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Saethre-Chotzen - A birth defect characterized by an unusually short or broad head. In addition, the eyes may be spaced wide apart and have droopy eyelids, and fingers may be abnormally short and webbed.

Safe sex - taking precautions when having sexual relations to prevent transmission of disease, e.g., using condoms. However, many healthcare professionals believe there really is no such thing as "safe" sex, and the only way to be truly safe is to abstain as all forms of sexual contact carry some risk.

Salicylic acid - a keratolytic drug (a drug that removes the outer layer of skin) that is used to treat various skin conditions.

Saline solution - a solution containing sodium chloride (salt).

Saliva - mixture of water, protein, and salts that makes food easy to swallow and begins digestion in the mouth.

Salmonella - bacterium that may cause intestinal infection and diarrhea.

Salmonella infections - diarrheal infections caused by the bacteria Salmonella. There are many kinds of Salmonella bacteria that cause diarrheal illnesses in humans.

Salpingectomy - surgical removal of one or both fallopian tubes.

Salpingo-oophorectomy - surgery to remove the fallopian tubes and ovaries.

Sarcoidosis - condition that causes small, fleshy swellings in the tissue around the organs, usually in the liver, lungs, and spleen.

Saturated fat - a type of fat that is found in foods from animal meats and skin, dairy products, and some vegetables.

Scabies - a skin disease caused by an infestation of mites in the skin characterized by small pimples that itch.

Scales - dead skin cells that look like flakes or dry skin.

Scapula - shoulder blade.

Scar - a growth of skin tissue that occurs as the body's natural way of healing and replacing lost or damaged skin. A scar is usually composed of fibrous tissue. Scars may be formed for many different reasons, including as a result of infections, surgery, injuries, or inflammation of tissue.

Schiller test - a diagnostic test in which the cervix is coated with an iodine solution to detect the presence of abnormal cells.

Schizoid personality disorder - a psychiatric condition in which a person is often cold, distant, introverted, and has an intense fear of intimacy and closeness. A person with schizoid personality disorder is often too absorbed in his/her own thinking and daydreaming that he excludes himself from attachment with persons and reality.

Schizophrenia - a psychiatric condition in which a person has difficulty distinguishing between real and fantasty situations and experiences. The condition is characterized by an inability to think logically, respond with normal emotions, or behave appropriately in social situations.

Schizotypal personality disorder - similar to schizoid personality disorder, persons with this disorder are often cold, distant, introverted, and have an intense fear of intimacy and closeness. Yet, with schizotypal personality disorder, persons also exhibit disordered thinking, perception, and ineffective communication skills. Many symptoms of schizotypal personality disorder resemble schizophrenia, but are less mild and intrusive.

Sciatica (also called lumbar radiculopathy) - a condition in which pain, weakness, numbness, and/or tingling occur in the leg. It is called sciatica because it originates along the sciatic nerve, which runs from the hip down the leg.

Sclera - the white, visible portion of the eyeball. The muscles that move the eyeball are attached to the sclera.

Scleroderma - a disease of the body's connective tissue that causes thickening and hardening of the skin, as well as changes in the blood vessels, muscles, and internal organs.

Sclerosing adenosis - a benign breast condition that involves excessive growth of tissues in the breast's lobules, often resulting in breast pain.

Sclerotherapy - method of stopping upper gastrointestinal (GI) bleeding. A needle is inserted through an endoscope to administer hardening agents to the location that is bleeding.

Scoliosis - a lateral, or sideways, curvature and rotation of the back bones (vertebrae), giving the appearance that the person is leaning to one side.

Scotoma - an area of partial or complete loss of vision surrounded by an area of normal vision.

Screening - checking for disease when there are no symptoms.

Screening mammogram - an x-ray of the breast used to detect breast changes in women who have no signs of breast cancer.

Scrotum - the bag of skin that holds the testicles.

Seasonal affective disorder (SAD) - a mood disorder characterized by depression related to a certain season of the year - especially winter.

Sebaceous glands - glands in the skin that secrete oil to the surface of the skin.

