Vagus nerve

It is the 10th cranial nerve in vertebrates, and after leaving the brain, as its name suggests, it has a very complex course and distribution. It leaves the skull, goes down the neck, enters the thoracic cavity, and then reaches the abdominal cavity, where it is widely distributed to the internal organs of the thorax and abdomen (excluding the pelvis), controlling their sensation, movement, and secretion. It has the widest distribution of all the cranial nerves, and in the cervical and thoracic region it is distributed to the pharynx, larynx, heart, lungs, esophagus, etc., and in the abdominal region it is distributed to the intestines from the stomach to the upper half of the large intestine, liver, pancreas, spleen, kidneys, etc. It is mainly composed of parasympathetic nerve fibers, and while acting in antagonism with the sympathetic nerves, it regulates the movement of smooth muscles in the internal organs and the distribution of glands.

[Yasumi Arai]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

脊椎(せきつい)動物の第10脳神経で、脳を出たのち、その名のようにきわめて複雑な走行と分布を示す。頭蓋(とうがい)を出て、頸(けい)部を下って胸腔(きょうこう)に入り、さらに腹腔に達して、広く胸腹部（骨盤を除く）の内臓に分布し、その知覚、運動、分泌を支配する。分布範囲は脳神経のなかでいちばん広く、頸胸部では咽頭(いんとう)、喉頭(こうとう)、心臓、肺、食道など、腹部では胃から大腸上半部までの腸管、肝臓、膵臓(すいぞう)、脾臓(ひぞう)、腎臓(じんぞう)などに分布する。主として副交感神経繊維からなり、交感神経と拮抗(きっこう)しながら、内臓の平滑筋の運動と腺(せん)の分布を調節する。

［新井康允］

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