Sacro-iliac joint  - synovial joint formed between the medial surface of the ilium and the lateral aspect of the upper sacral vertebrae; a fibrous joint, comprising and surrounded by very strong ligamentous structures; major function is to transmit body weight, but also has a

Saline solution - a solution containing sodium chloride.

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

Salpingectomy - surgical removal of one or both fallopian tubes.

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

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

Scapula - commonly known as the shoulder blade.

Sciatica - traditionally defined as pain in the sciatic nerve, or its branches, that is caused by direct pressure or irritation.

Scintigraphy - see radionuclide scans.

Sclerotherapy - method of stopping upper gastrointestinal bleeding. A needle is inserted through an endoscope to bring hardening agents to the place that is bleeding.

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

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

Secretin - hormone made in the duodenum; causes the stomach to make pepsin, the liver to make bile, and the pancreas to make digestive juices.

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

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

Sella turcica - bony structure 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.

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

Septum - the muscle wall that divides the heart chambers.

Serum - a clear fluid that separates when blood clots.

Sesamoiditis - inflammatory condition affecting the two sesamoid bones in the flexor tendon of the great (big) toe.

Sexually transmitted disease (std) - infection spread through sexual intercourse and other intimate sexual contact.

Shigellosis - infection with the bacterium shigella; usually causes a high fever, acute diarrhea, and dehydration. (see also gastroenteritis.)

Short gut syndrome - see short bowel syndrome.

Shunt - a connector that allows blood flow between two locations.

Shwachman's syndrome - digestive and respiratory disorder of children in which certain digestive enzymes are missing and white blood cells are few.

Sialorrhea - drooling.

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

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

Silent ischemia - ischemia 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 (also called paranasal sinuses.) - air cavities within the facial bones, lined by mucous membranes similar to those in other parts of the airways.

Sinus node - the cells that produce the electrical impulses that cause the heart to contract.

Slump test - a test for assessing the mobility of the pain-sensitive structures in the vertebral canal.

Small bowel enema - x-rays of the small intestine taken as barium liquid passes through the organ. (see also lower gi series.)

Small intestine - organ where most digestion occurs; measures about 20 feet and includes the duodenum, jejunum, and ileum.

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

Smell disorder - temporary or permanent inability to perceive odors.

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

Soft-tissue - generally, 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 in the pancreas that helps tell the body when to make the hormones insulin, glucagon, gastrin, secretin, and renin.

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

Spasmodic dysphonia - momentary disruption of the voice caused by involuntary movements of one or more muscles of the larynx (or voice box).

Spastic colon - see irritable bowel syndrome (ibs).

Specific language impairment (sli) - difficulty with the organized-symbol-system communication in the absence of problems such as mental retardation, hearing loss, or emotional disorders.

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

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 impairments, that affect their ability to communicate.

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

Sphincter of oddi - muscle between the common bile duct and pancreatic ducts.

Sphygmomanometer - the instrument used to measure blood pressure.

Spinal anesthetic - an anesthetic which is injected into the spinal canal fluid for surgery in the lower abdomen, pelvis, rectum, or other lower extremities.

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

Spine - a column in the body consisting of 33 vertebrae.

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

Spleen - organ lying between the stomach and diaphragm that stores red blood cells and filters blood.

Splenectomy - surgical removal of the spleen.

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

Spondylosis - a condition of the spine involving a degenerative process.

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

Squamous intraepithelial lesion (sil) - like cervical intraepithelial neoplasia (cin), sil is a term used to classify the degree of precancerous change in cells of the cervix in a condition called cervical dysplasia.

Stage - the measurement of 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 - condition in which the body cannot absorb fat.

Steatosis - see fatty liver.

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

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 - opening in the abdomen that is created by an operation (ostomy); must be covered at all times by a bag that collects stool.

Stomach - main organ of digestion which lies between the esophagus and the small intestine.

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

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

Streptokinase - a clot-dissolving medication.

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

Stress fracture - fracture caused by non-traumatic, cumulative overload on a bone; caused by a number of factors including overtraining, incorrect biomechanics, fatigue, hormonal imbalance, poor nutrition, and osteoporosis.

Stress incontinence - involuntary leaking of urine which may be caused by coughing or straining.

Stress ulcer - upper gastrointestinal 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. (see also esophageal stricture and pyloric stenosis.)

Subacromial joint - a joint made up by the humorous and a superior arch, consisting of the acromion process and the coracoid process of the scapula; joined by the coraco-acromial ligament and lined by the synovium of the subacromial bursa.

Subacromial space - region of the shoulder that is bordered by the subacromial joint.

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

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.

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.

Sudeck's atrophy - condition characterized by severe pain, swelling, and disability; commonly seen in the foot, but may occur in other joints of the lower limb.

Sun protection factor (spf) -

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 find out 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 tremor (also called postural tremor.) - a tremor of a limb that increases when the limb is stretched.

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 neur

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

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

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

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

Systemic treatment (also called systemic 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 heart.