In brief
The digestive tract runs from the mouth to the anus. With help from the liver and pancreas, it breaks food down, absorbs nutrients and removes waste.
- The parasympathetic nervous system stimulates digestion, while the sympathetic nervous system slows it.
- Stomach acid can kill most microbes, and the gut's mucous lining contains antibodies.
- Blood from the digestive system filters through the liver before it travels anywhere else in the body.
How it works
Muscular contractions move food along. In the duodenum, at the start of the small intestine, food mixes with digestive enzymes from the pancreas and bile from the liver. Nutrients are absorbed in the ileum, the last part of the small intestine, which is lined with millions of finger-like projections called villi.
The large intestine, or bowel, removes water and stores the waste as faeces in the rectum. A large reservoir of microbes, such as bacteria, lives in the large intestine. The bowel also has its own separate nervous system, called the enteric nervous system.
Looking after it
See your doctor as soon as possible if you notice blood in your poo, a change in your bowel habits, weight loss without trying, or ongoing or severe tummy pain.
Connections
10 connections on the map. Select a topic to read its page.
Gut and digestive system includes
A large reservoir of microbes, such as bacteria, lives within the large intestine.
Source: Better Health Channel (Victorian Government), Digestive system explained
The liver makes bile, which is stored in the gall bladder and helps break down dietary fats.
Sources: Better Health Channel (Victorian Government), Liver; Better Health Channel (Victorian Government), Digestive system explained
The pancreas adds digestive juices and enzymes to food through a small duct into the duodenum.
Sources: Better Health Channel (Victorian Government), Pancreas; Better Health Channel (Victorian Government), Digestive system explained
Nutrients are absorbed through the lining of the small intestine, which has millions of finger-like projections called villi.
Source: Better Health Channel (Victorian Government), Digestive system explained
Gut and digestive system is linked with
The gut's mucous lining contains antibodies, and stomach acid can kill most microbes.
Source: Better Health Channel (Victorian Government), Immune system explained
- Serotonin Emerging
Gut microbes produce many brain chemicals, but there is no conclusive evidence that serotonin made by gut microbes reaches the brain.
Source: Australian Academy of Science, Gut bacteria: the inside story
Stress can affect digestion, according to healthdirect.
Source: healthdirect Australia, Stress
Gut and digestive system is affected by
Heartburn happens when acid from the stomach rises up into the oesophagus.
Bowel cancer starts in the inner lining of the bowel wall.
Source: Better Health Channel (Victorian Government), Bowel cancer
Gut and digestive system is controlled by
The bowel has its own nervous system. The parasympathetic system stimulates digestion and the sympathetic system slows it.
Source: InformedHealth.org (IQWiG), NCBI Bookshelf, In brief: How does the nervous system work?
Medicines and supplements
General education only. Never start, stop or change a medicine without your prescriber.
Sources
- Digestive system explained
- In brief: How does the nervous system work?
- Immune system explained
- Liver
- Bloating
Each connection above names its own source. See every source AskBioMap uses.
Summarised from the Better Health Channel and InformedHealth.org. Sources read on 13 and 16 October 2026. General education only, not medical advice. Spotted a mistake? Please tell us through the HuBu-Intel contact page.