. After the egg cell is fertilized, it divides into multiple cells, which then vigorously divide and increase in number to form the basic structure of the body. In this process, the fates of the cells are determined by their large-scale migrations and interactions. These cells then form structures such as the brain, heart, and gastrointestinal tract, and ultimately form the basic structure of the entire human body. Humans continue to grow and develop various functions from birth until the reproductive age. After humans pass their reproductive age, their functions gradually deteriorate, they age, and they eventually die.
The mechanisms responsible for the formation of our body and aging are becoming increasingly clear due to recent research. In this chapter, based on recently discovered knowledge, we will discuss the mechanisms that form our body. We will also learn how modern knowledge of molecular developmental biology is being applied to new treatments for diseases.