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The Digestive System Glossary of Terms

 Absorb: 1. To take something in, as through the skin or the intestine.

2. To react with radiation and reduce it in intensity, as with a dose of radiation or transmitted light.
See also: Absorbed dose; Absorption; Malabsorption; Reabsorption.

Absorbed dose: In radiology, the amount of energy that is deposited in any material by ionizing radiation. The unit of absorbed dose, the rad, is a measure of energy absorbed per gram of material. An alternative unit of absorbed dose is the gray. One gray equals 100 rads.

Absorption: Uptake. In the biomedical sciences, absorption has diverse specific meanings.
See the entire definition of Absorption

Absorption: Uptake. In the biomedical sciences, absorption has diverse specific meanings.

In the body, absorption is the process whereby a cell, tissue or organ takes up a substance.

In the intestinal tract, absorption is the uptake of food (or other substances) from the digestive tract.

In radiology, absorption refers to the taking up of energy by matter with which the radiation interacts.

In immunology, absorption is the process by which an antibody or antigen is used to remove a corresponding antigen or antibody from a mixture.

Anus: The opening of the rectum to the outside of the body.
See the entire definition of Anus

Anus: The opening of the rectum to the outside of the body.

The word "anus" comes straight from the Latin. It referred to the same structure to the Romans. It also meant a "ring" in the sense of an encirclement which was entirely appropriate since the anus encircles the outlet of the bowel.

Appendix: A small outpouching from the beginning of the large intestine (the ascending colon). Formally called the vermiform appendix because it was thought to be wormlike.
See the entire definition of Appendix

Appendix: A small outpouching from the beginning of the large intestine(the ascending colon). Formally called the vermiform appendix because it was thought to be wormlike.

See also: Appendicitis; Appendix cancer.

Appendicitis: Inflammation of the appendix, the small worm-like projection from the first part of the colon. Appendicitis usually involves infection of the appendix by bacteria that invade it and infect the wall of the appendix. Appendicitis can progress to produce an abscess (a pocket of pus) and even peritonitis (inflammation of the lining of the abdomen and pelvis).

The most common signs and symptoms of appendicitis are fever, and abdominal tenderness, and right lower quadrant abdominal pain most marked at what is called McBurney's point. Appendicitis is suspected on the basis of the patient's history and physical examination. A white blood cell count, urinalysis, abdominal x-ray, barium enema, ultrasonography, CT scan, and laparoscopy also may be helpful in diagnosis.

Because of the varying size and location of the appendix and the proximity of other organs to the appendix, it may be difficult to differentiate appendicitis from other abdominal and pelvic diseases. The treatment for appendicitis is antibiotics and appendectomy (surgery to remove the appendix). Complications of appendectomy may include wound infection and abscess.

The most exquisitely tender area of the abdomen in the early stage of appendicitis, this point is named after the New York surgeon Charles McBurney (1845-1913), the leading authority in his day on appendicitis. In 1889, McBurney showed that incipient appendicitis could be detected by applying pressure to a particular spot in the right lower abdomen, a point he called the "seat of greatest pain," which corresponds to the normal location of the base of the appendix.

Bacteria: Single-celled microorganisms which can exist either as independent (free-living) organisms or as parasites (dependent upon another organism for life). 
See the entire definition of Bacteria

Bacteria: Single-celled microorganisms which can exist either as independent (free-living) organisms or as parasites (dependent upon another organism for life).

Examples of bacteria include:

• Acidophilus, a normal inhabitant of yogurt,
• Chlamydia, which causes an infection very similar to gonorrhea,
• Clostridium welchii the most common cause of the dreaded gasgangrene,
• E. coli, the common peaceful citizen of our colon and, upon occasion, adangerous agent of disease, and
• Streptococcus, the bacterium that causes the important infection of the throat strep throat.

