Morphology and Ciliary Motion of Mucosa in the Eustachian Tube of Neonatal and Adult Gerbils

Abstract

The Eustachian tube is a small canal that connects the tympanic cavity with the nasal part of the pharynx. The epithelial lining of the Eustachian tube contains a ciliated columnar epithelium at the tympanic cavity and a pseudostratified, ciliated columnar epithelium with goblet cells near the pharynx. The tube serves to equalize air pressure across the eardrum and drains mucus away from the middle ear into the nasopharynx. Blockage of the Eustachian tube is the most common cause of all forms of otitis media, which is common in children. In the present study, we examined the epithelial lining of the Eustachian tube in neonatal and adult gerbils, with a focus on the morphological and functional development of ciliated cells in the mucosa. The length of the tube is ∼8.8 mm in adult gerbils. Scanning electron microscopy showed that the mucosal member near the pharyngeal side contains a higher density of ciliated cells and goblet cells than that near the tympanic side. The cilia beat frequency is 11 Hz. During development, the length of the Eustachian tube increased significantly between postnatal day 1 (P1) and P18. Scanning electron microscopy showed that the mucosa contained a high density of ciliated cells with a few goblet cells at P1. The density of ciliated cells decreased while the density of goblet cells increased during development. At P18, the mucosa appeared to be adult-like. Interestingly, the ciliary beat frequency measured from ciliated cells at P1 was not statistically different from that measured from adult animals. Our study suggests that the Eustachian tube undergoes significant anatomical and histological changes between P1 and P18. The tube is morphologically and functionally mature at P18, when the auditory function (sensitivity and frequency selectivity) is mature in this species.

Morphology and Ciliary Motion of the Middle Ear Mucosa of Neonatal and Adult Gerbils

“…A significant reduction of the density of ciliated cells was found between P8 and P18 (p < 0.05). This is consistent with morphological changes seen in the Eustachian tube at the same time period [5]. It is not clear, though, why the number of ciliated cells decreased during development at birth.…”

“…Middle ear effusion is found in all newborn animals within 3 h after birth, most effusion is clear within 3 days after birth [8]. The Eustachian tube is morphologically and functionally mature at P18 [5], so it may not explain this phenomenon only by the drainage of the tube. Recent evidence suggests that the effusion could be quickly clear by itself from the middle ear cavity.…”

“…The tissues were also scanned by scanning electronic microscope (SEM). The method is described in our previous study [5]. …”

“…Ciliary motion was measured and calibrated by a photodiode-based measurement system mounted on the Leica upright microscope as described in detail in previous publications [5]. …”

Cilia distribution and polarity in the epithelial lining of the mouse middle ear cavity

“…Despite the potentially significant role that cilia may play in middle ear function and pathology, ciliation in the middle ear epithelium is not well understood1314151617. A recent study used genetic tracing tools to illustrate the dual origin of the epithelium lining the mammalian middle ear cavity, and determined the developmental timeline of the maturation of the middle ear cavity in mice171819.…”