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Internal carotid plexus
Sympathetic connections of the ciliary and superior cervical ganglia. (Carotid plexus visible center top.) Note that the label "Sympathetic Efferent Fibres" above the nerves arising in the midbrain is an error. This label should read "Parasympathetic Efferent Fibres" as the sphincter pupillæ and ciliary muscle are innervated only by parasympathetic fibres.
Diagram of the cervical sympathetic. (Carotid plexus visible center top.)
Hal Blumenfeld, "Neuroanatomy through Clinical Cases", Sinauer Associates, 2002, p543
Patestas, Maria A.; Gartner, Leslie P. (2016). A Textbook of Neuroanatomy (2nd ed.). Hoboken, New Jersey: Wiley-Blackwell. p. 367. ISBN978-1-118-67746-9.
Richard L. Drake, Wayne Vogel & Adam W M Mitchell, "Gray's Anatomy for Students", Elsevier inc., 2005