It forms the roof of the mouth and is made of two distinct sections, the hard palate and the soft palate. The hard palate is located anteriorly and the soft palate posteriorly.
The tongue serves several purposes:
Contains taste buds for the ability to taste food and differentiate between sour, sweet, bitter, and spicy.
Manipulates food that is being chewed by gripping it and repositioning it between the teeth for mastication.
Helps mix saliva with food in order to form a compact mass or bolus of food.
During swallowing, the tongue helps to push the food bolus or liquids into the pharynx for further digestion.
In speech, the tongue aids in the formation of various consonants, such as d, k, l, n, t, and w.
The tongue is made up of two different types of muscles: extrinsic and intrinsic. Extrinsic muscles allow the tongue to change position, protrude, retract, move laterally, or wiggle. Intrinsic muscles allow the tongue to change shape to flat, round, firm, and relaxed.
The filiform papillae lend a rough surface to the tongue, allowing it to grasp food and manipulate it during mastication. The filiform papillae are very numerous and give the tongue its whitish appearance, lining up in parallel rows.
The fungiform papillae have a vascular core that gives them a reddish appearance. Fungiform papillae, like their name "fungi," actually have a mushroom-like appearance.
The posterior third of the tongue, or the root of the tongue, is considered part of the oropharynx and contains lingual tonsils. Many individuals who have had their tonsils surgically removed can continue to get tonsillitis; however, this type of tonsillitis is called lingual tonsillitis and is treated with antibiotics.
They produce saliva, which is a complex mixture of water, ions, mucus, and enzymes. This complex contains a bicarbonate buffer that neutralizes bacteria-producing acids to help prevent tooth decay, provides proteins that stimulate the growth of good bacteria, and contains antiviral substances, antibodies, and a cyanide compound, which kills harmful microorganisms.
small intrinsic salivary glands
are located throughout the mouth, in the mucosa of the tongue, palate, lips, and cheeks and are responsible for maintaining a moist mouth.
Large extrinsic salivary glands
lie external to the mouth, but their ducts connect to it. They secrete saliva only when we eat or when we anticipate eating. There are three pairs of extrinsic salivary glands: parotid, submandibular, and sublingual.
allow us to masticate (chew) our food by tearing, grinding, and breaking it into tiny pieces that can then be digested. There are two sets of teeth (dentitions) present at birth. The first set to erupt are the deciduous teeth (baby teeth), followed by the permanent teeth.
This is the outermost covering of the alimentary canal. In most of the digestive tract (stomach and intestines), it consists of a thin layer of loose connective tissue covered by mesothelium (a type of squamous epithelium [single layer of skin cells] that lines body cavities within the peritoneal cavity). This structure is also referred to as visceral peritoneum, as it covers all of the vital organs.
Tunica muscularis (inner and outer)
This gives the alimentary canal the ability to be motile (having the ability of spontaneous movement). In most of the alimentary canal, muscularis consists of two thick layers (inner and outer muscularis) of smooth muscle (involuntary muscles with a single nuclei, spindle-like in appearance). The muscle fibers of the inner layer are aligned circularly, whereas those in the outer layer are aligned longitudinally. This combination of circular and longitudinal smooth muscle gives the tube an ability to perform complex movements that squeeze and propel solid or liquid nutrients in the lumen (a process called peristalsis).
This layer lies between the mucosal and inner muscularis layers. This layer is highly vascular (containing many blood vessels). It is composed of elastic and collagen fibers, and its function is to serve the mucosal layer. The submucosa also contains the submucous plexus, a critical component of the digestive tract's nervous system that provides nervous control to the mucosa.
This is the innermost layer of the alimentary canal that lines the digestive tract. Of the four tunic layers, the mucosa is the most widely varied. It allows the lumen the ability to perform digestive tasks along its length. Included within the tunica mucosa are epithelium cells vital to the functions of absorption and more. Beneath the epithelium, but still within the tunica mucosa, is a layer called the lamina propria, which is loose connective tissue. Blood vessels and lymphatics course through the lamina propria to supply the epithelium. Beneath the lamina propria is the lamina muscularis mucosae, a thin layer of smooth muscle that allows the mucosa to move and fold.
the state of being enlarged or allowing for an increased capacity. This occurs most notably in the stomach.
the process of absorbing or assimilating nutrients, such as in the small intestine, or the absorption of water in the colon.
where the glandular parts secrete digestive enzymes into the cavity to break down food, such as in the stomach.
