Definition: a loop in the cervical plexus consisting of fibers from the first three cervical nerves. Fibers from a loop between the C1 and C2 spinal nerves accompany the hypoglossal nerve for a short distance, leaving it as the superior root of the ansa cervicalis. Fibers from a loop between the C2 and C3 spinal nerves form the inferior root of the ansa cervicalis. Most commonly the roots merge, forming the ansa cervicalis, which gives rise to branches innervating infrahyoid muscles.
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Examples: glitazone, GI cocktail, etc.