Digestion and the Digestive System: Everything You Need to Know

Takeaway: The digestive system has two significant roles in maintaining the overall health of the body. First, it helps breakdown food into nutrients such as carbs, fats, proteins, and vitamins – all of which are required by the body to function normally. And second, it helps the body get rid of waste products after digestion. The digestive system is made up of various organs, each having a specific role in the digestion process. It cannot function properly without all of them working together since one organ is inevitably affected by the other.

The digestive system is one of the more intricate structures in the human body. In a nutshell, our digestive system has two main functions. The first involves converting food into usable energy, and the second is to help the body get rid of waste.

The digestive system requires a network of organs to work with one another in getting the job done. Without one or the other functioning normally, the digestive system isn’t the only victim of a possible health problem but the whole body as well.

Our bodies rely on our digestive system to break down nutrients from the food and drink we consume into fats, carbohydrates, proteins, and vitamins. And as we all know, these are all essential for the body to function and for maintaining optimal health.

To understand the function and importance of the digestive system in the body, let us first take a look at what digestion means and how each part of the digestive system contributes to the overall health of the human body.

Digestion Definition

What is digestion? A dictionary definition would tell us that it refers to a person’s capacity to digest food. But, drawing from science and biology, the digestion process is the breakdown of food into nutrients such as carbohydrates, fats, proteins, and vitamins.


Carbohydrates play a big role in the digestion process.

Carbs can be one of many things in food. They can be sugar, starch, or fiber and is common in almost any food. Moreover, carbohydrates also fall into two categories: simple or complex, depending on their chemical structures.

Some examples of simple carbs are the sugars found in fruits, vegetables, and dairy products. Sugars used in food processing are also simple carbs. Meanwhile, complex carbohydrates are starches and fiber. Common examples of such are whole-grain bread, starchy vegetables such as potatoes and legumes, as well as cereals.


Fats help the body absorb vitamins

Apart from carbohydrates, fats are also a great source of energy for the body. But, unlike carbs, they are also capable of helping the body absorb vitamins. However, it is important to note how fats aren’t always good for the body. Some sources of healthy fat include a variety of oils such as olive, sunflower, corn, and safflower to name a few. Meanwhile, examples of less healthy fats include oily snacks, butter, and shortening.


The body breaks protein down into amino acids.

The modern diet is considerably high in protein. Meat-eaters get their protein from meat and eggs, while those who follow a vegan diet get their share of proteins mainly from beans and tofu. These food sources contain protein molecules that the body breaks down into amino acids.

Once the body absorbs these amino acids, the small intestine helps transport them into the bloodstream. And if you recall, the body requires these amino acids to perform various bodily functions.


Last but not least, the digestive system is also responsible for sourcing vitamins from the food that we eat. There are two types of vitamins: water-soluble and fat-soluble.

The body stores fat-soluble vitamins such as vitamins A, D, E, and K in the liver and the body’s fatty liver. Meanwhile, the body utilizes only the required amount of water-soluble vitamins and excretes the excess in the form of urine.

How Long Does Digestion Take?

Although distinctively different from one another, all animals in the animal kingdom have a digestive system. That said, we all digest food differently. Did you know that a snake takes about three to four days to digest its food, while a crocodile may take two to three weeks?

Thankfully, for us humans, digestion time is typically about six to eight hours. It’s hard to imagine carrying the dinner we ate the night before for many more weeks to come!

Although the exact time may vary between men and women, the human digestive system follows the same process. After eating, the food passes through the stomach and the small intestine. It then enters the large intestine for further digestion and the absorption of water until finally, the body gets rid of the undigested food as waste.

Organs in the Digestive System

As mentioned earlier, the digestive system consists of a network of organs. To get to know each of them and their contributions to the human digestive system, read on below.

Gastrointestinal Tract (GI Tract)

The gastrointestinal tract, also known as the GI tract, is a group of hollow organs joined together by a long twisting tube that stretches from the mouth down to the anus. The GI tract includes smaller organs such as the mouth, esophagus, stomach, small intestine, large intestine, and lastly, the anus.


When people think about digestion and the digestive system as a whole, the first thought that comes to mind is the stomach. But actually, the digestion process starts from the mouth. In a sense, it is perhaps one of the most crucial steps of digestion. Otherwise, the food that we consume remains in their original form, possibly causing digestive problems.

The mouth is the point of entry for food. And believe it or not, the body preps itself even before the first bite. If you notice, our mouths start to salivate after taking a whiff of delicious-smelling food. Our salivary glands release saliva into our oral cavity which helps in breaking down food into smaller particles. Our teeth cuts and grinds the food we consume while our tongue helps in mixing the food with our saliva. And together with the help of the soft palate (the roof of the mouth), it helps move food to the pharynx and esophagus.


Following the chewing and grinding process, the food then enters into a transition from the mouth to the esophagus. The pharynx has two possible pathways at this point.

Food can either go through the esophagus and into the stomach or through the windpipe and down to the lungs. Of course, the latter is not the ideal, but due to the complexity of the act of swallowing, it can happen.


