The purpose of this course is to instruct on basic anatomy and physiology of the digestive system (GI), itís disorders, changes in aging, and the nurses role in each aspect of the GI system and its diseases and prevention of.


  1. Upon completion of this course you should be able to:
  2. The student will be able to describe the anatomy, physiology of the GI system, changes that can occur, and the nurses role.
  3. The student will be able to verbalize their knowledge of disorders/ disease in the GI system and educate their patients.
  4. The student will have verbal knowledge of congenital and inherited disorders of the GI system.
  5. The student will be able to identify changes in the GI system that come with aging, they will be able to educate the patient with this knowledge when needed.
  6. The student will verbalize the knowledge to complete a nursing assessment on the GI patient.
  7. The student will have a verbal knowledge of treatments and test that are associated with the GI system & their responsibilities in relation to.


The gastrointestinal (GI) system is also called the digestive system because of its function to digest and absorb food. This system begins in the mouth and ends in the anus. The digestive system breaks down food and changes it. This allows it to be used by the cells within the body for both chemical and mechanical processes.


The mouth is also called the bucal, or oral cavity. Three sets of salivary glands secrete into the mouth through ducts. The teeth and the tongue are considered helpers or accessory organs of digestion. The esophagus which leads from the mouth to the stomach, it is located in the mediastium in the thoracic cavity, anterior to the spine and posterior to the trachea and heart. It is a collapsible tube about 10 inches in length; it becomes distended when food is being passed through it. A sphincter muscle called the cardiac sphincter, guards the opening to the stomach from the esophagus; this is called the esophagogastric junction. This flap or muscle relaxes to allow the passage of food and fluids, and after the passage is complete the muscle contacts to prevent the backflow of food and fluids.

The stomach is a pouch like structure located in the upper portion of the abdomen to the left of the midline, just under the liver and diaphragm. The stomach is a distensible pouch with the ability to hold approximately 1500 ml. The stomach is divided into three parts; the fundus, the upper portion nearest to the esophagus; the middle section, or body; and the pylorus, which is the lower part. The outlet leading out of the stomach is the pylorus and it contains the pyloric sphincter, which like the cardiac sphincter keeps food in the stomach and allows it to leave the stomach at the appropriate time.

The small intestine is the longest segment of the GI tract. It is approximately 20 feet in length. It is folded back and fourth on itself to make room for its length; it occupies a major portion of the abdominal cavity. The small intestine consists of three sections: The section nearest to the stomach, the upper section is called the duodenum, the middle section is the jejunun, and the lower section is known as the ileum. The common bile duct, the conduit for bile and pancreatic secretions, empties into the duodenum. Most of the digestion and absorption of food takes place in the small intestines.

The junction between the small and large intestines usually lies in the right lower portion of the abdomen, the large intestines is only six feet in length but it has a larger diameter then the small intestines. The large intestine has three sections to it. The cecum, which begins where the large intestines join the small intestines; the cecum is only a few inches long, this is where the vermiform appendix can be found it is located at the end of the cecum. The vermiform appendix is a small worm shaped tube with no known purpose. The ileoceal valve is located at this site it is similar to the pyloric or cardiac valve where it prohibits the backing up of digestive product. Then there is the colon, the colon ascends from the cecum upward on the right side of the abdomen, then it crosses over the abdomen below the stomach and continues downward on the left side. The colon as been separated into three areas; ascending, transverse, and descending. As the colon descends, the final portion is shaped like an S and is called the sigmoid colon. The sigmoid then joins the rectum, which are approximately seven to eight inches in length. The final inch makes up the anal canal. The opening from the anal canal to the exterior is guarded by two sets of muscles, the internal sphincter and the external sphincter, which unlike any other sphincter muscle in the GI tract it is composed of striated muscle and is under voluntary control. The final opening to the exterior is the anus. The GI tract is lined with muscles that contract involuntarily to produce a wave like action called peristalsis. 3

The liver, gallbladder, and pancreas are accessory organs. They assist the process of digestion by contributing specific secretions and enzymes essential for normal digestion and use. The liver, located on the right side of the body under the diaphragm, is the largest of the organs. The liver has many functions and is considered one of the most vital organs in the body.