The lesser omentum extends from the lesser curvature of the stomach to the underside of the liver.
The greater omentum extends from the greater curvature of the stomach to the transverse colon.
It is the most distended portion of the alimentary canal. It serves primarily as storage for food before it passes into the intestines. Although some digestion occurs at this point, food is primarily only converted into a pasty material.
It is the junction between the esophagus and the stomach. This is also frequently referred to as the GE junction (gastroesophageal junction). Although no true sphincter exists at this point, the muscles here are in a constant state of contraction in order to prevent the stomach contents from flowing backward.
It is the dome-shaped portion of the stomach that extends slightly above the cardiac orifice.
body (of the stomach)
It is the widest portion and is located between the lesser and greater curvatures.
It opens into the colon and has the appendix, a small finger-like projection that is attached to its medial portion.
The second portion of the large intestine. Different areas of the colon have specific terms assigned to them. At approximately the liver, the colon bends sharply, and this area is referred to as the hepatic flexure. The colon then extends in a horizontal direction, and that portion is called the transverse colon. At the left abdominal wall, there is another sharp bend in the colon. This is called the splenic flexure and is the beginning of the descending colon, or that portion of the large intestine that goes downward (descends). Finally, the colon terminates in an S-shaped bend that is referred to as the sigmoid colon.
Next is the rectum, which is a tube approximately 15 cm long located between the sigmoid colon and the anal canal.
It forms a muscular opening in the muscles of the pelvic floor that is called the anus. This is surrounded by both involuntary and voluntary muscular sphincters.
The largest gland in the body. It is made up of many liver lobules that produce bile. Bile is continuously secreted into the intestines and is very important to digestion.
It is a sac-like organ that is attached to the undersurface of the liver. It stores and concentrates bile. The cystic duct drains the gallbladder. It unites with the hepatic duct to form the common bile duct that conveys bile into the duodenum.
It is involved in both the digestive and the endocrine systems. For its role in digestion, it creates juices and secretes them into the duodenum for the breakdown of foods.
The audible rumbling sounds of gas moving through the intestinal tract. This is the plural form. The singular form is borborygmus or borborygmos.
Infrequent or difficult evacuation of feces. This term could be classified as either a symptom or a disease. Patients can subjectively relate that they are experiencing the discomfort of constipation, and it can also be the diagnosis.
This is a subjective feeling of difficulty swallowing. It occurs when there is impaired progression of the food bolus from the pharynx to the stomach.
An elevation in temperature above normal. This is also called pyrexia. If a patient has a fever, physicians will usually refer to that patient as being febrile.
Gas produced by bacterial action on waste matter in the intestines. Composed primarily of hydrogen sulfide and methane.
Melan(o)- is a combining form that means black. The term melena refers both to the passage of dark and pithy stools stained with blood pigment, and black vomit. Although the combining form is spelled with an A, it is important to note that the term melena or melenic stools is spelled with an E.
An unpleasant sensation in the epigastric and abdominal area, which often results in vomiting.
Straining, especially ineffective and painful straining during a bowel movement or urination.
Also called emesis. The forcible expulsion of stomach contents through the mouth. (Try not to think about it.)
This is an impairment of normal esophageal peristalsis. (You may remember that peristalsis is the movement of the muscles in the alimentary canal to propel the food bolus.) It also affects the ability of the lower esophageal sphincter to relax. The most common symptoms are dysphagia, regurgitation, nocturnal cough, and chest pain.
This is a mental condition characterized by an individual's refusal to eat enough to maintain a minimal body weight, usually fueled by an intense fear of becoming obese.
Inflammation of the vermiform appendix. (The term appendix is actually a general term which means a supplementary, accessory, or dependent part of a main structure.) This is the first, but many individual structures which are found in the body (GI system and elsewhere) can be individually affected by infection which causes inflammation. You will notice that the suffix -itis appears in several disease processes.
