Definition Systemic lupus erythematosus (also called lupus or SLE) is a disease in which a person's immune system attacks and injures the body's own organs and tissues. Almost every system of the body can be affected. Description The body's immune system is a network of cells and tissues responsible for clearing the body of invading organisms, like bacteria, viruses, and...

Definition Syphilis is an infectious systemic disease that may be either congenital or acquired through sexual contact or contaminated needles. Description Syphilis has both acute and chronic forms that produce a wide variety of symptoms affecting most of the body's organ systems. The range of symptoms makes it easy to confuse syphilis with less serious diseases and ignore its early signs....

Definition Sympathectomy is a surgical procedure that destroys nerves in the sympathetic nervous system. The procedure is performed to increase blood flow and decrease long-term pain in certain diseases that cause narrowed blood vessels. It can also be used to decrease excessive sweating. This surgical procedure cuts or destroys the sympathetic ganglia, which are collections of nerve cell bodies in clusters...

Definition Sydenham's chorea is an acute but self-limited movement disorder that occurs most commonly in children between the ages of 5 and 15, and occasionally in pregnant women. It is closely associated with rheumatic fever following a throat infection. The disorder is named for Thomas Sydenham (1624–1689), an English doctor who first described it in 1686....

Definition Swallowing disorders (also called dysphagia) are any conditions that cause impairment of the movement of solids or fluids from the mouth, down the throat, and into the stomach. Description Swallowing disorders are a significant source of disability. They can have a severe effect on overall calorie intake and nutritional status, and they can adversely affect an individual's...

  Definition Surfactant is a complex naturally occurring substance made of six lipids (fats) and four proteins that is produced in the lungs. It can also be manufactured synthetically. Purpose Surfactant reduces the surface tension of fluid in the lungs and helps make the small air sacs in the lungs (alveoli) more stable. This keeps them from collapsing when an individual exhales. In preparation...

Definition The superior vena cava is the major vein in the chest that carries blood from the upper part of the body in to the heart. A restriction of the blood flow (occlusion) through this vein can cause superiorvena cava syndrome (SVCS). Description Superior vena cava syndrome is a partial occlusion of the superior vena cava. This leads...

Definition Sunscreens are products applied to the skin to protect against the harmful effects of the sun's ultraviolet (UV) rays. Purpose Everyone needs a little sunshine. About 15 minutes of exposure a day helps the body make Vitamin D, which is important for healthy bones and teeth. But longer exposure may cause many problems, from wrinkles to skin cancer. One particularly deadly form of...

Definition Sunburn is an inflammation of the skin caused by overexposure to ultraviolet radiation from the sun. Description Sunburn is caused by exposure to the ultraviolet (UV) rays of the sun. There are two types of ultraviolet rays, UVA and UVB. UVB radiation causes most sunburn (about 85%). However, most UVB rays are absorbed by sunscreens , but only about half the UVA rays...

Definition Sulfonamides, sometimes called sulfa drugs, are medicines that prevent the growth of bacteria in the body. The sulfonamides have largely been replaced by the antibiotics which generally are safer and more effective. Description Sulfonamides are used to treat many kinds of infections caused by bacteria and certain other microorganisms. Physicians may prescribe these drugs to...

Definition Sudden infant death syndrome (SIDS) is the unexplained death without warning of an apparently healthy infant, usually during sleep. Description Also known as crib death, SIDS has baffled physicians and parents for years. In the 1990s,advances have been made in preventing the occurrence of SIDS,...

Definition Sudden cardiac death (SCD) is an unexpected death due to heart problems, which occurs within one hour from the start of any cardiac-related symptoms. SCD is sometimes called cardiac arrest. Description When the heart suddenly stops beating effectively and breathing ceases, a person is said to have experienced sudden cardiac death. SCD is not the...

Definition Substance abuse and dependence refer to any continued pathological use of a medication, non-medically indicated drug (called drugs of abuse), or toxin. They normally are distinguished as follows. Substance abuse is any pattern of substance use that results in repeated adverse social consequences related to drug-taking—for example, interpersonal conflicts,...

