The human body is self-repairing and self-replenishing. According to one estimate, almost 200 billion cells die each hour. In a healthy body, dying cells are simultaneously replaced by new cells.
| Cell Type |
Length of Time |
| Red blood cells |
120 days |
| Lymphocytes |
Over 1 year |
| Other white blood cells |
10 hours |
| Platelets |
10 days |
| Bone cells |
25–30 years |
| Brain cells* |
Lifetime |
| Colon cells |
3–4 days |
| Liver cells |
500 days |
| Skin cells |
19–34 days |
| Spermatozoa |
2–3 days |
| Stomach cells |
2 days |
*Brain cells are the only cells that do not divide further during a person’s lifetime. They either last the entire lifetime or, if a cell in the nervous system dies, it is not replaced.
