Department of Biology, Lund University, Sölvegatan 35, 22362, Lund, Sweden.
J Morphol. 2021 Mar;282(3):419-426. doi: 10.1002/jmor.21313. Epub 2021 Jan 22.
The glabrous skin around the nostrils in mammals is called a rhinarium or planum nasale. Rhinarium skin has multiple epidermal domes that are generally assumed to form a tactile surface. The rhinarium is innervated by a branch of the trigeminal nerve which is associated with stimuli such as touch, chemical irritants and temperature. In this study, our aim was to correlate variation in rhinarium skin sensory innervation with different feeding behaviors while also covering a broad systematic spectrum. Using histological and immunohistological methods, we studied skin morphology, nerve fiber density and nerve fiber distribution in the rhinarium epidermal domes of four species: cow, ring-tailed lemur, brown bear, and dog, that all exhibit different feeding behaviors. All species share similar traits in rhinarium skin morphology, but glands were only found in cow rhinarium skin. The most substantial differences were observed in the innervation pattern. Mechanosensory skin organs were found only in the ring-tailed lemur. Dog epidermal domes possess a pronounced central dermal papilla containing a nerve bundle in its top, close to the skin surface. The abundance of free epidermal nerve fibers in epidermal domes of all species, suggest that the rhinarium skin is a sensory surface, that can be used to detect fine touch, chemical irritants or temperature. In the species where the whole epidermal dome was examined, the intraepidermal nerve fiber density is higher in the central part of the domes. The nerve distribution and the central positioning of a single gland duct in cow and the dermal papilla top organ in dog indicates that each epidermal dome can be considered a functional unit. The observed differences in innervation hint at different sensory functions of rhinaria in mammals that may be correlated to feeding behavior.
哺乳动物鼻孔周围无毛的皮肤称为鼻前庭或鼻平面。鼻前庭皮肤有多个表皮穹隆，通常被认为形成了一个触觉表面。鼻前庭由三叉神经的分支支配，与触觉、化学刺激物和温度等刺激有关。在这项研究中，我们的目的是将鼻前庭皮肤感觉神经支配的变化与不同的进食行为相关联，同时涵盖广泛的系统谱。使用组织学和免疫组织化学方法，我们研究了四种具有不同进食行为的物种（奶牛、环尾狐猴、棕熊和狗）的鼻前庭表皮穹隆的皮肤形态、神经纤维密度和神经纤维分布。所有物种的鼻前庭皮肤形态都有相似的特征，但只有奶牛的鼻前庭皮肤有腺体。在神经支配模式上观察到了最显著的差异。机械感觉皮肤器官仅存在于环尾狐猴中。狗的表皮穹隆有一个明显的中央真皮乳头，其顶部有一个神经束，靠近皮肤表面。所有物种的表皮穹隆中都有大量的游离表皮神经纤维，这表明鼻前庭皮肤是一个感觉表面，可以用来检测精细触觉、化学刺激物或温度。在检查了整个表皮穹隆的物种中，穹隆中央部分的表皮内神经纤维密度更高。在奶牛中，每个表皮穹隆的神经分布和单一腺体导管的中央定位，以及狗中的真皮乳头顶部器官，表明每个表皮穹隆可以被视为一个功能单位。观察到的神经支配差异表明，哺乳动物的鼻前庭具有不同的感觉功能，可能与进食行为有关。
