Anatomy/Digestive System

The digestive system is a topic of the event Anatomy. It scheduled to be a part of the event during the 2018 season with the respiratory system and the immune system.

For a list of secretions in the digestive system, see the Digestive Secretion List.

Overview
The digestive system is the system that breaks down food and returns water and nutrients to the blood stream. It is necessary because it provides energy to the cells in your body. The digestive system is made up of organs such as the esophagus, stomach, liver, and the intestines.

Functions
It provides nutrients by:


 * Taking in food (ingestion)
 * Breaking down food (digestion)
 * Absorbing digested molecules (absorption)
 * Eliminating waste (elimination)

Summary of the Digestive Tract


The digestive tract is about 8 meters, or 28 feet long. It can take from 15 to 72 hours for food to pass from the mouth to the anus.

The mouth is where the digestion of food starts. The mouth is a good example of mechanical digestion and chemical digestion at work. The teeth chomp, chew, and tear food down into smaller pieces (mechanical digestion). The molecular structure of the food does not change in mechanical digestion. Then, the salivary glands secrete saliva into the mouth, breaking down starches into dextrin and maltose (chemical digestion). Saliva is a form of chemical digestion because it changes the molecular structure of the food. These digestive processes create food boluses.

After food boluses are developed in the mouth, they go down the pharynx. The pharynx is a shared connection between the nasal cavities, the mouth, the air tract, and the esophagus. Therefore, there must be a structure to prevent the boluses from entering the trachea (passage to the lungs). This is why we have an epiglottis. The epiglottis is a small flap which can open and close the entrance to the trachea. When food boluses travel through the pharynx, the epiglottis folds down to protect the airway. However, in instances like when you talk and eat, the epiglottis can get confused. In order to talk, the epiglottis must be open. In order to swallow, the epiglottis must be closed. Therefore the epiglottis might malfunction and you could choke. This is why you shouldn't talk with food in your mouth.

After the pharynx, food bolus is transported to the stomach via the esophagus/oesophagus. The esophagus is a muscle-walled tube that goes from the throat to the lower digestive tract. To help food get down, muscular contractions called peristalsis push food down towards the stomach. To demonstrate peristalsis motions, imagine a sphere in a rubber tube. the diameter of the sphere is a little more then the diameter of the tube. If you wanted to get the ball out, you would squeeze the tube from one end, and slowly move your hand towards the ball while squeezing to push it out. The reason peristalsis is important is when we are working against gravity. For example, when you eat upside down, the food bolus is still able to move to the stomach because of peristalsis contractions.

Next in the digestive tract comes the stomach. When we think of digestion, the first thing that comes to mind is the stomach. It acts like a waiting room for food bolus. While the food boluses are waiting, the stomach breaks the food down into a liquid-like mixture by churning the food (mechanical digestion) and secreting gastric acid (chemical digestion). Gastric acid also kills bacteria that may be in the food.

When food boluses are ready to be further digested, they transfer to the duodenum by contractions of the stomach walls. The duodenum is the first part of the small intestine and is about 25 cm in length. The duodenum is stationary, and is fixed behind sheets of connective tissue called peritoneum. Glands in the duodenum secrete a thick alkaline fluid that counteract the acidic nature of the chemicals the food bile has absorbed. The gall bladder also secretes pancreatic juice and bile into the duodenum.

The liver is a very important part of the digestive system, even though food does not directly pass through it. The liver produces bile (a greenish fluid which aids in the digestion of fats), which is stored in the gall bladder. When bile is needed, it joins with secretions from the pancreas and goes through the common bile duct into the duodenum.

After the duodenum comes the two other parts of the small intestine, the jejunum and the ileum. These are what make up the bulk of the small intestine. The jejunum is the first part while the ileum is the second part. Here, food boluses are digested even further, and some nutrients are absorbed through the walls.

After passing through the duodenum, jejunum, and the ileum (the small intestine), food bolus makes its way through the large intestine. The large intestine is actually shorter then the small intestine, but larger in diameter. Water and electrolytes are removed in the large intestine. Also, microbes such as bacteria aid in further digestion. Finally, food bolus comes out of the anus as feces.

The Oral Cavity
The oral cavity is another name for the mouth. It is the first part of the digestive tract.
 * The lips, formed by the orbicularis oris muscles, help in food intake and determining temperature of food.
 * The buccinator muscles assist in the process of mastication, or chewing. Mastication is the first process of digestion
 * The tongue, a large muscle, helps move the food around the oral cavity. It also is necessary in swallowing.
 * The surface that forms the top of the oral cavity is called the palate. It is split into two parts.
 * The hard palate is the most anterior section. It contains bone. This is often referred to as the "roof of the mouth".
 * The soft palate is more posterior. It separates the oral cavity from the nasal cavity. It helps by preventing food from entering the nasal cavity.
 * The tonsils are part of the lymphatic system. They are tissues to the right and left of your mouth.
 * The uvula is also part of the lymphatic system. It is an extension of the soft palate, and is hanging down from it. The uvula is often wrongly referred to as the tonsil.

Teeth
The teeth chew and break down the food mechanically. An child has 20 deciduous teeth while an adult has 32 permanent teeth. There are four types of teeth: Incisors, canines, premolars, and molars.

Teeth consist of the crown, the neck, and the root.
 * The crown is the upper surface of the tooth. Bumps on the crown are called cusps.
 * The neck is the region under the crown, but above the alveolar bone.
 * The root is the region inside the alveolar bone.



Salivary Glands
The salivary glands produce saliva, which is secreted into the oral cavity. There are three pairs of salivary glands: the parotid, submandibular, and sublingual.
 * The parotid glands are the largest. They are located slightly posterior to the cheeks.
 * The submandibular glands are below the mandible bone. They procuce more serous saliva.
 * The sublingual glands are the smallest. They are below the floor of the oral cavity. They produce mostly mucus.

The Pharynx
The pharynx is often referred to as the back of the throat. Food pieces, now called bolus, travel from the oral cavity to the pharynx in the process of deglutition, or swallowing. The pharynx is also a shared passageway, connecting the nasal cavity, oral cavity, air passageway, and epiglottis. There are certain structures inside the pharynx to conduct the movement of air and food.
 * During deglutition, the soft palate elevates to prevent food from entering the nasal cavity.
 * Another structure, the epiglottis, bends down to prevent food from entering the air passageway.
 * If the epiglottis fails to function, food bolus may be lodged in the air passageway (choking).

