We all have a digestive system, but we usually don’t like to talk about it. Yet even still, digestive problems are quite common in the United States. In fact, according to the National Institute of Diabetes and Digestive and Kidney Diseases (a division of the NIH), about 70 million Americans are affected by some type of digestive disorder each year. That also means tens of millions of visits to doctors’ offices and hospitals as well as disruptions to one’s quality of life. In a surprisingly large number of these cases, though, the disorder can be prevented or adjusted for. The first step is to understand more about how the digestive system works.
What is the Purpose of the Digestive System?
All body systems are crucial for life, of course, but the digestive system is important because it is the means by which we acquire all the energy—or fuel—needed to continue functioning. In the simplest terms, the digestive system takes ingested food and processes it into energy that can be used by all the cells in the body. The digestive system also then gathers anything left over from that process and eliminates it from the body as waste.
In definition digestion is simple, but in practice it is a complex process with many different parts (and likewise many different things that “malfunction”). The gastrointestinal tract makes up the majority of the digestive system and includes the mouth, esophagus, stomach, small intestine, large intestine, and anus. In addition to the GI tract, the liver, pancreas, and gallbladder contribute various digestive juices that all aid in the process of breaking down food and absorbing nutrients into the bloodstream.
As noted, one of the most important functions of the digestive system is to turn the fats, carbohydrates, and protein found in food into energy in the form of glucose; additionally, excess glucose is stored as fat for future use. Yet providing energy to be used by cells isn’t the only goal of digestion. Food also contains crucial vitamins, minerals, and other nutrients that are vital for body growth and repair. Through the digestive process, the body extracts what it needs and excretes the remnants along with other waste products (such as old or damaged cells).
How Does Digestion Work?
The basic function of the gastrointestinal tract is to take whole food and break it down into smaller and smaller parts through successive sections of the system. This is largely achieved through a process known as peristalsis, a series of contractions in the smooth muscle that surrounds most of the GI tract. These peristaltic contractions, along with enzymes from digestive juices, gradually move a mass of ingested food through the digestive system. This process is assisted by the enteric nervous system and a variety of hormones.
Mouth: The mouth is obviously the entry point for the digestive system, and the teeth and tongue are the first step in breaking down food. The teeth, aided by secretions from the salivary glands, mash and grind up the food into a swallowable mass so the tongue can push it down the throat (pharynx). A small flap of tissue called the epiglottis automatically covers the windpipe to prevent choking.
Esophagus: Once you’ve swallowed and the food enters the esophagus, the digestive process becomes automated all the way until the final act. Through gravity and peristalsis, the chewed food (known as a food bolus) makes its way down the esophagus and past the lower esophageal sphincter to the stomach; this sphincter muscle also closes automatically to prevent stomach contents from backing up into the esophagus.
Stomach: By the time the food bolus reaches the stomach, it has already been broken down quite a bit. The peristalsis process and stomach acid further break it down until it is mostly a liquid known as chyme. This material empties into the small intestine via the duodenum.
Digestive Juices: The duodenum is a transition point where the contents of the stomach are mixed with gastric juices from the liver, pancreas, and gallbladder. The combination of these elements mark the last main phase of breaking down food materials.
Small Intestine: In addition to helping break down any solids still remaining in the chyme, the gastric juices also contain digestive enzymes that help extract nutrients. The walls of the remaining sections of the small intestine (jejunum and ileum) absorb some water and the majority of the nutrients that the body will use. After the long journey through the small intestine, the remaining substance is primarily liquid waste materials.
Large Intestine: Though the waste material entering the large intestine is mostly liquid, it also can include indigestible food parts and even old cells from the lining of the GI tract. As peristalsis continues to move the material from the ascending colon to the transverse colon to the descending colon, most of the water is absorbed and stool begins to form. The stool comes together finally in the sigmoid colon and the rectum, where it awaits evacuation.
Anus: As stool is stored in the rectum, your conscious control comes back into the picture. A complex (and unconscious) process moves the stool through an internal sphincter until a signal is sent to the brain in the form of an urge to defecate. Sphincters in the rectum and anus then push out the stool during a bowel movement.
Digestive Health Considerations
Because of how complex the digestive system is, there are numerous ways it can get disrupted or become damaged. Two of the most common gastrointestinal problems are diarrhea and constipation. Both conditions are related to bowel motility, which is the relative speed with which waste materials move through the colon; higher than normal motility tends to cause diarrhea and lower than normal motility tends to cause constipation.
A wide range of gastrointestinal disorders crop up because of inflammation along the digestive tract. Heartburn, GERD, ulcers, and hemorrhoids are just a few examples of conditions that involve inflammation along the inner lining of the GI tract that can lead to a variety of symptoms and complications. Unfortunately, there are also several types of cancer that can occur in the digestive system; colorectal cancer is one of the most common examples.
Yet even though there are a number of possible problems that can occur in the digestive system, the truth is that many can be prevented through lifestyle choices. What you eat, how much physical activity you get, and your smoking and drinking habits are all important factors in maintaining digestive health. By being mindful of these choices now, you can prevent future digestive health challenges.
Contact Cary Gastro for More Info
At Cary Gastro, we are dedicated to providing high quality, compassionate digestive care to all our patients. If you have been experiencing symptoms related to your GI tract, or if you have general concerns about your digestive health, contact us to request an appointment.