This illustrated guide to the penis explains how erections work and peeing and ejaculation. We also cover foreskin, the frenulum and find out about papules!
This guide can only really teach you some of the basics. You could have a look at your own penis (if you have one) to see how it works for you.
***pictures and drawings of dicks below***
***careful if you’re on the bus***
Resting vs aroused
As you will probably know, penises get hard. I’ll explain more about how that works below. As you can see here, there’s a lot of variation in penis shapes and sizes, both when soft and also when hard.
Penises aren’t just hard or soft, or aroused or relaxed. They are often inbetween. We call this having a semi. Sometimes when penises are aroused they get bigger (longer and thicker), sometimes they don’t. There’s a lot of variation both between different penises, but also for the same penis.
The angle and shape of hard penises really varies too. Sometimes they bend down, or up, or to one side or the other. This is fine and normal. However if your erect penis has more of a kink to it you might just want to have a doctor look at it. Especially if you’ve had sex or injured your penis in the past.
You probably don’t need me to tell you that penises have two main functions: peeing and cumming. A penis needs to be hard in order to ejaculate. It is very very difficult to pee when the penis is erect. This is because the internal sphincter of the bladder spasms when the penis is erect and that traps the urine inside the bladder.
Erections can happen when someone is feeling really turned on but can also happen at other times. During sleep (and waking up from sleep), or in a classroom or on a bus. This can be embarrassing but there are ways that they can be hidden. Hands in pockets, sitting down, pulling top down or even wearing two pairs of pants if it happens a lot.
Fun fact: night time hard ons are thought to be caused by the sympathetic nervous system being switched off. The body is so relaxed (thanks parasympathetic nervous system) that the body send blood into the penis to ‘recharge’ the penis. This happens during the REM phase of sleep (when you dream). This doesn’t mean that your dreams are sexy, but they might be if you are aware of your arousal. Also this exact thing happens with vulvas too.
Read more about how to deal with stress, the nervous system, and the affect this has on genitals.
Sometimes erections don’t happen when we really want them too. Even when someone is really turned on and wanting sex sometimes they can get the flop. This can happen for medical reasons: but usually it’s a temporary problem that is often caused by not being relaxed. This can be because of stress generally, worries about ‘performance’ (ironically worrying about staying hard can make it harder to stay hard), anxiety about being seen naked or about safer sex. Any kind of tension or anxiety can make an erection go away.
Read more about the Hard On
How erections work
There is no bone in the penis, so how do they get hard? As you can see in this picture the penis is made up of blood vessels and loads and loads of tightly packed spongy blood cells. Blood rushes into the corpus cavernosa via the arteries and is trapped there making the penis hard. Imagine filling a balloon (or a condom) up with water and then squeezing one end to make it hard – that’s kinda what happens in the penis. Strong muscles around the bottom of the penis (inside the body) help to trap the blood in the penis. When the penis goes soft the blood exits via the dorsal vein (which you can probably see at the top of the penis).
Penises and clitorises work in a very similar way, so if you have a clitoris you can probably have a pretty good understanding of what a hard on feels like and how it works. There’s more on the similarities between clitorises and penises in my genitals article and video.
It’s also really important to remember that guys (with penises) aren’t machines. It’s really important for guys to spend time getting turned on too (kissing, stroking, etc). In porn you only see guys with erections because if they lose their erection the director shouts ‘cut’, so please don’t compare yourself.
Most penises are about the same size (around 5.5 inches) when erect but vary a lot more when they are soft. Guys who have a small looking penis when soft usually get a lot bigger when they get hard (grow-ers) and usually bigger looking soft penises don’t get much bigger, just harder (show-ers).
Penises come in lots of different shapes and sizes and there is a big variation. According to a recent study of adult men (full pdf is here) the average is 14.15 cm (5.5.inches) and an average erect circumference of 12.23 cm (4.8 inches) but the range of penis size is really big. There were reported erect penis lengths of 4 (1.6 inches) to 26 (10.2 inches) centimetres and erect penis circumferences of 3 (1.2 inches) to 19 (7.4 inches) centimetres. Also there’s no relationship between someone’s characteristics and their penis size (eg race, ethnicity, or sexuality).