The Esophagus
After food bolus passes through the pharynx, it goes through the esophagus, or oesophagus. The esophagus is directly under the pharynx. There is no defining structure that separates the pharynx from the esophagus. The esophagus is about 25 cm long in adults.

Muscular contractions called peristaltic waves propel food down the esophagus. This is why food can still travel through the esophagus if you are lying down or even upside-down.

The Stomach


The stomach is the first part of the gastrointestinal tract. Its main purpose is to store and churn food.


 * The layers, from innermost to outermost, are the mucosa (made of simple columnar epithelium), submucosa, oblique muscle (helps churn food), circular muscle (helps churn food), longitudinal muscle (helps churn food), and serosa (reduces friction between stomach and neighboring body parts).
 * There are three main sections to the stomach: the fundus, the body, and the pylorus. The fundus is the top part of the stomach, or the roof. The body is the bulk of the stomach. The leftmost region is the pylorus.
 * The texture of the inner surface of the stomach largely depends on how much food bolus it contains. If it does not contain much food bolus, the stomach is small and the inner surface has lots of folds. These folds are called rugae. If the stomach does contain lots of food bolus (like after a meal), the stomach is bigger and rugae are not present.

The Small Intestine


The small intestine is the next part of the digestive tract. The small intestine is about 6 meters long, and so it is the longest part of the digestive tract. Its main purpose is the digestion of food and absorption of nutrients. The small intestine consists of three sections: The duodenum (25 cm), the jejunum (2.5 m), and the ileum (3.5 m).

The layers are, from innermost to outermost, the mucosa, submucosa, muscularis - circular, muscularis- longitudinal, and serosa.

The mucosa has four major cell types:
 * Absorptive cells digest and absorb food
 * Goblet cells produce mucus
 * Granular cells protect from bacteria
 * Endocrine cells produce regulatory hormones

Since digestion only occurs at the surface, there must be a lot of surface area for effective digestion. To increase surface area,the small intestine has circular folds, villi, and microvilli. Villi are tiny finger-like projections. Microvilli are even smaller finger-like projections that are on the villi.

Chyme moves through the small intestine with two types of contractions.
 * Peristaltic contractions propel chyme forward. They are similar to the contractions in the esophagus.
 * Segmental contractions mix chyme by squeezing in outward motions.

The differences between the duodenum, jejunum, and ileum are as follows:
 * A gradual decrease in diameter (from duodenum to ileum)
 * a gradual decrease in thickness of intestinal wall
 * a gradual decrease in number of circular folds
 * a gradual decrease in number of villi.

Only the ileum contains Peyer's patches, which are clusters of lymph nodes.

Accessory Organs
The liver and gall bladder, along with the pancreas, are classified as accessory organs. However, they are not simply fashion garments. The accessory organs of the digestive tract are vital to the processes of the digestive system.

The Liver and Gall Bladder
The liver weighs about three pounds and is on the right-hand side of your body, right beneath the diaphragm. It consists of two major lobes, which are divided by the falciform ligament. The liver is attached to the underside of the diaphragm by the coronary ligament.

The liver is a part of more than one anatomical system. As well as functions associated with the digestive system, the liver also stores nutrients, cleans blood, and makes blood proteins. However, because this is the digestive page, we will be focusing on the digestive functions.

The main function of the liver is the production of bile. The liver produces and secretes about 700 mL of bile every day. The groups of cells that produce bile are called hepatocytes. Bile helps make fat digestion easier by braking fat particles into smaller, more manageable ones. Bile is stored in the gall bladder until it is needed. Then, it is transported to the duodenum. Note that bile is NOT a digestive enzyme.

The Pancreas
The pancreas is an accessory organ that secretes enzymes into the duodenum. It is located underneath and a little to the left to the liver. It is made up of endocrine and exocrine tissue. The endocrine tissue produce hormones, and the exocrine tissue produce digestive enzymes.

The digestive enzymes are created by acinar cells in the pancreas. Secretions of the pancreas travel through the pancreatic duct and join the common bile duct. They enter the duodenum through the duodenal papilla. (Check the Digestive Secretion List for a list of pancreatic secretions.)

The pancreas also produces hydrogen carbonate (HCO3-) which helps counter the acidic quality of chyme that enters the duodenum from the stomach. This stops pepsin digestion, but makes the other secretions of the pancreas more effective.

The Large Intestine
The large intestine is the final part of the digestive tract. It is about 5 feet long, and consists of the cecum, colon, rectum, and anal canal. Note that it is shorter than the small intestine. The reason it is called the large intestine is that it's wider thank the small intestine. The large intestine is mobile, and undergoes several muscular contractions called mass movements. Mass movements propels the colon towards the anus to help move food along with peristalsis. Note that the large intestine generally does not absorb nutrients. Although some nutrients such as vitamin K are absorbed, the main site of nutrient absorption is the small intestine. The large intestine mainly only absorbs water and salt.

The Cecum
The cecum, or caecum, is the first part of the large intestine. Food from the small intestine enters the cecum through the ileocecal valve.

A small pouch-like attachment to the cecum is the appendix. The appendix has no real function, as it was probably lost through human evolution. Organs that have no real function like the appendix are referred to as vestigial organs. Scientists believe the appendix was used do digest a diet with a lot of cellulose (plant fiber). Today, the appendix may store helpful bacteria, although this is not an important function.

The Colon
The colon makes up the bulk of the large intestine. There are three parts to the colon- the ascending colon, the transverse colon, the descending coon, and the sigmoid colon. The ascending colon is the first part, being right after the cecum. Food travels upwards through it. Next is the transverse colon. Food travels from left to right. Then, food goes down through the descending colon and sigmoid colon.

The colon is where chyme is converted to feces. Water and salts are absorbed in the large intestine, and microorganisms such as helpful bacteria help break down components of the feces. The colon stores the feces until defecation, where the feces is transported out of the digestive tract through the anus.

The inner wall of the large intestine is lined with mucus. It also has straight, tubular glands called crypts that have goblet cells to produce the mucus. Longitudinal, smooth muscle does not have its own layer in the large intestine. Instead, it exists in the form of three strips called teniae coli. Attached to the outer wall are small fatty sacs called appendices epiploicae.

