How fast does the human body replace itself

A new lining of the stomach in 5 days

The lining of the stomach is renewed after every few days. While being constantly under assault by digestive acid and lasting only five days intestinal epithelial cells need faster regeneration pace.

New skin after every 2-3 weeks

The surface layer of the skin is renewed after every two to three weeks.

2-3 weeks for lung’s surface renewal

The cells on the lung’s surface renew after every 2-3 weeks. The alveoli of the lungs have longer regeneration period, over a year. It’s the place where the exchange of oxygen and gases takes place.

Rebuilt bone cells in about 3 months

New bone cells are rebuilt in as little as over 3 months. But it takes 10 years to grow an entirely new skeleton and bones, in general, are refreshed once a decade.

Red blood cells live about 4 months

The red blood cells, the most common type of blood cell, last around 120 days. Red blood cells are delivering oxygen to the body tissues. They take up oxygen in the lungs and release it via blood’s circulatory system.

White blood cells in more than a year

White blood cells take more than a year to regenerate. White blood cells are the cells of the immune system. They are involved in protecting the body against both infectious disease and foreign invaders.

Renewed liver in 1-2 years

An adult human liver has a renewal time of 300 to 500 days. The liver synthesizes proteins, detoxifies various metabolites, and produces biochemicals necessary for digestion. It also regulates glycogen storage, decomposition of red blood cells and the production of hormones.

10 years for fat storage cells

Fat-storage cells renew roughly once per decade.

Heart

It was thought the heart couldn't renew itself. Until a study at New York Medical College found that heart it is actually dotted with stem cells that constantly rejuvenate it. The researchers say that it is thought to happen at least three or four times over a lifetime.

Others

• Sperm cells live only about 3 days.
• Heart endothelial cells: 6 years.
• Intercostal skeletal muscle cells: 15 years.
• Internal intestinal cells: 16 years.
• Hippocampal neurons: 20-30 years.

Parts that never renew

• Tooth enamel
• Visual cortex

Hair and nail growth

• Fingernail grows 0.1 mm per day.
• Head hair grows 0.35 mm per day.
• Toenails grow 1 mm per month.

It takes about 5 months for a nail to grow or replace itself from bottom to top. For the hair, it depends on the length of the hair.

Fun fact

The liver is the only complex organ that can “grow back". It will return to its normal size in 1-2 weeks following the removal of even more than 50% of its original mass. But it won’t happen to other parts of the body. For example, if someone's hand is accidentally cut off then the natural repair that follows will never result in a replacement of the new hand. But there are creatures that can regrow some parts of their body. Lizards and hydras for example.

Last update: 2019-01-06 (Y,M,D)

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