The Digestion Process (Organs and Functions)

The digestive system involves organs that turn food into energy and eliminate waste.

The energy required for all the processes and activities that take place in our bodies is derived from the foods we ingest. The digestive system allows us to take food from such diverse sources as meat from an animal and the roots of a plant and utilize them as an energy source. Whether it is the ability to coordinate the chewing of food without injuring our tongue and lips or the propulsion of the food from the stomach into the duodenum while releasing the appropriate enzymes, our digestive system allows us to manage the process without much thought and often while performing other tasks.

The process of digestion is a fascinating and complex one that takes the food we place in our mouths and turns it into energy and waste products. This process takes place in the gastrointestinal tract, which is a long, connected, tubular structure that starts with the mouth and ends with the anus. The food is propelled forward within the system, altered by enzymes and hormones into usable particles, and absorbed along the way.

Other organs that support the digestive process are the liver, gallbladder, and pancreas. The time it takes for food to travel from entering the mouth to be excreted as waste is around 30 to 40 hours.

The mouth is the entry point for food.

The mouth is the entry point for food, but the digestive system often gets ready before the first piece of food even enters our mouth.

Saliva is released by the salivary glands into our oral cavity when we smell food. Once the food enters the mouth, chewing (mastication) breaks food into smaller particles that can be more easily attacked by the enzymes in saliva. Our teeth can perform a cutting as well as grinding function to accomplish this task. The tongue assists in mixing the food with the saliva and then the tongue and roof of the mouth (soft palate) help move the food along to the pharynx and esophagus.

The pharynx (throat) is the transition area from the mouth to the esophagus. From the pharynx there are two paths that the food bolus can take, including:

1. The wrong path, which is down the windpipe (trachea) into the lungs
2. The correct path into the esophagus and then the stomach

The act of swallowing is a complex process that closes the windpipe (to protect our lungs) and moves food into the esophagus. This process is mostly automatic (reflex) but it is also partially under our direct control.

Once it enters the esophagus, food is moved down the esophagus and into our stomach. The esophagus is a muscular tube that contracts in a synchronized fashion (peristalsis) to move food down towards the stomach. While the muscles behind the food product contract, the muscles ahead of the food relax, causing the forward propulsion of the food. Peristalsis is the main mechanism by which food moves through our digestive system.

Once the food approaches the stomach, a muscular valve (the lower esophageal sphincter) relaxes and lets the food pass into the stomach. This sphincter has the important function of closing the stomach so no food or stomach acid reenters the esophagus (and therefore avoids heartburn or regurgitation).

Illustration of the stomach and intestine.

From glands that line the stomach, acid, and enzymes are secreted that continue the breakdown process of the food. The stomach muscles further mix the food. At the end of this process, the food you placed in your mouth has been transformed into a thick creamy fluid called chyme.

This thick fluid is then pushed into the duodenum (the first part of the small intestine). With the help of enzymes from the pancreas and bile from the liver, further breakdown of the food occurs in the small intestine.

The small intestine has three segments:

• The first segment is the duodenum where the further breakdown of the food takes place.
• The next two parts of the small intestine (jejunum and ileum) are mostly responsible for the absorption of nutrients from processed food into the bloodstream through the walls of the intestine.

After the small intestine, the leftover waste leaves the upper gastrointestinal tract (upper GI tract) which is made up of everything above the large intestine and moves into the large intestine or colon (the beginning of the lower GI tract).

Illustration of the digestive system. Anatomy of colon and rectum.

The role of the lower GI (gastrointestinal) tract is to solidify the waste product (by absorbing water), store the waste product until it can be evacuated (going to the bathroom), and help with the evacuation process.

The large intestine (colon) has four parts:

1. Ascending colon
2. Transverse colon
3. Descending colon
4. Sigmoid colon

All together the colon is approximately 7 feet long and connects to the rectum. Here as in most other parts of the GI system, the waste product is moved along by peristalsis. As the waste product passes through the colon, water is absorbed and stool is formed.

The stool from the colon is stored in the rectum. The anal sphincter provides control over releasing stool or holding it. Once stool arrives in the rectum, feedback to the brain makes the person aware of the need for a bowel movement. Voluntary control over the anal sphincter lets us hold the stool until we go to the toilet.

The liver produces bile for fat digestion and elimination.

Three other organs are instrumental in the digestive process.

1. Pancreas: Although the pancreas is mostly known for its blood sugar regulatory function with the production of insulin (as part of the endocrine system -- insulin goes directly from the gland into the bloodstream), it is the main producer of digestive enzymes as part of the exocrine system (the enzymes produced by the gland pass through a duct into the intestines). These enzymes are released into the duodenum and help with the digestion of fats, proteins, and carbohydrates.
2. Liver: The liver produces bile for fat digestion and elimination. In addition, nutrients are stored in the liver, and toxins and chemicals are filtered by the liver.
3. Gallbladder: Bile is stored and released from the gallbladder. When fatty food enters the duodenum, the gallbladder contracts, and releases bile.

Annually about 70 million Americans are impacted by digestive system diseases. These can include indigestion, gastroesophageal reflux disease (GERD), and irritable bowel syndrome (IBS). Indigestion is a common sign of digestive issues. It describes discomfort in the abdomen and feeling immediately full after beginning to eat. It can be a symptom of numerous concerns. Everyone may experience indigestion differently. The symptoms can appear occasionally or even daily.