The vermiform appendix specifically identifies the diverticulum of the cecum. However, healthcare professionals commonly drop the term vermiform when referring to this particular appendix.
Tightly packed, partially digested agglomerations of hair or vegetable matter. Seeds, bubble gum, medication, and other materials can mimic true bezoars.
A type of food poisoning caused by the production of the bacteria Clostridium botulinum in improperly canned foods. It is characterized by vomiting, abdominal pain, difficulty seeing, dryness of the mouth and pharynx, dyspepsia, cough; it often results in death.
Inflammation of the gallbladder. There are different types of cholecystitis, the most common being chronic and acute. An acute infection generally indicates severe infection and often necessitates a cholecystectomy, which is removal of the gallbladder. This is an extremely common procedure.
This refers to a group of liver diseases in which the normal hepatic structure is destroyed over time by nodules. It is the third leading cause of death in North America for people 45 to 65 years of age. In North America it is often caused by chronic alcohol abuse. (In other parts of the world it can be caused by untreated and highly communicable strains of hepatitis.)
A condition that results from an excessive loss of body water. This can occur on a hot day without a drinking fountain close by, but also occurs when there is vomiting, diarrhea, diabetes, mental disorder, coma, or when a patient is taking diuretic medications (those which promote the excretion of urine). It can be life-threatening.
Tooth decay. Although this is a component of the dental specialty, because it directly affects the teeth, which are responsible for masticating food, it is significant to the function of the GI system.
Abnormal frequency and liquidity of fecal discharges. Diarrhea is actually a symptom that suggests the presence of a disorder. However, it often is short in duration, is easily identifiable by a patient, and often does not require any treatment.
The plural form of diverticulum. (The plural of diverticulum is NOT diverticuli; this is a common dictation/transcription error.)
The presence of diverticula with the absence of diverticulitis, especially in the colon.
Any of a variety of disorders marked by inflammation of the intestines, especially the colon. The symptoms include pain in the abdomen, tenesmus, and frequent stools containing blood and mucus.
The most common type of dysentery, due to an ulceration of the bowel caused by amebiasis.
General term which means impairment to the power or function of digestion. It often refers to discomfort in the epigastric region following a meal, or what many people call "indigestion."
Inflammation of the intestine, especially the small intestine. Often this is combined (e.g., enterocolitis).
A form of enteritis that is spread by food and water contaminated with feces. It is much more common in Third World countries.
An intestinal concretion (the process of becoming harder or more solid) formed around a center of fecal matter.
An abnormal passage or communication between two organs or from an internal organ to the surface of the body. There are several different types. It can occur because of trauma, infection, inflammation, degeneration, necrosis, or other causes.
Inflammation of the stomach. This is commonly combined (e.g., gastroenteritis). This is often a result of a bacteria, and symptoms include anorexia, nausea, diarrhea, abdominal pain, and weakness. Gastritis is also a problem frequently associated with alcohol abuse.
gastroesophageal reflux disease
The reflux of stomach contents into the esophagus. It is often represented by the acronym GERD (gastroesophageal reflux disease). This is usually caused by an incompetent lower esophageal sphincter. The major symptom is heartburn, although it can lead to several more severe disorders.
Offensive breath. This can be real as the result of ingested substances, gingival disease, fermentation of food in the mouth, or associated with systemic diseases such as diabetic acidosis. It can also be imagined and the result of anxiety disorders, obsessive disorders, paranoia, or hypochondria.
Inflammation of the liver. Hepatitis can be due to viral, bacterial, or parasitic factors. They are generally classified by letters (i.e., hepatitis A, hepatitis B, hepatitis C). Some strains are transmitted through feces/oral contact, some through the blood (IV drug use), and some are sexually transmitted. Hepatitis can be chronic and active, in which case it is often fatal. Some forms are highly contagious.
The protrusion of a loop or knuckle of an organ or tissue through an abnormal opening. There are several classifications of hernias. The most common types follow.
