The Gastrointestinal (Digestive) System Reference Sheet
Goal of Digestion: To break down food, macromolecules, into usable nutrients and
energy that the body can absorb for different purposes. A by product of this process is
the formation of waste.
The Digestive System begins at the mouth, where food enters the body, and ends at the
rectum where waste is excreted. Following the GI tract, food is then broken down for
Organs Involved in Digestion: Mouth, esophagus, stomach, small intestine, large
intestine (colon), and rectum
Ancillary Organs Involved in Digestion: Liver, gall bladder, and pancreas
Enzymes Involved in Digestion: Saliva, bile, pepsin, lipase, hormones, and digestive
Process of Digestion:
Mouth- Starts the breakdown of food for the Digestive System by metabolizing it
into smaller pieces. Using saliva excreted from the salivary glands and teeth for
fast, effective digestion, the food will be able to fit through the esophagus
After food is swallowed, it is moved into the esophagus by a process known as
peristalsis, wave contractions that push food downward into a tube that connects
the mouth and stomach
Esophagus- This organ continues the digestion of food, but focuses on pushing
the remnants down into the stomach for a more detailed process
Stomach- After passing through the esophagus, food then enters the stomach.
The stomach then starts one of its main goals for digestion: secretion of digestive
juices that will break down the larger macromolecules into smaller, usable
nutrients. While some of these nutrients will be absorbed in the stomach, most of
them will be utilized later on. The stomach then liquefies the food so it is suitable
for entry into the small intestine.
Liver- An ancillary organ, addition for extra support and effective digestion, the
liver has a key role in the break down of food. The liver secretes an enzyme
called bile that helps the absorption of fatty products when released into the small
Gall Bladder- Working closely with the liver and located right near it, the gall
bladder takes the bile and stores it until it needs to be released into the duodenum,
a section of the small intestine. This bile will then be put to work throughout the
small intestine and help speed up the breakdown of food. While also being an
ancillary organ, it is very essential to digestion.
Pancreas- Also an ancillary organ, the pancreas is an exocrine gland that secretes
important hormones into the small intestine which regulate blood glucose levels
and break down food using other necessary digestive enzymes.
Small Intestine- After the liquefied food passes through these added organs, it
enters the busiest part of the digestive system known as the small intestine. The
small intestine is made up of three segments: the duodenum, jejunum, and ileum.
The duodenum is where the stomach and small intestine meet and is the height of
all the interaction. The most effective digestion gets done here as bile and,
digestive enzymes, and hormones are all released to get work done. The jejunum
is designed specifically to break down carbohydrates and proteins using specific
enzymes known as pepsin and lipase, which will then be converted into nutrients.
Finally, the ileum is specifically designed to function in the process of breaking
down fatty products and left over bile salts.
Large Intestine- After joining the large intestine, also known as the Colon, the
food that cannot be digested moves as a waste product throughout this tube until it
reaches the rectum
Rectum- The last organ in the process of digestion, the rectum is the bottom
portion of the small intestine. The rectum stores the waste products until they
firm up and the body is ready to rid of them
Special Cell Types Involved in Digestion:
Epithelial Cells- Line the inner surface of the stomach for protection against acid
and also secrete gastric juices helpful in digestion. In the small intestine, these
cells secrete a watery mucus in order to make the process more effective at a rapid
Exocrine Cells- Secrete digestive enzymes and hormones into the small intestine
from the pancreas in order to regulate blood glucose levels and aid in digestion
Parietal Cells- Secrete hydrochloric acid from the gastric glands that helps with
the breakdown of proteins
Chief Cells- Secrete pepsinogen, the precursor to pepsin, which will also help in
the breakdown of proteins
Villi Cells- The villi are fingerlike projections in the small intestine that contain
many cells. Goblet cells found in the villi secrete mucus while paneth cells help
sterilize all the contents in the small intestine. The villi also contain stem cells
and others that aid in the breakdown of sugars and peptides in order to speed up
the digestion process.
Crohn’s Disease Info.
Crohn’s disease is an inflammatory bowel disease, the general name for diseases
that cause swelling in the intestines.
- No definite cause is known
o Theories Include:
o Genetic problems
Most common in Caucasians and Jews, Family History
1 of 5 people with Crohn’s disease has a relative with an
inflammatory bowel disease.