The Rectum and Anal Canal
After food travels through the sigmoid colon, it enters the rectum. The rectum is a straight, muscular tube. The muscle layers are very thick to push food into the anal canal. The anal canal is the last 2-3 centimeters of the digestive tract. The anal canal has an even thicker muscle layer.

The peritoneum is a serous membrane that surrounds the abdominal cavity and organs. The inner layer is called the visceral peritoneum, and the outer layer is called the parietal peritoneum. A double layer of peritoneum is called mesentery.

Regulation of Digestive Secretions and Processes
Digestive secretions are regulated by the brain and the hormones.

Digestion, Absorption, and Transport of Nutrients
Digested molecules of food and water, as well as minerals from the diet, are absorbed throughout the small intestine. These molecules pass through the mucosa via absorptive cells. Lipids are absorbed last of the three main food groups, since they must first be broken down by lipase and bile salts. (See also: Mineral Absorption)

Diseases of the Digestive System
There are many different diseases and disorders that affect the digestive system. In the subcategories below describe how the disease or disorder affects the body, from the cellular level up to the entire organism. The first six diseases/disorders are required for all levels, with the remaining 4 being necessary for the national level competition only.

Stomach and Duodenal Ulcers


Ulcers occur when the mucus in the stomach or the intestines deteriorates, leaving the flesh directly exposed to the acid contained in these organs. Ulcers can also occur in the esophagus, but the focus is on the stomach and intestines.

These ulcers can occur for several reasons:
 * 1) (60% of stomach, 90% of duodenal) A bacteria, Helicobacter pylori, inflames the tissue by living in the mucus.
 * 2) An extreme intake of either sour or spicy foods with a high acid content.
 * 3) The use of NSAID's may also play a role in this condition. NSAID's block the body's ability to make more mucus, thus the mucous layer breaks down, giving the gastric acid an exposed portion of the skin.

Ulcers can be either benign or harmful, with most duodenal ulcers being benign.

Ulcers can be treated by using common drugs. Avoid smoking and drinking, as both inhibit healing of the ulcers.

Cancers of the Digestive System
If a tumor affects the digestive system, it is called a neoplasm. These neoplasms can occur in a variety of places in the system, including the esophagus, stomach, small intestines, and colon. There are several variations of cancer in each of these sub-groups, listed in their appropriate section below.

Esophageal (Oesophageal) Cancers
There are two major types of cancer occurring in the esophagus, as the other types are exceptionally rare. There are:
 * 1) Squamous cell cancer (approximately 90%-95% of all cases, worldwide)
 * 2) Adenocarcinoma (fastest growing in United States, responsible for most of the rest of the approximately 5%-10%)

There are several major symptoms of esophageal cancers. They include vomiting blood, regurgitation of food, heartburn, difficulty swallowing, and having chest pain that has nothing to do with eating.

Tests include:
 * Barium swallow (must swallow a drink containing barium, then x-rays are taken to look for any abnormalities in the travel of the liquid)
 * chest MRI (used for determining the progression of the cancer)
 * endoscopic ultrasound (also used for the progression of the disease)
 * esophagogastroduodenoscopy (use of a small camera inserted through your mouth to view the tissue in the throat, stomach, duodenum)
 * biopsy
 * PET scan (used to determine stage of disease/whether surgery is possible to remove cancerous growth).

For these cancers, surgery, chemotherapy, or radiation are the most common treatments. Chemotherapy and radiation are most often used to help reduce the cancer to a point where surgery can be used, or to help reduce the symptoms (the latter case is generally when the cancer is considered incurable).

Stomach Cancers
Stomach, or gastric, cancer is defined as a cancer that develops in the lining of the stomach. There are a number of factors that influence a person's vulnerability and likelihood to develop this form of cancer, but some of the most important are:
 * The presence of Helicobacter pylori in the stomach, or ulcers caused by this bacteria, and surgery performed on any such ulcer (accounts for approximately 60% of all cases)
 * Smoking
 * Anemia
 * Long-term gastritis
 * Obesity
 * A diet high in salted and/or pickled foods
 * Heavy drinking (severe alcohol abuse usually results in gastric lining damage)
 * Genetics (hereditary forms account for 10 to 13% of all cases)

When the cancer is in early stages, the symptoms seem rather innocuous, appearing as indigestion, nausea, heartburn, bloating, and/or a loss of appetite. As the cancer progresses, the symptoms often become far more severe, including, but not limited to, moderate to severe stomach pain, blood in stool, weight loss, vomiting, continued bloating and heartburn, and yellowing of the eyes and skin.

An overwhelming majority of cases of gastric cancer are classified as carcinomas, meaning the cancer develops in the epithelial tissue inside the stomach. However, other forms of cancer, such as lymphomas, may arise in other portions of the stomach, but are considered far rarer. Because the initial symptoms are similar to that of many lesser diseases, the warning signs are usually passed off as the ill effects of a food or a virus. Stomach cancers tend to develop slowly over a period of several years as a result.

There are several tests or examinations performed to determine if a patient has a form of gastric cancer. The most common is a gastroscopic examination (upper endoscopy), using a camera attached to a wire to view the inside of the stomach. Other common diagnosis methods are an Upper GI series and various CT (computed tomography) scans of the abdominal region. Biopsies are also commonly used to determine the malignancy of the tumor. A new method, utilizing a breathalyzer-like device, is being developed by Chinese and Israeli scientists, with a successful clinical study performed in 2013-2014.

Treatment methods remain very few and ineffective for gastric cancers. Surgical removal of the tumor is the most effective manner of treatment, with chemotherapy, radiation, and targeted therapy mostly being used to reduce the size of the tumor and provide palliative care. Survival rates for stomach cancer are extremely low (five-year survival rate is below 10%) for several reasons. First, this particular form of cancer is primarily found in geriatric patients (median age of presentation is between 70 and 75 years of age). Also, by the time symptoms are attributed to something serious, the cancer has generally metastasized.

