Department of Cell Biology, Interdisciplinary Research Structure for Biotechnology and Biomedicine (BIOTECMED), University of Valencia, Spain.
Departments of Neurosurgery and Neuroscience, Yale University School of Medicine, New Haven, Connecticut.
Anat Rec (Hoboken). 2019 Mar;302(3):405-427. doi: 10.1002/ar.23816. Epub 2018 Apr 23.
The olfactory nerve constitutes the first cranial pair. Compared with other cranial nerves, it depicts some atypical features. First, the olfactory nerve does not form a unique bundle. The olfactory axons join other axons and form several small bundles or fascicles: the fila olfactoria. These fascicles leave the nasal cavity, pass through the lamina cribrosa of the ethmoid bone and enter the brain. The whole of these fascicles is what is known as the olfactory nerve. Second, the olfactory sensory neurons, whose axons integrate the olfactory nerve, connect the nasal cavity and the brain without any relay. Third, the olfactory nerve is composed by unmyelinated axons. Fourth, the olfactory nerve contains neither Schwann cells nor oligodendrocytes wrapping its axons. But it contains olfactory ensheathing glia, which is a type of glia unique to this nerve. Fifth, the olfactory axons participate in the circuitry of certain spherical structures of neuropil that are unique in the brain: the olfactory glomeruli. Sixth, the axons of the olfactory nerve are continuously replaced and their connections in the central nervous system are remodeled continuously. Therefore, the olfactory nerve is subject to lifelong plasticity. Finally seventh, the olfactory nerve can be a gateway for the direct entrance of viruses, neurotoxins and other xenobiotics to the brain. In the same way, it can be used as a portal of entry to the brain for therapeutic substances, bypassing the blood-brain barrier. In this article, we analyze some features of the anatomy and physiology of the first cranial pair. Anat Rec, 302:405-427, 2019. © 2018 Wiley Periodicals, Inc.
嗅神经构成第一对颅神经。与其他颅神经相比，它具有一些非典型特征。首先，嗅神经不形成独特的束。嗅轴突与其他轴突结合形成几个小束或纤维束：嗅丝。这些纤维束离开鼻腔，穿过筛骨的筛板并进入大脑。这些纤维束的整体就是所谓的嗅神经。其次，嗅感觉神经元的轴突整合嗅神经，在没有任何中继的情况下将鼻腔和大脑连接起来。第三，嗅神经由无髓轴突组成。第四，嗅神经既不包含施万细胞也不包含包裹其轴突的少突胶质细胞。但它包含嗅鞘胶质细胞，这是一种仅存在于该神经中的神经胶质细胞。第五，嗅轴突参与特定神经胶状间质的球形结构的回路，这些结构在大脑中是独特的：嗅小球。第六，嗅神经轴突不断被替换，其在中枢神经系统中的连接不断重塑。因此，嗅神经具有终身可塑性。最后第七，嗅神经可以成为病毒、神经毒素和其他外源性物质直接进入大脑的门户。同样，它也可以作为治疗物质进入大脑的门户，绕过血脑屏障。在本文中，我们分析了第一对颅神经的解剖和生理学的一些特征。解剖记录，302：405-427，2019。© 2018 Wiley Periodicals，Inc.
