I just recently noticed this on my penis: As I look down at it and pull back my foreskin, I notice this raised vein or lump. It's kind of soft and doesn't hurt if I press down on it. It's a bluish color and is not noticeable unless I have my foreskin pulled back. It there even when erect. What is the cause of this? Is it something to be worried about? Should I see my doctor?
Nathan (age 17)
You correctly identified what you are seeing. It is a vein. All men can see veins on their penises and, yes, they do stick up.
To understand this, take a close look at the skin on your arm. Depending on the pigmentation of your skin, you probably will faintly see veins underneath the skin, especially near your wrists and on the back of your hands. Arteries, which bring blood out from the heart and lungs, run deep inside you. Veins, which are the return path for blood, run closer to the surface of your skin. The design is to protect you from cuts. The blood in arteries is under high pressure. If cut, you could lose a lot of blood in a short period of time. Veins are larger, but also are under low pressure. Cuts are still serious, but the lack of pressure allows cuts to be sealed quickly.
Now, take a look at the skin on your penis. Which is thinner, your arm skin or your penis skin? The skin on your penis is noticeably thinner. As a result, you can see through the skin easier than you can your arm. Hence, you can see more of your veins. This is especially true when you have an erection. The erection stretches the skin (which is why it is thin in the first place), making it even more transparent.
Next, recall from the discussion in this book how erections take place. Your penis fills with blood to pump it up like a balloon. When the erection is over, your veins take all that accumulated blood and returns it to your body. Hence, the return path needs to be large or else it would take a long while for your erections to go down. Those large veins are seen just under the surface of your skin on your penis. To cause an erection, your body has small muscles that clamp down on the exit point of your veins from your penis. The back pressure is what causes the penis to swell during an erection. However, that same back pressure makes the veins in your penis to stand out during erections.
There is one more thing, though that I would like you to consider. Now that you realize that the skin on your penis is thin and that a good deal of blood is flow just underneath that skin, can you see why a number of diseases are transmitted sexually? Your skin serves as a barrier to keep diseases out of your body, but the skin of your penis is less of a barrier than say the skin of your arm. And when you have an erection, that skin is stretched even more. Diseases can easily cross through the thin skin of your penis and quickly enter your blood stream.
This is one reason sex outside of marriage is dangerous. People who are willing to have sex with someone they are not married to are highly likely to have multiple sex partners. They can easily pick up numerous diseases and those disease will be transferred to you as well if you have sex with such people. See Chapter 7 on the Dangers of Getting Too Close for more information.