Glossary S

S

Satiety

Feeling of fullness.

Scientific knowledge

The current set of peer-evaluated consensus models about how natural phenomena work, which often differ between groups of researchers at the research frontier.

Scientific progress

The cumulative growth of a system of knowledge over time, in which useful features are retained and nonuseful features are abandoned, based on the rejection or confirmation of testable knowledge.

Scintigraphy

An imaging method in which a mild dose of a radioactive substance is swallowed to show how material moves through the GI tract.

Sensitization

Enhancement of a response by an organism that is produced by delivering a strong, generally noxious, stimulus. A neuron becomes more excitable or responsive; it may respond more intensely to naturally occurring stimuli, either peripherally (in the viscera) or centrally (in the brain).

Serotonin (5-hydroxytryptamine, or 5-HT)

A chemical neurotransmitter (a chemical that acts on the nervous system to help transmit messages along the nervous system). It is found in the intestinal wall and the central nervous system. It is now widely understood that 95% of the serotonin in the body resides in the gut.

Sigmoid colon

The S-shaped section of the colon that connects to the rectum.

Sigmoidoscopy

Examination of the inside of the sigmoid colon and rectum using an endoscope -- a thin, lighted tube (sigmoidoscope). Samples of tissue or cells may be collected for examination under a microscope. Also called proctosigmoidoscopy.

Significant or statistically significant

A statistical term indicating that the results of a study are stronger than would be expected from chance alone.

Skin test

A test for an immune response to a compound by placing it on or under the skin.

Small intestine

The part of the digestive tract that is located between the stomach and the large intestine.

Somatic

Skin and muscle.

Somatization

Physical symptoms and no recognizable physical abnormality.

Sphincter

Ring of muscle that opens and closes.

Sphincter of Oddi

A muscle at that juncture of the bile and pancreatic ducts and the small intestine. It functions by opening and closing these ducts.

Sphincter of Oddi Dysfunction

An abnormality of the contractions of the sphincter of Oddi, which may be seen with a biliary and/or pancreatic type of pain in the upper right and middle parts of the abdomen (below the breastbone). It most commonly occurs in middle-aged women who have had their gallbladder removed. Treatment may involve surgery or medicines aimed at decreasing resistance to the flow of bile or pancreatic juice caused by the sphincter dysfunction.

Spinal cord

A column of nerve tissue that runs from the base of the skull down the back. It is surrounded by three protective membranes, and is enclosed within the vertebrae (back bones). The spinal cord and the brain make up the central nervous system, and spinal cord nerves carry most messages between the brain and the rest of the body.

Squamous cell

A flat cell that looks like a fish scale under a microscope. Squamous cells cover internal and external surfaces of the body.

Stress

The neurophysiological and subjective response to stimuli. In contrast to the common interpretation of the term "stress" as a psychological phenomenon, it should be understood as any real or perceived perturbation of an organism's homeostasis, or state of harmony or balance. Stress may disrupt the function of nerve and even immune cells in the GI tract and in the brain. The central stress system involves the release of chemical stress mediators in the brain, which in turn orchestrate an integrated autonomic, behavioral, neuroendocrine, and pain modulatory response. This biological response in turn will alter the way the brain and the viscera (internal organs such as the gut/intestines) interact, and this altered brain-gut interaction can result in worsening of symptoms in functional GI disorders. For example, stress can increase GI symptoms by changing how the brain controls unwanted and painful sensation.

Stressor

Internal or external factors or stimuli that produce stress. They can be physical, biological, environmental, or psychological; each can activate central stress circuits in an individual. For example, worry about the untimely and unpredictable onsets of uncontrollable abdominal pain or an uncontrollable bowel movement qualify as stressors sufficient to activate the central stress system.

Stricture

Abnormal narrowing of a body opening.

Syndrome

A set of symptoms or conditions that occur together and suggest the presence of a certain disease or an increased chance of developing the disease.

Systemic

Affecting the entire body.