How does the human penis get hard?

i would like to see some scientifically answers about the penis geting hard, does the human penis has different muscles then the other body part or what?
Answer:
Probably the easiest way to understand how the penis becomes erect is to think about a balloon. If a balloon has no air in it, it is limp. As you inflate a limp balloon with just a little air, it becomes elongated and rigid.

The penis uses a similar mechanism, but instead of using pressurized air to become rigid, the penis uses pressurized blood. The penis contains two cigar-shaped structures, called corpus cavernosa (singular - corpus cavernosum), that it uses to become erect.

Think of the corpus cavernosa as balloon-like tubes. Arteries bring blood into these two tubes, and veins carry blood away from them. The penis can be either limp or erect, depending on the flow of blood:

1%26gt;In a non-erect state, the arteries that bring blood into the corpus cavernosa are somewhat constricted, while the veins that drain the blood from the penis are open. There is no way for pressure to build inside the penis. In this state, the penis is limp.

2%26gt;When a man becomes aroused, the arteries leading into the penis open up so that pressurized blood can enter the penis quickly. The veins leaving the penis constrict. Pressurized blood is trapped in the corpus cavernosa, and this blood causes the penis to elongate and stiffen. The penis is erect.

If the arteries leading to the penis do not open up properly, it is difficult or impossible for a man to become erect. This problem is the leading cause of erectile dysfunction.

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its becuz of the blood flow. Alot of blood rushes into the penis which makes it hard

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