Cell differentiation is the development of a generic cell into a cell with a specific function, which is directed by various triggers. This differentiation is essential for the renewal of cells and for embryonic development, and occurs numerous times in the development of a single-celled zygote to a multi-cellular organism with many different cell types. It is also essential for cellular turnover, the continuous maintenance of most multi-cellular organisms. Through differentiation, a cell drastically changes its size, shape, membrane potential, metabolic activity and responsiveness.
During the cell differentiation process, a naïve cell specializes itself towards a specific cell type with a specific function. Signals which direct this differentiation can arise from the surroundings of the cell or from internal changes. During differentiation, the genome residing in the cells remains the same. However, changes in the expression of the DNA sequence change the internal composition, cell surface and structural matrix of a cell drastically during differentiation, resulting in physical distinctions as well as variations in membrane potential, metabolic activity and responsiveness.
Zygotes and blastomeres are totipotent cells, which allows them to differentiate into all possible cell types. Pluripotent cells are undifferentiated cells of the adult organism which can develop to any cell type except placental tissue. Embryonic stem cells are also pluripotent cells; as they have the potential to differentiate and evolve to specific cells according to signals of their surroundings when implanted. Adult stem cells can be found in several areas of the body, specially in the bone marrow, where all types of blood cells find their origin.