Let's Look at the Digestive System...
If You've Got the Stomach for it.
Happiness is a good digestive system. How do I know? Jean-Jacques Rousseau, the French philosopher, said so.I love his quote; “Happiness: a good bank account, a good cook, and a good digestion.”
Jean-Jacques had it right!
Nothing can ruin our quality of life faster than a disruption or disease of our gastrointestinal (GI) tract. Just ask someone who has one of the more common GI problems.
Diseases of the digestive system can include, from top to bottom; acid reflux, stomach ulcers, diverticulitis,irritable bowel syndrome, Crohn's disease, cancers of the colon, pancreas, liver, and several more. Some arejust uncomfortable or embarrassing; others range from excruciating to sometimes fatal.
Our digestive system is the major pipeline of the body; would you believe a continuous tube, roughly 40 feet long from lips to anus. The control system that keeps things moving and working properly is exquisitely complex with feedback loops, valves, signals, and a symphony of mechanics, chemistry and electrical activity.
The graphic below is a good representation of the whole digestive system from start to finish.
Ready to Dive into the Digestive System?
Let's Follow the Flow.
As I write this, Thanksgiving of 2008 is two days past so if our digestive system was working right, the turkey has come and gone.
The process sounds so simple.
We put food in our mouth; grind it up with our teeth, and enzymes in saliva start breaking down the carbs and fats.
The food, now called a bolus, goes down the esophagus to the stomach. The esophagus is just a tube with no absorption taking place. The bolus is moved down the esophagus via muscular contractions; not gravity.
In 5 or 6 seconds it's in the stomach.
In theory, we should be able to hang upside down and still swallow. Please don't try it; I didn't mean that as a recommendation.
The stomach can be thought of as an enlargement and rotation in the digestive system whose function is to mix and digest. The stomach is more complex than we might think; a lot more than just a bag of acid. In fact it has four functional divisions and several specialized layers.
After mixing in the stomach, Thanksgiving dinner is now a liquid called chyme. Upon receiving the green light, the stomach squirts a measured amount of chyme into the duodenum, the first twelve inches of the intestinal part of the digestive system.
Within 2 to 4 hours, most of that dinner should have left the stomach, depending on how many helpings you had and how much fat was in grandma's gravy.
Three digestive system organs; the pancreas, liver and gallbladder, deliver digestive juices to the duodenum to continue the process. The chyme continues through the remaining 24 feet or so of the small intestine where most absorption of nutrients and some water take place; then it’s on to the colon.
The main function of the colon, about five feet long, is to recover water from the remaining mixture, and deliver the waste products of the digestive system to the rectum for elimination.
We don't want stuff handing around in the colon toolong and we will talk about fiber later on. Fiber keeps it moving through the last stages of the digestive system.
What could be simpler? From here on, we'll do a short, basic overview of each of the major components of the digestive system. Relax; we're not going to med school here. Then we will look at what can go wrong and wrap up with choices we can make for good digestive system health.
The Body Parts of the Digestive System
We'll start with the stomach, but first a comment on the mouth.
The digestive system starts in the mouth. That saliva we mentioned earlier that breaks down fats and carbohydrates comes from three glands, the parotid (in front of and below the ear), the submandibular gland and the sublingual gland (both in the lower jaw). Ever seen anyone with the mumps? The mumps virus lives in the parotid gland and that's what swells up when we get the mumps.
The enzymes are delivered into the mouth via ducts. Picture what a quart and a half
container of milk looks like...that's how much saliva we produce in a day. That's a lot of spit, kids.
Also that little thing hanging down in the back of your throat is called the uvula and detects the passing of food and signals the soft palate to rise up and block food from going up into your nose. It doesn't work very well if your laughing and drinking milk at the same time.
Ok, now for the stomach
Lots of digestion goes on here but not much absorption. Let's be sure we know what we're talking about.
Digestion is the breakdown of gross nutrients into particles that are suitable for absorption.
Absorption is the moving of broken down nutrients across the digestive tract into the bloodstream.
Starting at the top of the stomach is a valve called the lower esophageal sphincter that prevents food (chyme)
in the stomach from going back up into the esophagus. Most of the time it works but when it doesn't, we can
get a hiatal hernia or GERD. More on that below.
The stomach has four divisions where digestion continues. The cardia is first because it is nearest the heart,
then the fundus, next the body of the stomach and finally, the antrum. The antrum is the last part of the
stomach before the pylorus muscle which forms a true anatomic sphincter to prevent food from entering the
small intestine until it is ready.