Definition A subdural hematoma is a collection of blood in the space between the outer and middle layers of the covering of the brain. It is most often caused by torn, bleeding veins as a result of a head trauma. Description The covering of the brain (meninges) has three main layers. The outside is a tough, fibrous covering called the dura mater. The middle layer is the arachnoid mater, and the...

Definition A subarachnoid hemorrhage is an abnormal and very dangerous condition in which blood collects beneath the arachnoid mater, a membrane that covers the brain. This area, called the subarachnoid space, normally contains cerebrospinal fluid. The accumulation of blood in the subarachnoid space can lead to stroke, seizures, and other complications. Additionally,subarachnoid hemorrhages...

Definition Subacute sclerosing panencephalitis (SSPE) is a long-lasting (chronic) infection of the central nervous system that causes inflammation of the brain. The infection is caused by an altered form of the measles virus. The symptoms appear years after the initial infection, following re-activation of the latent virus. Description SSPE is one of three types of encephalitis that...

Definition Stuttering is a speech disorder in which there is a disruption in the normal flow of speech (disfluency). Disfluencies include repetitions of a sound, syllable, or word; silent blocks (drawing out a sound silently); and prolongations (drawing out a voiced sound). Certain behaviors such as eye blinks, facial twitches, or body movements may also accompany stuttering. Stuttering may...

Definition Brain cells need oxygen and nutrients to function properly. When blood flow to the brain is interrupted, brain cells can begin to die and a person can experience a stroke, also called a brain attack. Damage from a stroke can temporarily or permanently disable a person's movement, speech, and cognition. Description A stroke occurs when blood flow to the brain is blocked...

Definition Stridor is a term used to describe noisy breathing in general and to refer specifically to a high-pitched crowing sound associated with croup , respiratory infection, and airway obstruction. Description Stridor is a symptom, not a disease. It occurs when air is forced through breathing passages narrowed by the following: ·        ...

Definition A stress test is primarily used to identify coronary artery disease. It requires patients to exercise on a treadmill or exercise bicycle while their heart rate, blood pressure, electrocardiogram (ECG), and symptoms are monitored.  Purpose The body requires more oxygen during exercise than at rest. To deliver more oxygen during exercise, the heart has to pump more oxygen-rich...

Definition Stress is the body's normal response to anything that disturbs its natural physical, emotional, or mental balance. Stress reduction refers to various strategies that counteract this response and produce a sense of relaxation and tranquility. Purpose Although stress is a natural phenomenon of living, stress that is not controlled and that continues for a...

Stress is mental, emotional, or physical tension brought about by internal or external pressures such as anxiety or overwork. Thus, it is a negative way that a person frequently responds to environmental demands or pressures. Researchers have found significant biochemical changes that take place in the body during stress. Exaggerated, prolonged, or genetic tendencies to stress cause destructive...

Definition Streptococcal (strep) infections are communicable diseases that develop when bacteria of the family Streptococcus invade parts of the body and contaminate blood or tissue. Description Most people have some form of strep bacteria in their body at some point. A person who hosts bacteria without showing signs of infection is considered a carrier. Types of infection Primary strep infections invade...

Definition If left untreated, upper respiratory or skin infections caused by Group A streptococci (Streptococcus pyrogenes) can develop complications, called sequelae. These include scarlet and rheumatic fever and a kidney disease called post streptococcal glomerulonephritis (a sequalea to respiratory but not skin infections). Streptococcal antibody tests detect antibodies...

Definition Strep throat is a contagious infection caused by the bacterium Streptococcus pyogenes. Description Strep throat primarily affects children, especially those between the ages of five and 15. Adults whose immune systems have been weakened by stress or other infections are also at risk. Most sore throats are associated with viral infections such as the common...

