The importance of gut health
The health of the gut is vital for it to perform its function of digesting and absorbing food. Another important gut function is protection of the body from illness and infection. Impairment of the gastrointestinal barrier or disruption of the commensal bacteria increases the risk of gut-related disorders or infections but also extra-intestinal infections, as well as immune-mediated and metabolic disorders.
- Bischoff SC (2011) 'Gut health': a new objective in medicine? BMC Medicine 9:24
Did you know? The gut...
- Has a surface area of 300m2 (about the size of a tennis court)
- Uses 40% of the body's energy expenditure
- Contains 108 neurons
- Is where the majority of the immune system is located
The components of the gastrointestinal tract
1. The mouth - Seeing and smelling food starts the digestive process by increasing the flow of saliva in the mouth. Biting and chewing breaks up the food, mixing it with saliva containing amylase, which hydrolyses starch to dextrins and maltose.
2. The oesophagus - This muscular tube generates peristaltic waves to drive the bolus of food down to the stomach in about six seconds.
3. The stomach - Food is stored here for just a few minutes or up to a few hours. The gastric acid is not only a protection against pathogens but also helps to hydrolyse proteins to large peptides.
4. The small intestine - About six metres long and comprising the duodenum, jejunum and ileum. Fat is broken down further here, by the emulsifcation of large fat globules by bile to smaller ones, followed by hydrolysis to fatty acids and glycerol. The duodenum receives pancreatic secretions and bile, and produces an alkaline mucus for protection, lubrication and chyme neutralisation.The ileum is where most of the soluble products of digestion are absorbed. The vast surface area of this part of the gut helps ensure nutrients are absorbed quickly and thoroughly.
5. The large intestine - This is where the vast majority of the intestinal microbiota resides; these bacteria ferment undigested fibre and starch. Some vitamins (B and K) are synthesised colonic bacteria. Water is removed and reabsorbed in the colon. Faeces are stored in the rectum before explusion.
6. The pancreas - This secretes an alkaline pancreatic juice, which neutralises acid from the stomach and contains enzymes that break down protein, fat and carbohydrates. The hormones insulin and glucagon are also produced here.
7. The liver - This is the chemical factory and warehouse of the body, receiving nutrients from the blood for metabolism in different ways and storing nutrients such as vitamins A and B12. It produces bile, which is secreted via the bile duct to the gall bladder.
8. The gall bladder - This stores and concentrates bile, and delivers it to the small intestine when necessary.