the Penis. An illustrated guide from BISH

The Penis

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.

Soft relaxing penises. Chilling with their homies

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.

Hard ons. Hey I drew these, so don’t take the piss

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.

Penis anatomy

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.

The penis anatomy. Glans. Bell end. Urethra. Frenulum. Foreskin. Shaft.
I based these drawings on pictures I found on the internet. There are penises on the internet.

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

how the penis gets hard. cross section of penis

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.

Read: Can You Break Your Penis?

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.

Penis size

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.


how foreskin works

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).

Please leave a (nice) comment below if you like or ask me a question here.

© Justin Hancock, 2024 Find out more about me and BISH here.

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I’ve been a sex and relationships educator since 1999 (with a background in youth and community work). In that time I’ve taught and given advice about sex and relationships with thousands of young people in person and millions online. I’ve worked with many charities, local governments, schools and youth organisations facilitating training and workshops. My two books, Enjoy Sex (How, When, and If You Want To) and Can We Talk About Consent? are widely available around the world. I’ve been on the telly and the radio and have written articles for newspapers and magazines. I’m also a member of the World Association for Sexual Health. Read more about me and BISH here. Find out about my other work here Justin Hancock

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15 thoughts on “The Penis

  1. Hi BISH I have a question regarding papules. I have a significant number of papules across my scrotum, which are not ingrown hairs as the papules have singular hairs growing out of them. It is also definitely not an STI like syphillis or ghonorhea as I am 15 and have never had sex before. I would really like to know what they are and how to treat them as I don’t want to transmit anything to potential future partners, and I am not sure how to access services as it would be really embarrassing if anyone, especially my parents found out about it. I am also concerned it could be cancer as I have found a small lump on my teste and my nipple.

    1. As I say above, papules are normal. I’m not medically trained, but papules such as these are common on the scrotum too. From reading about it they are either Fordyce spots or sebacious hyperplasia that are a normal variant on scrotal skin. So absolutely nothing for you to worry about. What you describe can’t be an STI because you haven’t had sex. If you want some reassurance you might want to speak to your doctor or a local sexual health service (who you can speak to confidentially, they don’t tell your parents).

  2. With regard to the frenulum you neglected to mention how INCREDIBLY sensitive it is. I have a partial circ with my frenulum completely intact. My wife stroking it sends my body into convulsions. I only have frenulum orgasms and love it!!!!!!!

  3. I was circumcised as a child and feel psychologically it has affected my sexual confidence and question my sexuality immensely . My mother never made me feel anything other than normal but my age and females siblings were a cause of breakdown and almost start of having sexual doubts and feeling of being behind physically and mentally to my peers . Up until 12 , nudity , erections all natural obviously weren’t an embarrassment or thought in my mind .my female household never made my body an issue but unfortunately it was their love and lack of understanding in male sexualit

    1. Yes you can use a condom for sex with short frenulum, in fact putting a bit of water based lubricant on it before putting the condom on might also help if feel more comfortable. There’s some useful information about this here including some advice about how you might be able to stretch it.

  4. When my wife and I have sex and we both cum i don’t seem to have much that comes out of me I am 65 years old.but we do have great sex live. Thanks

  5. When I have an erection it is a hang down erection. It has pretty much always been that way. It is fully hard but has no rise or lift to it. Is there any way I can get it to point straight out of up? I am not interested in surgery. Are there any kind of muscle exercises that I can do to get to lift. I understand that what I have may simply be what I have? I am happy with my penis but would like more lift if I can get it. Help a guy out if you can. Thanks.

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