Other interesting facts about stomach cancer:
 * Occurs twice as often in males as in females
 * 5th leading cause of cancer
 * 3rd leading cause of death from cancer
 * Before 1930's, since most food was pickled or salted before refrigeration was developed, it was the most common cause of cancer-related death.
 * Most commonly found in East Asia and Eastern Europe. (Much less common elsewhere)

Colorectal Cancers
Colorectal cancer (CRC), also known by various other names (such as colon cancer, bowel cancer, and rectal cancer), refers to the neoplasms affecting the lower portion of the large intestine, which is known as the colon, and the rectum. A majority of colorectal cancer cases are a result of the lifestyle of the patient. Factors include, but are not limited to, the following:
 * Age (geriatric patients are at higher risk)
 * Race (people of African descent are at higher risk)
 * Obesity
 * Diabetes
 * Smoking
 * Sedentary lifestyle (exceptionally low levels of exercise)
 * Excessive consumption of red or processed meats
 * Excessive alcohol consumption
 * Crohn's disease, ulcerative colitis, and IBS (irritable bowel syndrome)
 * Genetic disorders such as familial adenomatous polyposis

Symptoms for this form of cancer include rectal bleeding, blood in stool, unexplained weight loss, a change in bowel movements (either constipation or diarrhea) that lasts for four or more weeks, and weakness or fatigue that is unexplained. A large portion of patients reported no early signs or symptoms for the disease, so regular screening past 50 years of age is recommended. Because more than 80% of colorectal cancer cases arise from a certain form of polyp called "adenomatous polyps," regular screening can pick up these early indicators up to 2-3 years before symptoms even begin to appear.

There are several testing methods, but the most common include: In some countries, such as the United Kingdom, testing is organized for all persons older than 50. In the United States, it is recommended that those at high risk start regular screening at 40, and those with normal risk begin at 50, but no organized testing is performed nationwide.
 * Fecal Occult Blood Testing (FOBT)
 * Flexible sigmoidoscopy
 * Colonoscopy
 * Multitarget stool DNA screening test

The treatment methods for colon and rectal cancer vary slightly from each other, in part due to the difference in physiology between the two areas, and also how they react to the treatment types. If caught early on, the cancer is removed by laparotomy (a cut in the abdomen) to remove the cancerous section, and the colon is reattached. If the tumor takes up, or has spread to, a large portion of the colon, a colostomy may be necessary. If the tumor is larger, chemotherapy is used to shrink the tumor before surgery. Radiation therapy is generally not used in any stage of colon cancer due to the sensitivity of the lower intestine to radiation. The major difference in treatment between rectal and colon cancer is the use of radiation in second stage (and higher) tumors for rectal cancer, since the sensitivity is much lower in that region. Palliative care is usually the only course of treatment if the cancer has progressed to an advanced stage, especially for colon cancer. After successful removal of a tumor, the patient is encouraged to exercise quite regularly, as there is some evidence that indicates that exercise reduces the risk of re-emergence of cancer.

Interesting facts about colorectal cancer:
 * Drinking 5 or more glasses of water a day is linked to lower risk for these cancers
 * The five-year survival rate is below 60% but the rate is approximately 100% if caught in the M0 stage or earlier, and approximately 90% if caught in the T1 or T2 stages.
 * Metastasized colorectal cancer usually spreads to the liver and then the lungs
 * In 2012, 1.4 million people were diagnosed with new cases
 * 65% of all cases are found in developed countries

Diarrhea
Diarrhea — or loose, watery bowel movements that occur more frequently than usual — is one of the most commonly reported ailments in the United States (second only to respiratory infection), according to the American College of Gastroenterology (ACG). While diarrhea does not typically cause serious complications for most patients, it can be a fatal ailment for young children, especially those who are malnourished or have compromised immune systems. Diarrhea is the second leading cause of death in children under five years old, killing around 525,000 children each year, according to the World Health Organization (WHO).

Types of diarrhea and causes
Diarrhea that lasts no more than two weeks is referred to as acute diarrhea and is most often caused by a viral infection. The most common diarrhea-causing virus for adults is norovirus, which is often referred to as "cruise ship diarrhea" due to its unfortunate tendency to infect sea-faring vacationers. Rotavirus, another diarrhea-inducing virus, is very common in young children.

Other causes of acute diarrhea include bacterial infection, which is often referred to as "traveler's diarrhea," or, in some parts of the world, "Montezuma's revenge." But those who come down with this uncomfortable ailment aren't the victims of an ancient curse; they're usually the victims of the bacteria enterotoxigenic Escherichia coli (ETEC).

A final common cause of acute diarrhea is parasites, which can be ingested when a person consumes contaminated food or water.

Diarrhea that lasts longer than four weeks is known as chronic diarrhea. Like acute diarrhea, chronic diarrhea has many causes. These causes include:
 * Infectious causes (most commonly parasites)
 * Osmotic and malabsorption causes (which result in too much water being absorbed into the bowel), such as Celiac disease and lactose intolerance
 * Inflammatory causes, such as ulcerative colitis or Crohn's disease
 * Intestinal ischemia, or lessened blood flow to the intestine
 * Certain cancer therapies, like radiation
 * Certain medications, such as antibiotics

Diarrhea and deaths from it are more prevalent in third-world countries. This is due to lack of clean drinking water and poor sanitation conditions. Many organizations like PATH and WHO, are working to solve problems that lead to diarrhea deaths in children by providing:
 * Immunizations for certain causes
 * Filters for drinking water
 * Education for families
 * Better diagnosis and treatment plans

Complications
Diarrhea can be nothing to worry about, or it can be potentially life-threatening. The underlying cause of a patient's diarrhea is what determines the seriousness of this uncomfortable ailment. The primary complication of diarrhea is dehydration caused by the loss of large amounts of water, salt and nutrients. According to the Mayo Clinic, dehydration can lead to other serious conditions such as low blood pressure, seizures, kidney failure or even death. Those with ongoing diarrhea should seek medical attention if they experience:
 * Dark urine or small amounts of urine
 * Rapid heart rate
 * Dry, flushed skin
 * Headaches or light-headedness
 * Fatigue
 * Irritability or confusion
 * Severe abdominal or rectal pain
 * Blood in the stool or black, tar-like stools

Diagnosis and Tests
Diagnosing diarrhea itself isn't always as simple as one might think; people often experience changes in their bowel movements and think that they have diarrhea when, in fact, they do not. But if a patient is having three or more watery or soft bowel movements a day, then they likely do have diarrhea. To diagnose diarrhea, a doctor may want to determine the condition's cause, especially for patients whose symptoms are severe and/or ongoing.