The gallbladder is shaped like a pear and lies under the liver. The gallbladder stores and concentrates bile and releases it into the duodenum during the process of digestion.

The pancreas is a slender organ, fishlike in shape; it is located at the back of the stomach. Located within the pancreas are cells called islands of Langerhans. These cells are responsible for the production of insulin.

Since the GI tract is so long the blood supply comes directly from the arteries that run along the entire length of the thoracic and abdominal aorta. This is the largest artery in the body.


In order to perform all of the above functions, all cells of the body require nutrients, which must be derived from the intake of food that the body consumes. Digestion is a process by which food is prepared so that it may be absorbed and utilized by the body in the most efficient way. The body needs protein, fat, carbohydrates, vitamins, and minerals, as well as cellulose, fibers and other vegetable matter. This diet provides energy the body needs to maintain optimum body weight and health. The intake of food is involuntary and it is controlled by a conscious sensation of hunger, modified by learned behavior.

The process of digestion starts with the act of chewing, in which food is broken down into small particles (mastication) that can be swallowed and mixed with digestive enzymes. The first secretion encountered is saliva, which is secreted in the mouth by the salivary glands at the rate of about 1.5 liters each day. Saliva contains enzymes; ptyalin, or amylase. These help in the digestion of starches. It also stimulates the taste buds to taste. The smell, sight or taste of food will stimulate the production of saliva. The major function of saliva is to lubricate the food as it is chewed.

It is from the mouth to the stomach that the food is passed with the help of mucus from these same salivary glands, and from the mucus secreting glands along the esophageal walls.

Swallowing is a voluntary act and is the first act of braking the food down. As one swallows the esophagus widens and pushes the bolus of food down into the stomach through the esophagus enter the stomach through the cardiosphinter valve. The muscle relaxes to allow food to enter the stomach and then contracts to prevent the possibility of back flow.

The pyloric sphincter controls when the semi fluid contents of the stomach (chyme) enter into the small intestine (duodenum) their passage. Food is moved along the entire length of the GI tract by a wavelike muscular contraction called peristalsis.

Mechanical digestion can be best described as cutting, grinding, and pulling apart of. Some times this is done for a patient prior to delivery of their meal to them. An elderly person who has lost their teeth and have no dentures will have a problem chewing their food. This is when a mechanical soft diet may be ordered. In this process the meat will be cut up in very small pieces. with this diet the patient misses the importance of the normal food breakdown. As this action goes on, numerous enzymes are being secreted that chemically act on the variety of ingested foods. 5

Chemical digestion is the action of enzymes on the proteins, carbohydrates, and the fats by breaking them into simple compounds in preparation for absorption. The major part of chemical digestion occurs in the small intestine, where all foods undergo an enzymatic action. The breakdown of carbohydrates starts with digestion in the mouth with the breakdown of starches by the salivary amylase. The end result is small sugar molecules called disaccharides. Glucose is the major carbohydrate that the tissues use for fuel.

Proteins are long chains of amino acids linked together chemically. The hydrochloric acids in the stomach breakdown these proteins into smaller particles, which are easier to absorb.

Ingested Fats begin with a breakdown of fats. This occurs as a result of the break down process within the stomach and duodenum. The tissues use fat for fuel. Excess fat is stored in the fat cells that are widely distributed throughout the body.

Vitamins in the diet are absorbed essentially unchanged from the GI tract.

Minerals in the diet, such as calcium and iron, are absorbed in the small intestine. Calcium absorption requires the presence of vitamins.

There are no enzymes in the large intestines. After the residue from the small intestine passes through into the colon, water and some electrolytes such as sodium and chloride are absorbed into the blood.

Bacteria in the colon completes the digestion of any undigested foods and synthesize of vitamin K and vitamins B12, B2, and B1, which produce gas that assists in propelling feces toward the anus. The urge to defecate is a reflex stimulated by distention of the rectum. Voluntary relaxation of the rectal sphincter assists defecation. It takes approximately 24 to 40 hours for feces to pass through the large intestine.

