Gastrointestinal Processes Focus: Large Intestine Operations
Article Title: The Unseen Heroes in Our Gut: The Large Intestine's Resident Bacteria
The large intestine, a crucial component of the human digestive system, plays a pivotal role in our health. Measuring approximately 1.5 meters in length and with an average diameter of about 6 cm, it is home to a vast and diverse community of bacteria[1].
This microbial population, numbering more than the cells in our body[2], perform a host of useful functions. They aid digestion by breaking down complex carbohydrates that escape digestion in the small intestine, fermenting these fibers into beneficial short-chain fatty acids (SCFAs) such as butyrate[3]. These SCFAs serve as energy sources for colon cells and have anti-inflammatory effects[1][2][4][5].
These gut microbes also produce vitamins like vitamin K and some B vitamins, metabolize bile acids which influence host metabolism, and generate signaling molecules that modulate gene expression and immune responses[2][3][4]. A balanced gut microbiota protects against harmful pathogens, thus maintaining gut barrier integrity and preventing infection or inflammation[1][2][3][4].
The interaction between different gut bacterial species affects microbial balance and health. For example, Faecalibacterium prausnitzii, a beneficial butyrate-producer, inhibits harmful bacteria implicated in inflammation and colon cancer, promoting a healthy gut environment[1].
The large intestine, consisting of the caecum, colon, rectum, and anal canal, absorbs most of the remaining water[6]. As the remnant food material moves through the colon, it is mixed with bacteria and mucus, and formed into faeces for temporary storage before being eliminated[7].
The 'second brain', a network of interconnected nerve cells lining the large intestine, is capable of directing messages to the brain and controlling the release of hormones that influence the movement of food down the gut, feelings of wellbeing, and the sensations of being hungry or of being full[8]. This new field of scientific research, known as neurogastroenterology, is helping to explain how diseases such as inflammatory bowel disease develop and how they can be prevented[9].
Most of these bacteria can only survive in oxygen-free environments and are referred to as anaerobes[10]. They ferment some of the undigested food components, converting them into SCFAs and releasing gases like carbon dioxide, hydrogen, and methane[11].
The ileocaecal valve controls the entry of material from the last part of the small intestine, called the ileum, into the large intestine[12]. Estimates suggest that there are approximately 500 species of different bacteria found inhabiting the adult colon[1].
Maintaining a healthy bacterial population in the large intestine is key to our sense of wellbeing[13]. The human appendix, while having no known function, is thought to be a remnant from a previous time in human evolution[14].
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- The diverse community of bacteria in the large intestine not only aids digestion but also produces vitamins like vitamin K and certain B vitamins, which are essential for overall health and wellness.
- The balance of bacteria in the large intestine plays a significant role in fitness and exercise, as it influences host metabolism, generating signaling molecules that modulate gene expression and immune responses, ensuring a healthy body and promoting a suitable environment for optimal exercise performance.
