1. What part of the human body produces insulin?

2. What is the only internal human organ capable of regenerating itself completely from as little as 25% of its original tissue?

3. What is responsible for the 'lub-dub' sound of a heartbeat?

4. What is the name of the tiny air sacs in the lungs where gas exchange occurs?

5. Which protein in red blood cells uses iron to transport oxygen throughout the body?

6. Besides fingerprints, which of the following is unique to every individual and can be used for biometric identification?

7. Approximately how often does the human body replace its taste buds?

8. Which enzyme in saliva is responsible for beginning the digestion of starches in the mouth?

9. If uncoiled, the DNA from all the cells in a single human body would reach approximately how far?

10. Which muscle in the human body is considered the strongest based on its weight and ability to exert force?

11. Which organ in the lymphatic system acts as a major filter for the blood?

12. Which part of the brain is primarily responsible for regulating body temperature, hunger, and thirst?

13. What is the primary function of melanin in the human skin?

14. Which antibacterial enzyme is found in human tears and helps protect the eyes from infection?

15. Which mineral is essential for the thyroid gland to produce its metabolism-regulating hormones?

16. What is the name of the fluid that lubricates and reduces friction in human joints?

17. What are the tiny projections in the small intestine that increase surface area for nutrient absorption?

18. What is the name of the fatty insulation that speeds up nerve impulses?

19. What two gases are exchanged across the blood-air barrier in the lungs?

20. What is the primary evolutionary purpose of the human blink reflex triggered by the eyelashes?