File talk:Pharyngeal arch cartilages.jpg

Morphogenesis of the second pharyngeal arch cartilage (Reichert's cartilage) in human embryos

J Anat. 2006 Feb;208(2):179-89.

Rodríguez-Vázquez JF, Mérida-Velasco JR, Verdugo-López S, Sánchez-Montesinos I, Mérida-Velasco JA.

Abstract

This study was performed on 50 human embryos and fetuses between 7 and 17 weeks of development. Reichert's cartilage is formed in the second pharyngeal arch in two segments. The longer cranial or styloid segment is continuous with the otic capsule; its inferior end is angulated and is situated very close to the oropharynx. The smaller caudal segment is in contact with the body and greater horn of the hyoid cartilaginous structure. No cartilage forms between these segments. The persistent angulation of the inferior end of the cranial or styloid segment of Reichert's cartilage and its important neurovascular relationships may help explain the symptomatology of Eagle's syndrome.

PMID 16441562

Human fetal hyoid body origin revisited

J Anat. 2011 Aug;219(2):143-9. doi: 10.1111/j.1469-7580.2011.01387.x. Epub 2011 May 22.

Rodríguez-Vázquez JF, Kim JH, Verdugo-López S, Murakami G, Cho KH, Asakawa S, Abe S.

Abstract

The hyoid body is traditionally believed to have a dual origin from second and third arch mesenchyme, but this theory remains controversial. We examined paraffin-embedded sections from the hyoid region of 12 embryos and fetuses at 5-7 weeks of gestation (11-22 mm cranio-rump length). We found that the second (Reichert's cartilage) and third arch mesenchymal condensations did not reach the median area at the base of the tongue. Rather, a midline mesenchymal condensation was seen, and it separated from these arches at an early stage. This condensation was triangular and plate-like, and the cranial part was narrow between the bilateral Reichert's cartilages, while the caudal part was wide along the mediolateral axis between the bilateral primitive greater horns. We considered the midline mesenchymal condensation as the hyoid body anlage. At 7 weeks, a cartilaginous mass appeared in the midline condensation. The hypoglossal nerve changed its direction at the superolateral ends of the midline condensation. We propose that: (i) the hyoid body originates from the hypobranchial eminence via the midline condensation; (ii) the lesser horn originates from the caudal end of Reichert's cartilage; and (iii) the greater horn of the hyoid and the superior cornu of the thyroid cartilage originate from the third arch cartilage. The second and third arches may not regulate early hyoid body morphology. © 2011 The Authors. Journal of Anatomy © 2011 Anatomical Society of Great Britain and Ireland.

PMID 21599659