Considered a Complex trait: Several genes at different locations
contribute to having the disease.
digestive tract inflammation seen in people with Crohn's disease is
also seen with other types of infections
No known bacterial, viral, fungal or parasitic cause of Crohn’s.
o Problems with the Immune System
The body's immune system reacts abnormally in people with
Crohn's disease, mistaking bacteria, foods, and other substances for
being foreign. The immune system's response is to attack these
"invaders." During this process, white blood cells accumulate in
the lining of the intestines, producing chronic inflammation, which
leads to ulcerations and bowel injury.
Several symptoms of Crohn’s disease are known to be related to an
immune system problem.
Foreign substances (antigens)
Body’s reaction to these antigens is inflammation
A protein produced by the immune system, called anti-tumor
necrosis factor (TNF), may be a possible cause of the inflammation
associated with Crohn's disease.
Inflamed intestinal wall
Because the symptoms of Crohn’s disease are similar to
other intestinal disorders, such as irritable bowel
syndrome and ulcerative colitis, it can be difficult to
In Crohn’s disease, all layers of the intestine may be involved, and normal healthy
bowel can be found between sections of diseased bowel.
Crohn’s disease affects men and women equally and seems to run in some
About 20 percent of people with Crohn’s disease have a blood relative with some
form of inflammatory bowel disease, most often a brother or sister and sometimes
a parent or child.
Crohn’s disease can occur in people of all age groups, but it is more often
diagnosed in people between the ages of 20 and 30.
People of Jewish heritage have an increased risk of developing Crohn’s disease,
and African Americans are at decreased risk for developing Crohn’s disease.
Complete Gastrointestinal Tract
Abdominal pain (lower right area)
Bleeding may be serious and persistent, and can lead to anemia. Children with Crohn’s
disease may suffer delayed development and stunted growth. The range and severity of
How it’s diagnosed:
Blood tests may be done to check for anemia, which could indicate bleeding in
the intestines. Blood tests may also uncover a high white blood cell count, which
is a sign of inflammation somewhere in the body. By testing a stool sample, the
doctor can tell if there is bleeding or infection in the intestines.
The doctor may take an x ray of the upper GI
series to look at the small intestine. For this test,
the person drinks barium, a chalky solution that
coats the lining of the small intestine, before x
rays are taken. The barium shows up white on x-
ray film, revealing inflammation or other
abnormalities in the intestine.
The doctor may also do a visual exam of the
colon by performing either a sigmoidoscopy or
a colonoscopy. For both of these tests, the doctor inserts a long, flexible, lighted
tube linked to a computer and TV monitor into the anus. A sigmoidoscopy allows
the doctor to examine the lining of the lower part of the large intestine, while a
colonoscopy allows the doctor to examine the lining of the entire large intestine.
The doctor will be able to see any inflammation or bleeding during either of these
exams, but a colonoscopy is usually a more effective test because the doctor can
see the entire large intestine.
The doctor may also do a biopsy, which involves taking a sample of tissue from
the lining of the intestine to view with a microscope.
Blockage of the intestine due to thickening of the intestinal wall due to scar tissue.
Crohn’s may also cause sores or ulcers that permeate into other surrounding
Protein, vitamin, and mineral and calorie deficiencies may be experienced due to
the body attacking food thinking that it’s an invader.
Kidney Stones, Gall stones
Drugs, Nutritional Supplements, Surgery, or a combination of those
o Goals: to Control inflammation, correct nutritional deficiencies, and
relieve symptoms such as abdominal pain diarrhea or rectal bleeding.
Some individuals may experience long periods of remission
o Drugs containing mesalamine, a substance that helps control inflammation
o Treated with drugs containing mesalamine, a substance that helps control
inflammation, for individuals who cannot tolerate mesalamine treatment
Cortisone or Steroids:
o In the beginning, when the disease it at its worst, prednisone is usually
prescribed in a large dose. The prednisone is used to reduce inflammation
and relieve pain. The dosage is then lowered once symptoms have been
Immune System suppressors;
o Immunosuppressive agents work by blocking the immune reaction that
contributes to inflammation
o These drugs may cause side effects like nausea, vomiting, and diarrhea
and may lower a person’s resistance to infection
o Often used in conjunction with corticosteroids.
o The first of a group of medications that blocks the body’s inflammation
o Used for crohn’s disease that does not response to mesalamine treatments.
