How does the Digestive System Work?

The digestive system is the main functional system in the human body. It helps provide essential energy and nutrients in our body by performing ADME (Absorption, Distribution, Metabolism, and Excretion) of the foods, drinks, or anything we ingest.

In other words, the digestive system is a series of responsible organs that help to produce energy and digest foods in a human body.

Organs of the Human Digestive System

Several functional and auxiliary organs are involved in the digestion of foods. Organs of the upper and lower gastrointestinal tract are directly involved in the digestion process.

• Upper Gastrointestinal Tract: Mouth, teeth, tongue, pharynx, esophagus, and stomach.
• Lower Gastrointestinal Tract: Small intestine, large intestine, and anus.

Auxiliary Organs: Liver, pancreas, and gall bladder are also part of the digestive system, but as they indirectly involve in digestion, they're considered as auxiliary organs.

How the Digestive System Works?

1. Mouth and Pharynx: When food enters into the mouth, it mixes with saliva. As the teeth break down the food into small particles, the saliva starts to dissolve the particles to form a watery mixture. The tongue then forces back these particles into the throat (pharynx).
2. Swallowing Reflex: Particles in the pharynx stimulate the swallowing reflex. As a result, the larynx is called upward to connect with the epiglottis and block off the trachea.
3. Esophagus and Stomach: The crushed food drives from the larynx to the esophagus and travels down the esophagus by peristalsis. As the peristaltic wave touches the esophageal sphincter, these particles enter into the stomach. In the stomach, hydrochloric acid and other digestive enzymes break down the food into smaller pieces and release nutrients. These thick, smaller semifluid mass of partly digested food is called chyme.
4. Small Intestine: From the stomach, the chyme passes through the pyloric sphincter and enters the small intestine (duodenum). Bile from the liver and digested enzymes from the pancreas enter the duodenum to aid in digestion. The small intestine consists of three parts: duodenum, jejunum, and ileum. Most of the tasks of absorption, distribution, and metabolism are done in the small intestine. Absorbed nutrients pass from the lumen of the small intestine into the blood and lymph.
5. Large Intestine: Finally, the undigested particles from the small intestine go to the ileo-cecal valve and move into the colon or large intestine. The undigested residue passes through the cecum, ascending colon, transverse colon, descending colon, and sigmoid colon. The colon of our digestive system:
   • absorbs water,
   • produces vitamins and mucous,
   • forms stool, and
   • defecates feces
6. Rectum and Anus: The rectum stores feces until nervous stimulation initiates the defecation reflex, resulting in elimination through the anal canal.

Common Misconceptions About the Digestive System

1. Myth: Digestion only occurs in the stomach.

   • Fact: Digestion begins in the mouth with the help of saliva. The process continues throughout the gastrointestinal tract before ultimately concluding in the large intestine.

2. Myth: Drinking water during meals hampers digestion.

   • Fact: Drinking water during meals can actually aid digestion by helping to break down food and move it smoothly through the digestive system.

3. Myth: Spicy foods cause ulcers.

   • Fact: Spicy foods may irritate an existing ulcer, but they do not cause ulcers themselves. The bacterium Helicobacter pylori often causes the most ulcers. Long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs) may also lead to ulceration.

Tips for Improving Digestive Health

• Follow a balanced diet that helps your digestion.
• Drink plenty of water throughout the day.
• Exercise regularly to promote healthy digestion and prevent constipation.
• Avoid overeating and eat smaller, more frequent meals.
• Limit the intake of processed and high-fat foods.
• Perform relaxation techniques like meditation or yoga to manage stress.

Final Thoughts

By understanding the complex process of digestion and addressing common misconceptions, we can better appreciate the essential role our digestive system plays in maintaining overall health. Follow the practical tips provided in this article to improve digestive health and support the proper functioning of this vital system.

Resources and Further Reading

• Ogobuiro I, Gonzales J, Tuma F. Physiology, gastrointestinal. InStatPearls [Internet] 2021 Apr 25. StatPearls Publishing.
• Sensoy I. A review on the food digestion in the digestive tract and the used in vitro models. Current research in food science. 2021 Jan 1;4:308-19.
• Cheng LK, O'Grady G, Du P, Egbuji JU, Windsor JA, Pullan AJ. Gastrointestinal system. Wiley Interdisciplinary Reviews: Systems Biology and Medicine. 2010 Jan;2(1):65-79.