Morphological, Histological and Morphometrical Aspects of Auditory Ossicles in Pig Fetuses (Sus scrofa domestica)

The detailed study of the morphology and morphometrics of the auditory ossicles in swine became a topic for investigation due to their resemblance to the human ear. The methods used in this study cover the typical macroscopical investigation of gross morphology: a detailed metrical and histological assessment through H&E standard protocol on auditory ossicles originating from eight pig fetuses originating from four distinctive sows. The ossicular assembly in the malleus, incus and stapes present in 66-day fetuses shows all the features generally described in swine. The malleus comprises two uneven laminae of mineralized hyaline cartilage and a medullary cavity. The areas of the head and neck show a high degree of vascularization. The incus has two similar cortical fascicles separated by a compartmentalized medullary cavity, with the highest degree of mineralization found at the distal part of the long process. Stapes show an early degree of mineralization at the level of the crura, lacking medullary cavities. The ossicular chain shows typical morphological elements, similar to adults, and from a dimensional perspective, our investigations point to an uneven degree of development of the ossicles, according to gestational age: the malleus and stapes reach almost 80% and the incus about 50-60% of their adult sizes.