Functions of the Digestive System
The digestive system is roughly 30 feet long. The digestive process is complex, involving a series of organs and substances that aid in the breaking down of food and the absorption of nutrients.
Digestion is the process by which your body turns the food you eat into nutrients that are used for energy, growth, and cell repair. It is one of the key metabolic processes, and involves a complex series of organs that move food through the digestive system so it can be broken down and absorbed by the body.
When food is digested, it must be broken down into smaller molecules so nutrients can be absorbed. The body breaks food down into four main types of molecules, depending on the composition of the food, which you may be familiar with as the sources of nutrition.
• Carbohydrates: Sugars, starches, and fiber are all examples of carbohydrates. Simple carbohydrates, which have a simple chemical structure, can be found naturally in fruits, vegetables, dairy products, and as sugar that is added to food. Complex carbohydrates, which have a more complex chemical structure, are starches and fiber that may be found in starchy vegetables and whole-grain products.
• Protein: Proteins are comprised of smaller molecules called amino acids, which the body absorbs through the digestion of meat, eggs, and beans.
• Fats: Some fats are healthier than others, but fat molecules may help the body absorb vitamins, and can be a source of energy. Certain oils, such as olive oil or sunflower oil, are examples of healthy fats, whereas butter and greasy snack foods are less healthy fats.
• Vitamins: Every vitamin has a different role in the body’s growth and health. Vitamins are classified by the fluid in which they dissolve: all the B vitamins and vitamin C are water-soluble, and vitamins A, D, E, and K are fat-soluble.
The Physiology of the Digestive System
The process of digestion is very complex. Digestion is the metabolic process that converts foodstuffs within the body for use. The process begins in the mouth, where it is chewed and mixed with saliva to prepare it for swallowing. After swallowing, the food is pushed through the esophagus, which transports it to the stomach, where it is further diluted and mixed with enzymes, breaking down the food to be absorbed in the intestines. Most of the absorption process begins to take place in the small intestine. Macronutrients, minerals, vitamins, trace elements and water are absorbed here before reaching the colon. The nutrients pass through the small intestine’s wall, which contains small, finger-like structures called villi. The blood, which contains the absorbed nutrients, is carried away from the small intestine and goes to the liver for filtration, toxin removal and nutrient processing. The primary function here is regulation of blood glucose levels through a process of temporary storage of excess glucose that is converted in the liver to glycogen in response to insulin. The colon is the final step in the digestion process. The remaining water is reabsorbed in the colon as well as any substance that cannot pass through the villi such as dietary fiber. Digestion is a complex process, which is controlled by several factors. The gastrointestinal tract is also a prominent part of the immune system. The low pH (ranging from 1 to 4) of the stomach is fatal for many microorganisms that enter it. Similarly, mucus neutralizes many of these microorganisms. Other factors in the GI tract help with immune function as well, including enzymes in the saliva and bile. Because the typical diet consist of many foods unintended for digestion, maintaining a healthy digestive tract is important to the overall health of the body.
The digestive tract, primarily known as the gastrointestinal (GI) tract, is the portion of the digestive system that physically moves food through your body and absorbs nutrients. It is aided in breaking down this food by the liver, gallbladder, and the pancreas.
The GI tract is comprised of various tube-like organs, including:
• Esophagus: The esophagus connects your mouth to the GI tract; food passes down your throat, through this organ after you’ve chewed and swallowed.
• Stomach: The stomach is a muscular organ that stores food, and mixes it with digestive juices and enzymes (which we’ll talk about shortly) that further aid in breaking it down.
• Small Intestine: Food passes from stomach into the small intestine, where the majority of digestion and the absorption of nutrients takes place. Here, the small intestine mixes food with digestive juices from the pancreas and liver. Nutrients pass from the walls of GI tract into the bloodstream so they can be delivered to the body.
• Large Intestine: Whatever is left from digestion by the small intestine passes through the large intestine as waste. The large intestine absorbs any remaining water or nutrients, and excretes it as waste.
Digestion involves the movement of food through the GI tract, which, as you can gather, is a long process that requires the effort of several key organs. So, how does digestion work? The movement required to digest food is actually involuntary, which is how this process occurs without much conscious effort besides chewing – and deciding what you’re going to eat for lunch, of course!
The organs of the GI tract are hollow. The organs are lined with smooth muscle. The smooth muscle lining the esophagus, stomach, and intestines contracts to push food through the digestive system. This process of involuntary muscular contractions is known as peristalsis.
Along the way, digestive juices are used at each stage to break down food particles into smaller molecules. In addition to these juices, two other important substances are present in the digestive system: enzymes and probiotics.