Seborrheic keratosis - a condition in which flesh-colored, yellow, brown, or black wart-like spots on the skin.

Sebum - oily substance produced by sebaceous glands in the skin.

Secondary tumor - a tumor that forms as a result of spread (metastasis) of cancer from the location where it originated.

Secretin - hormone made in the duodenum that causes the stomach to produce pepsin, the liver to make bile, and the pancreas to produce a digestive juice.

Segmental mastectomy - surgery to remove a portion of the breast.

Segmentation - process by which muscles in the intestines move food and wastes through the body.

Seizure - occurs when part(s) of the brain receives a burst of abnormal electrical signals that temporarily interrupts normal electrical brain function.

Self-monitoring blood glucose - method for people with diabetes to find out how much glucose is in their blood.

Sella turcica - bony structure in the head that houses the pituitary gland.

Sensorineural hearing loss - hearing loss caused by damage to the sensory cells and/or nerve fibers of the inner ear.

Sepsis - the presence of bacteria, virus, fungus, or other organism in the blood or other tissues and the toxins associated with the invasion.

Septal defect - a hole in the wall of the heart.

Septoplasty - the surgical correction of defects and deformities of the nasal septum (the partition between the nostrils).

Septum - the muscle wall that divides the heart chambers.

Serology - the study of blood serum (the clear fluid that separates when blood clots).

Serotonin - a chemical necessary for communication between nerve cells.

Serum - a clear fluid that separates when blood clots.

Sexually transmitted disease (STD) - infection spread through sexual intercourse and other intimate sexual contact. Also referred to as a sexually transmitted infections, or STI.

Shigellosis - infection with the bacterium Shigella, usually causing a high fever, acute diarrhea, and dehydration.

Shin splints - damage to one of two groups of muscles along the shin bone that cause pain.

Shock - impaired body function due to blood loss or a disturbance in the circulatory system.

Short bowel syndrome (Also called short gut syndrome.) - problems related to absorbing nutrients after removal of part of the small intestine.

Shunt - a connector to allow blood flow between two locations.

Shwachman's syndrome - a rare genetic disorder that affects the functioning of the pancreas and the bone marrow. Pancreas effects include problems with absorbing fats and other nutrients, and bone marrow effects include decreased levels of blood cells.

Sialorrhea - drooling.

Sickle cell anemia - an inherited blood disorder characterized by defective hemoglobin, which causes red blood cells to form an abnormal shape (usually sickle shaped) at times.

Sigmoid colon - lower part of the colon that empties into the rectum.

Sigmoidoscopy - a diagnostic procedure that allows the physician to examine the inside of a portion of the large intestine, and is helpful in identifying the causes of diarrhea, abdominal pain, constipation, abnormal growths, and bleeding. A short, flexible, lighted tube, called a sigmoidoscope, is inserted into the intestine through the rectum. The scope blows air into the intestine to inflate it and make viewing the inside easier.

Sign language - language of hand shapes, facial expressions, and movements used as a form of communication.

Silent ischemia - ischemia (lack of blood flow to body tissues) not accompanied by chest pain.

Simple mastectomy - surgical removal of the breast and possibly a few of the axillary lymph nodes close to the breast.

Sinus node - a specialized group of cells that produce the electrical impulses that cause the heart to contract.

Sinuses - air cavities within the facial bones, lined by mucous membranes similar to those in other parts of the airways.

Sinusitis - inflammation of the membranes lining the facial sinuses, often caused by bacterial or viral infection, or allergic reaction.

Skilled nursing facility (SNF) - an out-of-home care option for elderly persons who require continuous nursing care. SNFs can provide extensive care services, such as intravenous feedings, blood pressure monitoring, medication injections, and care for patients on ventilators.

Skin (cutaneous) diphtheria - one type of diphtheria; the symptoms are usually milder and may include yellow spots or sores (similar to impetigo) on the skin.

Skin cancer - a malignant tumor that grows in the skin cells.

Skin grafts - a skin graft may be used to cover skin that has been damaged and/or is missing. This surgical procedure involves removing healthy portions of skin from one part of the body to restore normal appearance and/or function to another portion of the same body. The location where the skin is removed is called the donor site. There are various types of skin grafts that may be utilized, depending upon the size and location of needed skin.

