Casali A M, Lucchi M L, Millo R, Milintenda Floriani F, Ferreri Santi L, Re G, Cavalli G
Arch Ital Anat Embriol. 1989 Jan-Mar;94(1):1-53.
The recognition of the role played by the subfornical organ (SFO) in the central regulation of body water balance has recently aroused new interest in this anatomical formation which remained ignored for a long time. The SFO is included in the group of the circumventricular organs. In higher vertebrates it is adherent to the ventral surface of the fornix and protrudes into the third ventricle at the level of the interventricular foramina, partially covered by the choroid plexus. The SFO appears as a small nodule, rounded or ovoidal in shape, consisting of highly vascularized nervous tissue and lined by ependyma at the ventricular surface. Its structural organization is fundamentally constant and presents only minor differences in the various species. The SFO neuronal perikarya show different aspects which have been classified in four types. However, it is not yet clearly defined if such aspects refer to distinct cell types or to different transitional features. Nerve and glial cell processes form a dense plexus through the SFO and the subependymal area, as well as in the connective tissue perivascular spaces. These may be narrow or wide and surround fenestrated and non-fenestrated capillaries, assuming sometimes a labyrinthine aspect. The ependymal lining of the SFO ventricular surface shows large variations and regional differences concerning the cell height, the number and development of microvilli, the cilia distribution. The structural properties of SFO, which is characterized by a rich and highly permeable capillary bed, by a wide surface area of contact and exchange with the cerebrospinal fluid, by direct and indirect neural connections with a number of regulatory structures, have been considered as the basis for the role of neurohumoral integration that SFO plays in regulating physiological and behavioral responses to water-mineral changes. Much experimental evidence substantiates this function. However, the studies on SFO are increasingly enriching the literature with new experimental, especially physiological and cytochemical, data which may suggest for this organ connections even more extensive and functions even more complex than those until now ascertained.
室周器官中穹窿下器官（SFO）在机体水平衡中枢调节中所起作用的认识，最近引发了人们对这一长期被忽视的解剖结构的新兴趣。SFO属于室周器官组。在高等脊椎动物中，它附着于穹窿腹面，在室间孔水平突入第三脑室，部分被脉络丛覆盖。SFO呈小结节状，圆形或椭圆形，由高度血管化的神经组织构成，脑室表面衬有室管膜。其结构组织基本恒定，在不同物种中仅存在细微差异。SFO神经元胞体呈现出不同形态，已被分为四种类型。然而，这些形态是指不同的细胞类型还是不同的过渡特征，目前尚未明确界定。神经和胶质细胞突起通过SFO、室管膜下区域以及结缔组织血管周围间隙形成致密丛。这些间隙可能狭窄或宽阔，围绕有窗孔和无窗孔的毛细血管，有时呈现出迷宫样外观。SFO脑室表面的室管膜衬里在细胞高度、微绒毛数量和发育、纤毛分布方面表现出很大差异和区域差异。SFO的结构特性，其特点是有丰富且高度通透的毛细血管床、与脑脊液接触和交换的广泛表面积、与许多调节结构的直接和间接神经连接，被认为是SFO在调节对水盐变化的生理和行为反应中发挥神经体液整合作用的基础。许多实验证据证实了这一功能。然而，关于SFO的研究正越来越多地用新的实验数据，尤其是生理学和细胞化学数据丰富文献，这些数据可能表明该器官的连接比迄今确定的更为广泛，功能更为复杂。
