Penis
AKA: chopper, dangly bits, dong, john thomas, lunch box, manhood, meat, member, knob, sausage, old man, package, organ, rod, schlong, todger, tool, willy, winkle.
Job: Peeing (several times a day) and sex (though please remember: sex under 16 - the age of consent - is illegal)
Measuring up: Average length (over 18 years): 6-10 cm soft; 12-19 cm erect
Starts growing age: 12-13
Percentage of UK males with foreskin removed (circumcised): 25%
Remember: Everyone is different. Smaller penises enlarge more when they get hard. Real men don't care about penis size. Nor do real women.
Problems: Burning when you pee, redness, sores or pain in the penis? Head for the doctor - even if it seems to go away. Take no chances on the health of your tackle.
Testicles
Job: To produce and store sperm.
Measuring up: Average size (over 18 years): 5 x 2 x 3 cm
Starts growing age: 11-12
Problems: Painful testicles should always be checked by a doctor. As should any lumps or swellings. Look after yourself.
Sperm
Job: Reproduction of the species
Average size: Microscopic. 1500 are found in a drop of semen the size of a full stop.
Number made every day: 150 million
Number released per orgasm: 40-600 million
Number needed to get pregnant: 1
Problems: STIs are carried in sperm. Avoid these and unwanted pregnancy, with a condom.
Further help and advice
• BBC Science: Boy's growth
• avert.org/puberty
(Scroll down for penis diagram)
Disclaimer: the BBC can't be held responsible for the content of external websites.
Pictures posed by models.
