Digestion Explained! Heres How The Tummy Works, Literally

When we eat food or take a drink, multiple organs will swing into action to help turn that food into energy. These organs are collectively known as the digestive system. They work together to down foods and liquids into their primary nutrient components that are absorbable and usable by the rest of the body – think proteins, fats, carbs, fiber, etc. The body relies on these nutrients for powering essential mechanisms including cellular growth and repair. As such, a proper functioning digestive tract is vital for maintaining optimal health. 

This blog post will serve as a step-by-step guide that explains exactly how digestion works. 

What is the digestive tract?

The digestive tract is made up of numerous organs, which can be categorized into two groups: major organs and accessory organs.

Major organs of the digestive system

The major organs involved in digestion play a primary role in breaking down foods and liquids into smaller nutrients. Ultimately, the goal is to extract as many nutrients as possible so that the body can use them for energy.

Here’s a list of the major organs involved in digestion:

• Mouth
• Esophagus
• Stomach
• Small intestine
• Large intestine

Additionally, there are several organs that provide secondary support for specific digestive processes. These are called accessory organs. 

The liver, gallbladder, and pancreas are known as the accessory organs of the digestive system.

As you can see, the digestive system is more than just the stomach. It’s a group of organs that work harmoniously together to help break down foods and liquids. 

Step-by-Step Digestion Process

Six simple steps explain digestion from start to finish. Each one involves different major and accessory organs and are essential for the complete breakdown of foods and liquids. 

Step 1: Chewing 

Surprisingly, digestion actually begins in the mouth. In fact, it begins at the moment that you start chewing your food.

Chewing is a form of mechanical digestion. This mechanical process involves the teeth breaking down large food particles into smaller pieces. Simultaneously, saliva is released from the salivary glands to provide amylase, an enzyme that helps kick-start the breakdown of carbohydrates.

As food is chewed and mixed with saliva, it transforms into a soft mixture called bolus, a finely processed substance primed for easy swallowing.

Step 2: Swallowing & Peristalsis

As bolus is swallowed, it moves from the mouth to the esophagus, a muscular tube connecting the throat to the stomach. This movement relies on the coordination of various muscles in the mouth and throat, allowing the food bolus to move smoothly downward. 

As the bolus travels down the esophagus, a sphincter located at its upper end acts as a gateway, preventing the entry of air. This helps to guarantee that the esophageal pathway remains exclusively dedicated to the passage of food.

Once in the esophagus, the journey is propelled by a wave-like movement called peristalsis. Essentially, peristalsis pushes the food bolus down the esophagus using rhythmic contractions of the esophageal muscles. This sequential squeezing motion continues until the bolus reaches the lower esophageal sphincter, the final gateway to the stomach.

Step 3: Mechanical and Chemical Breakdown

Once the food bolus reaches the stomach, it will initiate the release of gastric juices. 

Gastric juices further break down food through chemical digestion. It is termed chemical digestion because the juices consist of hydrochloric acid and enzymes. These juices further break down the bolus into smaller, more absorbable components. As a result, the bolus turns into a more digested semi-liquid substance called chyme.

If you’re wondering, hydrochloric acid is what helps create an optimal acidic environment in the stomach. It also initiates the release of digestive enzymes such as pepsin, an enzyme crucial for the digestion of proteins. 

Simultaneously, the stomach engages in mechanical digestion by physically promoting churning and mixing movements via contraction of the stomach muscles. Chemical and mechanical digestion work in tandem to thoroughly break down the chyme and support the exposure of nutrients to the digestive enzymes. 

Step 4: Nutrient Absorption

After leaving the stomach, the chyme enters the small intestine. Think of the small intestine as a lengthy tube that primarily helps with nutrient absorption and further digestion. 

Here, the liver releases pancreatic enzymes and bile, exposing the chyme to essential digestive processes. Pancreatic enzymes, including amylase, lipase, and protease, act on carbohydrates, fats, and proteins, respectively. As a result, they are broken down into smaller, more absorbable compounds. At the same time, the liver produces bile, to help digest fats. 

The absorbed nutrients, now in their most absorbable forms, make their way into the bloodstream through the walls of the small intestine. This absorption process allows for nutrients such as glucose, amino acids, and fatty acids to enter the bloodstream, becoming readily available for distribution to cells throughout the body. 

Step 5: Passage Through The Large Intestine

Then, any remaining undigested material, now referred to as residue, makes its way to the large intestine. This transition marks the start of the final steps of digestion. 

The large intestine’s role is to focus on reclaiming water from the residue and consolidating the remaining indigestible substances into feces.

As the large intestine processes the residue, it progressively absorbs water, transforming the semi-liquid into a more solid form. Ultimately, helping to maintain the body’s fluid balance and prevent dehydration. The absorption of electrolytes and additional nutrients also takes place, further filtering the material within the large intestine.

Further, the residue is shaped into feces within the rectum. Feces consist of water, undigested food particles, bacteria, and waste products.

Step 6: Elimination

Finally, the body transports feces to the rectum, a muscular reservoir located at the end of the large intestine. The rectum serves as a temporary storage site before elimination.

The last stage of digestion involves the excretion of waste through the anus. This process, known as defecation, is a controlled and coordinated action. The anal sphincters, muscular rings around the anus, regulate the release of feces, allowing for a gradual and voluntary expulsion. 

All in all, the culmination of the digestive process is essential for maintaining overall health and preventing the accumulation of unnecessary byproducts within the body.

How Long Does It Take for Food to Digest?

Several factors influence how long it will take for food to digest. Firstly, the type of food consumed plays a significant role, as different nutrients require varying degrees of digesting.