The Small Intestine – An Overview. Part 4 of the 5 Phases of Digestion

The small intestine or small bowel is a highly convoluted tube, in the digestive tract, that absorbs about 90% of the nutrients present in the food we eat. It’s also the largest and most active component of our immune system. And, it has more impact on our emotional state than the brain. Impressive? I think so.

First of all, the small intestine is, in fact, not even small. it’s over twice the length of the large intestine measuring around 20-22 feet in length. This is the same length as a 1979 Barth RV with a 350HP, V8. The small bowel earned its “small” moniker because it’s only 1 inch in diameter, making it less than half the diameter of the large bowel.

The primary role the small intestine is to, hopefully, break down the food, just eaten, into individual units of protein, carbohydrate, and fats called peptides, monosaccharides, and fatty acids, respectively. As a result, these singular units are now in a format that can be broken down further, if needed, or absorbed as is, by specialized digestive cells.  This will only happen if all of the digestive steps, up until now, are working sufficiently (see my last two emails for more clarification).

Step 1

The partially digested food, now called chyme, leaves the stomach as a very acidic stew. The small bowel does not like this one single bit. Thank goodness the bile duct and pancreatic duct are right there, at the duodenum (duō-dē-num), the mouth of the small intestine. There, alkaline bile, pancreatic enzymes, and bicarbonate squirt out to assist further digestion of the chyme and raise the pH to a suitable level for the delicate small intestine. Therefore, without a healthy liver, gallbladder and pancreas none of this can happen. Fruits, vegetables, healthy fats, exercise, water, salt, and sleep are all needed to make this orchestra work as a team.

Step 2

Having been more thoroughly broken down, the chyme moves along its merry way to where the magic happens, the middle of the small intestine, the jejunum (jej-u-num). The vast majority of all nutrient absorption, again, if everything is working perfectly, happens here. In this part of the small intestine lies one of the most amazing cells within the body, the digestive cell extraordinaire, the enterocyte , or Intestinal absorptive cell. This cell resides in thousands of microscopic folds, which increase the intestinal surface area for increased nutrient absorption, called villi and microvilli.

step 3

The end section of the small intestine and the piece that attaches to the large intestine is called the ileum (ill-ē-um). Unique to the ileum is that vitamin B12 and bile salts are taken up here. Like the jejunum, it is also filled with enterocytes, but to a lesser degree. Strong muscles in the small intestine push the nutrient soup along the entire length of the small bowel. As it moves over the villi and microvilli of the ilium, the last bit of nutrients are absorbed, before moving through the ileocecal (ill-ē-ō-see-cal) valve and into the colon or large intestine.

This scenario is called “LEAKY GUT.”

If the cells within the villi and microvilli are damaged (bad diet, antibiotics, gluten, pesticides, herbicides, heavy metals, stress..) and are not functioning properly, disease or ill health is the most common conclusion.

  • We will not absorb nutrients effectively
  • We can absorb things that we shouldn’t (antigens/foreign proteins)
  • We can have altered immune function
  • We can have altered mental function (depression, anxiety, ADD/ADHD, phobias)
  • We can have skin problems (acne, eczema, psoriasis, boils, rashes)
  • We can have asthma and allergies
  • We can have lactose (milk) and fructose (fruit) intolerance
  • We can have autoimmune diseases
  • We can have chronic inflammation
  • We can even increase our risk of cancer

The good news, if detected or suspected, it can be reversed. The sooner it’s caught the easier it is to fix.

If you or a loved one has a symptom, of any kind or anywhere, it means that something is not working right – there is a problem. Why not get it checked out? Do not ignore it and do not mask it with a medication, drugs or alcohol. Your body is trying to tell you something – listen to it and treat it with the respect it deserves. You will live a longer and happier life because of it. If you would like my help. you know where and how to find me.

I will leave you with some, Small Intestine Fun Facts.

    • In a healthy adult, 1 gallon of intestinal secretions (2 cups of saliva,  8 cups of stomach acid/HCl, and 6 cups of pancreatic and gallbladder secretions) are produced in response to the 2-3 quarts of food and drink consumed each day
    • Sodium is the key nutrient that drives nutrient uptake from the small intestine into the blood stream (protein, sugar) and lymphatic system (fats, glycerol)
    • 70+% of the body’s immune system is within the small intestine
    • The gut contains 100 million neurons – more than the spinal cord. It is our second brain. This where theses expressions come from, “your gut instinct”, “gut feeling”, and “what does your gut tell you.”
    • 95% of the neurotransmitter serotonin is in the small bowel. Serotonin is the main neurotransmitter related to the initiation of peristalsis (movement of chyme through the intestines. Lack of it may cause constipation and depression). Fear also causes the vagus nerve to “turn up the volume” on serotonin circuits in the intestines. Thus over stimulated, the intestines go into overload and diarrhea results.
    • The gut also is a rich source of benzodiazepines – the family of psychoactive chemicals that includes such ever popular drugs as Valium and Xanax.
    • Prozac works on serotonin receptors in the gut as well as in the brain. In small doses can treat chronic constipation. Prozac in larger doses can cause constipation

Phases of Digestion Series

Part 1 of the 5 Phases of Digestion – How Our Stress Level Affects Digestion And Assimilation
Parts 2 and 3 of the 5 Phases of Digestion – The Mouth and The Stomach
Part 4 of the 5 Phases of Digestion – The Small Intestine
Part 5 of the 5 Phases of Digestion – The Large Intestine/Colon

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Thanks for reading! Have a wonderful weekend.

Dr. Ettinger

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