The term bacteria was devised in the 19th century by the German botanist Ferdinand Cohn (1828-98) who based it on the Greek bakterion meaning a small rod or staff. In 1853, Cohn categorised bacteria as one of three types of microorganisms -- bacteria (short rods), bacilli (longer rods), and spirilla (spiral forms). The term bacteria was preceded in the 17th century by the microscopic animalcules described by Antony van Leeuwenhoek (1632-1723).

Bile: Bile is a yellow-green fluid that is made by the liver, stored in the gallbladder and passes through the common bile duct into the duodenum where it helps digest fat. The principal components of bile are cholesterol, bile salts, and the pigment bilirubin.
See the entire definition of Bile

Bile: Bile is a yellow-green fluid that is made by the liver, stored in the gallbladder and passes through the common bile duct into the duodenum where it helps digest fat. The principal components of bile are cholesterol, bile salts, and the pigment bilirubin.

An imbalance between these components of bile -- cholesterol, bile salts, and bilirubin -- leads to the formation of gallstones. Cholesterol is normally kept in liquid form by the dissolving action of the bile salts; an increased amount of cholesterol in the bile overwhelms the dissolving capacity of the bile salts and leads to the formation of cholesterol gallstones. Similarly, a deficiency of bile salts promotes cholesterol gallstone formation.

Pigment gallstones are frequently associated with chronic infection in the bile, especially in certain Asian countries where parasitic infection of the bile ducts is common. Patients with blood diseases that cause excessive breakdown of red blood cells can have increased amounts of bilirubin (breakdown product of red cells) in the bile, thus causing bilirubin gallstone formation.

Bowel: Another name for the intestine. The small bowel and the large bowel are the small intestine and large intestine, respectively.
See the entire definition of Bowel

Bowel: Another name for the intestine. The small bowel and the large bowel are the small intestine and large intestine, respectively.

The word "bowel" originated from the Latin "botulus" meaning "sausage" because the outside of the intestine looked like a sausage to the Romans. Intestine: The long, tubelike organ in the abdomen that completes the process of digestion. It consists of the small and large intestines.Small intestine: The part of the digestive tract that extends from the stomach to the large intestine.Large intestine: Comes after the small intestine. Large because it is wider than the small intestine.

Brain: That part of the central nervous system that is located within the cranium(skull). The brain functions as the primary receiver, organizer and distributor of information for the body. It has two (right and left) halves called "hemispheres."

entral nervous system (CNS): The central nervous system is that part of the nervous system that consists of the brain and spinal cord.

The central nervous system (CNS) is one of the two major divisions of the nervous system. The other is the peripheral nervous system (PNS) which is outside the brain and spinal cord.

The peripheral nervous system (PNS) connects the central nervous system (CNS) to sensory organs (such as the eye and ear), other organs of the body, muscles, blood vessels and glands. The peripheral nerves include the 12 cranial nerves, the spinal nerves and roots, and what are called the autonomic nerves that are concerned specifically with the regulation of the heart muscle, the muscles in blood vessel walls, and glands.

The early English word "skulle" came from the Nordic words "skal" and "skul" meaning a bowl. It is also thought that the Nordic toast "Skoal!" came from "skal" since ceremonial drinks were served in a bowl (or skull).

Carbohydrates: Mainly sugars and starches, together constituting one of the three principal types of nutrients used as energy sources (calories) by the body. Carbohydrates can also be defined chemically as neutral compounds of carbon, hydrogen and oxygen.
See the entire definition of Carbohydrates

Carbohydrates: Mainly sugars and starches, together constituting one of the three principal types of nutrients used as energy sources (calories) by the body. Carbohydrates can also be defined chemically as neutral compounds of carbon, hydrogen and oxygen.

Carbohydrates come in simple forms such as sugars and in complex forms such as starches and fiber. The body breaks down most sugars and starches into glucose, a simple sugar that the body can use to feed its cells. Complex carbohydrates are derived from plants. Dietary intake of complex carbohydrates can lower blood cholesterol when they are substituted for saturated fat.

Carbohydrates are classified into mono, di, tri, poly and heterosaccharides. The smallest carbohydrates are monosaccharides such as glucose whereas polysaccharides such as starch, cellulose and glycogen can be large and even indeterminate in length.

