The Small Intestine - Continuing our Journey through the Digestive Tract

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The Small Intestine: Continuing our journey through the digestive tract we are ready to take a look at the small intestines. The small intestine is located in between the stomach and the large intestine. This is an important part of the digestive tract because this is where most of the absorption and digestion of the food that you have eaten takes place. It is actually a 20 ft. tube that is winding and tightly folded. The gastrointestinal tracts mucosal membrane surface is the largest interface between our internal body and the external world– It covers more than 400 square meters, which is over 200 times greater than the surface area of the skin.

For such a simple seeming structure, the small intestine actually plays an incredible important role in the digestive tract and any problems that are found here should be looked into quickly so that larger problems do not arise. With all of the important functions that happen in the small intestine, there is a lot that can go wrong.

Overview of Function

Now that you know the basics of the small intestines, let’s take a closer look at what parts make up this important digestive organ and closely look at what each of these parts contributes to the digestive system. There are actually three parts that make up the small intestine, the duodenum is the first part.

The duodenum is a structure that is shaped like a “C” and is a short structure about 9 to 11 inches long, that will be found surrounding the head of the pancreas. It is connected to the stomach, which means that it receives the gastric chyme from it. It also gets digestive juices from the pancreas, which are digestive enzymes and pancreatic bicarbonates, and from the liver/ gallbladder, it receives bile. These digestive enzymes are part of the digestive process and are responsible for assisting in the breakdown of the food you eat. The bile is responsible for emulsifying fats turning into micelles making the fats easier to digest and absorb.

The duodenum contains Brunner’s glands. These glands produce a secretion that is mucus-like and contains bicarbonate.

These things work together to neutralize the stomach acids that are found in gastric chime therefore protecting the intestinal walls from gastric juices.

The next part, located in the middle part of the small intestine, is the jejunum. It contains plicae circulares which are transverse folds as well as villi which are minute finger like projections. These structures increase the area of the secreting and absorbing surface. Most products of digestion, which include things like amino acids, sugars, and fatty acids, will be absorbed into the bloodstream from this location.

The final part, the ileum, is the third part and it connects to the colon. There are also villi, located along the lining here as well. The ileum is the final structure that makes up this organ. The job of the ileum is to primarily absorb vitamin B12, K and bile salts. It will also absorb any other remaining nutrients that need to be absorbed.

In addition to digestion, the small intestine is also responsible for helping to support the body’s immune system. Peyer’s patches which are schools of the white blood cells make up the gut Associated Lymphoid Tissue (Galt) which is part of the mucosal associated lymphoid tissue. Interestingly about 60% of the body’s immune system is found in the digestive tract and it is an important first line of defence against exogenous substrates, such as food antigens and pathogenic bacteria.

As you can see from this, the small intestine is the location where the chemical digestion primarily takes place.

After the items have been degraded through this chemical digestion process, they can then be absorbed through the bloodstream by passing through the walls of the small intestine.

In a healthy intestinal tract, the intestine’s tight junctions limit the transport of large molecules across the epithelium, in an unhealthy intestines the tight junctions become “leaky” and these large molecules, which can include unprocessed proteins or large amino acids that have intact antigenic sites on them, can then slip into circulation– ‘leaky gut’ (increased intestinal permeability) which unfortunately is fairly common today.

It is seen in people presenting with intestinal inflammation, food allergies and intolerances, and celiac disease, after radiation, chemotherapy treatments and is frequently induced by stress.

When it’s not healthy

Because there is a lot that goes on within the small intestine, there can be a lot of things that go wrong here. Some problems are quite common; people can experience some of these at some point in their lives. Here is a closer look at some of these dysfunctions.

Food intolerance

Food intolerances, such as a gluten, egg white and dairy, can cause some damage within the small intestine and will prevent it from properly digesting important nutrients. Symptoms of food intolerance can include:

  • Bloating
  • Nausea
  • Brain fog
  • Diarrhea, which occurs around a half-hour later
  • Abdominal pain
  • Food cravings
  • Fatigue
  • Heartburn
  • Joint pains

If you suspect that you are reactive to certain foods then you can try an elimination diet, which involves taking out the suspected food for a period of time then reintroducing it and monitoring for changes during the time period you were not consuming the food and when you reintroduced it. You can also do food sensitivity tests through various labs.
Increased intestinal permeability

While it is normal to have intestinal permeability, it is only normally permeable enough where only the good things enter the bloodstream while keeping harmful bacteria and large particles of food from crossing the barrier. With increased permeability, these harmful bacteria and food particles can get into the bloodstream and contribute to your body developing health problems and possible autoimmune problems. Stress and infections can worsen this problem.

Following are some symptoms associated with increased intestinal permeability:

  • Abdominal dissention and pain
  • Cognitive and memory deficits
  • Diarrhea
  • Fatigue and malaise
  • Food intolerances
  • Mood swings
  • Poor exercise tolerance
  • Skin rashes
  • SIBO

Bacterial overgrowth is a condition that is referred to as Small Intestinal Bacterial Overgrowth, or SIBO.

Bacteria are normally present throughout the entire gastrointestinal tract, but in varied amounts. The small bowel has some bacteria but most of the bacteria of the digestive tract are found in the colon, the types of bacteria normally present in the small bowel are different from those in the colon. SIBO is a condition where the number of bacteria has increased and/or there are changes in the types of bacteria present in the small bowel. In most people, SIBO is not caused by a single type of bacteria, but is an overgrowth of the various types of bacteria that should normally be found in the colon levels in the small intestine are at the level of what would be seen in the colon.

Some of the symptoms of this include:

  • Distention or abdominal bloating
  • Constipation
  • Diarrhea
  • Excessive wind
  • Abdominal pain/discomfort
  • Vitamin deficiencies.

Simple Tips to Help Remedy Dysfunction

Some simple tips that can help remedy dysfunctions of the small intestines involves managing your stress levels, creating a great cephalic response consistently, eating in a quiet, calm environment and chewing your food as close to liquid as possible. Avoid any foods that you are intolerant to such as gluten and consulting with a practitioner if you suspect SIBO to get the relevant tests and guidance.

Avoid overusing certain medications like NSAIDs, as they can irritate the lining of your intestine and will cause you problems.

These are only a few of the simple tips that you can follow, but they are definitely some of the more important ones that you need to follow not just to maintain a healthy digestive tract but to help you maintain your overall health in a better manner.

Appropriate Natural Healing Remedies

There are a variety of natural remedies that you can take to help your small intestine dysfunctions, including:

  • Broad spectrum digestive enzymes
  • Swedish bitters
  • Probiotic supplements
  • Foods or supplements that contain omega-3
  • Glutamine supplements
  • Bone broths / gelatin
  • Zinc supplements
  • Slippery elm / marshmallow powder
  • Regular movement


Fully Functional Gut course – Emma Lane @ Integrative Health Education
Liska et al (2004). Clinical nutrition. A functional approach. Gig Harbour:The Institute for functional medicine.p.202
Pizzorno J, Murray M (2007). Textbook of natural medicine. e‐dition. Missouri:Elsevier
Lipski E, Digestive wellness, updated 2nd edition 2000
Balch P: Prescription for nutritional healing Avery 2000
Liska D, Bland J (2007). Digestion and Excretion. Integrative Medicine Journal (2007) Dec Vol. 5, No. 6
World Journal of Gastroenterology: WJG Baishideng Publishing Group Inc.
Small intestinal bacterial overgrowth syndrome Jan Bures, Jiri Cyrany, and Marcela Kopacova

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