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Purpose: To describe topographic and endoscopic anatomy of guinea pig ear for development of surgical approaches in experimental studies., Methods: Experimental study. Eight adult guinea pigs (Cavia porcellus) were used in this study. Four animals were described through endoscopic view and four animals were used to describe topographic anatomy., Results: The main structures of middle ear were well identified through endoscopy view: oval and round window, ossicles and vascular structures. Temporal bone position, landmarks and its relations to skull are perceived with topographic description., Conclusion: Topographic anatomic description allowed exposition of temporal bone relations for external surgical approaches. Alternatively, grooves and middle ear structures were identified and may be used to transcanal accesses.

Purpose: To evaluate the tissue response of the mucosa of the tympanic cavity of guinea pigs, when receiving biodegradable implant., Methods: A total of 20 male guinea pigs were divided into 2 groups. After paracentesis in both ears, a biodegradable polymer of poly lactic-co-glycolic acid was implanted in only one middle ear. Histological analysis using neutrophil exudate and vascular neoformation (acute inflammation) and fibroblast proliferation and mononuclear inflammatory cells (chronic inflammation) as parameters was performed after 10 and 30 days of survival (groups 1 and 2, respectively)., Results: Four ears in group 1 and 7 in group 2 had an increase of neutrophil exudate. Vascular neoformation occurred in ears with or without the implant, in both groups. Fibroblast proliferation and mononuclear inflammatory cells (lymphocytes and macrophages) increased in ears with implant in group 2., Conclusion: The tissue response by histological analysis of the mucosa of the tympanic cavity of guinea pigs, when receiving biodegradable implant, showed no statistically significant difference between ears with or without the implant.