The fastest replicating human cells are red blood cells found in the bone marrow. These cells divide at a rate of two million per second, and the process is known as "mitosis."
Additional fast replicating cells in the human body include cells in the intestines and skin cells, which only live for three weeks. The slowest dividing cells in the body are muscle, nerve and liver cells. Muscle cells fail to carry on mitosis after creation, and nerve cells stop dividing once they reach maturity. Liver cells only divide when a section is removed, such as during a liver transplant.