Definition Strabismus is a condition in which the eyes do not align in the same direction. It is also called crossed eyes or squint. Description With normal vision, both eyes focus on the same spot and send the brain the same message. This binocular fixation (both eyes looking directly at the same object) is necessary to see three-dimensionally and to aid in depth perception. When an eye is misaligned,...

Definition The stool O & P test is the stool ova and parasites test. In this test, a stool sample is examined for the presence of intestinal parasites and their eggs, which are called ova. Purpose The ova and parasites test is performed to look for and identify intestinal parasites and their eggs in persons with symptoms of gastrointestinal...

Definition Stool fats, also known as fecal fats, or fecal lipids, are fats that are excreted in the feces. When secretions from the pancreas and liver are adequate, emulsified dietary fats are almost completely absorbed in the small intestine. When a malabsorption disorder or other cause disrupts this process, excretion of fat in the stool increases. Purpose This test evaluates...

Definition Stool culture is a test to identify bacteria in patients with a suspected infection of the digestive tract. A sample of the patient's feces is placed in a special medium where bacteria is then grown. The bacteria that grow in the culture are identified using a microscope and biochemical tests. Purpose Stool culture is performed to identify bacteria or other organisms...

Definition Stomatitis is an inflammation of the mucous lining of the mouth, which may involve the cheeks, gums, tongue, lips, and roof or floor of the mouth. The word "stomatitis" literally means inflammation of the mouth. Description Stomatitis is an inflammation of the lining of any of the soft-tissue structures of the mouth. It is usually a painful condition, associated with redness, swelling,...

Definition Stomach flushing is the repeated introduction of fluids into the stomach through a nasogastric tube, and their subsequent withdrawal by nasogastric suction. Purpose Stomach flushing is performed to aid in controlling gastrointestinal bleeding or to cleanse the stomach of poisons. Controlling stomach bleeding Bleeding from the esophagus due to ruptured...

Definition Stomach cancer (also known as gastric cancer) is a disease in which the cells forming the inner lining of the stomach become abnormal and start to divide uncontrollably, forming a mass called a tumor. Description The stomach is a J-shaped organ that lies in the left and central portion of the abdomen. The stomach produces many digestive juices and acids that...

Definition Stockholm syndrome refers to a group of psychological symptoms that occur in some persons in a captive or hostage situation. It has received considerable media publicity in recent years because it has been used to explain the behavior of such well-known kidnapping victims as Patty Hearst (1974) and Elizabeth Smart (2002). The term takes its name from a bank robbery in Stockholm, Sweden,...

Definition A stillbirth is defined as the death of a fetus at any time after the twentieth week of pregnancy.Stillbirth is also referred to as intrauterine fetal death (IUFD). Description It is important to distinguish between a stillbirth and other words that describe the unintentional end of a pregnancy. A pregnancy that ends before the twentieth week is called a miscarriage rather...

Definition Stem cells are basic human cells that reproduce (replicate) easily, providing a continuous source of new, sometimes different types of cells. A stem cell transplant is a procedure that replaces unhealthy stem cells with healthy ones. Purpose Physicians use stem cell transplants to treat many diseases that damage or destroy bone marrow, found in the soft...

Definition Starvation is the result of a severe or total lack of nutrients needed for the maintenance of life. Description Adequate nutrition has two components, necessary nutrients and energy in the form of calories. It is possible to ingest enough energy without a well-balanced selection of individual nutrients and produce diseases that are noticeably different from those resulting from an overall...

Definition Staphylococcal scalded skin syndrome (SSSS) is a disease, caused by a type of bacteria, in which large sheets of skin may peel away. Description SSSS primarily strikes children under the age of five, particularly infants. Clusters of SSSS cases (epidemics) can occur in newborn nurseries, when staff in those nurseries accidentally pass the causative bacteria between patients....

Definition Staphylococcal (staph) infections are communicable diseases caused by certain bacteriaand generally characterized by the formation of abscesses. They are the leading cause of primary infections originating in hospitals in the United States. Description Classified since the early twentieth century as among the deadliest of all disease-causing...