The energy produced by carbohydrates is 4 calories per gram. Proteins also provide 4 calories per gram. Fats are high-cal; they provide 9 calories per gram.

Etymology: Carbohydrates are called carbohydrates because the carbon, hydrogen and oxygen they contain are usually in the proportion to form water with the general formula Cn(H2O)n.

See the entire definition of Colon

Colon: The part of the large intestine that runs from the cecum to therectum as a long hollow tube that serves to remove water from digested food and let the remaining material, solid waste called stool, move through it to the rectum and leave the body through the anus. .

The colon measures about 5 ft (1.5 m) in length. It goes up (the ascending colon) on the right side of the abdomen, across the abdomen (thetransverse colon) beneath the stomach, and then down (the descending colon) on the left side of the abdomen and makes a sharp turn in the left lower portion (the sigmoid colon) to merge with the rectum.

The colon is sometimes inaccurately called the large intestine or large bowel. It is only a part of the large intestine/bowel. The confusion may have arisen because the word "colon" came from "kolon" which to the ancient Greeks meant the large intestine.

See the entire definition of Digestive system

Digestive system: The organs that are responsible for getting food into and out of the body and for making use of it. These organs include the salivary glands, the mouth, esophagus, stomach, small intestine, liver, gallbladder, pancreas, colon, rectum, and anus.

The digestive system has a series of hollow organs joined in a long, twisting tube from the mouth to the anus. Inside this tube is a lining called the mucosa. In the mouth, stomach, and small intestine, the mucosa contains tiny glands that produce juices to help digest food. Two solid organs, the liver and the pancreas (both of which are embryologically derived from the digestive tract), produce digestive juices that reach the intestine through small tubes known as ducts. In addition, parts of other organ systems (for instance, nerves and blood) play a major role in the digestive system.

Duodenum: The first part of the small intestine. The duodenum extends from thepylorus at the bottom of the stomach to the jejunum, the second part of the smallintestine. The duodenum is a common site for the formation of peptic ulcers. We often live with words without thinking where they come from or what they originally meant. That is the case for me with the duodenum. For decades, this writer knew the duodenum as a short but troubled sector of the small intestine. Only today did I learn that the duodenum began as the dodeka-daktulon, twelve fingers to the Greeks, who astutely observed that the duodenum is about 12 finger-breadths long. In German, the popular term for duodenum is Zwolffingerdarm, the 12-finger intestine.

Enzymes: Proteins that act as a catalysts in mediating and speeding a specific chemical reaction.
See the entire definition of Enzymes

Enzymes: Proteins that act as a catalysts in mediating and speeding a specific chemical reaction.Chemical reaction: A process in which one substance is transformed into another. Thousands of different types of chemical reactions occur in the body and are essential to its structure and function.

What is phenylketonuria?

Phenylketonuria (commonly known as PKU) is an inherited disorder that increases the levels of a substance called phenylalanine in the blood. Phenylalanine is a building block of proteins (an amino acid) that is obtained through the diet. It is found in all proteins and in some artificial sweeteners. If PKU is not treated, phenylalanine can build up to harmful levels in the body, causing intellectual disability and other serious health problems.

What are the symptoms of PKU?

The signs and symptoms of PKU vary from mild to severe.

The most severe form of this disorder is known as classic PKU.

• Infants with classic PKU appear normal until they are a few months old. 
  
  
• Without treatment with a special low-phenylalanine diet, these children develop permanent intellectual disability. 
  
  
• Seizures, delayed development, behavioral problems, and psychiatricdisorders are also common. 
  
  
• Untreated individuals may have a musty or mouse-like odor as a side effect of excess phenylalanine in the body. 
  
  
• Children with classic PKU tend to have lighter skin and hair than unaffected family members and are also likely to have skin disorders such as eczema.

