How your tummy works: from top to bottom

Inside the mouth

Even just smelling or thinking of food can make your mouth water. Digestion begins in the mouth, where food is broken down both physically (with your teeth) and chemically (with the special proteins called enzymes in your saliva). These enzymes cleverly break down carbohydrates and fats from your meal. Have a go at chewing some bread for a longer time and you might even taste this in action, as the carbohydrates turn into simple sugars with a sweeter taste!

Inside the oesophagus

Once chewed and ready to move on, your mushed up food travels down your food pipe (also known as the oesophagus) as you swallow.

The way your muscles push food through the oesophagus and intestines is called peristalsis.

Ever felt food going down ‘the wrong way’? Most of the time, your windpipe will be cleverly covered when you swallow to avoid choking, thanks to a well-coordinated flap called the epiglottis. It acts as a little lid that stops food and drink going down your airways. Occasionally, especially if you’re distracted, rushing or talking at the same time, something can slip down by accident (known as aspiration), and a quick cough will usually fix it.

Inside the stomach

From your food pipe, your chewed food slides into your stomach. It stays here for a few hours, where it mixes with digestive juices and is churned into chyme. Acid and enzymes, such as pepsin that breaks down protein, help to digest it even more.

Our stomach acid, mainly made up of hydrochloric acid, is really important for activating these essential digestive enzymes (including pepsin), so it can turn those proteins into amino acids, ready to be absorbed into our bloodstream. This awesome acid also helps to kill harmful microbes that might be attempting to invade.

On the flipside, having low stomach acid could impact your digestion, making it less efficient and in turn risking nutritional deficiencies.

To stop this acidic chyme going back up the wrong way (hello, reflux!), the stomach closes its clever trap door, called the lower oesophageal sphincter.

More sphincters are found at each stage, separating the sections for a smooth ride from top to bottom. These are between the stomach and small intestine (the pyloric sphincter), the colon (the ileocecal sphincter) and finally, at the very end of the rectum (the anal sphincter).

Inside the small intestine

This smoothie-like chyme then moves down into your small intestine, also called your small bowel.

The small bowel is folded up tight and might have ‘small’ in its name, but it’s more like an entire tennis court in your tummy! If you spread out its huge surface area, that is.

How does it have a large surface?

The walls of the small are packed with very tiny structures, like little fingers (the villi) with tiny hairs (the microvilli). These structures help to super-size the surface area and aid the absorption of much-needed nutrients from our food. Here, your liver and pancreas also get involved. Bile, more enzymes and bicarbonate are released to reduce the acidity.

Why is that important?

An alkaline environment is the aim for the enzymes to do their job well.

Exploring these enzymes further

They’re responsible for breaking down proteins, carbs and fats, speeding up crucial chemical reactions so our bodies can absorb nutrients.

There are a whole bunch of enzymes playing essential roles – here are a handful you’ll want to know about

Struggling with milk?

Sometimes, some people might find they don’t have enough lactase, aka the enzyme that breaks down lactose. This results in tummy troubles like gas, bloating and poop problems.

By the time our small intestine has done its thing, which can take between 2 to 6 hours, your food has mostly been broken down, allowing nutrients to be absorbed into the bloodstream and delivered to key parts of the body.

Inside the colon

Your colon (aka the large intestine or large bowel) is home to billions of marvellous microbes, which are teeny tiny living things – not just bacteria, but also yeast, viruses and parasites. Not all parasites are bad. Fibre can’t be digested in the small intestine, so, along with any other bits that haven’t been absorbed so far, it makes its merry way down to the colon.

And this is where the microbe magic happens. Those little microbes are powerful and help to break down fibre, producing chemicals. These chemicals are called short chain fatty acids, that are linked to a whole host of health benefits. This feasting and fermentation also releases some gases (like hydrogen and methane).

Ever feel bloated or bunged up? Methane could be the culprit!

Our gut microbes work hard to support our health, digestion and even our immune system. But if those gut bugs are out of balance (also known as ‘dysbiosis’), excess methane can be made and bloating, wind and constipation could be in store.

Your colon takes its sweet time compared with the small intestine. Depending on what you’ve eaten, it can take anywhere from 10 to 36 hours, or more, for food to move through.

Your poop

As the remaining liquid is absorbed, your poop begins to form into a more solid shape. What’s in your poop? Well, it’s a mix of the leftover fibre and other waste products from the body, with more than half made up of the microbes themselves!

At the end of your large intestine, you’ll find your rectum. This stores your waste until your brain tells it to go ahead and release – sending you on a trip to the toilet. (Another example of that gut-brain axis in action)

Now you know the ins and outs, it’s time to get your tummy back on track.