From the moment you put a food or beverage into your mouth, it takes an exceptional journey through the body, from the mouth to the anus. On its way, it encounters several organs and processes, each of which breaks down the substance further to extract any nutritional value or energy your body may need to perform other vital functions. The organs and processes substances encounter make up what is called the digestive system. Every part of the digestive system is important, but some organs play larger roles than others.
Below is an overview of the digestive system’s function, what organs make it up and which organs shoulder the greatest responsibility.
The digestive system consists of the gastrointestinal tract and a series of organs, including the liver, gallbladder and pancreas. These organs are connected to each other via the mouth and anus, with the mouth being the first part of the GI tract and the anus being the last.
The digestive system is designed to turn food and drinks into the energy and nutrients your body needs to survive. When it harnesses all the nutrients possible out of a substance, it packages the remaining waste neatly into the form of stool, which your body extricates via a bowel movement.
Your digestive system processes food into the nutrients and energy your body needs to perform vital functions, making it one of the most important systems in the body. Not only that, but it cannot continue to accumulate waste, as doing so would turn the body toxic. The digestive system’s primary function is to breakdown and absorb nutrients — including proteins, carbohydrates, vitamins, minerals, fats and water — for the purpose of growth, energy and repairing cells. Anything that cannot be used effectively gets discarded as waste through faeces or urine.
The digestive system is made up of 10 distinct components. Below is a list of each component, in their order of function, along with a brief description of what they do.
The digestive tract and the digestive process both begin with the mouth. In fact, the digestive process begins before you place even a single crumb or drop in your mouth. When your brain senses you are about to eat, the salivary glands activate, producing saliva. Salvia mixes with the foods you break down with your teeth, making the particles easier for your body to absorb for use. When you are ready to swallow, your tongue pushes the food to the back of your mouth and into your oesophagus, where it continues on its journey through the second part of the digestive process.
Once you swallow, your oesophagus receives the food particles from your mouth. To prevent food or beverages from going into your windpipe, which is nearby, and therefore, the epiglottis folds over it as you swallow. A series of muscle contractions within the oesophagus help to deliver the food to the stomach.
However, before your oesophagus can deliver food to your stomach, the lower oesophageal sphincter — a ring-like muscle near the end of the oesophagus — must relax to let food in. At the same time, the sphincter must contract to prevent the contents from the stomach going back into the oesophagus, a phenomenon that contributes to heartburn and acid reflux.
The stomach is an empty organ that serves as a “container” of sorts for undigested food. Once in the stomach, it mixes with stomach enzymes, which effectively begin the process of breaking food down for nutritional and energy purposes. These enzymes are a by-product of a secretion of strong stomach acids and enzymes that come from the cells that line the stomach. Once the stomach contents are in a usable form, the stomach releases them into the small intestine.
The small intestine plays the largest role in the digestive process. Made up of three segments — the ileum, jejunum and duodenum — the small intestine is approximately 20-feet of muscle that breaks food down from mostly solid particles into a liquid substance. It does this with the help of water, enzymes from the pancreas, bile from the liver, mucus and an organ called the peristalsis — the latter of which is responsible for moving food through the small intestine and mixing it with the digestive fluids from the liver and pancreas.
The duodenum makes up the first part of the small intestine. This segment is primarily responsible for breaking food particles down into nearly liquid form. The jejunum and ileum are responsible for absorbing nutrients into the blood stream for the body’s use. Once most of the nutrients have been absorbed, the small intestine passes the residual liquid to the large intestine — also commonly called the colon.
The pancreas is the component that discharges digestive enzymes into the duodenum for the digestion of fats, proteins and carbohydrates. It also makes insulin, the principal hormone in the metabolization of sugars. Insulin passes directly into your bloodstream to help your body maintain healthy blood sugar levels.
The liver is responsible for over 500 vital functions. However, its number one job as a digestive organ, aside from providing bile to the small intestine for digestive purposes, is to process the nutrients that the small intestine absorbs.
Often referred to as the body’s “chemical factory,” the liver transforms the raw materials that the small intestine absorbs into the various chemicals your body requires for optimal function. It also detoxifies potentially harmful substances that could cause serious and/or long-term harm to your health, including drugs and alcohol.
The gallbladder stows and concentrates bile from the liver. When necessary, it then releases that bile into the duodenum for the digestion and absorption of fats.
The colon is another muscular tube that is approximately 6 feet in length. It connects the small intestine to the rectum and processes waste for easy excretion from the body.
The colon, like the small intestine, consists of several parts. Those include the cecum, the ascending (right) colon, the descending (left) colon, the traverse (across) colon and the sigmoid colon. The sigmoid colon is the part of the colon that connects the organ to the small intestine.
