Medical Dictionary Definitions A-Z List
Medical Dictionary Definitions A - Z - «S»:
Sperm motility: The percentage of all moving sperm in a semen sample. In a semen sample, 50% or more of the sperm should normally be moving rapidly....
Sperm stem cell
Sperm stem cell: A cell that is incapable of fertilizing an egg cell but can give rise to cells that develop into sperm. Sperm stem cells can be grown in laboratory culture, providing a ready source of
these cells, as was first demonstrated in mice. Also called a spermatogonial
Spermatic cord: A group of structures which go through the
inguinal canal to the testis. The structures include the vas deferens, arteries, veins,
lymphatic vessels, and nerves. ...
Spermatocide: Any agent that is destructive to spermatozoa (that is, kills sperm).
Nonoxynol-9 is the most commonly encountered spermatocide in the United States. (The nonoxynols, technically speaking, are nonionic surfactant [surface active] mixtures that vary in the number of repeating ethoxy grou...
Spermatogenesis: The process of sperm formation.
The term was created from the prefix "spermato-" (Greek sperma, the seed or germ) + "genesis" (the coming into being of something) = the coming into being of sperm.
Spermatogenesis is in contrast to oogenesis, the process of egg (ovum) formation....
Spermatogonial stem cell
Spermatogonial stem cell: See: Sperm stem cell....
Spermicide, vaginal: A vaginal spermicide is a substance that will kill sperm in the vagina.
Vaginal spermicides are available in foam, cream, jelly, film, suppository, or tablet forms. All types contain a sperm-killing chemical.
Studies have not produced definitive data on the efficacy of spermicid...
SPF (sun protection factor): A number on a scale for rating the degree of protection provided by sunscreens. SPF stands for Sun Protection Factor.
SPF numbers on a package can range from as low as 2 to as high as 100. These numbers refer to the product's ability to screen or block out the sun's bu...
Sphenoid: 1. Shaped like a wedge.
2. Relating to the sphenoid bone (which is wedge-shaped)....
Sphenoid bone: A prominent, irregular, wedge-shaped bone at the base of the skull. The sphenoid bone has been called the "keystone" of the cranial floor since it is in contact with all of the other cranial bones.
The Greek physician Galen wrote that the sphenoid bone was "like a wedge thrust betwee...
Sphenopalatine neuralgia: A distinctive syndrome of headaches, better known today as cluster headache. There are two main clinical patterns of cluster headache -- the episodic and the chronic:
Episodic: This is the most common pattern of cluster headache. It
is characterized by 1-3 short attacks o...
Spherocytosis, hereditary (HS)
Spherocytosis, hereditary (HS): A genetic disorder of the red blood cell membrane clinically characterized by anemia, jaundice (yellowing) and splenomegaly (enlargement of the spleen).
In HS the red cells are smaller, rounder, and more fragile than normal. The red cells have a spherical rather than...
Sphingomyelin lipoidosis: Also called Niemann-Pick disease, this is a disorder of the metabolism of a lipid (fat) called sphingomyelin that usually causes the progressive development of enlargement of the liver and spleen (hepatosplenomegaly), "swollen glands" (lymphadenopathy), anemia and mental an...
Sphingomyelinase deficiency: Also called Niemann-Pick disease, this is a disorder of the metabolism of a lipid (fat) called sphingomyelin that usually causes the progressive development of enlargement of the liver and spleen (hepatosplenomegaly), "swollen glands" (lymphadenopathy), anemia and menta...
Sphygmomanometer: An instrument for measuring blood pressure, particularly in arteries. The two types of sphygmomanometers are a mercury column and a gauge with a dial face. The sphygmomanometer in most frequent use today consists of a gauge attached to a rubber cuff which is wrapped around the uppe...