| Cell Type |
Average Lifespan |
| Blood cells: Red blood cells |
120 days |
| Blood cells: Lymphocytes |
Over 1 year |
| Blood cells: Other white cells |
10 hours |
| Blood cells: 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 they die during a person’s lifetime they are not replaced. |
Epithelial tissue, also called epithelium (from the Greek epi, meaning “on,” and thele, meaning “nipple”), covers every surface, both external and internal, of the body. The outer layer of the skin, the epidermis, is one example of epithelial tissue. Other examples of epithelial tissue are the lining of the lungs, kidney tubules, and the inner surfaces of the digestive system, including the esophagus, stomach, and intestines. Epithelial tissue also includes the lining of parts of the respiratory system.