Numerous factors affect gut health. This includes body makeup, family history, and genetic history. These are things you cannot control, but there are factors you can influence, such as diet and stress. A healthy gut has a healthy balance of bacteria that help the body process food. A healthy gut can:

• Clear toxins
• Get energy from the foods you eat
• Boost your mood
• Fight against disease

When your gut is healthy, you will seldom encounter signs like constipation, gas, and bloating.

Sometimes, your digestive system may not be working as it should, causing issues like indigestion and more. Some of the things that should tell you that you have a problem with your digestion include:

• Bloating
• Stomach ache
• Feeling like your stomach is full
• Feeling sick
• Belching
• Passing gas
• Acid reflux (a bitter fluid or food coming back up to your mouth)
• Heartburn (getting a burning sensation in your chest, mostly after eating)

Eating certain foods can help improve digestion, such as:

• Whole grains. Whole grains (like brown rice and brown bread) contain more fiber and nutrients than refined grains and food made with them (like pasta, white rice, and white bread). The “good bacteria” found in your gut ferment the fiber in whole grains and produce short fatty acids that keep the colon cells healthy. Fiber helps your digestive tract work more efficiently. Whole grains also contain essential nutrients like omega-3 fatty acids.
• Low-fructose fruits. High-fructose (fruit sugar) fruits such as mangoes, apples, and pears can cause gas and bloating. Consider low-fructose fruits such as oranges, berries, and grapefruit to avoid these issues. Their low fruit sugar content is easier for your gut to digest. Other fruits like bananas contain huge amounts of fiber and a substance called inulin, which promotes the growth of good gut bacteria.
• Green leafy vegetables. Green leafy vegetables such as kale or spinach contain high fiber content and nutrients like folate and vitamins A, C, and K. These leafy vegetables promote the growth and efficiency of the gut bacteria involved in digestion.
• Avocados. Avocados are known to have numerous health benefits. They are also low-fructose fruits and contain a lot of fiber. Avocado is easy for your stomach to tolerate and helps avoid gas. High fiber and potassium content promotes digestion and the health of your digestive tract.
• Lean protein. Lean proteins contain lower fat content than fatty meats. That makes lean protein a healthier option. This type of protein is preferred for people with bowel sensitivity or internal bowel syndrome. Red meats (beef, pork, and lamb) often have a high fat content that can cause colon contractions.

Implementing some lifestyle changes can improve digestive efficiency. These changes include regular physical exercise, avoiding extremely spicy food, and drinking adequate fluids.

• Exercise. Regular physical exercise helps move food and waste efficiently through your gastrointestinal tract. Consider activities as simple as walking weekly. Making this part of your routine may help you keep your digestive system healthy.
• Avoid excessively spicy food. While many people prefer spicy food, others may experience stomach upset, heartburn, or even diarrhea after eating spicy food. If you are one of them, try to avoid foods that contain spices like chilies, garlic, and onions.
• Drink adequate fluids. Always make sure that you drink enough fluids, especially water. Fluids help promote the transport of waste through your digestive tract. It also helps to make your bowel movements softer. The fiber absorbs moisture making it easier to pass stools without causing constipation. Try to avoid drinks containing caffeine. Caffeine is known to cause heartburn.

Other tips that you can use every day to improve your digestion include:

• Try to eat about five fruit and vegetable servings daily. Try getting adventurous when it comes to choosing fruits and vegetables. Choose different colors and kinds, as many as you can find.
• Choose healthier cooking methods. Use moist cooking methods like stewing, steaming, braising, poaching, boiling, or microwaving when you cook. These methods are healthier options than frying with oil and grilling. Also, always make sure you thoroughly cook meat to reduce the risk of bacterial contaminants like salmonella.
• Eat foods that contain probiotics. Probiotics are “healthy bacteria” that help prevent the development of “unhealthy bacteria” in your gut. The good bacteria also produce chemicals that keep the gut working efficiently.
• Develop a routine. Consider eating around the same time every day. Your gut may work better if you implement an eating schedule.
• Try eating smaller portions. Eating in moderation promotes digestion by not overfilling the stomach. Overeating may lead to reflux. The food you've eaten may even come back up.
• Keep consumption of sugary and fatty foods at a minimum. Try to eat foods that are low in sugar to avoid the gut issues that may be caused by sugar. Sugars can cause bloating and damage to the gastrointestinal tract after consumption for a long time. Also, avoid animal fats (like poultry skin) and high-fat dairy (like cheese and butter).
• Eat properly. When eating, make sure that you chew your food well before swallowing. Proper chewing may prevent consuming a lot of air, thus, helping your body to sense better whether you are full.
• Manage stress. Stress can make it harder for your body to execute the process of digestion. To avoid this, try to find healthy ways to manage your stress. Consider methods like breathing, exercise, relaxation, and mindfulness.

Having digestive issues such as gas, diarrhea, heartburn, and constipation from time to time is normal. However, if these conditions happen more frequently, they may have huge effects on your lifestyle.

If you are experiencing symptoms like chronic pain and suspect you may have a digestive disorder, call your doctor for medical attention. This can be during your annual physical or at a problem-focused visit specific to your indications. Mention your bowel habits and any recurrent stomach issues. Speak about your pain rating, any recent lifestyle and diet changes, and future goals.

Some GI symptoms can be resolved simply; others can be serious and ultimately affect your quality of life. The sooner you are diagnosed, the sooner treatment can begin.