Skin tags - soft, small, flesh-colored skin flaps on the neck, armpits, or groin.

Small intestine - the section of the digestive tract between the stomach and the large intestine. Most of digestion occurs here as nutrients are absorbed from food.

Smallpox - a highly contagious disease caused by a type of poxvirus; symptoms usually include a fever and a blistery-like rash.

Smell - to perceive odor or scent through stimuli affecting the olfactory nerves.

Smell disorder - inability to perceive odors that may be temporary or permanent.

Smooth muscle - muscle that performs automatic tasks, such as constricting blood vessels.

Social phobia - an anxiety disorder in which a person has significant anxiety and discomfort related to a fear of being embarrassed, humiliated, or scorned by others in social or performance situations.

Soft tissues - the ligaments, tendons, and muscles in the musculoskeletal system.

Somatosensory - refers to sensory signals from all tissues of the body including skin, viscera, muscles, and joints.

Somatostatin - a hormone made in the pancreas and in the hypothalamus that helps tell the body when to make the hormones insulin, glucagon, gastrin, secretin, and renin.

Sound vocalization - ability to produce voice.

Spasm - a condition in which a muscle or group of muscles involuntarily contract.

Spasmodic dysphonia - a condition in which involuntary movements (spasms) of one or more muscles of the larynx (voice box) cause a brief disruption of the voice.

Spasms - muscle movements such as those in the colon that cause pain, cramps, and diarrhea.

Spasticity - increased muscle tone that results in a tightening and shortening of a muscle.

Specific language impairment (SLI) - difficulty with spoken language in the absence of problems such as intellectual disability, hearing loss, or emotional disorders.

Specific phobia - a type of phobia characterized by extreme fear of an object or situation that is not harmful under general conditions.

Speech - making definite vocal sounds that form words to express thoughts and ideas.

Speech disorder - defect or abnormality that prevents an individual from communicating by means of spoken words.

Speech processor - part of a cochlear implant that converts speech sounds into electrical impulses to stimulate the auditory nerve.

Speech-language pathologist - health professional trained to evaluate and treat people who have voice, speech, language, or swallowing disorders, including hearing impairment, that affect their ability to communicate. A minimum of a bachelor's degree is necessary to practice in the field, and a master's degree is required to become certified by the Council for Clinical Certification (CFCC) of the American Speech-Language-Hearing Association (ASHA).

Sperm disorders - problems with the production and maturation of sperm; the single most common cause of male infertility. Sperm may be immature, abnormally shaped, unable to move properly, or, normal sperm may be produced in abnormally low numbers (oligospermia).

SPF - Sun Protection Factor.

Sphincter - ring-like band of muscle that opens and closes an opening in the body.

Sphincter muscles - circular muscles that help keep urine from leaking by closing tightly like a rubber band around the opening of the bladder. Sphincter muscles are found elsewhere in the body, as well, such as in the rectum.

Sphincter of Oddi - circular groups of muscles that regulate the flow of digestive juices from the liver and pancreas into the small intestine.

Sphincterotomy - a procedure to open the muscle sphincter - a ring of muscle around a natural opening that acts like a valve in order to improve the flow through the sphincter.

Sphygmomanometer - the instrument used to measure blood pressure.

Spider angioma - a small collection of blood vessels just under the skin with a red spot in the center and tiny blood vessels radiating out from the center.

Spinal anesthesia - injection of an anesthetic into the area around the spinal cord to block pain sensation during surgery.

Spinal cord - a bundle of nerves that carries messages between the brain and the rest of the body.

Spinal instability - increased motion between vertebra, usually resulting from an injury; pain typically feels like tingling in the neck or arms.

Spinal stenosis - narrowing of the nerve openings either around the spinal cord or nerve roots that can cause symptoms similar to a pinched nerve; pain is described either as an aching or an electrical feeling down the arm.

