spinal stenosis Narrowing of the spinal canal. Spinal stenosis is most commonly caused by degeneration of the discs between the vertebrae. The result is compression of the nerve roots or spinal cord by bony spurs or soft tissues, such as discs, in the spinal canal. This most commonly occurs in the low back (lumbar spine)…
spinal tap See lumbar puncture.
spine 1 The column of bone known as the vertebral column that surrounds and protects the spinal cord. The spine can be categorized according to the level of the body: cervical spine (neck), thoracic spine (upper and middle back), and lumbar spine (lower back). See also vertebral column. 2 Any short prominence of bone. For…
spiral CAT scan A specialized computerized axial tomography (CAT) scan technique that involves continuous movement of the patient through the scanner with the ability to scan faster and with high definition of internal structures. Spiral CAT scanning permits greater visualization of blood vessels and internal tissues, such as those within the chest cavity, than regular…
spiral fracture See fracture, torsion.
spirochete A microscopic bacterial organism in the Spirochaeta family that has a worm-like, spiralshaped form and wiggles vigorously when viewed under a microscope. Treponema pallidum, the cause of syphilis, is a particularly well-known spirochete.
spleen An organ that is located in the upper-left part of the abdomen, not far from the stomach, that produces lymphocytes, which are important elements in the immune system. The spleen is the largest lymphatic organ in the body. The spleen also filters blood, serves as a major reservoir for blood, and destroys blood cells…
spleen, ruptured Rupture of the capsule of the spleen that is a potential catastrophe and requires immediate medical and surgical attention. Splenic rupture permits large amounts of blood to leak into the abdominal cavity, and it is severely painful and life threatening. Shock, and ultimately death, can result. Patients typically require immediate surgery. Rupture of…
S1–S5 Symbols that represent the five sacral vertebrae.
spasm A brief, automatic jerking movement. A muscle spasm can be quite painful, with the muscle clenching tightly. A spasm of the coronary artery can cause the pain of angina. Spasms in various types of tissue may be caused by stress, medication, and overexercise.
spastic colitis See irritable bowel syndrome.
spasticity See hypertonia.