6 The liver plays an important role in the breakdown of carbohydrates, fats and proteins. The liver assists with the regulation of blood glucose as needed. When glycogen levels are low, the liver removes ammonia from the amino acids and turns it into glucose, glycogen or keytones for energy.( When there is damage to the liver these processes are not complete; see hepatitis). The liver also plays a role in the breakdown of proteins, helping with tissue repair. It also works on the prothrombin and fibrinogen for blood coagulation, (to prevent bleeding). The liver stores vitamins, including vitamin K the other oil-soluble vitamins, it is also the primary site for vitamin B12 storage.


Constipation: Seems simple, no big deal. Constipation can lead to impaction, and can be fatal. Constipation is the most common disorder of the GI tract. Many people think that if you donít have a bowel movement every day it will result in absorption of poison. This is not true, the average person needs to defecate at least every three days; again this varies per individual. Many things effect bowel movements; diet, fluid intake, age, stress level, decreased activity level, and medications,, chronic use of enemas/suppositories, lack of privacy, and pregnancy can be factors as well. The defining characteristics are decreased frequency of elimination, a hard formed stool, straining while defecating, feeling of rectal or abdominal pain, nausea, decreased appetite, and headache.

The treatment of constipation must be based on the type of constipation and the individuals needs. Frequently used methods are laxatives, such as milk of magnesia, then suppositories, and then if those do not work and enema is usually given. If constipation is not remedied quickly, the hard stool backs up and causes impaction. Impactions can be very serious, first you try to get the hardened stool to come down into the large intestine with a strong liquid laxatives, such as citrate of magnesium. Impaction can lead to perforation of the bowel, if this happens life threatening disorders such as peritonitis may occur. Patients can end up dead or with a colostomy. Bowel movements are very important. 7

Gastritis: An inflammation of the stomach lining of which two forms are known. Acute which may be caused by severe burns, major surgery, aspirin and other anti-inflammatory medications, steroids, food allergens, viral, and bacterial. Signs and symptoms are anorexia, nausea, vomiting, discomfort after eating, and most often goes away after the causative factor is removed.

Chronic gastritis : This is usually a sign of an underlying disease, such as peptic ulcer, stomach cancer, Zollinger- Ellison syndrome, or pernicious anemia. a scope and biopsy is necessary for proper diagnosis.

Ulcertive Colitis: This is an inflammatory disease of the colon,(the large intestine). It is characterized by the inflammation and ulceration of the inter most lining of the colon. Symptoms include diarrhea with or without rectal bleeding, and abdominal pain. Other disorders that are very similar to ulcerative colitis are, Irritable bowel syndrome, which is abnormally increased motility of the small and large intestines, caused by stress. Symptoms are very similar to ulcerative colitis and are frequently seen in young adults. Chrons disease, is a chronic inflammatory bowel disease of unknown origin. It can effect different parts of the intestinal tract, they call this skipped lesions. Symptoms are severe abdominal pain, diarrhea, nausea, fever, chills, weakness , and weight loss.

Treatments for all of the above GI disorders are; remove the causative agent. many times this is STRESS. The person needs to find a healthy way of dealing with lives ups and downs. If you internalize all of your worries, it will show up, many times in your GI tract. Nutrition has to be provided and encouraged. Rest and fluids are very important, many times these patients are not hungry but they need to get nutrients and hydration. Sometimes these disorders are treated with antibiotics, anti-inflammatory, anti-anxiety medications.

Hepatitis: Simply means inflammation, or irritation, and enlargement to the liver and is one of our major killers these days. There are numerous kinds of hepatitis, A-G, and all of these affect the liver in a serious way.

Hepatitis has become such a deadly disease (I have decided to touch it briefly here and if you need or want more information on the subject , you can look at the course on Hepatitis).

The most important factor as a health care worker it is to follow standard precautions; blood to blood is the form of transmission for this deadly disease, and only you can prevent that.

Cirrhosis: Scarring of the liver. This is a disease in which the cells of the liver undergo degeneration and are replaced by fibrous tissue. These cells do have potential for regeneration, if the causative agent is removed, such as alcohol, legal and illegal drugs. We will examine this more in depth in the course on Addiction. Cirrhosis develops slowly and the progression causes the liver to fail. Once the liver has failed completely the patient has a high probability of dying.

