- Ejaculation: During an ejaculation, sperm leave the epididymis, travel up the vas deferens and on the way pick up fluids from the seminal vesicles and prostate gland. These fluids help the sperm move through the urethra. The sperm and fluids together are called semen. Semen leaves the body through the urethra, the tube that passes through the penis. Around a teaspoon of semen is released during an ejaculation. This thick fluid, also known as ejaculate, is usually milky white in color.
- Erection: An erection happens when blood fills the spongy tissue in the penis, making the penis hard and erect. Erections begin to happen from the time of birth and continue throughout life. They become more frequent during puberty. Erections can be caused by common events such as lifting heavy items, exposure to cold, being anxious or excited, waking up with a full bladder, or for no apparent reason. It can be embarrassing, but if a boy thinks about something else, like homework, the blood will flow back to the body and the penis will become soft again.