Digestive System: Function, Parts, and Main Organs

The human digestive system is one of the most important of your internal functions.

It’s the reason that the food you eat and the liquids you drink get turned into energy but also takes care of eliminating waste.

The journey food takes through your digestive organs ensures that your body is able to get the nutrients it needs for healthy function.

In this blog post, we’ll take a deep dive into the full digestive process, from the time food enters the human body until the time it is eliminated as waste products.

We’ll examine what the digestive tract consists of, what organs get involved, and how food travels along the step-by-step digestion process from start to finish. We’ll also dig into a few of the most common digestive issues and what you can do to keep your digestive system healthy.

Introduction to the Digestive System

The digestive system (also called the gastrointestinal tract or “GI tract”) is responsible for breaking down the food and drink you consume. The broken-down drink and food particles are absorbed into your body to be distributed by the bloodstream to every muscle, organ, and tissue.

The nutrients you consume keep all your internal systems and organs functioning. They power your brain, facilitate hormone production, ensure your muscles are fueled up, strengthen your bones, and more. Without the digestive system to absorb nutrients, your body would break down.

The digestive system is also crucial for ensuring proper hydration by absorbing and facilitating the storage of fluids.

Primary Functions of the Digestive System

The digestive system performs essential functions that support the bodys overall health and energy balance. These functions include breaking down food, absorbing nutrients, and eliminating waste efficiently.

Ingestion

The digestive tract begins at your mouth, which is responsible for ingesting fluids and foods (aka, the “raw materials”). The food enters your mouth, where your teeth break it down into particles small enough to be swallowed.

Once swallowed, the food passes down your esophagus to be delivered into the stomach, where the next step in the digestive process takes place.

Digestion

Digestion is “is the process of mechanically and enzymatically breaking down food into substances for absorption into the bloodstream.” [1]

In your stomach there are digestive juices that break down food into smaller particles that can then pass into the small intestines. There, digestive enzymes and bacteria continue to break down the food even more, until the particles are small enough to be absorbed.

Absorption

Lining the walls of your small intestines are villi, which absorb the broken-down food particles into your bloodstream.

From there, those nutrients are delivered to your liver and other organs for processing, then distributed throughout your body.

Excretion

Excretion is the last step in the digestive process.

Once the nutrients have been fully absorbed, the food travels on to the large intestines, where the last of the water is extracted before what’s left—the waste products—is sent on its way out of your body to be eliminated.

Main Parts of the Digestive System

The digestive system consists of a lot of very important and very complicated organs. Understanding how they all work together will give you greater insight into what you can do to improve your digestive health and facilitate better digestive function.

Let’s take a closer look at how the digestive system is made, starting with the main organs.

Mouth

Digestion starts in the mouth, also known as the oral cavity.

When you smell food, your submandibular salivary glands are triggered and saliva is released. Saliva production increases once the food hits your tongue and the nerve sensations your brain translates as “taste” register.

Saliva contains enzymes and other substances that initiate carbohydrate digestion and the process of breaking down the food. That’s why the teeth are such a crucial component of the gastrointestinal tract. Their job is to begin the breakdown process and turn the food you eat into small enough pieces so the saliva can more efficiently continue the breakdown.

Saliva also carries food along the next steps of its journey down your esophagus.

Esophagus

The esophagus is the long muscular tube that connects your mouth to your stomach. Food and fluid travel down the esophagus, helped along by the muscles in your throat as well as muscular contractions (peristalsis) in the muscles lining the esophagus.

At the bottom, fluids and food pass through the lower esophageal sphincter into the stomach.

The lower esophageal sphincter is a one-way opening that allows food to pass through on its way to your stomach. It prevents the food from coming back up, protecting the stomach lining from potential damage caused by stomach acid.

Stomach

Your stomach is where the real work begins.

The strong muscular walls of the stomach act like grinders to further break down the food particles present in your stomach. At the same time, powerful stomach acids and enzymes break down the food on a chemical level. Food broken down mechanically and chemically is turned into a sort of paste or liquid that the stomach muscles push through to the small intestines beyond.

Any food that can’t be fully broken down is also passed along but is ushered through the intestines to be eliminated as waste.

Small Intestine

The small intestine is made up of three segments:

• The duodenum, where intestinal digestion begins when the food digested in your stomach is mixed with bile from the liver and more digestive enzymes from the pancreas. It is then squeezed along by muscle contractions of the intestinal walls to be delivered down the line.
• The jejunum absorbs nutrients. Here, amino acids, fatty acids, and digested sugars are pulled from the food to be absorbed into the body via mucosal membrane folds in the intestinal walls.
• The ileum, where villi in the intestinal walls absorb the last of the vitamins and minerals, along with the bile acids from the digested food.

Once the food has passed through these three parts of the digestive system, it’s a semi-solid material that is exhausted of nutrients and largely made up of waste materials and liquid.

Large Intestine

The large intestine is made up of four sections:

• The cecum, the part connected to the small intestine
• The ascending colon (on your right side)
• The transverse colon (which crosses your body right-to-left)
• The descending colon (on your left side)

These four sections of the large intestines absorb water from the waste material, which helps hydrate your body.