Residual waste from the digestive process eventually ends up in the colon. As this waste, or stool, moves through the colon in its liquid form, the colon removes water from it until it becomes mostly solid. Once in a solid form, the sigmoid colon — an s-shaped section of the organ — stores the stool until there is enough of it for a mass movement, a movement which ultimately empties the stool through the rectum. This typically occurs twice a day.
In most cases, it takes stool approximately 36 hours to make its way through the colon and out the rectum. In those 36 hours, the good bacteria from the food debris perform several beneficial functions, including the processing of waste products and food particles, synthesizing various vitamins and protecting the body against harmful bacteria. Once the descending colon becomes full of stool, it empties into the rectum for a process we know as a bowel movement.
The rectum is a straight, 8-inch segment that connects the colon to the anus. The rectum receives the stool from the colon and informs the brain that a stool is ready to be eliminated. Once the brain receives the message, it determines whether rectal contents are ready for release. If it determines that they are, the brain sends a message to the sphincters to relax. When this happens, the rectum contracts, a process that forces the stool out of the body. If the brain determines that rectal contents are not ready for elimination, it will tell the sphincters to relax, a movement that signals the rectum to accommodate the stool until there is enough for elimination.
The anus is the final part of the digestive system. The anus is a 2-inch-long canal that consists of two distinct parts — the anal sphincters and the pelvic floor muscles, otherwise known as the external and internal anus. The lining of the upper section of the anus can detect rectal contents. It tells the brain whether the contents are solid, liquid or gas and, therefore, what to do about them.
The sphincter muscles are responsible for controlling the contractions that either keep stool in or let it out. Without them, the body would release stool uncontrollably. The pelvic floor muscles create an angle between the rectum and the anus, an angle that keeps stool in when the body is not ready to release it. The internal sphincter’s job is to keep us continent, meaning “tight” until stool enters the rectum. Continence is necessary for preventing our bodies from expelling stool at inappropriate times.
The external sphincter allows us to keep stool in our rectums until we reach a toilet. Only once our brains send the signal will the external sphincter relax enough to release the contents.
Despite its name, the small intestine is actually rather large, at a whopping 22 feet long when unfurled. It is in this organ that most of the digestive process takes place, breaking nearly solid food waste into a liquid substance and then absorbing the nutrients from that substance into the blood stream for the body’s use. Almost everything that takes place before food waste enters the small intestine and after it exits, is minor compared to these functions.
If the small intestine fails to function properly, it can disrupt the entire digestive process. When the digestive process is disrupted, it can lead to discomfort, pain and whole-body health issues. Some disorders of the small intestine are temporary and may clear up with dietary changes. Others, however, are chronic and require treatment to resolve.
There are several conditions that may affect how the small intestine functions. Below are just a few of the more common disorders:
SIBO is often associated with other conditions, including IBS, diabetes and autoimmune conditions. For this reason, it is often difficult to diagnose and treat.
Some symptoms of small intestine disorders are so commonplace, most people would be unconcerned by them. However, others are more alarming, especially when they persist for more than one or two days. Common symptoms of small intestine disorders are as follows:
Though the first group of symptoms on this list may be unalarming and are likely to resolve themselves within just a few days, the latter group of symptoms should be cause for concern. Moreover, any of these symptoms, when persistent, should be enough to prompt you to seek medical attention and a diagnosis.
Because symptoms of small intestine disorders often resemble those of other, less concerning conditions, it may take even the most skilled doctor time to order appropriate tests and make a diagnosis. However, if your doctor does suspect a small intestine condition, he or she may order the following tests:
Treatment for small intestine disorders depends largely on the disorder in question. However, the most common treatment for disorders of the small intestine and the GI tract in general include lifestyle and dietary changes. Eating healthy foods and avoid processed foods, sugary foods and beverages, fatty substances and toxic substances can go a long way to preventing digestive disorders and clearing up existing ones.
That said, lifestyle and dietary changes do not always cure more intense conditions. Some conditions, such as celiac disease, may require you to avoid certain foods and substances for the rest of your life. Others, such as SIBO, may require antibiotics to clear up. Obstructions may require surgery for removal.
Keeping your digestive tract healthy is crucial for helping it function optimally. The best ways for maintaining a healthy digestive system and small intestine are as follows:
Some diseases of the small intestine are common and typically resolve on their own. Others, however, are more serious and may require medical intervention. Unfortunately, many of the symptoms of both serious and not-so-serious digestive conditions overlap, making detecting conditions based on symptoms alone difficult. For this reason, if you experience chronic gas, bloating, diarrhoea, stomach pain, constipation, nausea or vomiting, consult with your doctor right away. Your doctor can perform the appropriate tests to rule out certain conditions or detect others and come up with an appropriate treatment plan.