Treatment is to remove the causative agent, good nutrition. Depending on what stages the patient is in, frequently diuretics are given to eliminate some of the fluids that the body is unable to. Detoxify medications are given to rid the blood of accumulating poisons that the liver usually breaks down and disposes the body of. Jaundice,(yellowing of the skin) can cause itching and much discomfort. Medications and medicated baths can help this problem. The cells in the liver are one of the few we can regenerate, so the most important treatment of this fatal disease is to stop the cause.

Cholelithiaisis: Presence of stones in the gall-bladder. These stones are frequently composed of cholesterol, calcium, and bilirubin. They can be very large, measuring inches across, or very small as a grain of sand. Gallstones many times block the duct and prevent the release of bile; the bile then accumulates and causes inflammation to the inside walls of the gallbladder causing a lot of pain. If the blockage persists the gallbladder can become gangrenous. A good diagnostic tool is to assess the patientís pain after they have eaten, especially fatty foods. This will cause serve pain in the right upper quadrant of the abdomen. Treatment can be as simple as medications that can dissolve the stones or many times surgery is necessary to remove the stones.

Cancer: There are many kinds of cancers in the GI system, starting with the mouth, lips and tongue. The cancers in this area may be malignant or benign. Cancer of the tongue is the most common mouth cancer, and the cause is usually cigarettes, alcohol, dental appliances and rough jagged teeth. Cancer of the mouth metastasizes (spread) quickly. Treatment is radiation, and removal of the area.

Esophageal cancer claims over 6000 deaths in the US each year. Difficulty swallowing is the primary problem and leads to malnutrition. This cancer metastasizes much slower and if caught early can have a good outcome. Many of these patients end up with a gatrostomy tube. A gastrostomy tube, is a tube that is surgically placed into the stomach to allow nutrition to be given via an external tube.

Stomach cancer: The occurrence of this cancer has diminished. People who do not produce enough stomach acids are more likely to get stomach cancer. Diet has been identified as an contributing factor. Early symptoms are poor diet feeling of fullness, epigastric pain, nausea, vomiting, weight loss, and coffee ground emesis, (blood coming from high up in the system).

Many people put off seeing a doctor and the cancer spreads; by the time it is discovered it is to late for treatment. Treatment would be removal of the cancer, radiation, chemotherapy and prayer.

Cancer of the small intestines. Cancer in this area is less frequent, symptoms include upper abdominal pain, and bleeding. Treatment involves removal of the cancer as this cancer spreads quickly and has a poor prognosis.

Colon-Rectum Cancer: These cancers are the most common internal cancers in the USA. Early diagnosis is the most important tool to cure. Patients with other diseases of the GI tract are more prone to getting this cancer. There is a link of low fiber diets and colon cancer. symptoms include rectal bleeding, alternating diarrhea and constipation, excessive flatus and cramp like pains in the lower abdomen with abdominal distention.

Treatment is always surgical, with postop radiation therapy. Many of these patients end up with a colostomy.

Colostomy: A surgical creation of an artificial anus on the abdominal wall by incising the colon and bringing it to the surface. This procedure is commonly done for cancer. Once the surgery is complete the patient will have to be taught to use the colostomy appliances; the wafer and the colostomy bag. This is a nursing responsibility, the nurse must always take into consideration the altered body image this patient is facing and offer all of the appropriate measures to ensure the patients dignity.

Nursing Assessment:

Many of the nursing responsibilities have been covered in the above materials, but the major things the nurse wants to look for are:

Pain- Look at the location, character of the pain, duration, frequency, if they have just eaten, or defecated.

Indigestion- did they eat fatty foods, spicy foods, where is the complaint coming from.

Intestinal ďGASĒ (Belching or flatulence).

Vomiting- note color and consistency, remember Coffee ground emesis (Hematemesis) can be fatal.

Diarrhea- Also look for color and consistency here, dark, black sticky tar looking stool can be signs of bleeding and should be dealt with soon (iron and pepto bismol can also cause dark tar stools). A person loses a lot of potassium with increased liquid stools this can cause other complications.

Constipation- we covered this well in the pervious section, please just remember this can be a serious problem.

In conclusion the GI system is one of the most intense systems and many things can go wrong within it. As the nurse your assessment skills and promptness can make a difference between comfort and misery and life and death. Always remember to give the patient the utmost dignity when it comes to dealing with issues related to their GI system, this is a very private and personal area of our lives please treat it as such.

God Bless You..