MALE REPRODUCTIVE SYSTEM (genitals)
Penis
Your penis is the male organ for sexual intercourse (sex). It is the exit for semen as well as urine. It is shaped like a cylinder and made of spongy tissue. It normally falls between your legs, unless you are having what is called an erection. Erections first start happening during puberty and it is when a man becomes sexually excited and the penis fills with blood. The blood pressure makes it grow and stiffen, also becoming 'erect' meaning that it will stick up at around a 90 degree angle. This is why the penis skin is loose and elastic because it has to be able to stretch and change shape and size during an erection. During an erection if a man is having sexual intercourse or a wet dream, semen, a fluid containing sperm, comes out of the penis. This is called ejaculation. On the penis I also foreskin. Foreskin is flappy and stretchy and is on top of the penis. Though some penis' can have to be circumcised which means the removal of the skin for some medical reason. It is very important that you always wash under your foreskin to make sure you are keeping clean.
Testes (testicles)
Testes are a very important organ because they produce sperm and testosterone. Sperm are shaped like tadpoles with 'tails' that help them swim. This is what fertilises the eggs during sexual intercourse. The testes need to be kept cool, so they are covered by the scrotum, a loose layer of skin, which hangs outside the body just behind the penis. During puberty it is important to check your testes every now and then to know what their regular size, shape and texture. It is very normal for one testicle to be bigger than the other, you should only be concerned if they change shape especially any lumps that form, it is important you tell a trusted adult or see a doctor. Though keep in mind during puberty they will grow in size, so make sure you are not confused.
Prostate gland
The prostate gland sits just in front of the bowel and below the bladder. It produces a milky or white fluid that makes up 50-75% of the volume of semen. The fluid gives better protection for the semen and makes it more motile (being able to move more actively, independently and more spontaneously).
Urethra
The urethra is a tube that runs from the tip of the bladder and through the penis. Urine is released through this tube as well as semen that comes from the connecting vas deferens (sperm ducts).
Seminal vesicle
The seminal vesicle is what produces semen. When sperm swims by it is released form the seminal vesicle and together they just become semen. The seminal vesicles are attached on top of either vas deferens (sperm ducts) and are sack-like organs.
Vas deferens (sperm ducts)
Vas deferens are tubes with thick walls which connect from either testes and go to the urethra. They have smooth muscles in the walls which contract reflexively to help propel the sperm forward. The vas deferens are also attached to the seminal vesicle were semen is added to the sperm moving through in preparation for ejaculation.