Dictionary

spider vein A group of widened veins that can be seen through the surface of the skin. The wheeland-spokes shape of the veins resembles a spider. Also known as spider telangiectasia.

spider telangiectasia See spider vein.

spider bite A bite from a spider. Bites from most spiders are irritating but not poisonous. Localized reddening and swelling are not unusual and should pass within a few days. A few spiders are poisonous, notably the black widow and brown recluse (brown fiddler) in the US. Bites from these spiders require emergency treatment, especially…

sphygmomanometer Blood pressure cuff, an instrument for measuring blood pressure, particularly in arteries. Digital and manual models are available. The two basic types of manual sphygmomanometers are the mercury column and the gauge with a dial face. The manual sphygmomanometer in most frequent use today consists of a gauge attached to a rubber cuff that…

sphingomyelinosis See histiocytosis, lipid.

sphingolipidosis One of a group of hereditary diseases that involve overproduction or accumulation of fatty substances called sphingolipids in the brain and nervous system. See also Anderson-Fabry disease; Gaucher disease; GM1-gangliosidosis, histiocytosis, lipid; Krabbe disease; leukodystrophy; Tay-Sachs disease; Sandhoff disease.

sphincter A muscle that surrounds and, by its contraction, closes a normal opening such as that from the intestinal tract or the urinary tract. Damage to the anal and urethral sphincters can cause fecal and urinary incontinence, respectively. Sphincters tend to be ring-like and, when contracted, to constrict the opening. From the Greek for “that…

spherocytosis, hereditary A genetic disorder of the red blood cell membrane that is characterized by anemia, jaundice, and enlargement of the spleen (splenomegaly). Abbreviated HS. In HS, the red cells are smaller, rounder, and more fragile than normal. They have a spherical shape rather than the biconcave-disk shape of normal red cells. These fragile red…

sphenoid bone A prominent, irregular, wedgeshaped bone at the base of the skull. The sphenoid bone has been called the “keystone” of the cranial floor because it is in contact with all of the other cranial bones.

SPF 1 Sun protection factor. 2 Specificpathogen free.

spermatic cord A group of structures that go through the inguinal canal to the testis. These structures include the vas deferens, arteries, veins, lymphatic vessels, and nerves.

sperm The male sex cell (gamete). The sperm has an oval head that contains its genetic matter, and it is propelled by a flagellating tail. A sperm is carried into the female reproductive tract within the semen (ejaculate). If the sperm is able to travel up into a fallopian tube, it must then break through…