Changes with puberty may occur gradually or several signs may become visible at the same time.

The male reproductive anatomy includes the bladder, epididymis, penis, scrotum, and prostate gland.

During the physical examination, the doctor will examine the genitals. Although this can be embarrassing for an adolescent male, it is necessary to help evaluate the presence of hernias or tumors.

In an uncircumcised boy, the foreskin will begin to separate from the glans, or the tip of the penis. This happens naturally while the male is an infant. This is called foreskin retraction.

During adolescence, the developing teenager acquires the ability to think systematically about all logical relationships within a problem.

Adolescent attention often shifts to a more intense focus on social interactions and friendships expanding from same sex friends to same sex groups of friends to heterosexual groups of friends.

Your body usually tells you when you are in danger -- your heart races, you breathe hard, your palms sweat. But when it comes to sexually transmitted diseases (STDs), you may not have any warning signs.

AIDS is caused by the human immunodeficiency virus, which kills or impairs cells of the immune system and progressively destroys the body's ability to fight infections and certain cancers.

The only safe sex is no sex, most health care providers say. But certain precautions and safe behaviors can minimize a person's risk of contracting a sexually transmitted disease.