The fifth arch only exists transiently, and no human structures are derived from the fifth arch. The cranial nerve supply to the sixth arch structures is the recurrent laryngeal branch of CN X (vagus nerve). The cranial nerve supply to the fourth arch structures is the superior laryngeal branch of CN X (vagus nerve). The muscles derived from the sixth arch include the intrinsic muscles of the larynx (except the cricothyroid). The muscles derived from the fourth arch include the pharyngeal constrictors and the cricothyroid. The fourth and sixth arches give rise to various cartilages including the thyroid, cricoid, arytenoids, corniculate and cuneiform. They are comprised of cartilage support (serving as a precursor to skeletal elements), arterial supply (from the aortic arch system) and cranial nerve supply. They are all derived from mesoderm and appear early in the third to fourth gestational week, and differentiate into terminal structures by the seventh to eighth gestational week. Hyoglossus lingual artery middle constrictor stylohyoid triticeal cartilage.The pharyngeal arches (also known as branchial arches) are a fundamental aspect of vertebrate head and neck development. The fiber arrangement suggested that, besides constriction of the pharynx, the ascending and descending fibers of the middle constrictor can act as an elevator muscle, and the irregular attachments could affect the functions of the muscles and vessels. The ascending and descending fibers rarely reached the top of the pharynx and the thyroid cartilage, respectively. Each quadrant consists of a major peripheral portion and a smaller marginal portion in the vermillion of the upper and. superior border of thyroid cartilage and also into the pharyngeal wall, elevates the larynx, glossopharyngeal nerve (IX). Orbicularis oris is subdivided into four quadrants (upper, lower, right and left). The three groups were inserted into the pharyngeal raphe, and the descending fibers joined the longitudinal pharyngeal muscles. Orbicularis oris muscle comprises both of its own fibers and those lent from the dilator muscles of the mouth, mainly the buccinator muscle. Some fibers attached to the hyoglossus, occasionally to the stylohyoid and the posterior belly of the digastric, but seldom to the lingual artery and the triticeal cartilage in the thyrohyoid ligament. The posteroinferior group fanned out from the posterior part of the greater horn, while the middle constrictor arose internally to the hyoglossus some fibers often passed externally, and their fibers sometimes intersected around the lingual artery, which ran between them. The middle group ascended posterosuperiorly from the greater horn and fanned out. The anterosuperior group ascended posterosuperiorly from the ligament and the lesser horn and fanned out. The middle constrictor arose from the stylohyoid ligament and the hyoid bone, and its fibers were divided into three overlapping groups. The gross anatomies of the pharyngeal and neighboring muscles were examined in 41 cadavers. This study investigated the attachments of the middle constrictor to clarify its configuration and re-examine its functions. Such arrangements make the interrelationships among pharyngeal muscles complicated. The pharyngeal muscles overlap each other and some of their parts have different areas of origin.
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