The Digestive System: Beyond the Stomach

The Digestive System: Beyond the Stomach

The processes that happen to our digested food once it leaves the stomach are the most important as this is where the nutrients from the food we eat is absorbed.

human_digestive_systemBelow explains how all of the components beyond the stomach fit together and their roles within digestion. I have put words in bold that refer to the picture above.

 

The duodenum (pictured in between the gall bladder and pancreas)

is the start of the small intestine and regulates the entering of chyme (stomach contents). As chyme enters it stimulates the release of cholecystokinin (no idea how to pronounce this one but all we need to know is that it is a hormone) secreted by cells in the duodenum.

As a result of this hormone the gall bladder, which stores bile that has been made in the liver, empties itself almost completely when it gets this message that food is arriving from the stomach. Between meals, it only lets out a dribble of bile. The bile travels down the bile duct to the duodenum. The pancreatic duct meets it there through a ring of muscle, or sphincter, controlling the release of bile pancreatic fluid into the duodenum.

The duodenum occupies a key position in the digestive system, linking the upper part of the mouth, gullet and stomach with the bowels. It lies just above the navel in a circle hugging the head of the pancreas. It also has a key role in the digestive process, as food arriving from the stomach is only half-digested so this is where essential digestion takes place. This includes starches and fats in particular but proteins are also incompletely digested. Fats at this point are virtually unchanged, it is only when it reaches the duodenum the digestion of fats can actually begin.

Digestive enzymes made in the pancreas, and bile manufactured by the liver, are both poured onto the part-digested food in the intestine, in response to an electro-chemical signal that fatty food is on its way.

First, bile acts on the fats in the food, breaking them down, then pancreatic enzymes, complete the digestion of the remaining starches, fats and proteins.

The enzyme lipase from the pancreas emulsifies the fats, breaking down the fat globules (known as lipids made up of fats and oils) into smaller globules (these are known as fatty acids and glycerol). Bile completes this process. It is only when globules are microscopically small that they can be absorbed into the bloodstream. If this does not happen fatty diarrhoea will be a result.

Which brings us onto the middle part of the small intestine is the jejunum. Villi increase the surface area inside the jejunum, these finger-like projection are one cell thick with a good blood supply, designed to easily absorb digested food molecules quickly into the blood stream by diffusion. (Going back to my GCSE Science here!)

The final section of the small intestine is the ileum. Any further products of digestion are absorbed here and due to the bigger pores so can vitamins such as vitamin B12, minerals and salts. The main difference is the high abundance of lymphoid tissue, this is part of the immune system to protect the body from invasion in the gut. Our digestive tract has the largest mass of lymphoid tissue in the body and is key to protecting us from infection.

Fibre, water and vitamins carry onto be broken down further in the large intestine. Water that has been used in the digestion process is now reabsorbed in the colon and any undigested food and fibre is sorted in the rectum which is then eliminated through the anus (and we all know what happens here).


There’s a ton of more processes and I have tried to keep it as informative but also understandable for anyone to read as well. I hope this gives you an insight into how amazing our digestive system is and how important it is to treat it well and with respect.

Join in the conversation by commenting below and following on Facebook and Twitter. Let’s educate ourselves on digestive health and support others to Find a Friend in Food.

Difference between Food Allergy and Food Intolerance

Both a food allergy and intolerance can make your body sensitive to a particular food or ingredient causing unwanted physical reactions whenever you eat the foodie culprit.

Only 2% of the adult population have a food allergy, where as 45% have a type of food intolerance.

Food allergy occurs when an antigen or trigger in the food reacts with specific immunoglobulin (also known as antibodies) in the immune system, as your body recognises the food as a foreign substance (allergen) when eating the food for the first time.

When you eat the offending food again, the antibodies attack the allergen, producing histamine and other chemical, setting off various types of symptoms.

Some foods are also naturally high in histamines. These include aged and fermented foods and alcohol (especially red wine), some people are sensitive to these types of foods.

‘Histamine poisoning’ can happen if you eat fish not kept at safe temperatures and has spoiled before you ate them. Those fish can build up high levels of histamines, which can make you sick.

Anaphylaxis is the most dangerous kind of an allergic reaction, involving the breathing and circulation, and causing faintness and shock, with a fall in blood pressure and in serious cases can lead to death (nut allergy, for example). Symptoms of food sensitivity include swelling of the lips, diarrhoea and vomiting. You may have eczema, a very runny nose or asthma.

Usually the reaction is acute and immediate, but it may be delayed, as in the case of coeliac disease (gluten being the allergen).

A food allergy can be tested by a patch test or blood test from your local doctors.

Food intolerance reactions are not caused by the immune system but is brought about by other mechanisms. For example, a milk intolerance (lactose intolerant) is due to a lack of a particular digestive enzyme, lactase.

Some active chemicals may be present in the food causing a reaction, such as caffeine, causing a racing heart and tremor. Some suffer from food additives provoked by hypersensitivity.

The timing of these symptoms vary, swelling tissues, vomiting and a runny nose appear within one hour. Rashes and diarrhoea may take longer, 2-24hours. Some disorders, headaches and irritability, may last for several days.

Long term problems relating to food include irritable bowel, hyperactivity disorder and migraine.

A food intolerance causes different reactions for different people so there is no definite test to find out your food intolerance. Monitor what you are eating and how it makes your body react and always seek professional advice from your local doctor.

In some cases, weeks or months of elimination of the intolerant food may well lead to reintroduction of the food without a reaction, as your body learns to build up a tolerance.


For further reading please see here there is a wealth of free food fact sheets on the Association of UK Dieticians website, all very useful and available here.