Less severe forms of this condition, sometimes called variant PKU and non-PKU hyperphenylalaninemia, have a smaller risk of brain damage. People with very mild cases may not require treatment with a low-phenylalanine diet.

Babies born to mothers with PKU and uncontrolled phenylalanine levels (women who no longer follow a low-phenylalanine diet) have a significant risk of intellectual disability because they are exposed to very high levels of phenylalanine before birth.

• These infants may also have a low birth weight and grow more slowly than other children. 
  
  
• Other characteristic medical problems include heart defects or other heart problems, an abnormally small head size (microcephaly), and behavioral problems. 
  
  
• Women with PKU and uncontrolled phenylalanine levels also have an increased risk of pregnancy loss.

• How common is phenylketonuria?

  The occurrence of PKU varies among ethnic groups and geographic regions worldwide. In the United States, PKU occurs in 1 in 10,000 to 15,000 newborns. Most cases of PKU are detected shortly after birth by newborn screening, and treatment is started promptly. As a result, the severe signs and symptoms of classic PKU are rarely seen.

  What genes are related to phenylketonuria?

  Mutations in the PAH gene cause phenylketonuria.

  The PAH gene provides instructions for making an enzyme called phenylalanine hydroxylase. This enzyme converts the amino acid phenylalanine to other important compounds in the body. If gene mutations reduce the activity of phenylalanine hydroxylase, phenylalanine from the diet is not processed effectively. As a result, this amino acid can build up to toxic levels in the blood and other tissues. Because nerve cells in the brain are particularly sensitive to phenylalanine levels, excessive amounts of this substance can cause brain damage.

  Classic PKU, the most severe form of the disorder, occurs when phenylalanine hydroxylase activity is severely reduced or absent. People with untreated classic PKU have levels of phenylalanine high enough to cause severe brain damage and other serious medical problems. Mutations in the PAH gene that allow the enzyme to retain some activity result in milder versions of this condition, such as variant PKU or non-PKU hyperphenylalaninemia.

  Changes in other genes may influence the severity of PKU, but little is known about these additional genetic factors.

  How do people inherit phenylketonuria?

  This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

  What other names do people use for phenylketonuria?

  • Deficiency Disease, Phenylalanine Hydroxylase 
    
    
  • Folling Disease
    
    
  • Folling's Disease 
    
    
  • Phenylalanine Hydroxylase Deficiency Disease 
    
    
  • PAH Deficiency 
    
    
  • PKU

  Source: Genetics Home Reference, National Library of Medicine, National Institutes of Health

In 1902 Archibald Garrod first attributed a disease to an enzyme defect: an inborn error of metabolism. Today, newborns are routinely screened for certain enzyme defects such as PKU (phenylketonuria) and galactosemia, an error in the handling (metabolism) of the sugar galactose.

Esophagus: The tube that connects the pharynx (throat) with the stomach. The esophagus lies between the trachea (windpipe) and the spine. It passes down the neck, pierces the diaphragm just to the left of the midline, and joins the cardiac (upper) end of the stomach. In an adult, the esophagus is about 25 centimeters (10 inches) long. When a person swallows, the muscular walls of the esophagus contract to push food down into the stomach. Glands in the lining of the esophagus produce mucus, which keeps the passageway moist and facilitates swallowing. Also known as the gullet or swallowing tube. From the Greek oisophagos, from oisein meaning to bear or carry + phagein, to eat.

Fats: Plural of the word "fat". See the definition of fat.

Gallbladder: A pear-shaped organ just below the liver that stores the bile secreted by the liver. During a fatty meal, the gallbladder contracts, delivering the bile through the bile ducts into the intestines to help with digestion. Abnormal composition of bile leads to formation of gallstones, a process termedcholelithiasis. The gallstones cause cholecystitis, inflammation of the gallbladder.