Mixing and grinding continues in the upper three stomach divisions but the antrum is where much of the
stomach acid acts on the chyme to break it down.
There's a neat feedback signaling mechanism here that releases a hormone called gastrin when the supply of acid
runs low. Gastrin travels via the blood vessels lining the stomach to the upper regions of the stomach where
the acid actually made. It tells specialized cells to secrete more acid.
Photo: Cross section of stomach wall; no, it's not smooth
Stomach acid denatures protein (breaks it apart), kills some bacteria, stimulates flow of bile, pancreatic
juices, hormones & gets chyme ready for the duodenum.
When the acid reaches a certain level (pH), it inhibits gastrin production which stops acid production until more is needed.
Intestines make up most of the digestive system.
The first 12 inches of small intestine is the duodenum; a very small organ no wider than our thumb.
The small intestine winds from the pyloric sphincter to another valve where it empties into the large intestine. The small intestine finishes the process of digestion, absorbs nutrients, and passes the residue on to the large intestine.
The liver, gallbladder, and pancreas are accessory organs of the digestive system that are closely associated with the small intestine. We will visit each in turn below.
The small intestine is divided into three distinct sections; the duodenum, jejunum, and ileum with each being composed of layers of specialized tissue.
Since this is where absorption takes place, the absorptive surface area is increased by fingerlike structures called villi, and microvilli. A whole family of enzymes is secreted by exocrine cells in the mucosa layer and hormones are excreted by endocrine cells of the mucosa.
Recall that exocrine means that the secretion goes into the organ and endocrine means it goes into the blood
These secretions are controlled by the presence of chyme and is largely a reflex action in response to
chemical and mechanical irritation from the chyme and distention of the intestinal wall. This is a direct
reflex action, thus the greater the amount of chyme, the greater the secretion
The large intestine: colon, rectum and anus
The large intestine is considerably larger in diameter than the small intestine and begins where the ileum (last section of small intestine) enters the large intestine, and ends at the anus.
The large intestine produces no digestive enzymes since chemical digestion was completed in the small intestine. Functions of the large intestine include the absorption of water and electrolytes and the elimination of feces.
The last 2 to 3 cm of the digestive tract is the anal canal, which continues from the rectum and opens to the outside at the anus. There is an external anal sphincter at the end of the anal canal. This sphincter is composed of skeletal muscle and is under voluntary control.
Outpouchings of the digestive system...
The pancreas is both endocrine and exocrine. The endocrine part secrets insulin and glucagon into blood
stream to elevate or lower blood sugar. These are hormones and hormones are regulators, so now we know how
blood sugar is regulated; except when the pancreas decides it doesn't want to play.
The exocrine part secretes digestive juices directly into the digestive system, not into the blood stream.
A bile channel from gallbladder and digestive juices from pancreas join together at a junction just before
The liver is our Largest organ. It is so vital to our bodies functioning that the creator gave it the ability
to replace itself, the only organ that can do that. It is also given extra protection from trauma by the rib
cage. Anything having to do with the liver is "Hep". Hepatitis is inflammation of the liver.
It performs many vital functions for the digestive system. It manufactures digestive enzymes, blood cells and is the
main organ of detoxification. Detoxification is where ingested material that might be toxic is rendered
harmless. Immune response cells are made in the liver. It's not called a vital organ for no reason.
The liver recieves blood from the intestines via a "portal" vein where it metabolizes or processes all the nutrients that were absorbed into the blood stream from the small intestines. This is where the incoming nutrients from that meal we ate get removed from the blood, processed and sent to the cells where they are put to use.
Both the kidneys and the liver perform an excretion function. Excretion occurs when waste products are brought
back into the bloodstream for later expulsion.
The gallbladder is a small digestive system organ that lives under the liver and joins the biliary tree. The biliary tree is a system of ducts that collects bile from the liver and drains it to common hepatic ducts where the two branches join.
These two branches of the "tree" are the left and right main hepatic ducts.
The Gallbladder has a cystic duct that connects to the common bile duct. It provides a slow drip to the duodenum.
When the "drip" sphincter is closed, bile backs up into the gallbladder and is stored until it is needed, for
example when we have eaten a fatty meal.
There is a common problem associated with the gallbladder. Often, it doesn't empty completely and organs that
don't empty completely cause trouble, usually from chemical or crystal precipitates
It's not all Sweetness and Light
with the digestive system
There are lots of problems that develop in the digestive system; some are self-inflicted, others not.