The protrusion of the stomach above the diaphragm. There are both a sliding hiatal hernia and a paraesophageal hiatal hernia.
sliding hiatal hernia
A hernia in which the stomach and a section of esophagus which joins the stomach slide up into the chest through what is called the hiatus (gap/passage).
paraesophageal hiatal hernia
A hernia in which part of the stomach squeezes through the hiatus, but the esophagus and stomach stay in their regular locations. Of concern is that the stomach can become strangled/have its blood supply shut down.
A hernia into the inguinal canal. There are both direct and indirect inguinal hernias.
Congenital megacolon, or a dilatation and hypertrophy of the colon due to the sustained contraction of the muscles of the rectosigmoid.
The temporary cessation of intestinal peristalsis, which often leads to obstruction. A common type is adynamic ileus.
A suspension of peristalsis because of paralysis or atony (lack of normal muscle tone or strength). This can be the result of drugs, toxemia, trauma, or surgery.
inflammation bowel disease
This can be used to describe a variety of bowel disorders which are inflammatory in nature, whose etiology cannot be directly determined. There are two common types of inflammatory bowel disease which you should know: Crohn disease & ulcerative colitis.
It is not known what causes Crohn disease; it can affect any part of the GI tract from the mouth to the anus, but is especially common in the ileocecal area. It frequently leads to obstruction and fistula and abscess formation.
A chronic, nonspecific, inflammatory, and ulcerative disease that arises in the colonic mucosa and usually involves the rectum. Its etiology is also unknown and it is most often manifested by bloody diarrhea.
This occurs when a segment of bowel advances and protrudes into the segment distal to it.
irritable bowel syndrome
Intermittent or constant abdominal distress and bowel dysfunction which has no demonstrable cause.
A syndrome characterized by the bile pigment in the skin, mucous membranes, and sclerae with a resulting yellow appearance. There are many types of jaundice and most of these indicate a problem with the liver.
A white patch on a mucous membrane that will not rub off. This occurs in the oral mucosa and is considered to be a premalignant (precancerous) lesion common in smokers.
Impaired intestinal absorption of nutrients. If the body is not absorbing nutrients properly, it can quickly result in an insufficiency of necessary nutrients. The combination of weight loss, diarrhea, and anemia indicate malabsorption.
An acute, highly contagious viral disease which causes painful enlargement of the salivary glands. Primarily infects children under age 15.
The state or condition of being clogged or blocked. In gastroenterology it usually refers to a complete arrest or serious impairment to the passage of intestinal contents. You can probably imagine the physical manifestations of obstructions. They are generally caused by adhesions, hernias, tumors, foreign bodies, inflammatory bowel disease, fecal impaction, and volvulus.
A plant or animal which lives upon or within another living organism at whose expense it obtains an advantage. It is not uncommon for a parasite to be present in foods that are consumed, and they are also communicable via person-to-person contact.
An intestinal protozoa that has a large sucking disc which adheres to the microvilli of the intestinal walls. There are many different kinds of parasites. However, except for Giardia, they are much more common in Africa and rarely impact Western medicine.
peptic ulcer disease
Inflammation and ulceration in the duodenum and stomach caused by gastric acid juice. Peptic ulcer occurs only if the stomach secretes acid.
Barrett esophagus is a chronic peptic ulcer of the esophagus and is commonly seen in medical reports
Inflammation of the peritoneum. Symptoms include abdominal pain and tenderness, constipation, vomiting, and moderate fever. Peritonitis sometimes follows abdominal surgery, such as an appendectomy.
This refers to any mass of tissue that arises from the bowel wall and protrudes into the lumen. They may be either sessile or pedunculated. They vary considerably in size and histologic (microscopic tissue structure) characteristics.
The falling down or sinking of a part. This pathology can affect the GI system through anal prolapse and rectal prolapse (where skin of the anus and mucosa of the rectum protrude through the anus).
A 2-4 mm mucosal structure, probably congenital in nature, which causes a ring-like narrowing of the lower esophagus.
A defect or excavation of the surface of an organ or tissue. There are many kinds of ulcers (peptic ulcer disease, stress ulcers, ulcerative colitis, etc.), many causes for ulcers, and many treatments for ulcers.