spondylosis Degeneration of the disc spaces between the vertebrae. Spondylosis is common with aging and affects virtually everyone to some degree after the age of 60 years. When severe, it can cause local pain and decreased range of motion of the spine, requiring pain and/or anti-inflammatory medications.
spondylolysis The breaking down (dissolution) of a portion of a vertebra. The affected portion of the vertebra is a bone segment called the pars interarticularis, which can separate. Spondylolysis can be a cause of abnormal movement of the spine (spondylolisthesis) and lead to localized back pain.
spondylolisthesis Forward movement of one vertebra in relationship to an adjacent vertebra.
spondylitis Inflammation of one or more of the vertebrae of the spine. Diffuse inflammation of the spine is seen, for example, in the disease ankylosing spondylitis. Localized spondylitis is seen with infections of a certain area of the spine, such as in Pott’s disease (tuberculosis of the spine).
split personality See dissociation; dissociative disorder.
splenomegaly Abnormal enlargement of the spleen. Splenomegaly is a sign of an underlying condition, such as severe liver disease, leukemia, or mononucleosis. Patients with splenomegaly should avoid activities that risk trauma to the abdomen, including contact sports, because of risk of bleeding from the injured spleen.
splenic fever See anthrax.
splenic artery A large and critically important artery within the abdomen that arises from a branch off the aorta called the celiac trunk. The splenic artery supplies blood not only to the spleen but also to the esophagus, stomach, duodenum, liver, and pancreas. See also aorta; artery.
splenectomy An operation to remove the spleen.
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…
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…
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.