The penis is part of a man’s external genitalia. The penis contains the urethra and three areas of spongy tissue. These fill with blood when the man has an erection so the penis gets stiff. When the man pees, the urine comes out through the urethra, this is also where semen exits during orgasm. The end of the penis is called the head or glans. If the man is not circumcised then the head of the penis is covered by the foreskin. This can be pulled back. The head is the most sensitive part of the penis. The size and appearance of the penis varies from man to man. Some boys worry that their penis is too small, but there is no need to worry. It’s not necessary to have a large penis in order to function well sexually.