Reexamination of the Origin and Early Development of the Human Larynx

Abstract

The respiratory primordium buds off the primitive foregut and grows caudally, on a lengthening stalk; the cephalic end of the stalk develops into the glottis and infraglottis, and the rest becomes the trachea. Compression by pharyngeal mesoderm cephalic to the respiratory diverticulum obliterates the foregut lumen ventrodorsally as far cranially as the 4th pharyngeal pouches, forming an epithelial lamina with a narrow pharyngoglottic duct along its dorsal border. The mesoderm also raises an epiglottic and two arytenoid swellings in the pharyngeal floor at the level of the 4th pouches; the triangular ‘cecum’, bounded by these swellings, grows caudally along the ventral border of the epithelial lamina to just above the glottis. Beginning at stage 21, the epithelial lamina separates cephalocaudally, bringing the cecal lumen into continuity with the pharyngoglottic duct to form the laryngeal vestibule; when the separation is complete, the vestibule is continuous with the infraglottic cavity. Meanwhile, bilateral pouches arising from the caudal end of the cecum form the ventricles, the lower lips of which become the vocal folds, and the pharyngeal mesoderm surrounding the laryngeal cavity gives rise to the laryngeal cartilages and intrinsic musculature. The cricoid chondrifies bilaterally from a single center in the ventral arch of a precartilaginous template that encircles the infraglottic cavity, and on meeting forms the dorsal lamina. Each arytenoid chondrifies from a single center, and each half of the thyroid cartilage chondrifies from two. Anlagen for the intrinsic muscles appear during stage 17, sites of individual muscles are recognizable by stage 23, and myofibrils are pfesent by the 12th week.

Ontogeny of the mouse vocal fold epithelium

“…Previously published data led to the proposal of two principle mechanisms responsible for the juxtaposition of lateral walls. It is either driven by intense proliferation of epithelial cells, thereby leading to epithelial bending which obliterates the lumen (Petrova, 1963; Lobcko et al, 1979; Sanudo and Domenech-Mateu, 1990), and/or by condensation of mesenchymal cells at the site of arytenoid swellings, thereby exerting the pressure on the lateral epithelial walls (Zaw-Tun and Burdi, 1985; Muller et al, 1985). Our data does not distinguish between these possibilities, as mitotic activity was detected in both epithelial cells and adjacent mesenchymal cells.…”

“…Existing studies describing the development of the larynx and VF in humans or other mammals such as mice consist of either morphological investigations based on conventional H&E staining (Hopp, 1955; Walander, 1955; Zaw-Tun and Burdi, 1985; Sanudo and Domenech-Mateu, 1990), or clinical investigations comparing normal versus pathological morphologies (Benjamin and Inglis, 1989; Kakodkar et al, 2012). These studies documented the basic steps of laryngeal cavity and VF development (Henick, 1993).…”

Foramen Thyroideum: A Comparative Study in Embryos, Fetuses, and Adults

“…From an embryological point of view, the FT is considered by some(Zaw‐Tun, 14 Kallius 16 ) to be an incomplete union of the cartilaginous elements of the fourth and sixth pharyngeal arches, from which the lamina is derived; and by others as a failure of the chondrification of the thyroid lamina caused by the presence of a vessel or a nerve (Frazer 12 ).…”

Ceratocricoid muscle: An embryological and anatomical study

“…The external ring is said to give rise to the inferior constrictor muscles of the pharynx and cricothyroid muscle together with the thyroid cartilage, and the internal ring to the other muscles and cartilages of the larynx. According to the individual mass theory (Soulie and Bardier, 1907;Lewis, 1910;Lisser, 1911;Zaw-Tun and Burdi, 1985) these rings do not exist, and the muscles appear as independent masses which later develop connections with each other, thus appearing to be sphincters.…”