GERD: Stands for Gastroesophageal Reflux Disease, a disorder in which there is recurrent return of stomach contents back up into the esophagus, frequently causing heartburn, a symptom of irritation of the esophagus by stomach acid. This can lead to scarring and stricture of the esophagus, which can require stretching (dilating). 
See the entire definition of GERD

GERD: Stands for Gastroesophageal Reflux Disease, a disorder in which there is recurrent return of stomach contents back up into the esophagus, frequently causing heartburn, a symptom of irritation of the esophagus by stomach acid. This can lead to scarring and stricture of the esophagus, which can require stretching (dilating).

10% of patients with GERD develop Barrett's esophagus which increases the risk of cancer of the esophagus. 80% of patients with GERD also have ahiatal hernia.

GI tract: Short for gastrointestinal tract. See: Gastrointestinal tract.

Gastrointestinal tract: The tube that extends from the mouth to the anus in which the movement of muscles and release of hormones and enzymes digest food. The gastrointestinal tract starts with the mouth and proceeds to the esophagus, stomach, duodenum, small intestine, large intestine (colon), rectum and, finally, the anus. Also called the alimentary canal, digestive tract and, perhaps most often in conversation, the GI tract.

Heartburn: An uncomfortable feeling of burning and warmth occurring in waves rising up behind the breastbone (sternum) toward the neck. It is usually due togastroesophageal reflux disease (GERD), the rise of stomach acid back up into the esophagus. Heartburn has nothing whatsoever to do with the heart. It is a popular nonmedical term. It is medically called pyrosis.

Ileum: The lowest part of the small intestine, located beyond the duodenum and jejunum, just before the large intestine (the colon). Pronounced "il-eum" in the US and "eye-leum" in the UK.
See the entire definition of Ileum

Intestine: The long, tubelike organ in the abdomen that completes the process of digestion. It consists of the small and large intestines.

Jejunum: Part of the small intestine. It is half-way down the small intestine between its duodenum and ileum sections.
See the entire definition of Jejunum

Large bowel: Another name for the large intestine.
See the entire definition of Large bowel

Large intestine: Comes after the small intestine. Large because it is wider than the small intestine.

Liver: An organ in the upper abdomen that aids in digestion and removes waste products and worn-out cells from the blood. The liver is the largest solid organ in the body. The liver weighs about three and a half pounds (1.6 kilograms). It measures about 8 inches (20 cm) horizontally (across) and 6.5 inches (17 cm) vertically (down) and is 4.5 inches (12 cm) thick.

Lungs: The lungs are a pair of breathing organs located with the chest which remove carbon dioxide from and bring oxygen to the blood. There is a right and left lung.

Mouth: 1. The upper opening of the digestive tract, beginning with the lips and containing the teeth, gums, and tongue. Foodstuffs are broken down mechanically in the mouth by chewing and saliva is added as a lubricant. Saliva contains amylase, an enzyme that digests starch. 2. Any opening or aperture in the body. The mouth in both senses of the word is also called the os, the Latin word for an opening, or mouth. The o in os is pronounced as in hope. The genitive form of os is oris from which comes the word oral.

Muscle: Muscle is the tissue of the body which primarily functions as a source of power. There are three types of muscle in the body. Muscle which is responsible for moving extremities and external areas of the body is called "skeletal muscle." Heart muscle is called "cardiac muscle." Muscle that is in the walls of arteries and bowel is called "smooth muscle."

Muscular: Having to do with the muscles. Also, endowed with above average muscle development. Muscular system refers to all of the muscles of the body collectively.

Organ: A relatively independent part of the body that carries out one or more special functions. The organs of the human body include the eye, ear, heart, lungs, and liver.

Palate: The roof of the mouth. The front portion is bony (hard palate), and the back portion is muscular (soft palate).

Pancreas: A fish-shaped spongy grayish-pink organ about 6 inches (15 cm) long that stretches across the back of the abdomen, behind the stomach. The head of the pancreas is on the right side of the abdomen and is connected to the duodenum (the first section of the small intestine). The narrow end of the pancreas, called the tail, extends to the left side of the body.

Pelvic: Having to do with the pelvis, the lower part of the abdomen, located between the hip bones.

Pelvis: The lower part of the abdomen located between the hip bones.