Diagnostic tests for diarrhea include:
 * Physical exam of the abdomen and questions about eating habits
 * Medication review, including over-the-counter drugs and supplements
 * Blood tests to rule out certain diseases
 * Stool culture to determine whether bacteria or parasites are present
 * Fasting tests, avoiding various foods to determine whether diarrhea responds to dietary changes
 * Sigmoidoscopy or colonoscopy, which allow doctors to view the colon and rectum internally
 * Imaging tests to rule out intestinal blockages or other abnormalities

Treatment and Medication
Most cases of diarrhea resolve spontaneously within a few days and all that is needed is to prevent dehydration by replacing lost fluids. In the meantime, various over-the-counter medications may help firm the stool and decrease the urgency for bowel movements. These include loperamide hydrochloride (commonly known as the brand name Imodium AD), bismuth subsalicylate (Pepto-Bismol) and attapulgite (Kaopectate). Avoid large doses of Imodium, though, as too much can be life-threatening.

These medications, however, are not recommended for diarrhea caused by bacterial infection or parasites because organisms will be trapped in the intestines if the diarrhea ceases before they are completely excreted. The Cleveland Clinic recommends drinking two to three quarts or liters of liquids daily while recovering from diarrhea. While water is fine, it does not replace lost salt or nutrients, so better choices are broth, tea with honey, sports drinks and pulp-free juices. Avoid milk products, caffeine, alcohol, and apple and pear juices, because they may worsen diarrhea. Soft, bland foods are recommended as well, including bananas, plain rice, toast, crackers, boiled potatoes, smooth peanut butter, cottage cheese, noodles and applesauce. Because yogurt, cheese and miso contain probiotics, which contain strains of bacteria similar to those in a healthy intestine, they are also good choices. Avoid fatty, high-fiber or heavily seasoned foods for several days.

Also take steps to prevent diarrhea, especially when traveling. These measures include drinking only bottled or boiled water, frequently washing your hands (especially before eating) and eating only freshly cooked foods.

Prevention
The best way to prevent diarrhea is thorough hand washing on a regular basis. Properly cooking meats, drinking bottled water while on vacation and avoiding spoiled food can help, as well. The US Department of Health and Human Services also states that eating some probiotics may also help prevent diarrhea caused by infections or antibiotics.

Lactose Intolerance
Lactose intolerance is the digestive system's inability to break down a sugar called lactose, hence the name. This most commonly occurs due to the body's lack or insufficient quantities of an enzyme, called lactase, used to break the lactose for energy. As a result, the person with this condition will experience pain because of their body's inability to digest the sugar. Most infants have a proper amount of lactase enzymes inside their bodies in order to break down the lactose found in their mother's milk. However, as they age, the amount of active lactase dramatically decreases in most cases. Lactose intolerance is the human normal, with lactose "tolerance" being a rather new human evolution, especially in those of Northern European descent. People with lactose intolerance should avoid consuming dairy products.

Hepatitis
Hepatitis is an inflammation of the liver. It’s commonly caused by a viral infection, but there are other possible causes of hepatitis. These include autoimmune hepatitis and hepatitis that occurs as a secondary result of medications, drugs, toxins, and alcohol. Autoimmune hepatitis is a disease that occurs when your body makes antibodies against your liver tissue. approximately 4.4 million Americans are currently living with chronic hepatitis B and C. Many more people don’t even know that they have hepatitis. Treatment options vary depending on which type of hepatitis you have. You can prevent some forms of hepatitis through immunizations and lifestyle precautions. Viral infections of the liver that are classified as hepatitis include hepatitis A, B, C, D, and E. A different virus is responsible for each type of virally transmitted hepatitis.

Types of Hepatitis
Hepatitis A

Hepatitis A is always an acute, short-term disease, while hepatitis B, C, and D are most likely to become ongoing and chronic. Hepatitis E is usually acute but can be particularly dangerous in pregnant women. It's caused by an infection with the hepatitis A virus (HAV). This type of hepatitis is most commonly transmitted by consuming food or water contaminated by feces from a person infected with hepatitis A.

Hepatitis B

Hepatitis B is transmitted through contact with infectious body fluids, such as blood, vaginal secretions, or semen, containing the hepatitis B virus (HBV). Injection drug use, having sex with an infected partner, or sharing razors with an infected person increase your risk of getting hepatitis B. It’s estimated that 1.2 million people in the United States and 350 million people worldwide live with this chronic disease.

Hepatitis C

Hepatitis C comes from the hepatitis C virus (HCV). Hepatitis C is transmitted through direct contact with infected body fluids, typically through injection drug use and sexual contact. HCV is among the most common bloodborne viral infections in the United States. Approximately 2.7 to 3.9 million Americans are currently living with a chronic form of this infection.

Hepatitis D

Also called delta hepatitis, hepatitis D is a serious liver disease caused by the hepatitis D virus (HDV). HDV is contracted through direct contact with infected blood. Hepatitis D is a rare form of hepatitis that only occurs in conjunction with hepatitis B infection. The hepatitis D virus can’t multiply without the presence of hepatitis B. It’s very uncommon in the United States.

Hepatitis E

Hepatitis E is a waterborne disease caused by the hepatitis E virus (HEV). Hepatitis E is mainly found in areas with poor sanitation and typically results from ingesting fecal matter that contaminates the water supply. This disease is uncommon in the United States. However, cases of hepatitis E have been reported in the Middle East, Asia, Central America, and Africa.

Causes of noninfectious hepatitis

 * Alcohol and other toxins: Excessive alcohol consumption can cause liver damage and inflammation. This is sometimes referred to as alcoholic hepatitis. The alcohol directly injures the cells of your liver. Over time, it can cause permanent damage and lead to liver failure and cirrhosis, a thickening and scarring of the liver.
 * Other toxic causes of hepatitis include overuse or overdose of medications and exposure to poisons.
 * Autoimmune system response: In some cases, the immune system mistakes the liver as a harmful object and begins to attack it. It causes ongoing inflammation that can range from mild to severe, often hindering liver function. It’s three times more common in women than in men.

Symptoms
If you have infectious forms of hepatitis that are chronic, like hepatitis B and C, you may not have symptoms in the beginning. Symptoms may not occur until the damage affects liver function. Chronic hepatitis develops slowly, so these signs and symptoms may be too subtle to notice.

