Progressive restriction of the developmental potential and increasing specialization of function which takes place during the development of the embryo and leads to the formation of specialized cells, tissues, and organs.
The process whereby descendants of a common parental cell achieve and maintain specialization of structure and function. In humans, for instance, all the different types of cells (e.g., muscle cells, bone cells, etc.) differentiate from the simple sperm and egg. In humans, the various blood cell types (e.g., red blood cells, white blood cells, etc.) differentiate from stem cells in the bone marrow. Cell differentiation is caused/triggered/assisted by colony stimulating factors (CSFs), growth factors (GFs), and certain other proteins.
Although all nucleated cells possess the same DNA, some of the specific DNA regions (genes) are not transcribed or translated. If translated, some gene products are not very active. Thus, not all cells have the same processes with the same degree of activity. Cellular differentiation has taken place such that muscle cells differ from fat cells that, in turn, differ from brain cells and so forth. In each cell type, there are processes and metabolic pathways that may be unique to that cell type. An example is the great lipid storage capacity of the adipocyte, a feature not found in a bone cell or a brain cell or a muscle cell, although each of these cells do contain lipid. Similarly, the capacity to form and retain a mineral appetite (a mixture of different minerals) is characteristic of a bone cell, and the synthesis of contractile proteins by muscle cells are also examples of cell uniqueness. Cells differ in their choice of metabolic fuel. Hepatic and muscle cells make, store, and use significant amounts of glycogen. Adipocytes and hepatocytes make, store, and sometimes use triacylglycerols. All of these special features have an impact on the composition of specific organs and tissues in the body that collectively comprise and contribute to body composition. One must consider the function of each organ and tissue in the context of the whole body. Similarly, the determination of the activity of a single process in a single cell type or organ may not necessarily predict the activity (and cumulative result) of that process in the whole body.
The process through which stem cells undergo differentiation to transform into various specialized cell types, including skin, heart, muscle, and blood cells.