Term of the Day

Internal Anal Sphincter: An involuntary sphincter surrounding the superior 2/3 of the anal canal. It is a thickening of the circular smooth muscle layer of the large intestine and is innervated by the pelvic splanchnic nerves. The sphincter responds to the pressure of feces in the rectal ampulla by relaxing.

Term of the Day

Splanchnic Nerve: A preganglionic autonomic nerve of the abdominopelvic viscera. Preganglionic, sympathetic fibers that pass through the paravertebral (sympathetic chain) ganglia without synapsing form splanchnic nerves. Instead, they synapse in a prevertebral (visceral) ganglion such as the celiac ganglion, the superior mesenteric ganglion, or the inferior mesenteric ganglion (e.g. thoracic -- greater, lesser, least -- splanchnic nn, lumbar splanchnic nn, and sacral splanchnic nn). Pelvic splanchnic nerves are parasympathetic and formed by branches of the ventral rami of S2, S3, and S4. Their ganglia are at or near the target organ.

P.S. Have a very Happy New Year!