Signs and symptoms of acute hepatitis appear quickly. They include:


 * fatigue
 * flu-like symptoms
 * dark urine
 * pale stool
 * abdominal pain
 * loss of appetite
 * unexplained weight loss
 * yellow skin and eyes, which may be signs of jaundice

Diagnosis
Sometimes the pancreas shows up on ultrasound images as well. This can be a useful test in determining the cause of your abnormal liver function.
 * History and physical exam: To diagnose hepatitis, first your doctor will take your history to determine any risk factors you may have for infectious or noninfectious hepatitis. During a physical examination, your doctor may press down gently on your abdomen to see if there’s pain or tenderness. Your doctor may also feel to see if your liver is enlarged. If your skin or eyes are yellow, your doctor will note this during the exam.
 * Liver function tests: Liver function tests use blood samples to determine how efficiently your liver works. Abnormal results of these tests may be the first indication that there is a problem, especially if you don’t show any signs on a physical exam of liver disease. High liver enzyme levels may indicate that your liver is stressed, damaged, or not functioning properly.
 * Other blood tests: If your liver function tests are abnormal, your doctor will likely order other blood tests to detect the source of the problem. These tests can check for the viruses that cause hepatitis. They can also be used to check for antibodies that are common in conditions like autoimmune hepatitis.
 * Ultrasound: An abdominal ultrasound uses ultrasound waves to create an image of the organs within your abdomen. This test allows your doctor to take a close at your liver and nearby organs. It can reveal:
 * fluid in your abdomen
 * liver damage or enlargement
 * liver tumors
 * abnormalities of your gallbladder
 * Liver biopsy: A liver biopsy is an invasive procedure that involves your doctor taking a sample of tissue from your liver. It can be done through your skin with a needle and doesn’t require surgery. Typically, an ultrasound is used to guide your doctor when taking the biopsy sample. This test allows your doctor to determine how infection or inflammation has affected your liver. It can also be used to sample any areas in your liver that appear abnormal.

Treatment
Treatment options are determined by which type of hepatitis you have and whether the infection is acute or chronic.
 * Hepatitis A
 * Hepatitis A usually doesn’t require treatment because it’s a short-term illness. Bed rest may be recommended if symptoms cause a great deal of discomfort. If you experience vomiting or diarrhea, follow your doctor’s orders for hydration and nutrition.
 * The hepatitis A vaccine is available to prevent this infection. Most children begin vaccination between ages 12 and 18 months. It’s a series of two vaccines. Vaccination for hepatitis A is also available for adults and can be combined with the hepatitis B vaccine.
 * Hepatitis B
 * Acute hepatitis B doesn’t require specific treatment.
 * Chronic hepatitis B is treated with antiviral medications. This form of treatment can be costly because it must be continued for several months or years. Treatment for chronic hepatitis B also requires regular medical evaluations and monitoring to determine if the virus is responding to treatment.
 * Hepatitis B can be prevented with vaccination. The CDC recommends hepatitis B vaccinations for all newborns. The series of three vaccines is typically completed over the first six months of childhood. The vaccine is also recommended for all healthcare and medical personnel.
 * Hepatitis C
 * Antiviral medications are used to treat both acute and chronic forms of hepatitis C. People who develop chronic hepatitis C are typically treated with a combination of antiviral drug therapies. They may also need further testing to determine the best form of treatment.
 * People who develop cirrhosis (scarring of the liver) or liver disease as a result of chronic hepatitis C may be candidates for a liver transplant.
 * Currently, there is no vaccination for hepatitis C.
 * Hepatitis D
 * No antiviral medications exist for the treatment of hepatitis D at this time. According to a 2013 study, a drug called alpha interferon can be used to treat hepatitis D, but it only shows improvement in about 25 to 30 percent of people.
 * Hepatitis D can be prevented by getting the vaccination for hepatitis B, as infection with hepatitis B is necessary for hepatitis D to develop.
 * Hepatitis E
 * Currently, no specific medical therapies are available to treat hepatitis E. Because the infection is often acute, it typically resolves on its own. People with this type of infection are often advised to get adequate rest, drink plenty of fluids, get enough nutrients, and avoid alcohol. However, pregnant women who develop this infection require close monitoring and care.
 * Autoimmune hepatitis
 * Corticosteroids, like prednisone or budesonide, are extremely important in the early treatment of autoimmune hepatitis. They’re effective in about 80 percent of people with this condition.
 * Azothioprine (Imuran), a drug that suppresses the immune system, is often included in treatment. It can be used with or without steroids.
 * Other immune suppressing drugs like mycophenolate (CellCept), tacrolimus (Prograf) and cyclosporine (Neoral) can also be used as alternatives to azathioprine for treatment.

Prevention

 * Hygiene: Practicing good hygiene is one key way to avoid contracting hepatitis A and E. If you’re traveling to a developing country, you should avoid:
 * local water
 * ice
 * raw or undercooked shellfish and oysters
 * raw fruit and vegetables
 * Hepatitis B, C, and D contracted through contaminated blood can be prevented by:
 * not sharing drug needles
 * not sharing razors
 * not using someone else’s toothbrush
 * not touching spilled blood
 * Hepatitis B and C can also be contracted through sexual intercourse and intimate sexual contact. Practicing safe sex by using condoms and dental dams can help decrease the risk of infection.

Vaccines
Vaccinations are available to prevent the development of hepatitis A and B. Experts are currently developing vaccines against hepatitis C. A vaccination for hepatitis E exists in China, but it isn’t available in the United States.

Complications
Chronic hepatitis B or C can often lead to more serious health problems. Because the virus affects the liver, people with chronic hepatitis B or C are at risk for:
 * chronic liver disease
 * cirrhosis
 * liver cancer

When your liver stops functioning normally, liver failure can occur. Complications of liver failure include:


 * bleeding disorders
 * a buildup of fluid in your abdomen, known as ascites
 * increased blood pressure in portal veins that enter your liver, known as portal hypertension
 * kidney failure
 * hepatic encephalopathy, which can involve fatigue, memory loss, and diminished mental abilities due to the buildup of toxins, like ammonia, that affect brain function
 * hepatocellular carcinoma, which is a form of liver cancer
 * death

People with chronic hepatitis B and C are encouraged to avoid alcohol because it can accelerate liver disease and failure. Certain supplements and medications can also affect liver function. If you have chronic hepatitis B or C, check with your doctor before taking any new medications.