Peristalsis: The rippling motion of muscles in the digestive tract. In the stomach, this motion mixes food with gastric juices, turning it into a thin liquid.

Pharynx: The hollow tube about 5 inches long that starts behind the nose and ends at the top of the trachea (windpipe) and esophagus (the tube that goes to the stomach).

Protein: A large molecule composed of one or more chains of amino acids in a specific order determined by the base sequence of nucleotides in the DNA coding for the protein.
See the entire definition of Protein

Rectum: The last 6 to 8 inches of the large intestine. The rectum stores solid waste until it leaves the body through the anus. The word rectum comes from the Latin rectus meaning straight (which the human rectum is not).

Reflex: A reaction that is involuntary. The corneal reflex is the blink that occurs with irritation of the eye. The nasal reflex is a sneeze.

Reflux: The term used when liquid backs up into the esophagus from the stomach.

Regurgitation: A backward flowing. For example, of food. Or the sloshing of blood back into the heart (or between chambers of the heart) when a heart valve is incompetent and does not close effectively.

Saliva: a watery secretion in the mouth produced by the salivary glands that aids in the digestion of food. Saliva also serves to moisten and cleanse the mouth, including the tongue and teeth, and contains substances that can play a role in the prevention of infection. Saliva aids digestion by moistening food and containsenzymes that begin the digestion process. Also known as spit.

Sensation: In medicine and physiology, sensation refers to the registration of an incoming (afferent) nerve impulse in that part of the brain called the sensorium, which is capable of such perception. Therefore, the awareness of a stimulus as a result of its perception by sensory receptors. (Sensory is here synonymous with sensation.)
See the entire definition of Sensation

Sigmoid: In human anatomy, the lower colon (the lower portion of the large bowel). "Sigmoid" is short for "sigmoid colon."
See the entire definition of Sigmoid

Small intestine: The part of the digestive tract that extends from the stomach to the large intestine.

Soft palate: The muscular part of the roof of the mouth. The soft palate is directly behind the hard palate. It lacks bone and so is soft.

Stomach: 1. The sac-shaped digestive organ that is located in the upper abdomen, under the ribs. The upper part of the stomach connects to the esophagus, and the lower part leads into the small intestine.
See the entire definition of Stomach

Stool: The solid matter discharged in a bowel movement.

Substance: 1. Material with particular features, as a pressor substance.
2. The material that makes up an organ or structure. Also known in medicine as the substantia.
3. A psychoactive drug as, for example, in substance abuse.

Taste: Taste belongs to our chemical sensing system, or the chemosenses. The complicated process of tasting begins when molecules released by the substances stimulate special cells in the mouth or throat. These special sensory cells transmit messages through nerves to the brain where specific tastes are identified. 
See the entire definition of Taste

Throat: The throat is the anterior (front) portion of the neck beginning at the back of the mouth, consisting anatomically of the pharynx and larynx. The throat contains the trachea and a portion of the esophagus.

Tongue: The tongue is a strong muscle anchored to the floor of the mouth. It is covered by the lingual membrane which has special areas to detect tastes. 
See the entire definition of Tongue

Transverse: In anatomy, a horizontal plane passing through the standing body so that the transverse plane is parallel to the floor. 
See the entire definition of Transverse

Vitamins: The word "vitamin" was coined in 1911 by the Warsaw-born biochemist Casimir Funk (1884-1967). At the Lister Institute in London, Funk isolated a substance that prevented nerve inflammation (neuritis) in chickens raised on a diet deficient in that substance. He named the substance "vitamine" because he believed it was necessary to life and it was a chemical amine. The "e" at the end was later removed when it was recognized that vitamins need not be amines.
See the entire definition of Vitamins

Voluntary: Done in accordance with the conscious will of the individual. The opposite of involuntary.
See the entire definition of Voluntary

Windpipe: The trachea, a tube-like portion of the respiratory (breathing) tract that connects the larynx (the voicebox) with the bronchial parts of the lungs.