Starting at the top, failure of the lower esophageal sphincter results in GERD (gastroesophageal reflux disease) and causes inflammation in the esophagus. Usually we just call it acid reflux or indigestion.Photo: Hiatal hernia shown in upper GI endoscopy
A hiatal hernia occurs when the sphincter relaxes to the point that the stomach itself tries to protrude into the esophagus. A hiatal hernia diagnosis is typically made through an upper GI series or endoscopy. It's not an uncommonproblem in the digestive system as we age. (see Photo)
Vomiting isn't a disease but the result of the digestive system trying to rid itself of toxins, excess material orpossibly the result of an obstruction downstream.
Vomiting is a normal response to overindulgence, one of thoseself-inflicted distresses, whether it be too much alcohol or over-eating. No matter, vomiting in this case is is what happens with huge gastric distention.
The stomach hates blood. If we get blood in the lumen (lining) of the stomach, vomiting is the quickest, shortestway to get it out. prolonged vomiting can cause massive imbalance in enzymes, hormones, pH levels, and chemicalsin the body. It should be viewed as a medical emergency.
Tearing of the veins in the esophagus, or worse, tearing through the wall of the esophagus are respectively labeledthe Mallary-Weiss syndrome and Boerhave's syndrome. Both are very serious and can cause vomiting of blood.
Stomach ulcers are not the dreaded condition that they used to be and surgery for ulcers is now rare. Pills that limit acid production have come to the rescue.
The big discovery regarding ulcers is that they are caused by a bacteria, the heliocobactor pylori, and antibiotics took care of it.
Another great development in ulcer treatment is the proton pump inhibitor. Stomach acid is hydrochloric acid (HCL)and the "H" in HCL is hydrogen, a proton. Surely you remember that a proton is a positively charged particle in the nucleus of an atom. HCL is made by parietal cells in the upper part of the stomach and pumped out into the stomach.
A non-toxic pill can stop the pumping action and doctors who used to perform surgery to remove the acid producing section or the signaling section call it a miracle drug. Nexium, Prilosec and Prevacid are threepopular proton pump inhibitors. How could we ever forget all those "purple Pill" commercials?
In the pancreas, pancreatitis, or inflammation of the pancreas, is a serious digestive system disorder caused when bile backs up into the pancreas due to a blocked duct to the duodenum.
Pancreatic cancer has to be the worse type of cancer imaginable. It is very hard to diagnose, is aggressive, little is known about its causes and even less as to how to prevent it. The five year survival rate is 2% with treatment and between 20-40% of pancreatic cancer patients will die from the surgery.
The cancer generally obstructs the bile duct causing bile to back up into the liver where it finds its way intothe blood stream. The first sign is an orange color in the eyes and a yellow pallor called jaundice.
The bile in the blood stream is actually micro-crystals and they cause an intense itching all over the body.In men, poor oral hygiene has been linked to pancreatic cancer. (more on this below)
The surgical treatment for pancreatic cancer is called the Whipple procedure and is the worse surgery there is. The surgeon will take out the pancreas, the duodenum, half of the stomach and then ties the second stage of thesmall intestine directly to the liver. At best, it is palliative surgery providing some degree of comfortfor several years.
Small Intestine; Celiac Disease
Celiac disease (CD) is a condition of the small intestine that is getting more attention these days. The breakthroughfor celiac sufferers was that the disease is actually a genetic condition leading to an autoimmune response to gluten, a protein in wheat, rye and barley.
The result of CD is a destruction of the villi of the small intestine and a severe degradation of nutrient absorption. The prevalence seems to be growing and a separate page about Celiac Disease was created to help CD sufferers understand its implications.
The colon is subject to several unpleasant afflictions. Irritable Bowel Syndrome, Diverticulosis, Crohn's Disease and Ulcerative Colitis (both referred to as inflammatory bowel disease).
The bad news on the last two is that the cause is unknown although there is speculation that it is the interaction of a virus or bacteria with the body's immune system.Photo right:
Colitis showing deep ulceration
Photo below: Colon cancer found while screening for Crohn's disease
IBS or irritable bowel syndrome is a disease as well as a functional disorder. By the way, anytime you see thatword "syndrome", it means that medical science doesn't have a clue what causes it. With IBS, there is apparentlya problem with the workings of the intestinal muscle action and a pain perception in the bowel.
The discomforts of IBS include gas, abdominal pain, constipation or diarrhea. The good news is that it does not lead to more serious conditions such as colon cancer and does not damage the digestive system as organic disease might.
Diverticulosis becomes quite common as we age. It can be very benign with people not even knowing they have ituntil it is discovered in an x-ray or routine colonoscopy.
