Citation: Hut , anu, E.; Damian, A.; Micl˘ aus , , V.; Rat , iu, I.A.; Rus, V.; Vlasiuc, I.; Gal, A.F. Morphometric Features and Microanatomy of the Lingual Filiform Papillae in the Wistar Rat. Biology 2022, 11, 920. https://doi.org/10.3390/ biology11060920 Academic Editor: Jukka Finne Received: 18 May 2022 Accepted: 15 June 2022 Published: 16 June 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). biology Article Morphometric Features and Microanatomy of the Lingual Filiform Papillae in the Wistar Rat Elena Hut , anu 1 , Aurel Damian 1 , Viorel Miclăus , 2 , Ioana A. Rat , iu 3, * , Vasile Rus 2 , Ion Vlasiuc 1 and Adrian F. Gal 2 1 Department of Anatomy, University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca, 400372 Cluj-Napoca, Romania; elena.hutanu@usamvcluj.ro (E.H.); aurel.damian@usamvcluj.ro (A.D.); ion.vlasiuc@usamvcluj.ro (I.V.) 2 Department of Cell Biology, Histology and Embryology, Faculty of Veterinary Medicine, University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca, 400372 Cluj-Napoca, Romania; vmiclaus@usamvcluj.ro (V.M.); vasile.rus@usamvcluj.ro (V.R.); adrian.gal@usamvcluj.ro (A.F.G.) 3 Department of Medical Sciences, Faculty of Medicine, University of Oradea, 410073 Oradea, Romania * Correspondence: ratiu_ioana@yahoo.com; Tel.: +40-740-234-773 Simple Summary: The tongue plays an important role in all animals but especially in mammals. It participates in food and water intake, as well as in some behavioral activities such as grooming. Its structure differs depending on the species. We aimed to provide a detailed macroscopic and microscopic description of the filiform papillae on the surface of rat tongue. We examined fragments on three regions of the tongue (tip, body, root) and observed an intensely keratinized epithelium on the whole surface of the tongue, with higher keratinization on the filiform papillae. We also identified differences in the density of the papillae dependent on the region examined, with the highest density being present on the back of the tongue. Additionally, we noted differences in the height of the filiform papillae, with the shortest being on the tip of the tongue and the tallest on the middle of the tongue. The unusual posteroanterior inclination of the filiform papillae from the tongue protuberance suggests they may play some other obscure roles compared to anteroposteriorly oriented filiform papillae. The study of macro and microanatomy in mammals is important since it helps in the assessment and understanding of anatomical and behavioral features of species. Abstract: The mammalian tongue plays a fundamental role in various physiological and behavioral activities. Significant morphological variations have been recorded in the tongue of several species. This study aims to obtain detailed histological and morphometric information about the filiform papillae on the surface of rat tongue. The tongues of five 10-month-old Wistar rats were utilized, which were later examined with a stereo-microscope. Fragments from the three regions of the tongue were collected for histological investigations. The tongue of the Wistar rat has an intensely keratinized stratified squamous epithelium, with the highest degree of keratinized epithelium covering the filiform papillae. The filiform papillae differ in density, with the highest density recorded on the posterior part of the lingual body and the lowest density on the protuberance. The shortest filiform papillae were observed on the apex of the tongue and the tallest on the anterior part of the lingual body. Interestingly, the orientation of the filiform papillae on the lingual protuberance was inclined posteroanteriorly, in the opposite way as compared to the papillae from all the other regions of the tongue. Histologically, a difference was recorded in the structure of the covering epithelium of the anterior vs. the posterior face of the filiform papillae. Keywords: tongue; filiform papillae; rat; microanatomy 1. Introduction The tongue first appeared in amphibians as an adaptive structure to terrestrial food and as a necessity for adaptation to a wider range of habitats. The epithelium lining on the Biology 2022, 11, 920. https://doi.org/10.3390/biology11060920 https://www.mdpi.com/journal/biology