Definition Stapedectomy is a surgical procedure in which the innermost bone (stapes) of the three bones (the stapes, the incus, and the malleus) of the middle ear is removed, and replaced with a small plastic tube surrounding a short length of stainless steel wire (a prosthesis). The operation was first performed in the United States in 1956.   Purpose A stapedectomy is performed to improve...

Definition The Stanford-Binet Intelligence Scale: Fifth Edition (SB: FE) is a standardized test that measures intelligence in children and adults, from age two through mature adulthood. Purpose The Stanford-Binet Intelligence Scale was originally developed to help place children in appropriate educational settings. It can help determine the level of intellectual and cognitive...

Definition Sputum is material coughed up from the lungs and expectorated (spit out) through the mouth. A sputum culture is done to find and identify the microorganism causing an infection of the lower respiratory tract such as pneumonia (an infection of the lung). If a microorganism is found, more testing is done to determine which antibiotics will be effective in treating...

Definition Sprain refers to damage or tearing of ligaments or a joint capsule. Strain refers to damage or tearing of a muscle. Description When excessive force is applied to a joint, the ligaments that hold the bones together may be torn or damaged. This results in a sprain, and its seriousness depends on how badly the ligaments are torn. Any ligament can be sprained, but the most frequently injured ligaments...

Definition Sports injuries result from acute trauma or repetitive stress associated with athletic activities.Sports injuries can affect bones or soft tissue such as ligaments, muscles, and tendons. Description Children are more likely to suffer sports injuries than adults since a child's vulnerability is heightened by immature reflexes, an inability to recognize and evaluate...

Definition Sporotrichosis is a chronic infection caused by the microscopic fungus Sporothrix schenckii. The disease causes ulcers on the skin that are painless but do not heal, as well as nodules or knots in the lymph channels near the surface of the body. Infrequently, sporotrichosis affects the lungs, joints, or central nervous system and can cause serious illness. Description The fungus...

Definition Splenic trauma is physical injury to the spleen, the lymphatic organ located in the upper left side of the abdomen just under the rib cage. The spleen weighs between 75 and 150 grams (between 0.16 and 0.33 pounds) in adults. Description The spleen is an organ that produces white blood cells, filters the blood (10-15% of the total blood supply every minute), stores red blood cells and platelets,...

Definition Splenectomy is the surgical removal of the spleen, which is an organ that is part of the lymphatic system. The spleen is a dark purple, bean-shaped organ located in the upper left side of the abdomen, just behind the bottom of the rib cage. In adults, the spleen is about 4.8 2.8 1.6 in in size, and weighs about 4 or 5 oz. (It measures 12 7 4 cm, and weighs between 113 and 141 grams.) Its functions...

Definition Spinal stenosis is any narrowing of the spinal canal that causes compression of the spinal nerve cord. Spinal stenosis causes pain and may cause loss of some body functions. Description Spinal stenosis is a progressive narrowing of the opening in the spinal canal. The spine is a long series of bones called vertebrae. Between...

Definition Spinal instrumentation is a method of straightening and stabilizing the spine after spinal fusion, by surgically attaching hooks, rods, and wire to the spine in a way that redistributes the stresses on the bones and keeps them in proper alignment. Purpose Spinal instrumentation is used to treat instability and deformity of the spine. Instability occurs when the spine...

Definition A spinal cord tumor is a benign or cancerous growth in the spinal cord, between the membranes covering the spinal cord, or in the spinal canal. A tumor in this location can compress the spinal cord or its nerve roots; therefore, even a noncancerous growth can be disabling unless properly treated. Description The spinal cord contains...

Definition Spinal cord injury is damage to the spinal cord that causes loss of sensation and motor control. Description Approximately 11,000 new spinal cord injuries (SCIs) occur each year in the United States. About 200,000 people are currently affected. Spinal cord injuries can happen to anyone at any time of life. The typical...