Anti-Diarrheal and Fluid Replacements
o Several antidiarrheal agents could be used, including diphenoxylate,
loperamide, and codeine. Patients who are dehydrated because of diarrhea
are be treated with fluids and electrolytes.
Nutritional supplementation may be necessary to compensate for dietary sacrifices that
are made as a result of having the disease
Surgery may be necessary when medication is no longer effective, and portions of the
intestine are removed.
The purpose of this study is to assess the effects of injectable treatment 5mg/kg
intravenous infusions to in prevent relapse of Crohn's disease after surgery. Patients will
initially receive either infliximab or placebo. Each patient who is allowed to join the
study is put into a group by chance (randomly), like flipping a coin. If a patient is initially
randomized to receive placebo and their study doctor confirms that they have had a return
of active Crohn's Disease symptoms, they can receive the injectable drug. If a patient is
initially randomized to receive the injectable drug and their study doctor confirms that
they are experiencing symptoms of Crohn's Disease they may receive an increase in their
Peptic Ulcer Information
Open sores that develop on the lining of esophagus, stomach, and small intestine.
Peptic ulcers that occur on the inside of the stomach are called gastric ulcers
Peptic ulcers that occur on the lining of the esophagus are called esophageal
Ulcers that occur on the small intestine are called
Causes: Bacterial infections or some medications
Pain- most common
o Caused by the stomach ulcer and is aggravated
by stomach acid
o Pain can be felt from navel to breastbone,
especially at night
o Pain can be relieved by eating foods that buffer stomach acid, or taking
o Pain may disappear and reappear every few weeks.
Vomiting of blood
Nausea and vomiting
Unexplained weight loss
Acid in the digestive tract eats away at the inner surface of esophagus, stomach,
or small intestine. Acid can cause the painful, open sores that may bleed
o Another cause of ulcers is the corkscrew-shaped bacterium Helicobacter
pylori. H. pylori bacteria live and multiply within the mucous layer that
covers and protects tissues of the stomach and small intestine. Usually, H.
pylori causes no problems. But sometimes it can disrupt the mucous layer
and inflame the lining of your stomach or small intestine, producing an
Regular use of painkillers
o Over the counter or prescription pain medications may cause inflammation
or irritation of the linings of the stomach or small intestine.
o Medications include: Aspirin, ibuprofen, naproxen, etc.
o Acetaminophen does not cause peptic ulcers
The main goals for treating a peptic ulcer include getting
rid of the underlying cause (particularly H. pylori infection
or use of pain medications), preventing further damage and
complications, and reducing the risk of recurrence.
Medication is almost always needed to alleviate symptoms
and must be used to eradicate H. pylori.
Surgery is required for certain serious or life-threatening
complications of peptic ulcers and may be considered if
medications are not working.
In a study conducted by the Zaozhuang Hospital of TCM, Shandong. Two hundred
patients afflicted with peptic ulcers, diagnosed by fiber-gastroscope, were treated with
Yuyang powder (YYP) and observed and compared with patients treated with cimetidine
(a drug usually used to treat most gastric ulcers) as a control. Results showed that the
curing rate of YYP on peptic ulcer was 88.1%, the total effective rate was 96%. But the
difference of recurrence rate (19.1% for YYP and 46% for control) between the two
groups was very significant, showing that YYP could be used as an effective cure for
peptic ulcers. YYP has a better rate of protecting the mucus lining of gastric tissues. This
study also shows that YYP is also relatively efficient in strengthening the gastric tissues.
Gastroesophageal Reflux Disease
GERD is the back flow of stomach contents which results in uncomfortable
There is no specific cause of GERD. It occurs when the Lower Esophageal
Sphincter relaxes. The
sphincter (LES) is a
band of muscles that
lies where the stomach
and esophagus connect.
The LES normally
works together with the
diaphragm as a barrier
in order to block
stomach acid from
entering the esophagus.
If this barrier is
relaxed, the acid can
enter and reflux occurs.
Too much reflux will
result in GERD.
Signs and Symptoms:
It is common for symptoms to not occur in GERD. However, if they do, the
patient can experience:
- Chronic heartburn- Can awake patient from sleep.
- Sore throat
- Difficulty/painful swallowing
- Hoarseness in the morning
- Regurgitation of acid
- Waterbash- Excess of saliva.
- Dysphagia- Food sticking to the esophagus.
