Learn the organs

It contains about 86 billion nerve cells (neurons) — the "grey matter". The human brain is the largest brain of all vertebrates relative to body size. The brain makes up about 2 percent of a human's body weight. It weighs about 3.3 lbs. The cerebrum makes up 85 percent of the brain's weight.

There are a total of 22 bones in the skull.

The lungs are the largest internal body parts about the size of two footballs. The right lung is slightly larger than the left one.