Also known as: SP., SP-
SP has various meanings in the Physiology category. Discover the full forms, definitions, and usage contexts of SP in Physiology.
A sphincter is an anatomical structure, a circular muscle that normally maintains constriction of a natural body passage or orifice and which relaxes as required by normal physiological functioning. Sphincters are found in many animals; there are over 50 types in the human body, some microscopically small, in particular the millions of precapillary sphincters. Sphincters relax at death, possibly releasing fluids.
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