1. Which blood type is known as the universal donor?

2. What gas do humans exhale when breathing?

3. How many chambers are in the human heart?

4. Approximately how many miles of blood vessels are found in a single human adult?

5. Where in the human body is the smallest bone (the stapes) located?

6. Which hormone is produced by the pineal gland to regulate the sleep-wake cycle in response to darkness?

7. Which bone is the longest and strongest in the human body?

8. What is the term for the brain's ability to reorganize and form new neural connections?

9. Where is the vestibular system, which controls balance and spatial orientation, located?

10. Which gland is often referred to as the 'master gland' of the endocrine system?

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

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

13. What is the name of the active growth phase of a hair follicle?

14. Which vitamin is essential for the production of blood clotting factors in the liver?

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

16. What is the name of the lining of the uterus that is shed during menstruation?

17. Which organ receives blood directly from the digestive tract to filter out toxins before the blood reaches the rest of the body?

18. Which bone in the human body is unique because it does not connect to any other bone?

19. What is the primary function of the gallbladder in the digestive process?

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