Here’s some helpful advice from me about having a small dick (there’s nothing actually wrong with having a small dick). Penis size has nothing to do with how good sex can feel and there’s not a lot you can do about increasing penis size anyway. There are a couple of cheats that can make guys feel a bit more satisfied with their penis size.
If you have foreskin it should be able to move forwards and backwards over the glans of the penis quite easily. Sometimes this happens by itself when the penis gets bigger, sometimes it needs a quick helping hand. The loosening of foreskin during puberty is a gradual process as the penis grows and through masturbation during adolescence, for a study on this click here.
Foreskin stretching exercises
If foreskin doesn’t roll back easily then it could get damaged during sex. It’s also important to be able to clean under the foreskin to prevent infections. If it is tight you can try some self-stretching exercises from NormUK.
Try stretching the foreskin forward and then backwards as far as it will go, hold it for a few seconds and then let go and repeat. It might help to do this in the bath or shower as warm water will help to stretch the skin. Little by little over a few weeks the hole (prepuce) will get bigger. So the foreskin should slide over the glans more easily. You should only do this if it is comfortable and be careful that it doesn’t get stuck. If it does get stuck move it back straight away or go to a doctor. If in any doubt see your doctor, who may prescribe a steriod cream to loosen it or recommend circumcision: removal of the foreskin.
Here’s a blog from a teenage guy who wrote an excellent diary about this years ago.
Glans aka ‘bell-end’
This is a really sensitive part of the penis because it’s packed with so many nerve endings. It’s very similar to the glans of the clitoris. Touching the glans, lightly or gently, can feel very pleasurable. They can feel great to be touched, stroked, licked, rubbed, sucked or buzzed with a vibrator. Everyone is different though, so find out for yourself what you and they like.
Even without very much foreskin this area is still very sensitive. People who have been circumcised may find they might like to use lubricant to keep the skin moist and sensitive. Condoms can also help to act as kind of replacement foreskin too.
This bit of skin attaches the foreskin to the glans and the shaft of the penis. It can be very very sensitive to touch. Sometimes it can be a little tight and uncomfortable when the penis is hard. Occasionally through rough handling, it’s possibly to damage this skin which can cause some bleeding. This may seem scary at the time but it usually heals itself after a couple of weeks. If this has happened to you, you might want to go see a doctor or a sexual health service.
There are often little spots under the penis or around the bell end. These spots are normal and they’re called papules. If you notice unusual spots you notice anything unusual you might want to get it checked out. You can also get spots in the pubic hair area which are caused by in growing hairs. Spots (or papules) are very common but unusual lumps and bumps should be checked out in case it’s a STI (sex infection).
Scroll down to leave a comment. I moderate all comments before they go live. Click here to ask me a question
© Justin Hancock, 2022
I hope you’ve found this website helpful. Now here are all the ways you can help us, if you can.
This is one of the leading sex and relationships education resources online. We need your funding, so can you become a member of our Patreon?
Or if Patreon isn’t your thing, you could make a one off or regular donation via Donorbox
Would you like a BISH podcast? Would you buy merch? If you like answering questions like this please take my survey. It will take you less than a minute.
If you a) are over 18 and b) have money, you might like my coaching service. So if you are struggling with sex, relationships, and you generally, you might find it really useful. It’s really effective and you may well only need one or two sessions. Find out more at my coaching page here.
Buy my book
You could also buy my Sex Ed Activity Book, a fun zine with over 50 worksheets to help you to work out how you can do sex, love, and you.
If you’re over 18 and really into sex ed I have a podcast you might like called Culture Sex Relationships.
If you are an educator please check out my very popular RSE resources at bishtraining.com
Justin Hancock has been a trained sex and relationships educator since 1999. In that time he’s taught and given advice about sex and relationships with thousands of young people in person and millions online. He’s a member of the World Association for Sexual Health.