Appendicitis
Sometimes, the appendix may become infected and inflamed, a condition called appendicitis. Appendicitis is tested by touching the McBurney's point on the patient. This is located about 1/3 away from the left pelvic bone to the belly button. If the McBurney's point is extremely sensitive to the pressure, there is a good chance the patient has appendicitis. Appendicitis can be treated in most cases with an appendectomy, where the appendix is removed.

Diverticular Disease
Diverticular disease is a general term used to describe the experience of symptoms related to diverticula (small bulges or pockets that develop in the intestine). Diverticular disease is related to two other conditions called diverticulosis and diverticulitis. All of these conditions affect the large intestine, especially the portion closest to the rectum which is called the sigmoid colon.

Diverticula are considered a normal part of aging, as most people develop them later in life. Doctors and health institutions estimate that approximately 5% of the population have developed diverticula by age 40, and over 50% by age 80. The exact cause of these bulges has not been determined yet, but there is a strong correlation between low fiber, high red meat diets and the development of the pockets (but not solid evidence). Other factors include:
 * Smoking
 * Obesity (and even just being overweight)
 * History of constipation
 * Long-term use of NSAIDS (i.e. ibuprofen, etc.)
 * Family history of developing diverticula before age 50

The symptoms most often associated with diverticular disease, before it progresses to diverticulitis, include:
 * Abdominal pain, usually in the lower quadrants
 * Bloating
 * Long-term changes in bowel movements (constipation and/or diarrhea)
 * Episodic constipation followed by diarrhea (a pattern often described as going to the bathroom repeatedly but only passing rabbit pellet stools)

Because these symptoms are generally minor and often not very painful, this disease is usually diagnosed during other tests. Only approximately one in every four people who develop diverticula experience symptoms such as the ones listed above. However, if the symptoms do appear to persist, and the doctor deems it necessary, typically a non-invasive test will be ordered to look for a source. These exams include CT scans, X-rays, and an ultrasound.

Treatment for this disease is generally not necessary, as the symptoms are not harmful, unless a complication is found during testing. A diet high in fiber and low in red meats is recommended to reduce the risk of more diverticula forming. Also, it is necessary to avoid the use of laxatives to treat the condition, and use of enemas should be reduced.

Diverticulosis
The overwhelming majority of people that have diverticula have no noticeable symptoms whatsoever, and the diverticula do not affect the function of their intestine. This condition is referred to as diverticulosis. In the long run, this condition can lead to the discomfort and other symptoms associated with diverticular disease, and eventually (in some, but not all, cases) diverticulitis. In rare cases, the diverticula can lead to perforation or stricture of the large intestine, fistulas, and rectal bleeding. For a more in-depth discussion of these symptoms, see the diverticulitis symptoms and complications section below.

Because diverticulosis does not normally present with any symptoms, there is no standard testing. Usually, the diverticula are discovered during any number of other routine tests for cancer or other diseases, such as a colonoscopy or sigmoidoscopy. There is no treatment necessary unless a complication is found during a test, though a diet high in fiber and low in red meats is recommended. It is also necessary to avoid intake of laxatives if diagnosed with this condition, and enemas are to be used infrequently.

Diverticulitis
As the name of the condition indicates, diverticulitis is when the diverticula become inflamed. This inflammation is thought to be caused by either a small perforation of one of the diverticula that the body is able to heal, or an infection of bacteria inside the bulge in the colon, although an exact cause is not currently known. Diverticulitis usually presents after the minor, more generalized, symptoms of diverticular disease. Risk factors that correlate to a likelihood to develop diverticulitis are essentially the same as diverticular disease. These include a diet low in fiber and high in red meat, smoking, being overweight or obese, a history of constipation, long-term use of NSAIDS (i.e. ibuprofen, naproxen, etc.), and a family history of developing diverticula before age 50.

The symptoms of diverticulitis are often far more severe than those of either diverticular disease or diverticulosis, and a number of secondary issues can occur, leading to complicated diverticulitis (referring to the complications). Some symptoms and potential complications include:
 * Severe abdominal pain, usually more noticeable and painful on the left side
 * A fever of 100.4 degrees Fahrenheit (approximately 38 degrees Celsius) or higher
 * Severe diarrhea
 * Rectal bleeding
 * Formation of a stricture (when a section of the colon narrows that prevents stool from passing through easily)
 * Formation of an abscess (basically a pocket of pus sealed off within the colon)
 * Formation of a fistula (this occurs when the diverticulum forms a connection with another organ or the skin). Commonly occurs with the fistula's tract leading to the bladder. Other potential sites include the uterus, vagina, skin, or another portion of the intestine.
 * Peritonitis (literally the inflammation of the peritoneum, which is the membrane tissue covering and surrounding the organs in the abdomen)

GERD
GERD (Gastroesophageal Reflux Disease) is a disease in which the contents of the stomach travel back up the esophagus, irritating the lower esophageal area (and sometimes the upper area too) and causing a sensation described as "heartburn" which is worsened by eating or lying down. GERD is caused by a dysfunctional lower esophageal sphincter (LES) which would typically function to close off the esophagus from the lumen of the stomach. Some of the atypical symptoms of GERD include difficulty swallowing, sore throat, and regurgitation of food.

Usually, a diagnosis can be made by a physician with a description of the symptoms which may be followed up by an endoscopy (more specifically, an esophagogastroduodenoscopy, or EGD) in which the physician searches for tissue erosions, thickening of the mucosal layer, and possibly ulcers in the esophagus to help confirm the diagnosis. For a more definite diagnosis, a pH monitor is placed over the LES, and the results (characterized by timely decreases in pH, indicating acid reflux) are compared with the patient's description of symptoms according to the time they occur. This is called "ambulatory pH monitoring."

There is no actual cure for GERD, but the symptoms of GERD can be treated.


 * 1) For heartburn, antacids can be taken after meals but relief will not last very long. For longer relief, proton pump inhibitors (PPIs) can be used to reduce the amount of HCl (hydrochloric acid) produced in the stomach.
 * 2) Acetaminophen can help relieve pain associated with GERD.
 * 3) Problematic foods should be avoided.

