また以下は「Wikipedia」の解説文となる。
The cricoid cartilage /ˌkraɪkɔɪd ˈkɑːrtɪlɪdʒ/, or simply cricoid (from the Greek krikoeides meaning "ring-shaped"), is the only complete ring of cartilage around the trachea.
【Structure】
The cricoid cartilage sits just inferior to the thyroid cartilage in the neck, and is joined to it medially by the median cricothyroid ligament and postero-laterally by the cricothyroid joints. Inferior to it are the rings of cartilage around the trachea (which are not continuous - rather they are C-shaped with a gap posteriorly). The cricoid is joined to the first tracheal ring by the cricotracheal ligament, and this can be felt as a more yielding area between the firm thyroid cartilage and firmer cricoid.
It is also anatomically related to the thyroid gland; although the thyroid isthmus is inferior to it, the two lobes of the thyroid extend superiorly on each side of the cricoid as far as the thyroid cartilage above it.
The posterior part of the cricoid is slightly broader than the anterior and lateral parts, and is called the lamina, while the anterior part is the band; this may be the reason for the common comparison made between the cricoid and a signet ring.
【Composition】
It is made of hyaline cartilage, and so can become calcified or even ossified, particularly in old age.
【Function】
The function of the cricoid cartilage is to provide attachments for the cricothyroid muscle, posterior cricoarytenoid muscle and lateral cricoarytenoid muscle muscles, cartilages, and ligaments involved in opening and closing the airway and in speech production.
【 語 句 】
・trachea：気管 ・thyroid cartilage：甲状軟骨 ・cricothyroid ligament：輪状甲状靭帯 ・cricothyroid joints：輪状甲状関節 ・cricotracheal ligament：輪状気管靭帯 ・yielding：しなやかな ・thyroid gland：甲状腺 ・thyroid isthmus ：甲状腺峡部 ・lobe：葉 ・lamina：薄板 ・ signet ring：認印[印鑑]つき指輪. ・hyaline cartilage ：硝子軟骨 ・calcified：石灰化した ・ossified：骨化した ・cricothyroid muscle：輪状甲状筋 ・ posterior cricoarytenoid muscle：後輪状披裂筋 ・lateral cricoarytenoid muscle：外側輪状披裂筋
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