It is a condition where small sacs or out-pouchings occur in the wall of the colon.
Only about 10% of those who develop it ever has complications such as bleeding, perforations or infection.Photo right:
Diverticulosis as seen endoscopically (looking down the throat)
Crohn's disease was first diagnosed in 1932 by Dr. Burrill Bernard Crohn who found it as an inflamation of the small intestine. Now Crohn's disease is widely thought to be an inflammatory autoimmune disease that can occur anywhere along the digestive system from mouth to anus.
It is also referred to as colitis (inflammation of the colon) or granulomatous. The latter condition is seen as a spherical mass of immune cells that forms when the immune system attempts to wall off substances that it perceives as foreign but is unable to eliminate.
When the immune system attacks a normal part of the intestine that it perceives as something foreign, then we have an autoimmune disease. See our page on essential sugars to learn how certain bioactive sugars help the body to distinguish between self-cells and invading cells.
Smart Choices for Digestive System Health
Avoid High Fructose Corn Syrup
As we might imagine, the digestive system uses hormones to regulate hunger and appetite. Hormones are made inthe various glands of the endocrine system and they are the body's regulators. The two digestive hormones areGhrelin and Leptin. Sounds like a couple of leprechauns.
Ghrelin increases the appetite. When the stomach is empty, ghrelin is secreted to tell us we're hungry and make us look for something to eat. Leptin is the opposite; it signals our brain that we are full.
High fructose corn syrup (HFCS) can really confuse the ghrelin and leptin hormones. It inhibits leptin secretion so the brain never gets the message that the stomach is full and the ghrelin never gets turnedoff. So even if we have food in our stomach, the hungry message is always coming in.
The problem is that it's almost impossible to avoid high fructose corn syrup. It's in all kinds of foods, especially sweet, processed foods. Consider salad dressing.
Salad dressing is the downfall of all of us who eat a lot of salads and like to dress them up with various dressings. It's probably more of a female issue since we know real men don't eat salads. I jest, I love my salads.
Anyway, salad dressing is full of high fructose corn syrup. Food manufacturers eliminated the fat but they made up for it by pouring in the HFCS; empty calories with no nutritional value. Try to develop a taste forextra virgin, cold pressed olive oil and vinegar on your salad instead of the processed junk.
Throw the cereal away and eat the box; it's probably healthier.
Fiber has no nutritional value and doesn't get digested but that's not why we need it. Fiber has the ability topick up water thus adding bulk and improving the travel time of undigested foods through the digestive system.The advantage to the colon is that with soft, bulky stools there is less strain on the bowel and less chance ofdeveloping those uncomfortable, embarrassing hemorrhoids.
There is also a lot of evidence that fiber protects against diverticulosis, a condition where pouches developin weak areas of the colon giving rise to infection and inflammation. If there is already intestinal bleeding, perforations or abscesses, a high-fiber diet would not likely be advised. This would be your doctor'scall.
It is also pretty well concluded that fiber from fruit, vegetables and oats can decrease low density lipids, thebad cholesterol, and thus reduce the risk of heart disease. Have you looked at a Quaker Oats box lately?
How about colon cancer? Reportedly colon cancer is almost non-existent in areas of the world where the dietary intake of fiber is high. Unfortunately, colon cancer is rampant in our processed, fast food culture.
The theory is that increasing the bulk of stools dilutes potential cancer causing agents and may bind to somecarcinogens so they are less available to cause problems. Also, since fiber moves waste material through the intestines faster, it may give the carcinogens less time to work.
Personally I eat All Bran for breakfast and supplement with a fiber, probiotic and enzyme product. Several years ago I was plagued with irritable bowel syndrome. No problemo, no mo!
Probiotics, prebiotics, enzymes and proteolytic enzymes, fiber, an endocrine support formula, antioxidant,natural vitamin and mineral formulation and bio-active sugars are all excellent things to use to support the digestive system as well as all the supporting systems in the body.
Colon health depends on the proper balance of good bacteria in the gut. Click on probiotics to access a page discussing the role of bacteria in supporting good colon health.
One of the best sources for probiotics and most informative websites I have ever seen on the subject is Udo's Choice Probiotic Blends; available in your local health food store. Udo Erasmus has a beautiful, informative website that can be seen at http://udoerasmus.com/index_main.htm. Take a look, you will be glad you did.
Proteolytic enzymes help the digestive system break down proteins; enzymes are catalysts that need to be presentin order to certain digestive operations to take place. Hormones from the various glands of the endocrine system are vital to the health and functioning of the digestive system.
