The steps
Start in the gut
Your digestive tract breaks food down, absorbs nutrients and removes waste, with help from the liver and pancreas. The bowel even has its own separate nervous system. Notice how many lines leave this node.
Sources: Better Health Channel (Victorian Government), Digestive system explained; InformedHealth.org (IQWiG), NCBI Bookshelf, In brief: How does the nervous system work?
Meet your microbes
Between 30 trillion and 400 trillion microbes live in your gut, most of them in the large intestine. They break down food, make some vitamins and turn fibre into short-chain fatty acids.
Sources: Australian Academy of Science, Gut bacteria: the inside story; Better Health Channel (Victorian Government), Digestive system explained
The defence network
Your immune system defends you against infection and keeps a record of every microbe it has defeated, which is how immunisation works. In the gut, the mucous lining contains antibodies.
Sources: Better Health Channel (Victorian Government), Immune system explained; Better Health Channel (Victorian Government), Digestive system explained
The fast messengers
The brain and spinal cord form the central nervous system. Its automatic branches prepare you for activity or look after the body at rest, and the parasympathetic branch stimulates digestion.
Sources: InformedHealth.org (IQWiG), NCBI Bookshelf, In brief: How does the nervous system work?; Better Health Channel (Victorian Government), Nervous system
The slow messengers
Hormones are chemical messengers made by glands such as the thyroid, the pancreas and the adrenal glands. The hypothalamus helps control the pituitary, the master gland that regulates other glands.
Source: healthdirect Australia, Endocrine glands and their hormones
The delivery system
Your heart pumps blood to every part of your body, about 60 to 100 beats a minute at rest. Smoking, high blood pressure, high cholesterol and too little physical activity are among the risk factors for heart disease.
Sources: Better Health Channel (Victorian Government), Heart explained; healthdirect Australia, Coronary heart disease
Quiz
1. Where do most of your gut microbes live?
Answer: The large intestine. A large reservoir of microbes, such as bacteria, lives in the large intestine.
Source: Better Health Channel (Victorian Government), Digestive system explained
2. Which part of the nervous system stimulates digestion?
Answer: The parasympathetic nervous system. The parasympathetic nervous system stimulates digestion, while the sympathetic nervous system slows it.
Source: InformedHealth.org (IQWiG), NCBI Bookshelf, In brief: How does the nervous system work?
3. Which gland is called the master gland?
Answer: The pituitary gland. The pituitary is called the master gland because it regulates other endocrine glands, and the hypothalamus helps control it.
Source: healthdirect Australia, Endocrine glands and their hormones