Summary
The digestive system is the body's complex network of organs and processes that are essential for the absorption of nutrients. It works in a north-to-south pattern, from the brain to the rectum, where each step is essential to ensure optimal breakdown and absorption of nutrients. This article provides a comprehensive review of the entire digestive process, including mechanical and chemical processes, as well as the importance of a healthy intestinal flora. Furthermore, we explore how imbalances in the digestive system can lead to health problems such as reflux, malabsorption, dysbiosis and chronic inflammatory diseases. Studies show that a well-functioning digestion is the key to overall health, and that every single component, from enzyme production to gut bacteria composition, plays a decisive role in this process
The digestive system and its importance for health
Digestion is a complex process that involves several organs and systems in the body. To understand how important digestion is to health, we need to look at each individual component and its function in the system.
The brain and the digestive response
Digestion does not start in the stomach, but in the brain. When we see, smell or even think about food, the parasympathetic nervous system is activated, which stimulates saliva secretion and prepares the stomach to produce stomach acid and digestive enzymes. This phase is called the cephalic phase of digestion. Without this initial stimulation, the body may have difficulty producing sufficient stomach acid and enzymes to effectively digest food.
The mouth – the first step in digestion
The food is mechanically chewed by the teeth, and mixed with saliva that contains the enzyme amylase. Amylase starts the first breakdown of carbohydrates, so that digestion can take place more efficiently further in the system. Saliva also contains lysozyme, an enzyme that helps kill harmful microorganisms and protect against infection. Poor chewing function can negatively affect the entire digestive process and lead to insufficient nutrient absorption.
The esophagus and peristaltic movements
When we swallow food, it moves through the esophagus using peristaltic movements, which are rhythmic contractions of the muscles in the esophagus. At the end of the esophagus is a small muscle valve called the lower esophageal sphincter, which opens to let food down into the stomach and then closes to prevent reflux. If this valve is weakened, acid from the stomach can leak into the esophagus and cause heartburn and GERD (gastroesophageal reflux disease).
Stomach – chemical digestion begins
When food reaches the stomach, it is mixed with stomach acid and enzymes such as pepsin, which break down proteins into smaller peptides. The stomach acid also helps to kill bacteria and other pathogens that may have entered the body via the food. If the body does not produce enough stomach acid, this can lead to poor protein digestion, reduced absorption of minerals such as iron and zinc, as well as an increased risk of bacterial infections in the gut.
Duodenum – further breakdown of nutrients
When the food has turned into a semi-liquid substance called chymus, the pyloric sphincter opens and lets it into the duodenum (duodenum). Bile from the liver and digestive enzymes from the pancreas are added here. Bile helps emulsify fats so they can be more easily broken down and absorbed, while the pancreas secretes enzymes such as lipase, amylase and proteases to complete the digestion of fats, carbohydrates and proteins.
The liver, gallbladder and pancreas – important players in digestion
The liver produces bile, which is stored in the gallbladder and released when fat enters the duodenum. The pancreas produces digestive enzymes and bicarbonate, which neutralize the stomach acid and provide optimal conditions for enzyme activity in the small intestine.
The small intestine – the main site of nutrient absorption
The small intestine has millions of microvilli, tiny protrusions that increase the surface area for nutrient absorption. Here, vitamins, minerals, amino acids and fatty acids are absorbed into the blood and distributed to the cells in the body. Disturbances in the function of the small intestine, such as celiac disease or SIBO (small intestinal bacterial overgrowth), can reduce nutrient absorption and lead to health problems.
Colon – recycling of water and production of short-chain fatty acids
In the colon, water is reabsorbed, and fiber is fermented by gut bacteria to produce short-chain fatty acids such as butyrate, which are important for gut health and inflammation regulation. The large intestine also plays a crucial role in the production of vitamin K and certain B vitamins.
The influence of intestinal flora on health
A healthy intestinal flora contributes to a strong immune response, regulates inflammation and affects mental health. Imbalances in the intestinal flora, known as dysbiosis, are linked to autoimmune diseases, metabolic disorders and neurological disorders.
References
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Gill, S.R., et al. (2006). Metagenomic analysis of the human distal gut microbiome. Science, 312(5778), 1355-1359
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Sekirov, I., et al. (2010). Gut microbiota in health and disease. Physiological Reviews, 90(3), 859-904
