capable of constant monitoring of circulating concentrations of glucose. This responsiveness to glucose again serves to solidify the SFO’s integral role as a regulator of energy homeostasis. Secretory organs Subcommissural organ Anatomy The subcommissural organ (SCO) is a small secretory organ located on the ventral surface of the posterior commissure near the anterior entrance of the cerebral aqueduct. It differs from other CVOs in that it does not have highly permeable capillaries. Its role as a neuroendocrine structure associated with the ventricular system qualifies it for classification as a CVO. Related to its secretory function, the SCO is partially composed of ependymal cells. These ependymocytes are characterized by elongated cell bodies that contain secretory materials and are covered in cilia. The most prominent of these is the glycoprotein SCO-spondin. Function One function of the SCO is the secretion of the glycoprotein SCO-spondin, which is released into the third ventricle where it aggregates to create Reissner's fiber. Reissner's fiber is a long fibrous projection that travels caudally through the Sylvian aqueduct and terminates in the spinal cord. This fiber is thought to contribute to the maintenance of the patency of the Sylvian aqueduct. While the function of the subcommissural organ remains under investigation, it may be part of the mechanism of aldosterone secretion and CSF detoxification, along with osmoregulation. The SCO is innervated by many systems, the most common of which is associated with the serotonergic system, which influences water and sodium intake. During water deprivation, it will also reduce its innervation to the SCO. The reduction of input to the SCO causes a marked decrease in RF production. This finding implies that the subcommissural organ and its associated Reissner's fiber are integral parts of fluid electrolyte balance and water homeostasis. Pituitary neural lobe The pituitary gland is subdivided into lobes the anterior pituitary, the intermediate pituitary, and the posterior pituitary (also known as the adenohypophysis and neurohypophysis (or neural lobe), respectively). Each one functions as a separate endocrine organ. The pituitary neural lobe consists of axonal projections that directly extend from cell bodies in the hypothalamus through the infundibulum. Under neurohumoral control, it secretes oxytocin and vasopressin, thereby qualifying it as a circumventricular organ with both neural and secretory functions. The anterior pituitary contains non-neural secretory cells derived from oral ectoderm which are indirectly controlled by "releasing hormones" from the median eminence of the hypothalamus, through the hypophyseal portal circulation.