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  • EDiao

Fun Facts About Upper Extremities

1. The palm cannot be tanned because it contains no melanin, just like the bottom of your foot. In addition, the palm cannot grow hair.

2. There are 27 bones in your hand, compared to the 14 in your face.

3. Cracking your knuckles isn’t good or bad for you. The “pop” is actually mostly carbon dioxide gas escaping the synovial fluid, which lubricates the joints, and expanding.

4. There are no muscles in your fingers; the muscles are in your palm and forearm.

5. The wrinkles behind your fingers are dimples, where the tendon attaches to the skin.

6. The most sensitive finger is the index finger. Studies show using your smartphone makes your finger even more sensitive.

7. Smaller fingers tend to be more sensitive.

8. The humerus, a big bone in the upper part of your arm, cannot be broken easily, and allows your arm to hold up to 300 pounds (136kg).

9. We get more ambidextrous as we get older.

10. The distance from your elbow to wrist is about the size of your foot.

This entry was prepared by Gigi Lu, an Enterprise for High School Students (EHSS) summer intern taking part in the EHSS Career Exploration Program. Founded in 1969, EHSS is a non-profit organization with a mission to prepare San Francisco high school students for future success in the workplace and higher education. They offer hundreds of opportunities for youth to develop life skills through engagement in work. Dr. Diao has sponsored EHSS students for 17 years in the Career Exploration Program at UCSF, in his private office, and at the San Francisco Surgery Center, and has served as an EHSS board member for 6 years.

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