The Anatomy and Physiology of Anal Sex.

Lately, I see lots of stories about anal sex.

Some writers explain why they like it, some writers explain why they don’t.

Some explain how amazing it feels as the receiver, others tell how good it is as the giver, and some are disgusted by the sheer thought of pushing anything inside the butt hole.

It’s great to learn from other people’s experience and I thank all the authors that are open enough to share their personal take on anal sex.

I read tips like taking it slowly and using lots (lots!) of lube.

But I usually like to get to the bottom of things. Excuse the pun.

Besides the hype, I want to understand:

The anatomy and physiology of this thing called anal sex.

The hype is pretty obvious.

We think the anus is tight, and tight = more friction, hence it should be awesome. Mainly for someone with a penis who appreciates a firm grip.

The reality is a tad more complicated than this.

It’s true that the butt hole (let’s call it the anus, for science’s sake) is very tight. It is comprised of two sets of sphincters — which is just a fancy word for round muscles. Their role is to keep the feces inside, so yes, they must be tight.

However, what you need to understand is, that the more you work to get them relaxed — which is needed if you’re planning on pushing something through them without causing too much pain — the looser they become. And once they get loose, they stay loose for some time.

Another important bit of information that most people are unaware of, is that the rectum (meaning, the bit that’s inside the anus) is not that narrow at all.

If you want to compare the rectum and the vagina, this illustration can help:

AdobeStock Image

As you can see, the vagina looks almost closed. That’s because the vagina, by default, collapses on itself. 

It only opens as something enters into it. Then it pretty much wraps itself around whatever is inside it.

On the other hand, the rectum is wide open apart from the very lower tip of it. And it stays this way when you insert something into it.

So yes, as someone with a penis, you will most probably enjoy the friction through the tighter areas of the anus, but it’s probably worth knowing that the tightness is only local.

Now I also want to understand,

Why does it feel good to receive anal sex?

So here’s the thing.

Sex feels good when erogenous zones in our body are being stimulated.

The erogenous zones we are all familiar with include the genitals, the nipples, the lips, etc. But the truth is, erogenous zones are spread all over our body. People differ in the amount of pleasure and the sexual connotation they have with specific areas of their body.

One erogenous zone that works for some and doesn’t work for others, is the perineum

The perineum is that area in between the anus and the vulva (vulva = the outside bits that surround the entrance to the vagina) in females. In males, it is between the anus and the scrotum (scrotum = the “balls’ sack”).

The perineum is loaded with nerve endings, and many people find stimulating it arousing. Hence “butt play” can feel so good for them. 

Other people don’t enjoy stimulation around the perineum.

It does not mean that there’s anything wrong with them, or that they are sexually closed-minded.

Exactly the same way some people can feel nothing when their toes are being licked, other people feel annoyed by it, and some people fly to the moon and back with excitement.

It’s normal and there’s nothing wrong with not being aroused by something that someone else finds to be extremely arousing.

The thing most people don’t want to mention when they talk about anal sex: poo.

Not many people like to talk about poo.

In the articles which I read about anal sex, I did not see that topic mentioned.

Well, sorry to burst your bubble, but if you are planning on having anal sex, there’s a chance you’ll encounter it.

When you push something through the anus it goes inside. Into the rectum. Which is the end bit of the guts. 

The rectum is considered to be a clean part of the guts. Meaning, up until recently, people believed the only time there’s poo in the rectum is when you feel the need to go to the toilet for a number two. However, more recent studies suggest that the rectum can hold some feces in it without the individual feeling the need to relieve themselves. 

This means that when having anal sex there is some chance to encounter a bit of feces on whatever was in there. Penis, dildo, finger, toys. Yes, even if you clean yourself really well. Some people suggest having an enema before anal sex (basically, flooding the rectum with water to expel whatever is inside it). But it’s not a foolproof plan.

Oh and another thing re poo.

Sometimes, it takes the sphincters a little while to go back to their natural closed state. So things might feel a bit saggy there after you had anal sex.

You can’t have a sex-ed talk without mentioning pregnancy and some nasty diseases now, can you?

If you think you can’t get pregnant while having anal sex, think again.

OK OK OK! I was just testing you to see if you are paying attention.

Of course you can’t get pregnant.

But there’s a higher risk of STD’s from anal sex as the tissues there are more prone to tearing and bleeding. Please be warned.

And another thing, make sure you clean everything that was in your rectum before it goes into your vagina. You don’t want to introduce gut bacteria into the vagina.

Oh and also, if you do end up having plenty of enemas to clean yourself before anal sex, you increase the risk of contracting an infection as they disturb the gut flora.

Last word of advice: things can get lost in the bowels.

I kid you not.

Make sure that whatever you put inside the anus has a plug so it doesn’t go disappearing into the rectum and beyond.


Now that you know why and how anal sex can be oh-so-much fun for some, and why it can be oh-not-so-much-fun at all for others, I hope this article helped you better understand if it’s an activity you wish to partake in or not.

You can decide to explore anal sex, you can decide to pass. Just remember that the choice is yours and that no one should ever guilt you for your decision. If they do, they’re just being a dick.