### Surprising and Educational Facts About the Penis 1. **Regular Erections Are Important**: To keep the penis in shape, it needs regular erections. This helps maintain the smooth muscle tone by enriching it with oxygen through blood flow. 2. **Automatic Maintenance**: Even if men don't have erections during the day, the brain has an automatic maintenance function that causes erections during the REM phase of sleep. 3. **Impact of Diabetes**: Men with diabetes may suffer from nerve or blood vessel damage, making it difficult to get erections. Without regular erections, the penile tissue can become less elastic and shrink, potentially shortening the penis by 1-2 centimeters. 4. **Vacuum Pumps**: For men who have trouble getting erections, devices like vacuum pumps can help maintain a healthy penis by forcing it to swell with blood. 5. **Size Variability**: There is no consistent relationship between the size of a flaccid penis and its erect length. Some penises grow significantly when erect, while others do not. 6. **Sensitivity Declines with Age**: The sensitivity of the penis decreases with age, starting from around 25 years old, with the sharpest decline between 65 and 75 years old. 7. **Bacterial Diversity**: The skin of the penis hosts a variety of bacteria. Circumcised and uncircumcised penises have different bacterial communities, with circumcised penises having fewer types of bacteria. 8. **Health Benefits of Circumcision**: Circumcision has been linked to a lower risk of HIV and other sexually transmitted infections, as well as a reduced risk of penile cancer and urinary tract infections. 9. **Vibrators for Men**: Vibrators can be effective for men too, especially those with spinal cord injuries, helping them achieve ejaculation. 10. **Hidden Length**: About half the length of the penis is inside the body, attached to the pubic bone, making it longer than it appears externally.