1. Human nerves cannot be reconnected if they are severed.

2. The fluid in the lympathic system is pumped by the heart.

3. Human skin cells divide only once.

4. The human body contains about 1 million neurons.

5. A typical adult human head weighs 20 kilograms.

6. Sitting on "pins and needles" involves the nerves.

7. People choose to be left-handed or right-handed.

8. Humans and apes share only a small number of genes.