Following the natural course, the food should then find its way through the esophagus. The esophagus is a tube-like muscle that contracts in a synchronized manner to transport food towards the stomach. This mechanism is called peristalsis – muscles behind the food contract while the muscles ahead relax, causing food to move through the digestive system.

When food reaches the stomach, the lower esophageal sphincter then allows the food to pass into the stomach. This gateway is crucial as it prevents food or stomach acid from re-entering the esophagus which may cause heartburn or regurgitation.


With the help of acid and enzymes secreted by stomach glands, the food is then mixed and broken down further until it transforms into a thick creamy fluid called chyme. Once the transformation process is complete, the produced chyme then moves into the duodenum also known as the first part of the small intestine.

Small Intestine

After reaching the first part of the small intestine or the duodenum, the food undergoes further breakdown in the next two parts of the small intestine (ileum and jejunum). In this process, not only is food broken down further but the body also begins to absorb nutrients from the food. The nutrients are then transported into the bloodstream through the walls of the intestine.

Large Intestine

The large intestine makes up the body’s lower GI tract. All the other organs before they are referred to as the upper GI tract. In the small intestine, we learn that the body has absorbed all the needed nutrients from the food consumed. All the excess or rather, the leftover waste is then transported to the large intestine or colon.

The large intestine or colon is approximately 7 feet long and is connected to the rectum. The large intestine also has four main parts: the ascending colon, transverse colon, descending colon, and the sigmoid colon. Its primary responsibility is to solidify waste product and to serve as storage for the waste until it can be excreted. To achieve this, the large intestine relies on peristalsis to move the waste product while absorbing water to solidify the waste, forming a stool.


Earlier, we learned that the lower GI tract is responsible for storing waste in the rectum. The final part of the GI tract is the anal sphincter. This organ controls the release of stool; it holds the waste product until it is ready to be evacuated.

Once stool reaches the rectum, the brain sends signals indicating the need for a bowel movement. The anal sphincter allows voluntary control which gives us the ability to hold stool until we reach the toilet.

Accessory Digestive Organs

The digestive system is also comprised of accessory organs that help with the overall process of digestion. The following organs are considered to be accessory digestive organs:


The liver is responsible for producing bile that aids in the digestion and elimination of fat. Additionally, most nutrients can be stored in the liver, and the liver also filters most toxins and chemicals.


The pancreas is more popularly known in its role in regulating blood sugar and in producing insulin. However, it is also the body’s main producer of digestive enzymes. As we’ve learned earlier, nutrients are absorbed in the small intestine. The enzymes produced by the pancreas are released in the duodenum which helps in the digestion of fats, carbs, and proteins.


The gallbladder stores and manages bile. Whenever fatty food enters the duodenum, the gallbladder takes action and releases bile.

Digestion of Fat, Carbohydrates, and Protein

Earlier, we discovered that the digestion process is required in breaking down food to nutrients such as carbs, fats, proteins, and vitamins. It is important to note that each nutrient is digested differently and certain body parts may be involved in each process. To learn more about the different digestion processes, read on below.

Fat Digestion

Where Does Fat Digestion Begin

The small intestine is the main organ that is involved in fat digestion. When fat reaches the small intestine, it produces hormones that stimulate pancreatic lipase release from the pancreas as well as bile from the liver. Both of which are required in the emulsification process of fats which leads to the absorption of fatty acids.

Carbohydrate Digestion

Where Does Carb Digestion Begin?

Interestingly, carbohydrate digestion starts in the mouth. As we’ve learned earlier, our salivary glands secrete saliva that not only helps moisten the foot, but it also helps in preparing the food for further breakdown. Along with chewing, our salivary glands also release an enzyme called salivary amylase. This marks the process of the breakdown of polysaccharides in foods containing carbohydrates.

Protein Digestion

Where Does Protein Digestion Begin?

Unlike fat and carbohydrate digestion, the digestion of protein happens in the stomach and the duodenum. In this process, three enzymes called pepsin, which is secreted by the stomach, trypsin, and chymotrypsin secreted by the pancreas, help in breaking down food proteins. The breakdown results in polypeptides that are then broken down again by various dipeptidases and exopeptidases to form amino acids.

How Does Asthma Affect the Digestive System?

Asthma can effect your digestive system

Some researches have shown that there is a link between asthma and the digestive system – particularly with a digestive condition called acid reflux.

Acid reflux happens when the muscle responsible for managing food and stomach acid loosens and allows stomach acids to come back up into the throat. When this happens, the acid may trigger the nerves and affect the lungs, causing the tightening of the airways as well as the symptoms of asthma. That said, those who are receiving treatment for asthma may still have difficulty breathing if they experience occasional stomach acid reflux.

To ease asthma symptoms brought about by acid reflux, it is crucial to treat the acid reflux first. This can be done by seeking medical help from a doctor. Most medical experts will recommend over-the-counter medications at first. But if that does not help, a prescription for other drugs may be made. Drinking tea for digestion or taking apple cider vinegar are said to be natural solutions to cure acid reflux. Overall, acid reflux can be cured by making healthy lifestyle changes.


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