What is the digestive system?

The digestive system (also known as the gastrointestinal system) is made up of the digestive tract (the gut) and other organs like the liver, pancreas and gall bladder. It is where your body breaks down food and absorbs nutrients.

The digestive system is a long, twisting tube that starts at the mouth. It goes through the oesophagus, stomach, small intestine, large intestine and ends at the anus (bottom or back passage).

The digestive system breaks down food into simple nutrients such as:

• carbohydrates
• fats
• proteins

These can then be absorbed into your blood, so your body can use them for energy, growth and repair. Anything not used becomes waste, and leaves the body as faeces (poo).

How does my digestive system work?

Each organ of your digestive system has an important role in digestion.

Mouth

When you eat, your teeth and tongue help to break food into small pieces. Glands in your cheeks and under your tongue make saliva to coat the food. This makes it easier to chew and swallow. Saliva also contains enzymes that start to digest the carbohydrates in food.

Oesophagus

Your oesophagus is a tube that carries food from the mouth to the stomach after it is swallowed. A ring of muscle at the end of the oesophagus lets food into your stomach and stops stomach contents from going back up to the oesophagus.

Stomach

Your stomach breaks down food with liquid (gastric acids). This helps with digestion and absorption of vitamins and minerals.

Small intestine

Food that is not digested in your stomach passes into your small intestine. The small intestine of an adult is around 5 metres long and has many bends and folds. The large surface area helps proteins, fatty acids, sugars, vitamins and minerals pass through its wall into the blood. Most chemical digestion of food (for example, proteins, fats and carbohydrates) happens in the small intestine.

Large intestine, rectum and anus

Your large intestine absorbs water, minerals and some vitamins. Undigested fibre is mixed with mucus and bacteria, which help break down some of the fibre and keep the large intestine healthy. Solid bowel motions (faeces or poo) are formed and stored in the last part of the large intestine (the rectum) before leaving the body through the anus as a bowel movement.

Gut microbiome

Your gut microbiome is made up of millions of different microorganisms naturally living within your digestive tract. These microbes help break down food and support a healthy immune system.

What are common health conditions of the digestive system?

Gastro-oesophageal reflux

Gastro-oesophageal reflux disease (GORD) is when stomach contents move from the stomach back up the oesophagus. Because it is acidic, it causes a burning sensation in the chest or throat.

Diverticulitis and diverticulosis

Diverticulosis is the formation of small pouches of tissue in the wall of the lower part of the large intestine. Diverticulitis is when these pouches become inflamed or infected. Around half of people over the age of 80 years have this condition.

Stomach ulcers

Stomach ulcers, also called peptic ulcers, occur in the stomach or the upper part of the small intestine. Helicobacter pylori (H. pylori) bacteria cause most stomach ulcers. Sometimes ulcers are triggered by stress or caused by using non-steroidal anti-inflammatory drugs (NSAIDs).

Haemorrhoids

Haemorrhoids are itchy or painful swollen veins in and around the anus.

Haemorrhoids can cause bleeding and pain. You might notice bright red blood on the toilet paper or in the bowl. Haemorrhoids are diagnosed by a doctor examining the anus and anal canal.

Other conditions

There are many other health conditions that affect the digestive system. Other conditions include:

• irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD)
• constipation
• diarrhoea and gastroenteritis
• coeliac disease
• cancers

When should I see my doctor?

You should speak to your doctor if you have any concerns, pain or discomfort with your digestion. See your doctor immediately if you:

• have chest pain
• have severe abdominal pain
• continue to vomit or are vomiting blood
• have symptoms that make it hard to eat, drink or sleep
• are losing weight without trying
• notice changes in your stool (blood, unusual colours)

How do I prevent digestive system problems?

You can help prevent digestive system problems by leading a healthy lifestyle, but there are some conditions that you can't prevent. Keeping your gut healthy will reduce your risk of digestive conditions.

Here are some things you can try:

• Lose weight if you live with overweight or obesity.
• Follow a balanced diet.
• Eat enough fibre.
• Drink water, avoid sugary drinks and alcohol.
• Aim for 30 minutes of physical activity every day.
• Stop smoking.
• Avoid straining when having a bowel movement.

Resources and support

Speak with your doctor about any concerns when it comes to your health.

• Visit the Gastroenterological Society of Australia (GESA) website for resources on digestive health and disease.
• The GI Cancer Institute has information and support for people with gastrointestinal cancers, including support groups.
• Visit Nutrition Australia for information about the gut microbiome and tips for maintaining gut health.
• The Gut Foundation has a guide to good gut health, including food and exercise suggestions.
• The Australian Dietary Guidelines give advice about the kinds of foods you need to eat for health and wellbeing.
• Visit the Lung Foundation Australia for information on quitting smoking to improve your gut health.

You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available 24 hours a day, 7 days a week.