Morphological Study Of Adenohypophysis Structural Features And Relationship With Subarachnoid Space

Hypophysis is a significant endocrine organ in our organism, according to the characteristic of embryology and histology, hypophysis was fractionated two parts of adenohypophysis and neurohypophysis, produced multiple peptide hormones. For the past few years, there are still some interrogatory questions about hypophysis research.First, there are still different viewpoints about to whether pituitary circumambience also have three tier velamens that is similar to brain tissue surface, some scholars thought that the tunic on pituitary surface was scleromeninx, beneath sellae diaphragma, there are no arachnoid and cerebral pia mater around pituitary, cerebral dura mater compactly connected with hypophysis surface. Some other scholars thought that because of circumferentia of majority sellae diaphragma openings away from hypophyseal stalk, the arachnoid of above sellae diaphragma reflex at the hypophyseal stalk, the arachnoid that about 8 percent to 56 percent individuals intruded into sellae diaphragma opening, the depth mostly less than 2 millimeter.Furthermore, some scholars think that the arachnoid can intruded into sellae diaphragma through sellae diaphragma opening, become the subarachnoid space around the hypophysis. On the basis of the appearances of the sella turcica imageology, Kaufman thought that around the hypophysis be coated arachnoid cyst.Second, about the releasing pattern and transport route for the polypeptide hormone secretory granules of adenohypophysis. Majority scholars thought polypeptide hormones of adenohypophysis was released into the tissue fluid by exocytosis, then was absorbed into blood circulation by fenestrated capillary of adenohypophysis to produced a marked effect. For the past few years, Li guang-rong etc. observed the adenohypophysis of cow and rat by transmission electron microscope, in intercellular space, founded the secretory granules was similar to neighbouring hypophyseal adenocyte internal secretory granules at size, shape and electron density. Yu pei-ling and Li zhao-te adopted the marking method of Immuno colloidal gold, observed the secretory granules of ACTH cell by transmission electron microscope, founded the secretory granules protruded from cell membrane below to exterior of cell, and the complete secretory granules that was marked by the Immuno colloidal gold at the exterior of cell. They presumed the hormone releasing pattern of ACTH cell possibly have the apocrine similar to exocrine gland except for exocytosis. Wang Bao-zhi etc. observed the monkey pineal body, human pancreatic islet tissue and rat neurohypophysis by electron microscope, found intact secretory granules coated with membrane in the perivascular space and the interspace of tissue. They presumed the excrete pattern of pinealocyte, pancreatic islet cell and neurohypophysis possibly was the whole releasing with the granule's membrane. For the above evidences indicate that the releasing of polypeptide hormone secretory granules of adenohypophyseal cells probably have the pattern of whole releasing, the secretory granules were transported to the cerebrospinal fluid firstly, but lack of the morphology evidences yet.Third, about the structure and function connection between hypothalamus and adenohypophysis, and how transported the hypophysiotropic hormone that released at hypothalamus to adenohypophysis educed function. Traditional knowledge thought there are no direct nerve connection between hypothalamus and adenohypophysis, they have functional tightly connection draw assistance from the hypophyseal portal system. The neuroendocrine cells in hypothalamic hypophysiotropic area mainly located hypothalamic medial basic part, their axons projected to median eminence, the axon ending contacted with primary capillary network of hypophyseal portal vessel. The neuroendocrine cells released regulatory peptide that created from hypothalamus to hypophyseal portal vessel firstly, Then the regulatory peptide along the hypophyseal portal vessel were transported to adenohypophysis, and escaped out of secondary capillary network (blood sinusoid) and adjust hypophyseal adenocyte secretory activity. But some scholars thought that hypothalamus regulatory peptide can through tissue space at hypophyseal portal vessel surrounding and directly were transported to adenohypophysis and play to functions.In our experiment, we observed SD rat adenohypophyseal surface characters, internal fine structure and ultrastructure features; observed if there are cerebral pia mater and arachnoid at pituitary circumambience. That can provide morphology evidences for the possible pathway of