Anatomical Boundary of the Tympanic Membrane Pars Flaccida of the Meriones unguiculatus (Mongolian Gerbil)

Abstract

The pars flaccida of the Meriones unguiculatus (Mongolian gerbil) was in previous studies shown to bulge almost spherically when pressurized, a behavior suggesting that it is suspended by a fixed circular boundary. The question arises whether this ''functional'' boundary is based on an underlying circular anatomical boundary, an important issue for modeling the middle-ear mechanics. In this article, the boundaries of the Mongolian gerbil pars flaccida were visualized in situ with otomicroscopy and in slides with light microscopy and by micro-CT radiology. For the major part of its circumference, the pars flaccida was found to be suspended by rigid bone, that is, the tympanic legs. The remaining boundary is made up of the terminal portion of the handle of the malleus and the soft tissue of the terminal arches. The attachment to these structures is simple and uncomplicated, and the geometry is regular and symmetric: deviating by only 3.5% from a perfect circular shape. The findings justify the use of a fixed circular boundary as a good approximation for the modeling of pars flaccida deformation in the Mongolian gerbil. Anat Rec, 294:987-995, 2011. V V C 2011 Wiley-Liss, Inc.

Structure and function of the mammalian middle ear. I: Large middle ears in small desert mammals

“…Among desert rodents with enlarged bullae, the auditory structures of kangaroo-rats and -mice in the family Heteromyidae, subfamily Dipodomyinae (Webster, 1961;Webster & Webster, 1975, and those of gerbils in the family Muridae, subfamily Gerbillinae (Oaks, 1967;Lay, 1972;Buytaert et al 2011;von Unge et al 2011;Salih et al 2012), have been particularly well described. The most familiar of these is the Mongolian gerbil or jird (Meriones unguiculatus), a domestic species that, in the wild, inhabits the steppes of central Asia (Gulotta, 1971).…”

Panel 2: Anatomy (Eustachian Tube, Middle Ear, and Mastoid—Anatomy, Physiology, Pathophysiology, and Pathogenesis)

“…97,100-115 However, imaging of soft and bony tissues with high spatial resolution for highly accurate models remains a challenge. 116 Several imaging methods have been investigated, including micro–computed tomography (micro-CT), 117,118 orthogonal plane fluorescence optical sectioning, 118 and accurate serial section imaging. 119,120 Muscle activation of the tympano-ossicular system was simulated by Gentil et al 103 ; viscoelastic properties of TM were studied by De Greef et al in a FE model 90 ; and Decraemer et al presented a complete view of gerbil ossicular vibration to validate mathematical models.…”

Anatomical features for an adequate choice of experimental animal model in biomedicine: II. Small laboratory rodents, rabbit, and pig

“…The tympanic bullae are very much developed, and gerbils can ear frequency peaks as high as 50kHz (Johnson and Marcotti, 2008). The pars flaccida of the tympanic membrane is circular and relatively large: it extends for about 10%-20% of the total surface, compared with only 2%-3% in humans (Von Unge et al, 2011). The ossicular system is of micro type, whereby the handle of the malleus is fused to the tympanic ring (Decraemer et al, 2014;de La et al, 2010).…”