Several studies have been done to document the anatomy of the sheep middle ear (Seibel et al. 2016), indicating that middle-ear mechanics in the sheep may be different from middle-ear mechanics in the human. 1) or stapes relative to the velocity at the umbo in the sheep is appreciably smaller than the corresponding magnitude ratio in the human (Dobrev et al. ( 2017), the magnitude ratio of the velocity at the lenticular process of the incus (the ovoid bony part attached to the distal end of the long process of the incus see Fig. For such comparisons, biomechanical models of the sheep middle ear are required but have not been established due to lack of data. 2018).Īlthough the sheep ear has been considered as a suitable animal model, comprehensive anatomical and biomechanical data and comparisons with the human middle ear do not exist. 2015), and assessment of new surgical techniques and hearing devices (Lavinsky et al. 2008), training of middle- and inner ear surgeries (Gocer et al. Thereby, the sheep has been used for research on bone conduction (Gerhardt et al. ( 2006a, b), the average size of the middle and inner ears of the sheep is approximately two-thirds the average size of the middle and inner ears of the human. The sheep has been considered as an animal model because it can be obtained easily and the size of the ear is similar to that of the human ear.
![auditory ossicles function auditory ossicles function](https://image1.slideserve.com/2247008/slide8-n.jpg)
Primates, being closer to human phylogenetically as well in size, can be an alternative, but they are prohibited for use in experiments except for exceptional cases. For example, the pig has been evaluated as a possible animal model, but the soft and fatty tissues overlying the mastoid make experimental approaches difficult (Schnabl et al.
![auditory ossicles function auditory ossicles function](https://render.fineartamerica.com/images/rendered/medium/phone-case/iphone8/images-medium-5/cutaway-diagram-of-human-ear-leonello-calvetti.jpg)
With an expectation to reflect the anatomy of the human ear more adequately, large animal models have been evaluated as well. Such limitations become more significant when the animal models are used as surrogates of human beings for clinical purposes. However, small animals are different from humans anatomically and physiologically (e.g., difference in shape and size of the middle ear shown in Hemila et al., 1995 and Nummela, 1995) therefore, the findings can differ widely. Small animals are widely used for these research purposes, most common being rats and mice, as well as other small vertebrate animals such as rodents (e.g., gerbils, chinchilla, and guinea pigs), rabbits, and cats. For clinical purposes, animal models can be used for training of various surgeries or for tests of new surgical techniques and devices in developmental stages. For basic hearing science, the aims are mainly to reveal the hearing capacity of the targeted animal or to perform experiments to reveal hearing mechanisms, which are generally difficult with live human subjects.
![auditory ossicles function auditory ossicles function](https://basicmedicalkey.com/wp-content/uploads/2016/06/c00008_f008-003-9780702053252.jpg)
Various animal models have been used for both basic science and clinical hearing research. Considering the substantial anatomical differences, outcomes of middle-ear surgeries would presumably be difficult to assess from experiments using the sheep middle ear. Analysis in this study suggests that structure and orientation of the middle-ear ossicles in the sheep are conducive to an increase in the hinge-like ossicular-lever-action around the anterior–posterior axis. The sheep middle-ear ossicles differed from those of human in several ways: anteroinferior orientation of the malleus handle, relatively small size of the incus with a relatively short distance to the lenticular process, a large area of the articular surfaces at the incudostapedial joint, and a relatively small moment of inertia along the anterior–posterior axis. Characteristic dimensions and inertial properties of the middle-ear ossicles of White-Alpine sheep ( n = 11) were measured from high-resolution micro-CT data, and were assessed in comparison with the corresponding values of the human middle ear. This study aimed to (1) collect anatomical data and inertial properties of the sheep middle-ear ossicles and (2) explore effects of these features on sound transmission, in comparison to those of the human. The sheep middle ear has been used in training to prepare physicians to perform surgeries and to test new ways of surgical access.