adenohypophyseal polypeptide hormones were directly released to cerebrospinal fluid and the structure and function connection between hypothalamus and adenohypophysis.1. Morphological observation of the surface structural features of the adenohypophysisObjective: To explore whether pituitary circumambience also have three tier velamens that is similar to brain tissue surface.Methods: Observed SD rat adenohypophyseal surface structure characters by tissue slice with HE staining light microscope, transmission electron microscope and scanning electron microscope.Results: Tissue slice with HE staining observation show that there are one layer velamen that composed of simple epithelial cells at the adenohypophyseal surface, still have a lamellar loose connective tissue below the velamen. Scanning electron microscope observation show that adenohypophyseal surface is pituitary capsule that composed of simple squamous epithelium, the epithelial cells exserted a lot of digitationes, formed superficial microvilli; There are epithelial opening (2~5μm) at neighbouring epithelial cells each other. Using transmission electron microscope observation show that adenohypophysis were invested by pituitary capsule that composed of simple squamous epithelium and the connective tissue below epithelium.Conclusion: Rat adenohypophysis circumambience have three tier velamens that stretched from brain tissue surface. The pituitary capsule was meninx vasculosa, there are epithelial opening, secretory granules and macrophage etc on pituitary capsule.2. Observation of the pathway of adenohypophyseal peptide hormones released into cerebrospinal fluidObjective: To explore the structural foundation of the pathway of adenohypophyseal polypeptide hormones were released into cerebrospinal fluid.Methods: Observed the conventional sample and DMSO freeze cracking sample of SD rat adenohypophysis used transmission and scanning electron microscope.Results: Scanning electron microscope observation show that there are epithelial opening (2~5μm) at neighbouring epithelial cells each other which at rat adenohypophyseal surface, we can watch globular secretory granules at the epithelial opening vicinity, watch rounded macrophage and much ecphyma macrophage yet. Transmission electron microscope observation and Scanning electron microscope observation of DMSO freeze cracking sample show that adenohypophysis is composed of various kinds of adenocytes mainly. There are a lot of intercellular spaces that was inequality of size among the adenocytes. The endothelium of the blood capillaries of adenohypophysis belongs to the fenestrated(50nm)type, separated from the perivascular connective tissue by basement membrane. The intact secretory granules(100~300nm)coated with membrane exist in intercellular space and perivascular space.Conclusion: The polypeptide hormone secretory granules of adenohypophysis have the releasing pattern of whole releasing with membrane; The adenohypophyseal polypeptide hormones or secretory granules that were released to tissue fluid, enter directly into cerebrospinal fluid of subarachnoid space more easy, via intercellular space, perivascular space and epithelial openings.3. The structural and functional connection between hypothalamus and hypophysisObjective: To explore the structural and functional connection between hypothalamus and hypophysis, and how transported the hypophysiotropic hormones to adenohypophysis and play to function.Methods: Observed SD rat hypophyseal stalk by tissue slice with HE staining light microscope and transmission electron microscope. Results: Light microscope and transmission electron microscope observation show that hypophyseal stalk was wrapped by velamen, within contain two main structures. One is hypothalamic hypophyseal tract that is longitudinal fiber bundle from hypothalamus to neurohypophysis, be composed of un-myelinated nerve fibers with unequal diameter; another one is hypophyseal portal vessel that is several vessels connected median eminence to adenohypophyseal capillary network. The hypophyseal portal vessels only composed of one layer fenestrated endothelial cell, caliber coarse, contain generous blood cells, belongs to capillary. There are broader loose connective tissue surrounding the blood vessels of hypophyseal portal vessel and hypothalamic-hypophyseal fiber bundle, also can observe fibroblasts and macrophages.Conclusion: Hypothalamic polypeptide hormones exclude through hypothalamic-hypophyseal tract were transported to neurohypophysis then releasing, through hypophyseal portal vessels were transported to adenohypophysis, also through tissue space of hypophyseal stalk directly were transported to adenohypophysis and play to function.