The digestive system is the primary system that makes digestion happens.

The digestive system consists of the Gastrointestinal tract. That starts from our mouth and finishes in our anus. The mouth, pharynx, oesophagus, stomach, and small and large intestine. These organs have direct contact with foods, which will move through them in a length of 5-7 metres. 

Teeth, tongue, and salivary glands are placed in the mouth, while the liver, gallbladder and pancreas are located in our abdomen. They make accessories for the digestive system. Some of them are in contact with food others aren’t. 

What is digestion? 

The digestion process consists of a group of chemical processes that helps our bodies to get the nutrients and compounds we need and discard the one we do not need.

Digestion involves different stages and phases. 

• Cephalic phase. That is the first stage of digestion. This stage involves our senses and nerves. When we hear food crackling, like popcorn or coffee roasting or blending, when we see appealing foods or when we smell nice food flavours such as bakery products, one part of our brain, termed the brainstem, activates specific nerves. These nerves activate salivary glands and gastric juices to get ready for digestion. The cephalic phase is significant because it starts the processes of ingestion, secretory, and motility.
• The gastric phase is the second stage. During the gastric phase, our nervous and endocrine systems organise all the gastric juices, enzymes, hormones and processes that will help the food journey from the mouth to the stomach. That happens precisely after the Cephalic phase. 
• The intestinal phase is the last. While the cephalic phase promotes motility and secretion, this phase has an inhibitory role. Our digestive system will relax and slow down until the digestion process finishes. During this phase, different hormones will produce a sense of satiety, and consequently, we will stop eating. 

The gastric and intestinal phases comprehend the stage of digestion, absorption, and defecation. 

What does happens from mouth to anus?

In the mouth, mechanical digestion starts. As soon we put food in our mouth, we start chewing with our teeth, 32 in normal conditions. Our cheeks old the food inside our mouth, saliva moisture the food during mastication. Saliva contains an enzyme that breaks down carbohydrates to smaller molecule, and the tongue help to move the food inside the mouth. The tongue also pushes the bolo(chewed food) through the larynx and oesophagus, then to the stomach. Deglutition is the term that describes the movement of food from the mouth to the stomach. That happens by peristalsis. Peristalsis is a cycle of contractions and relaxation that moves food throughout the gastrointestinal tract. It can be voluntary and involuntary. It depends on which are of the GI we consider. Stomach and Intestines. Our stomach works like a blender. The stomach parietal cell, Chief cells and G cells produce gastric juices to absorb vitamin b12, break down proteins and stimulate motility and absorption. Other structures such as muscular and pyloric sphincter help with blending and moving bolo (food). The pancreas promotes the digestion process. It produces pancreatic juices that help in the stomach and intestines, where the process of absorption occurs.

We are ready to see what happens in the small and large intestines. Duo their properties, some food does not go to the small intestine, but the stomach walls absorb it and from here through the bloodstream, they quickly reach different are of the body. Some of these substances are smaller molecules of sugars, short chains of fatty acids and water.

In the small intestine, the bolo (far different from the food we have eaten) is a chime. Gastric juices and specific enzymes break down carbohydrates, proteins, fats, vitamins, minerals and other substances into smaller molecules. They are absorbed by the bloodstream and brought through the liver. The liver works like a dept for our bodies. It promotes energy production and recycles proteins. In the liver, we store an excess of nutrients in the form of glycogen. The liver also detoxes alcohol and other drugs. The last digestion stage occurs in the large intestine, forming the faeces and recycling water. 

Nutrients and Diseases

As we saw, all the nutrients we need are absorbed between the stomach and small intestine. Man cannot manufacture nutrients. We need to get them from food. The right amount of nutrients and exercise give us a happier and more extended life. It helps our bodies to stay healthy and shaped and reduce the risk of chronic diseases. Excess nutrients and wrong nutrients can lead to obesity and related diseases, while deficiency of nutrients leads to deficiency diseases. 

Malabsorption affects our digestion. Some of the problems related to malabsorption are flatulence, big belly, diarrhoea, vomit, and skin rash. Also, as lactose and gluten intolerance.

Research has shown that absorption of alcohol associated with other drugs and caffeine can lead to IBS (Irritable Colon Syndrome).

In other words, the best way to stay healthy is avoiding to introducing harmful compounds into our bodies.

Nutrition and wellbeing. 

On the other hand, an excellent diet with the proper nutrients will provide many benefits. Firstly, you will be surprised to know that there is the Enteric Plexus in the wall of the GI. That is a complex group of nerves associated with the spinal cord, and it has disparate functions. That explains the relationship between food and mood. A smart diet leads us to think smartly.

Along with that, our brain loves glucose, alcohol and caffeine. Duo their chemical composition, these compounds are quickly absorbed by the gastrointestinal tract wall and brought to the brain. That explains the feeling when we drink coffee or sugary drinks. A better diet means better focus and better mental health. More opportunities to look after ourselves, exercise, and do the most things we love.

Summary

Digestion occurs in different stages and phases. It occurs in the gastrointestinal tract and involves different systems and organs. Most of the nutrients are absorbed in the stomach and small intestine, while the large ones conclude the digestion, absorb water, and produce faeces. 

Having the correct daily intake of nutrients helps us live longer, stay shaped, and reduce the risk of long-term diseases. On the other hand, a bad diet can negatively impact our mental health and bodies.

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