Crohn's Disease
Crohn's Disease is a form of IBD (Inflammatory Bowel Disease) which is characterized by chronic inflammation of the GI tract. Although it is usually associated with the large intestine, Crohn's disease can affect any part of the GI tract, as opposed to ulcerative colitis (which only affects the large intestine). It is categorized as an autoimmune disorder. This means that the body's immune system overreacts and starts attacking healthy body cells in the affected areas of the GI tract.

Individuals with Crohn's disease experience chronic pain due to the inflammation which results from the hyper immune response. Other symptoms include: pain with defecating, fever, diarrhea or constipation, abdominal pain, fatigue, bloody stool, and ulcers anywhere in the GI tract (including the mouth).

The exact cause of Crohn's disease is unknown. Heredity and environment factors has been shown to affect development of the disease. Risk factors include smoking and a family history of Crohn's disease. Crohn's disease can occur in individuals of any age or sex, but it has been observed to be most frequent in men ages 15-35.

There are several methods for diagnosis: There is no specific cure for Crohn's disease, although the symptoms can be controlled to some degree by medication and changes in diet. In severe cases, surgery (bowel resection) may be required to remove certain affected areas of the GI tract. Since the cause of Crohn's disease is unknown, there really aren't any known methods of prevention.
 * Colonoscopy, sigmoidoscopy, endoscopy, and enteroscopy to check for physical signs such as strictures and inflammation
 * MRI (Magnetic Resonance Imaging) or CT (Computed Tomography) scan
 * Upper GI series (x-rays or the stomach and esophagus) mainly to look for ulcers
 * Physical examination may reveal abdominal masses/lumps and tenderness when certain areas are palpated

Celiac Disease
Celiac disease is an autoimmune digestive disease that affects at least 1 in 133 Americans, roughly 1 percent of the population, according to the National Foundation for Celiac Awareness. Celiac disease is also called celiac sprue or gluten-sensitive enteropathy. Celiac disease is a poor immune response to foods that contain gluten, a protein found in grains. Gluten is found in foods made from grains such as wheat, rye and barley. Oats may contain gluten too if they are cross-contaminated with grains during manufacturing. In people with celiac disease, exposure to gluten damages the lining of the small intestine, interfering with the absorption of nutrients from food and often causing abdominal pain. In the past few years, awareness of the genetic disorder has increased and many food companies and restaurants now offer menus that cater to those with celiac disease.

Symptoms
Classic symptoms of celiac disease are diarrhea and weight loss. However, many people may not experience digestive symptoms, according to the Mayo Clinic. There are also symptoms that may appear later if someone is untreated, for example, nutrient deficiencies. People might have anemia and vitamin deficiencies because of mal-absorption. They don't absorb all the nutrients because of the damage in the small bowel. Some of the symptoms of celiac disease include:
 * Gas and bloating
 * Anemia or iron deficiency
 * Skin rashes
 * Delayed growth in children
 * Headaches or migraines
 * Diarrhea or constipation
 * Loss of bone density
 * Mood swings and fatigue
 * Joint pain
 * Acid reflux and heartburn

Causes
The cause of Celiac disease is pretty much unknown. It seems that most people with celiac disease have a genetic predisposition to Celiac disease. Studies show that men and women of any age and race can be affected by celiac disease, but is more prevalent in those of Northern European descent. People who have a family member with celiac disease are more likely to have the disease. There are two main genes related to celiac disease. 95% of people with celiac disease will have the HLA-DQ2 gene, and the other 5 percent have the HLA-DQ8 gene. Although genetic testing is possible, it is extensive, and may have confusing results. Having the gene doesn’t means that will develop the disease. When a person with celiac disease consumes gluten, the immune system overreacts and targets the body’s small intestine. The villi (hair-like structures in the small intestine) suffer shortening and flattening. This occurs in the lamina propria and crypt regions of the intestine when the patient eats specific food-grain antigens, or toxic amino acid sequences. These toxic amino acid sequences are found in wheat, rye and barley.

Diagnosis
Because there is such a wide variation of symptoms, diagnosis can be difficult and it may take several years for someone to get diagnosed. But a diagnosis can be made using a blood test that looks for specific antibodies that people with celiac disease have. These antibodies are signs of an immune reaction to gluten. The blood test can show whether a patient has celiac disease or suffers from other diseases like irritable bowel syndrome and Crohn’s disease, which have similar symptoms. Currently, doctors test for total IgA, IgA-tTG, IgA-EMA, and possibly IgG/IgA-DGP or IgG-AGA. It’s important that the patient continue to consume gluten before the blood tests, so that the test can measure the immune system’s response to that diet. If the blood test is positive, the doctors may then do an upper endoscopy to view and biopsy the small bowel. Upper endoscopy involves inserting a flexible tube with a camera into the patient’s mouth and advancing through stomach and into the small bowel. Doctors would take pieces of tissue from the small bowel so that a pathologist can examine the tissue under the microscope to see if there are any abnormalities.

Treatment
People diagnosed with celiac disease will have to strictly avoid gluten in their diet. Patients who do not follow a gluten-free diet may continue to suffer from pain and other digestive symptom, or go on to develop malnutrition. In children, untreated celiac disease can cause stunted growth, delayed development and behavioral issues. For women, untreated celiac disease can lead to infertility. Untreated celiac disease can cause bone weakness, and patients also have a small risk of developing cancer of small bowel cancer. Even the smallest amount of gluten can trigger damage to the small intestines and reverse the healing process. Full healing in children usually takes six months, while full healing can take much longer for adults. Some people who have had symptoms for an extended period of time may take longer than two years to heal, and some will never fully recover. Many gluten-free food alternatives are now available, like gluten-free bread, gluten-free pasta, and gluten-free baked goods. They are made with potato, rice, soy, or bean flour.

Gluten intolerance is different
Celiac disease shouldn't be confused with gluten intolerance. However, some people without celiac disease may feel they are sensitive to gluten, and report they feel better after following a gluten-free diet.

Outside References
American Society of Colon and Rectal Surgeons: Diverticular Disease

Mayo Clinic: Colon Cancer

National Health Service (UK): Diverticular Disease and Diverticulitis

Digestive System Disorder And Diseases