Gastrin, a hormone that regulates stomach acid is just one example. A glycoprotein is produced by the stomach lining that is vital to keep the stomach from digesting itself.
Essential sugars provide the polysaccharides the body uses to construct glycoproteins.
It is argued that if we eat a well balanced diet we don't need supplements but who eats a well balanced dietanymore and where can we get food these days that still has the full complement of nutrients that it used to have?I prefer to supplement and be sure than gamble on that I am getting what my body needs.
I heard a medical doctor on TV talking about a water study involving two groups of people. One group drank eight glasses of water daily and other drank no extra water; they got their fluids from food and liquid drinks but notwater. At the end of the study there was no difference in the two group’s health. Don't bother me with facts; I just plain don't believe it.
It so happens that I have a book this doctor wrote and in his book he strongly advocates drinking eight glasses ofwater a day (64 ounces). In the book he rationalizes that water lubricates our bodies, fights bad breath and helps avoid kidney stones. Digestion and absorption depend on water. All that fiber we mentioned above needs water to bulk up like it's supposed to.
Bottom line is drink the water but get a filter on your tap to remove the antibiotics, estrogen and other garbage from the water coming into your home. You can link here to "water health" to read about the stuff that our municipal treatment plants can't remove.
Exercise good oral hygiene
It may sound strange to discuss oral hygiene as part of the digestive system but several studies have found that men with a history of periodontal disease had a 64 per cent increased risk of pancreatic cancer than men with no such history.
In addition, increased severity of periodontitis, for example with recent tooth loss, had the greatest risk. No significant links were found between other types of oral health problems such as tooth decay and cancer of the pancreas.
It has also been shown that people with periodontal disease have an increased level of inflammatory markers such as C reactive protein (CRP) in their blood. These markers are part of an early immune system response to persistent inflammation and have been linked to the development of pancreatic cancer.
Pancreatic cancer is one of the most horrible diseases conceivable and if the referenced studies have anymerit, flossing the teeth is incredibly cheap insurance.
Dangerous toxins can creep in from the most unexpected places. We all know to avoid spoiled food, uncooked meat and fish and the picnic chicken, tuna and macaroni salads that have been sitting in the sun for several hours. The recommendation for cooking the meat and fish is to use a food thermometer to be sure that the inside of the food reaches 165 degrees for over 15 seconds.
We tend to get careless with things like the sponges in the kitchen that we use over and over again to wash our dishes. Bacteria grow on those sponges like the bacteria in the lab grow in the culture dish. If you have to use them, throw them out after two or three uses or use them to wash the car but not your dishes.
Buy a bunch of cheap wash cloths, use them once in the kitchen and then wash them in the machine. It could save you from a bout of vomiting and diarrhea.
As we mentioned, with Crohn's disease and ulcerative colitis, inflammation is a major factor. Inflammation can be both a cause and a result of some condition. Inflammation is the body's normal response to infection,trauma, or disease and characterized by swelling, redness, pain and heat. All these are the result of the immune reaction where blood rushes to the site of injury.
Inflammation is also an autoimmune reaction where the body perceives that there is an invader when there is noneand ends up attacking itself. There are about 60 or so autoimmune diseases of which Crohn's and colitis are two.
There is a huge body of evidence that autoimmune inflammation results when we have an imbalance in omega 3 and the other omegas, all of which are fatty acids. There should be a one-to-one ratio between omega 3 and omega 6.Most of us get way too much omega 6 and not enough omega 3.
When this happens, inflammation messengers known as arachidonic acid are created. Their role is to wake up the immune system and marshal the troops to fight the invading virus, bacteria, infection or whatever. If there is nothing to fight, they will attack a joint as in rheumatoid arthritis or a colon as in colitis.
Anytime we see the "itis" on the end of a disease, that means it is an inflammation.
The bottom line is to supplement with the best omega-3 you can find. Be sure it is pharmaceutical grade and molecularly distilled to remove heavy metals from the fish it came from. Also avoid foods that tend to createthe arachidonic acid cascade. A page on autoimmune diseases is included in this site.
Google Search Box for "Healthy by Nature" website
Leave Digestive System and return to Human Anatomy
Navigate to Cardiovascular System
Navigate to Respiratory System
Navigate to The Endocrine System
Navigate to The Musculoskeletal System
Navigate to The Immune System
Navigate to The Nervous System
Navigate to Cell Physiology
Return to Home page
Visit the Site Mall for dietary supplements to help the GI tract