Gut bacteria in your intestines are also largely responsible for breaking down the food further. Digestible matter is fermented by the gut bacteria over the 30 or 40 hours it spends traveling through the various sections of your large intestine.

By the time it’s “done” traveling through your small intestines, the last of the water has been extracted and it is now formed into solid waste matter, what we know as “poop”.

Rectum

The rectum is an eight-inch-long section connected to the colon by the sigmoid colon at the lower end. It is made up of walls that can stretch to expand and accommodate the poop being produced by your body.

When the walls have stretched to a certain point, nerve ends detect rectal contents and send signals to your brain that the waste is ready to be eliminated.

The rectum not only stores stool, but it also produces mucus that facilitates the elimination process once it begins.

Anus

The GI tract reaches its endpoint at the anus, the muscular opening through which poop exits the body.

The muscles in the anus give you control over your bowel movement, squeezing to keep the opening closed or relaxing to push food waste matter out.

Accessory Organs in The Digestive System and Their Roles

In addition to the main organs of the digestive system, several accessory organs play crucial roles in digestion by producing and storing essential enzymes and chemicals. These organs support the breakdown and absorption of nutrients to ensure the body functions efficiently.

Liver

The bile ducts in your liver release bile, the compound that enables your stomach and small intestines to digest fats and fatty acids.

The liver also processes nutrients absorbed by your small intestines so they can be distributed throughout the body.

The liver even plays a role in detoxification and protects your body from damage by chemicals or toxins that may be present in the food you eat.

Gallbladder

The gallbladder stores bile. It’s essentially a storage sac that houses any excess bile produced by your liver’s biliary system.

When too much bile is released into your small intestines or your small intestines signal they don’t need any more, excess bile travels to your gallbladder to await signals that more food has reached the small intestines and thus more bile is needed.

Pancreas

The pancreas produces enzymes released into your small intestines to break down fats, carbohydrates, and proteins.

The pancreas also produces insulin, the hormone that regulates the absorption and uptake of sugars from your food.

Salivary Glands

The salivary glands release saliva at the beginning of the digestion process when food hits your mouth.

Saliva both helps break down food chemically and facilitates the journey of the food that has been mechanically broken down by your teeth.

How the Digestive System Works: Step-by-Step Process

Here’s a very simple step-by-step process of how the digestive system work happens from beginning to end:

• Step 1: Food enters your mouth, where it’s mechanically broken down by your teeth and chemically broken down by your saliva.
• Step 2: Food travels down your esophagus, pushed along by the esophageal muscles, and passes through the lower esophageal sphincter into your stomach.
• Step 3: In your stomach, stomach acids, enzymes from your pancreas, and bile from your liver chemically break down your food while the powerful muscles lining your stomach walls mechanically break it down.
• Step 4: Liquefied food passes into your hollow organs: first, the small intestines, where the macro and micronutrients are absorbed to pass into your bloodstream, then the large intestines, where the last of the water is absorbed and the food particles are fermented by gut bacteria.
• Step 5: Solid waste matter passes into your rectum to be stored until ready for elimination.

This complex process not only fuels the body but also plays a huge role in preventing digestive and kidney diseases by supporting overall organ function. Additionally, the health of solid organs like the liver and pancreas is directly influenced by how efficiently the digestive system operates.

Common Digestive System Disorders

We all know what happens when our digestive system works well: it turns the food we eat into nourishment that keeps our body functioning properly and handles processing waste for elimination.

But what about when the digestive system breaks? What happens when certain organs don’t function properly, or internal issues impede proper digestion?

Let’s take a look at some of the more common digestive system disorders that may occur.

Gastroesophageal Reflux Disease (GERD)

Gastroesophageal Reflux Disease (also known as GERD) occurs when acid flows back up from your stomach, through the lower esophageal sphincter, and up your esophagus. This backwash of acid—called “acid reflux”—can irritate or even damage the lining of the esophagus. Repeated acid reflux that causes more serious damage is called “GERD”.

GERD can be caused by conditions that weaken the muscles of the lower esophageal sphincter, including obesity, hiatal hernia, pregnancy, delayed stomach emptying, and connective tissue disorders.

However, smoking, drinking coffee and alcohol, eating fatty and fried foods, eating highly acidic or spicy foods, and eating large meals (particularly late at night) can all contribute to higher risk of acid reflux that over time can develop into GERD.

Irritable Bowel Syndrome (IBS)

Irritable bowel syndrome, or IBS, typically includes severe GI symptoms like belly pain, cramping, bloating, and changes in the frequency and appearance of stool that persist over time.

The causes of IBS aren’t known, but some factors that may exacerbate the risk of IBS include issues with the nerves in your digestive system, issues with the digestive muscles, infections (gastroenteritis), and drastic changes in the gut microbiome.

Crohns Disease

Crohns Disease is an inflammatory bowel disease that causes pain, fatigue, weight loss, diarrhea, and malnutrition due to swelling and irritation of the digestive tract tissue. Typically, it affects primarily the end of the small intestine and beginning of the large intestine but may spread throughout the bowel.