Spinal tap (also called lumbar puncture) - a procedure in which a special needle is placed into the lower back, into the spinal canal. This is the area around the spinal cord. The pressure in the spinal canal and brain can then be measured. A small amount of cerebral spinal fluid (CSF) can be removed and sent for testing to determine if there is an infection or other problems. CSF is the fluid that bathes the brain and spinal cord.

Spine - a column of bones in the back consisting of 33 vertebrae.

Spirogram - a record of the amounts of air being moved in and out of the lungs.

Spirometer - an instrument that measures the amount of air moved in and out of the lungs (the amount of inhaled and exhaled air).

Spirometry - a pulmonary test of the lungs using a spirometer.

Spleen - organ that cleans blood and makes white blood cells.

Splenectomy - surgical removal of the spleen.

Splenic flexure syndrome - condition that occurs when air or gas collects in the upper parts of the colon.

Splint - a device for preventing movement of a joint or holding in place any part of the body.

Spondylitis - inflammation of the spine.

Spondylolisthesis - forward displacement of one vertebra on its lower neighbor.

Spondylosis - a degenerative process of the cervical spine that causes narrowing of the spinal canal and neural foramina, and produces compression of the spinal cord and nerve roots.

Sporadic - occurring by chance.

Sprain - a partial or complete tear of a ligament.

Sputum (also called phlegm) - mucus from the lungs.

Squamous cell cancer - a slow-growing cancer in cells in the top layer of the skin.

Squamous cell carcinoma - a form of skin cancer that affects about 20 percent of patients with skin cancer. This highly treatable cancer is characterized by red, scaly skin that becomes an open sore.

Squamous cells (also called keratinocytes) - the primary cell types found in the epidermis, the outer layer of skin.

Squamous intraepithelial lesion (SIL) - a term used to classify the degree of precancerous change in cells of the cervix in a condition called cervical dysplasia.

Stage - the extent of a cancer; whether the disease has spread from the original site to other parts of the body.

Staging - an evaluation of the extent of disease that provides the basis for making treatment recommendations.

Steatorrhea - the presence of fat in bowel movements.

Stem cell transplantation - removing stem cells from the patient's or a donor's bone marrow and re-infusing them into the patient to help produce healthy blood cells; a method of replacing stem cells which are destroyed by cancer treatment.

Stem cells - the blood cells that produce other blood cells. It is the stem cells that are needed in bone marrow transplantation.

Stenosis - the narrowing or constriction of a blood vessel or valve in the heart.

Stent - a device implanted in a vessel used to help keep it open.

Stereopsis - ability to perceive three-dimensional depth.

Sternum - the breastbone.

Stethoscope - the instrument used to listen to the heart and other sounds in the body.

Stirrups - technique of ankle strapping using rigid tape placed on the ankle, medial to lateral adhering to the undersurface of the heel, mimicking a stirrup.

Stoma - a surgically created opening in an organ.

Stomach - organ between the esophagus and the small intestine. The stomach is where digestion of protein begins.

Stomach ulcer (also called a gastric ulcer) - open sore in the stomach lining.

Stool (Also called feces.) - solid wastes that pass through the rectum as bowel movements. Stools are undigested foods, bacteria, mucus, and dead cells.

Stork bite (also called salmon patch) - small pink or red patches often found on a baby's eyelids, between the eyes, upper lip, and back of the neck.

Straight leg raise (SLR) - technique for measuring sciatic nerve mobility and/or hamstring length.

Strain - a partial or complete tear of a muscle or tendon.

Strawberry hemangioma - a bright or dark red, raised or swollen, bumpy area on the skin of a baby or child.

Streptokinase - a clot-dissolving medication.

Stress - mental or physical tension that results from physical, emotional, or chemical causes.

Stress fractures - weak spots or small cracks in the bone caused by continuous overuse.

Stress incontinence - the most common type of incontinence that involves the leakage of urine during exercise, coughing, sneezing, laughing, lifting heavy objects, or other body movements that put pressure on the bladder.

Stress ulcer - upper gastrointestinal (GI) ulcer from physical injury such as surgery, major burns, or critical head injury.

