輪状甲状関節（ りんじょうこうじょうかんせつ、英：cricothyroid joint ）
・「 It plays a key role in adjusting human voice pitch by changing the tension of the vocal cords.」（Wikipedia）
「Wikipedia」ではこの輪状甲状関節を3つのタイプに分類している。 A type ： 男の56%、女の66% 明瞭な関節面、頑丈な関節包、 3㎜の水平運動、2.5㎜の垂直運動（女の方が可動域が大きい） B type ： 男の24%、女の20%、タイプAほど関節面が明瞭ではなく、関節の 結合も柔らかね結合組織によって指示されるのみ。 水平、垂直運動も5㎜程度。 C type ： 関節面はほぼ平らで微小の結節がみられることもある。 水平運動5.1㎜、垂直運動3.8㎜。
The cricothyroid joint (or articulation) is a joint connecting the cricoid cartilage and the thyroid cartilage. It plays a key role in adjusting human voice pitch by changing the tension of the vocal cords. This tension is controlled mostly by the endolaryngeal vocalis and the extralaryngeal cricothyroid muscles which change vocal fold tension by narrowing the cricothyroid space created by rotation and gliding movements in horizontal and vertical direction allowed for by the cricothyroid articulation. 【Types】
Three types A, B, and C have been identified. Type B is in 24% of females and 20% of males. In contrary to type A it lacks a definite "facet" and the two cartilaginous parts of the articulation are joined only by soft connective tissue. Horizontal movement is 5.0 mm and vertical, 5.1 mm with no differences between them. Type C concerns all others and has a flat surface with or without a tiny protuberance. Horizontal movement is about 5.1 mm, and vertical 3.8 mm.
【 語 句 】 ・cricoid cartilage：輪状軟骨 ・thyroid cartilage：甲状軟骨 ・vocal cords：声帯 ・endolaryngeal：喉頭内の ・vocalis：声帯の ・extralaryngeal：喉頭外の ・cricothyroid muscles：輪状甲状筋 ・vocal fold：声帯ヒダ ・gliding movement：滑走運動 ・articulation：関節 ・facet：関節面 ・capsule：関節包 ・ligament：靭帯 ・concavity：凹面 ・groin：？ ・protuberance：結節
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