- Inflammation of gums
- Erosion of teeth enamel
There are two types of GERD: Non-erosive GERD and erosive GERD. Because
of the persistent exposure of acid to the esophagus, it is likely for tissue damage to occur.
The tissue damage signals that the patient has erosive GERD. However, there isn’t any
visible evidence of tissue damage.
Chronic heartburn can also cause complications. It can result in stricture or a pre-
cancerous disease known as Barrett’s Disease. This involves a cellular change in the
There are many ways to treat GERD. A patient can change their lifestyle, use
medications, or undergo surgery. The main goals of treatment are to control symptoms
and reduce inflammation.
Although diet does not cause GERD, changing eating habits can help relief
symptoms because certain foods can further irritate the body and cause heartburn and
reflux. Also, a patient can sit in an upright position after meals. This is to prevent food
from being pushed up into the sphincter by the abdominal muscles. The patient should
also avoid large meals late in the day. Experimentation with eating habits is the best way
for a patient to discover which habits irritate the symptoms the least. Because obesity can
further promote acid reflux, a patient of GERD should reduce their fat, onion, and
Another way to treat GERD is to use medications. Before using any medications,
the patient should consult their doctor to become aware of the risk factors. Patients with
non-erosive GERD may reduce their symptoms by using promotility drugs. There are
known adverse side effects of the drug cisapride (Propulsid) for patients who have
preexisting conditions. Another form of medication is H2 Blockers. These work to
decrease the amount of acid in the stomach which reduces the amount of symptoms
experienced. With a small amount of acid and other symptoms, the esophagus can begin
to heal. Although medication lessens the symptoms, patients may have to be on
medication for the remainder of their life.
Aside from medication and life style changes, a patient with GERD also has the
options of undergoing surgery. Complications may occur in about 5-20% of patients.
These side effects include difficulty swallowing or losing the ability to belch or vomit.
However, these side effects usually do not last. Also, surgery may not completely
eliminate acid reflux and the patient will have to continue with medication.
Cyclic Vomiting System
Cyclic Vomiting Syndrome is a disorder in which episodes of vomiting and
nausea occur with periods that are symptom free.
There is no direct cause of CVS. It can be brought on by many experiences. Some
triggers of CVS include infections, emotional stress and excitement, anxiety, panic
attacks, colds, allergies, certain foods such as cheese, or eating too much. Also, hot
weather, exhaustion, menstruation, and motion sickness cause trigger CVS.
In order to be diagnosed with CVS, the patient must meet the following criteria
for the last three months with symptom onset of at least six months:
1. Episodes of vomiting regarding onset.
2. Three or more discrete episodes in the past year.
3. Lack of nausea and vomiting between episodes.
The symptoms of CVS occur in a serious of four stages:
The first stage is the inter-episodic phase which occurs between vomiting
episodes when the patient for the most part does not experience any symptoms. This
phase usually last weeks to months. The next stage is the pre-emesis phase. This occurs
when the patient first senses the approach of a vomiting episode and experiences nausea
but is still able to take oral medications. This phase lasts minutes to hours. The third stage
is the emetic phase. This includes intense, constant nausea, vomiting, and other
symptoms that include abdominal pain, prostration, and lethargy. This phase lasts from
hours to days. The final stage is the recovery phase which begins with nausea
experienced diminishing. It ends when hunger, tolerance of oral intake and vigor returns
- Dehydration: Loss of water in the body due to vomiting.
- Electrolyte Imbalance: Loss of salts due to vomiting.
- Peptic esophagitis: The esophagus becomes injured because of the stomach
acid moving through it.
- Hematemesis: The esophagus bleeds because of irritation.
- Mallory-Weis tear: The lower end of the esophagus may tear. Also, the
stomach may experience bruising.
- Tooth decay: The enamel corrodes because of repeated exposure to acid.
The best way to treat CVS is with bed rest and sleeping in a dark, quiet room. If
nausea and vomiting becomes too severe, then the patient may have to be hospitalized
and be given intravenous fluids to prevent dehydration. Also, sedatives may be given to
the patient to help with the nausea. Medications can also help with patients suffering
from CVS. Medications include ondansetron (Zofran) or lorazepam (Ativan) for nausea
or ibuprofen (Advil, Motrin) for pain. To help the stomach and reduce the amount of acid,
ranitidine (Zantac) or omeprazole (Prilosec) are helpful. Also, while in the recovery
phase, patients should drink a lot of water to replace electrolytes.