Striatum - part of the basal ganglia; a large cluster of nerve cells, consisting of the caudate nucleus and the putamen, that controls movement, balance, and walking; the neurons of the striatum require dopamine to function.

Stricture (also called stenosis) - abnormal narrowing of a body opening.

Stroke (also called brain attack) - occurs when brain cells die because of inadequate blood flow to the brain.

Stuttering - frequent repetition of words or parts of words that disrupts the smooth flow of speech.

Subarachnoid hemorrhage - a stroke that occurs when a blood vessel on the surface of the brain ruptures and bleeds into the space between the brain and the skull (but not into the brain itself).

Subchondral tissue - the smooth tissue at the ends of bones, which is covered with another type of tissue called cartilage.

Subcutis (also called subcutaneous layer) - the deepest layer of skin.

Substantia nigra - a small area of the brain containing a cluster of black-pigmented nerve cells that produce dopamine, which is then transmitted to the striatum.

Subtotal or partial gastrectomy - surgical removal of a portion of the stomach.

Sudden deafness - loss of hearing that occurs quickly from such causes as explosion, a viral infection, or the use of some drugs.

Sudden death - death that occurs unexpectedly or immediately after onset of symptoms.

Sudden infant death syndrome (SIDS) - unexplained, sudden death of an infant up to 1 year of age.

Suicide - the intentional taking of one's own life.

Sunburn - a visible reaction of the skin to overexposure to the sun's invisible ultraviolet (UV) rays.

Sunscreen - a product that protects the skin again sunburns by blocking the penetration of the sun's ultraviolet (UV) rays.

Superior vena cava - the large vein that returns blood to the heart from the head and arms.

Suprarenal glands - another name for the adrenal glands.

Surgery - operation to remove or repair a part of the body, or to determine if disease is present.

Suspensory ligament of lens - a series of fibers that connect the ciliary body of the eye with the lens, holding it in place.

Sustention (postural) tremor - a tremor of a limb that increases when the limb is stretched.

Swallowing disorders - any of a group of problems that interfere with the transfer of food from the mouth to the stomach.

Synapse - a tiny gap between the ends of nerve fibers across which nerve impulses pass from one neuron to another; at the synapse, an impulse causes the release of a neurotransmitter, which diffuses across the gap and triggers an electrical impulse in the next neuron.

Syncope - light-headedness or fainting caused by insufficient blood supply to the brain.

Syndactyly - a congenital problem characterized by a union of fingers or toes.

Syndromic hearing impairment - hearing loss or deafness that is inherited or passed through generations of a family.

Synovial fluid - a clear, sticky fluid that is released by the synovial membrane and acts as a lubricant for joints and tendons.

Synovial membrane - a tissue that lines and seals the joint.

Synovitis - inflammation of the synovial membrane, the tissue that lines and protects the joint.

Synovium - a fibrous envelope that produces a fluid to help to reduce friction and wear in a joint.

Syphilis - a sexually transmitted disease caused by Treponema pallidum bacteria. The initial symptom of syphilis is a painless open sore that usually appears on the penis or around or in the vagina. If untreated, syphilis may go on to more advanced stages, including a transient rash and, eventually, serious involvement of the heart and central nervous system.

Syrup of ipecac - an emetic made from the dried root of a plant called ipecacuanha, which is grown in Brazil. An emetic is an agent that causes vomiting.

Systemic - disease or symptoms that affect many different parts of the body.

Systemic chemotherapy - chemotherapy taken by pill or needle injection into a vein or muscle.

Systemic juvenile rheumatoid arthritis - a form of juvenile rheumatoid arthritis that affects joints and, sometimes, internal organs.

Systemic lupus erythematosus (also called SLE or lupus) - a very serious, chronic, autoimmune disorder characterized by periodic episodes of inflammation of and damage to the joints, tendons, other connective tissues, and organs, including the heart, lungs, blood vessels, brain, kidneys, and skin.

Systemic treatment or therapy - treatment or therapy that reaches and affects cells throughout the body.

Systolic blood pressure - the highest pressure to which blood pressure rises with the contraction of the ventricles.