The Digestive System: The Stomach

We continue our journey through the digestive system, we have already learnt about processes in inside the mouth and in the oesophagus.

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The Stomach

This is where our food now a bolus is exposed to hydrochloric acid produced by the stomach for further digestion. Our saliva is slightly alkaline, so why this change in pH? In this case not only does the acidity destroy potentially harmful microorganisms which could have been swallowed with our food but also different enzymes, which breakdown food, are more effective at different pH values.

The enzyme pepsin for example is produced in the stomach and works best at a low pH level, thriving in an acidic environment. Pepsin breaks down protein into smaller peptides, it is known as a protease enzyme because it does this process by hydrolysis of peptide bonds. The resulting product: peptides, short chains of amino acids (the basic building blocks of the human body and essential for a healthy body). Protein found in meat, eggs, dairy and seeds are broken down by the enzyme pepsin.

This mixture of acid and enzymes are mixed thoroughly by the stomach muscles, softening, sterilising and digesting protein, making the bolus into chyme.

The stomach has three types of contractions:
Rhythmic, 3 per minute, synchronized contractions in the lower part of the stomach which create waves of food particles and juice which splash against a closed sphincter muscle to grind the food down into small particles.
Slow relaxations in the upper part of the stomach lasting a minute or more that follow each swallow and that allow the food to enter the stomach; at other times the upper part of the stomach shows slow contractions which help to empty the stomach.
Between meals, after all the digestible food has left the stomach, there are occasional bursts of very strong, synchronized contractions that are accompanied by opening of the sphincter muscle. The function is to sweep any indigestible particles out of the stomach. Another name for them is the migrating motor complex.

Chyme can stay in the stomach for up to 2-4 hours, this depends on dilution of the stomach acid (this is why it is best to avoid having a drink while eating your meal) and the amount of food you have eaten.

There are certain types of foods you may want to avoid, to decrease the chance of inflammation to the stomach lining. These irritants include:

  • Acidic and Spicy Foods
  • Animal Milks – Milk products are thought to increase acid production.
  • Coffee, Carbonated Beverages, Alcohol and Certain Fruit Juices, such as Citrus Juices
  • High-Fat Foods
  • Highly Salted Foods – can damage the gastric mucosa: the mucous membrane layer of your stomach.
  • Junk Foods and Processed Foods – often contain chemicals that irritate the stomach lining as the are hard to digest and increase acid production

If you are experiencing gastritis (an inflamed stomach lining), causing symptoms of indigestion, stomach pain, vomiting and feeling bloated, you may want to take Antacids. These come in chewable and liquid form and counteract / neutralise the acid build up in your stomach to relive pain, but these shouldn’t be taken on a regular basis.

The best thing is to try and avoid the type of foods above.

I hope this helps and explains the complex processes that are happening within your stomach, if you have a question or would like me to expand on any part please let me know in the comments section below and I will do my best to answer.

 

 

 

 

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The Digestive System: The Oesophagus

human_digestive_systemIn my last digestive system post I mentioned the importance of chewing your food properly to help in the process of digestion: Read more here.

Chewing, physically and chemically breaks down your food. In Channel 4’s recent programme of #HowToLoseWeightWell one experiment looked into this and found the group that chewed their food more consumed less calories and felt fuller faster.

It also looked at how our saliva continues to break down food after it has left the mouth.

 

The Oesophagus

Once our food is swallowed it enters the oesophagus, also known as the gullet. This approx. 8 inches long muscular tube forces the food, now a rounded mass of food called a bolus, down towards the stomach using peristalsis. This is the process where the muscles in the wall of the tube massage the bolus by constricting and relaxing in waves pushing the contents on its way. It is a quick process taking 8-10 seconds, or less than 5 seconds using gravity if the body is in an upright position.

The oesophagus has two sphincter muscles at either end of the tube. The upper oesophageal sphincter (UES). The muscles of the UES are under conscious control, used when breathing, eating, burping, and vomiting. While keeping food and secretions from going down the windpipe.

The lower oesophageal sphincter (LES) is a bundle of muscles at the low end of the oesophagus, where it meets the stomach. When the LES is closed, it prevents acid and stomach contents from traveling backwards from the stomach. The LES muscles are not under voluntary control. An incompletely closed LES allows acidic stomach contents to back up (reflux) into the oesophagus. This acid reflux can cause heartburn.

An indication at this point that you have eaten something your body can’t deal with will be the muscles walls constricting and swelling, this can happen due to an allergic reaction. Another can be a burning sensation and warmth in the gullet immediately after swallowing, this can be felt in the effects of  alcohol, which is actually causing the gullet to become inflamed.


Find out about the stomach in the next post about the digestive system.

The Digestive System: Inside the Mouth

In my first post I mentioned listing foods as ‘safe’, ‘tolerable’ and ‘intolerable’ based on how your gut reacts to them and gave you a list of generally safe foods and avoidable foods to give you something to start adding meals around.

The type of foods you are eating may not be the only problem to your digestive system but there are ways we can prevent and reduce any inflammation and upset.

Our bodies work like a machine and when it works well everything is in perfect harmony; input, process, output. Together, a combination of nerves, hormones, bacteria, blood, and the organs of the digestive system completes the complex task of digesting the foods and liquids a person consumes each day.

So with that in mind, let’s see what ‘equipment’ (our organs) we have to work with.

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The image above is a typical one you will find for the digestive system but it is worth remembering the effects on your digestion happen before you even start eating.

To aid digestion and reduce the risk of any upsets make sure you are mentally ready to eat. If you are stressed or unhappy it is best to give yourself some time to unwind before having a meal. When ready sit upright, dining chairs are ideal, as this does not constrict your stomach activity. Now you are ready to eat…

The Mouth

Your mouth is the first indicator whether a food is okay to eat, along with your sense of smell, take gone off milk for an example. If you like the smell and taste of the contents then your saliva glands will produce the enzyme ptyalin (also known as amylase), this is used to breakdown carbohydrates, converting starchy food, like bread, into maltose; a sugar which can be absorbed immediately.

It is thought that less than 5% of all starches consumed are digested within the mouth, before being swallowed as most of the digestive changes occur later on. This is because starch is a type of complex carbohydrate, which means that it’s made of long chains of sugars called polysaccharides. Foods high in starch, such as potatoes and some other tubers and root vegetables, are not as easily digested as simpler carbohydrates such as fruit, baked goods and pasta.

Therefore to help with this process it is important to chew your food as much as you can, it is recommended up to 32 times, if possible. Chewing for longer means your meal will last longer, making you eat smaller portions, one reason for this could be the time taken for your brain to signal that the stomach is full. This usually takes around 20 minutes.

When large particles of improperly chewed food enter your stomach, it may remain undigested when it enters your intestines. There, bacteria will begin to break it down, or in other words it will start to putrefy, potentially leading to gas and bloating, diarrhoea, constipation, abdominal pain, cramping and other digestive problems.

To reduce these problems, take smaller bites and swallow what you have already chewed before taking another bite. To reduce the symptoms of wind and bloating, try not to take down air when drinking or swallowing food.

Look out for more updates about processes throughout the digestive system coming soon.