Causes of Crohns Disease aren’t well known, but some risk factors may include genetics, smoking, NSAID use, age, compromised or imbalanced immune system, or atypical immune response.

Celiac Disease

Celiac disease is an autoimmune illness in which the body treats certain proteins found in wheat, barley, or rye products as “harmful” and triggers an immune response. This reaction can cause damage to the lining of your small intestines over time and prevent it from properly absorbing nutrients. Diarrhea, fatigue, anemia, and bloating are all common symptoms of celiac disease.

The precise causes of celiac disease aren’t known, but genetics are believed to play a factor and GI infections, gut bacteria composition, and stress on the body (such as pregnancy, viral infection, or childbirth) can all contribute.

Gallstones

Gallstones are hardened bile deposits that can form in your gallbladder. Excess bile production leads to high bile storage in your gallbladder. If your bile contains too much cholesterol or bilirubin or your gallbladder isn’t able to properly empty or empty frequently enough, the bile may harden and form gallstones.

Risk factors for gallstones include being female, over the age of 40, overweight or obese, pregnant, having diabetes, or having a family history of gallstones. People who eat a high-fat, high-cholesterol, low-fiber diet are also at significant risk.

Others

In addition to the common digestive disorders listed above, several other conditions can affect the digestive system and overall health:

• Leaky Gut Syndrome – A condition where the mucous membrane lining the intestines becomes damaged, allowing toxins, bacteria, and undigested food particles to pass into the bloodstream.
• Stomach Ulcers – Open sores that develop on the lining of the stomach or upper small intestine, often caused by Helicobacter pylori infection or long-term use of NSAIDs.
• “Stomach Flu” (Gastroenteritis) – Viral gastroenteritis, often called “stomach flu,” is an infection of the stomach and intestines caused by viruses (norovirus, rotavirus), bacteria, (E. coli, Salmonella), or parasites (Giardia lamblia). However, it is not the influenza virus. It leads to inflammation and symptoms like diarrhea, vomiting, and abdominal pain.
• Hiatal Hernia – Occurs when the upper part of the stomach pushes through the diaphragm, creating a twisting tube effect that can lead to acid reflux and discomfort.
• Pelvic Floor Dysfunction – Weak or uncoordinated pelvic floor muscles can disrupt bowel movements and contribute to constipation or incontinence.
• Oral Thrush – A fungal infection affecting the mucous membrane of the mouth and throat, which can impact digestion if the infection spreads.
• Cleft Soft Palate – A congenital condition where the soft palate does not fully develop, potentially causing feeding and swallowing difficulties.

These additional conditions highlight the complexity of the digestive system and the importance of early detection and management.

Maintaining Digestive Health

Your digestive organs are designed to do their job efficiently all day every day, but there are a few things you can do to help it function properly:

• Follow a balanced diet. Eat more high-fiber foods like fruits and vegetables, and reduce your intake of high-fat, high-cholesterol, and processed foods. Drink more water. Eat probiotics, which will reinforce the bacteria in your gut responsible for maintaining digestive health.
  
• Exercise regularly. Exercise has a positive impact on digestion by strengthening the muscles in your abdominal organs that push food along through your digestive tract. Exercise can also enhance gut motility and help you digest food more efficiently.
  
• Avoid risk factors. Quit smoking, avoid excessive alcohol intake, and curb stress. These risk factors can significantly increase the likelihood of developing digestive disorders or experiencing interruptions to healthy digestive function.
  
• Get routine check-ups. Have your doctor screen for digestive disorders, particularly if you’re at risk of health problems due to your age, lifestyle, weight, diet, or pregnancy.

Your digestive system is one of the most resilient systems in your body. If you follow these four suggestions and take care of it, it will take care of you in return.

Conclusion

As you’ve seen above, the digestive system is needed for the processing of food and water, the absorption of nutrients and energy, and the elimination of waste. It’s one of the most essential, complex systems in the human body—and one you need to take good care of.

Now that you understand how it all works, it’s up to you to get proactive with your digestive health. Eat right, exercise more, reduce your stress, and most important of all, get regular health checks to make sure your digestive system is in tip-top shape!

FAQs

How long does it take to digest food?

Food takes about 2 to 6 hours to break down in the stomach, another 2 to 8 hours to pass through the small intestine, and anywhere from 10 to 59 hours to pass through the colon. The entire digestive process will typically take between two and five days.

How do you know if your food is digested properly?

Signs that your food is being digested properly include regular bowel movements, no pain or irritation in your intestines, and good poop color, consistency, and ease of passing.

What are four signs of poor functioning of the digestive system?

The four most common signs that your digestive system is functioning poorly include bloating, constipation, diarrhea, nausea and vomiting.

Resources

Your Digestive System & How it Works

Digestive system explained

Human digestive system

Your Digestive System

Gastroesophageal reflux disease (GERD)

Irritable bowel syndrome

Crohns disease

Celiac disease

Gallstones