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Gut health has been hitting the headlines for a while, so it’s about time we got to grips with how it actually works.

Once you know how the various parts fit together, it’s easier to make sense of the symptoms you might feel if your digestive system becomes upset.

Hopefully you’ll also feel a bit more love for this very hard-working organ after reading this post.


Your gut (sometimes called the gastrointestinal tract) is a long tube stretching from mouth to bottom, with a series of important jobs. The Gut is a bit of a VIP, with arguably the most essential job in your body (sorry brain!)

In fact, if your Gut had a CV, it’d be an impressive one – the nine meter long organ is responsible for the breakdown, digestion and absorption of nutrients, coordinating the release of over 30 hormones that help break down the food you eat. It controls the movement of all the digestive tissues and the circulation of nutrients, not to mention defending against illness and removing unwanted waste.

Let’s look at these jobs (and the parts of the gut that are responsible for them) in more detail.


Before food even arrives into your mouth, saliva is released from your salivary glands to coat the inside of your mouth and prepare for the breakdown of carbohydrates from foods such as bread, pasta and potatoes. Even the smell or sight of food can set off saliva release.

Once food enters the mouth (yum) your teeth break down food into smaller pieces and enzymes in your saliva begin to break down some of carbohydrates into smaller sugars.


As you swallow, food moves from your mouth into the oesophagus, aka the food pipe. The oesophagus is a muscular tube coated with special cells to protect it from crunchy sharp pieces of food. Mucus helps food move down the oesophagus as the muscles contract in waves to help send food along its journey to the stomach.


Once food enters your stomach, the digestive mission goes full steam ahead. As the stomach detects food, it releases stomach acid, which kills harmful bacteria, and provides the right conditions for digestive enzymes to work. The enzymes in your stomach work best at around an acidic pH of 2, so they become activated once stomach acid is released.

When it comes to strength, the stomach is not left on the sidelines – three layers of muscle work together to break food particles into a liquid, called chyme. As well as digesting food into a liquid, the stomach also acts as a reservoir for food, which means you can eat a large meal without needing to stop after a few mouthfuls.

Although it’s a little different for everyone, it typically takes around four hours for a meal to empty from the stomach completely, but it can take longer if the meal is high in fat or protein.


Food (now called chyme) leaves the stomach through a valve and enters the small intestine – a narrow tube with a double layer of muscle, stretching about 5-6 metres long, coiling round on itself like a string of sausages.It might be small (in width) but the small intestine is mighty, responsible for the absorption of nearly all nutrients, which is why it’s so long! 📷

The small intestine is split into 3 parts – the duodenum (which neutralises stomach acid), the jejunum and the ileum, which is covered in finger like bumps called villi, which absorb nutrients. The villi have their own blood supply to whisk away nutrients into your blood stream.

The small intestine couldn’t do its work without the work of the liver, pancreas and gall bladder. The liver manufactures liquid called bile (stored in the gall bladder), which helps to break down fats. The pancreas releases enzymes that break down carbohydrates, proteins and fats into individual sugars, amino acids (the building blocks of proteins) and fatty acids that can be absorbed.


By the time your meal reaches the large intestine (which is around 1.5 metres long), virtually all of the useful nutrients will have been absorbed. The walls of the large intestine of the large intestine are covered in glands that reabsorb water, making your stools solid. Immune tissues in the lining of the large intestine also provide protection against harmful bacteria and infections.

As well as forming your stool, the large intestine has a range of other important jobs, which it can only do with the help of… your gut bacteria.

Although bacteria are found throughout the length of the gut, most bacteria live in the large intestine. Scientists estimate there are as many as 1000 bacteria per gram (about a quarter of a teaspoon) in your large intestine. This is why when it comes to gut bacteria, we’re mostly focused on the large intestine – because that’s where the majority of your gut bacteria live.

One of the main jobs of the bacteria living in the colon is converting dietary fibre (the part of plant foods we don’t digest) into compounds called short-chain fatty acids. These fatty acids have anti-inflammatory benefits and prevent potentially harmful bacteria from taking hold.

The bacteria in your large intestine also manufacture a range of vitamins (clever huh?) including vitamin K and biotin, a B vitamin.


The rectum is about 10cm long and forms the last part of the large intestine. The anus is the end of your digestive tract, and consists of 2 sphincters (internal and external). Stools move from the large intestine into the rectum once or twice a day. Sensors in your rectum send a message to your brain and let you know there are stools to be passed. If the brain says, yes ok! then both sphincters in the anus will relax and you will be able to poop.


Phew… digestive system DONE. I think you’ll agree it’s an impressive bit of kit, which is why it’s important we take care of it. I’ll be posting more on this topic over the coming weeks, but if you want to jump in with some further reading now, click here.


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