Meningeal relations of the rat hypothalamo-hypophyseal system. Extravascular fluid spaces in and around the median eminence.
Meningeal relations of the rat pituitary and basal hypothalamus including the pituitary stalk and median eminence, were studied by both light and electron microscopy, and by ink perfusion techniques. The dura mater encapsulates the pituitary gland. The arachnoid covers the basal surface of the hypothalamus except the caudal two-thirds of the median eminence and the pituitary stalk. No arachnoidea, i.e. no subarachnoideal space, was found in the sella. Pia mater covers the entire basal surface of the hypothalamus, including the median eminence and the pituitary stalk, but encapsulates only the posterior lobe of the pituitary. The superficial portal vessels (primary plexus and portal veins) are located in the subdural space, covered by the pia mater. The deep vessels in the median eminence are surrounded by the perivascular space, which is bordered by the vascular and neuropil basement membranes, and separated from the external fluid space around the median eminence only by the pia mater. This special topography suggests that molecules present in the portal vessels or in the cerebrospinal fluid, or in and around the pituitary gland, readily move from one liquid space to another.
D000818:Animals; D005110:Extracellular Space / Q000166:cytology*; D005260:Female; D007030:Hypothalamo-Hypophyseal System / Q000166:cytology* / Q000648:ultrastructure; D008297:Male; D008473:Median Eminence / Q000166:cytology* / Q000648:ultrastructure; D008578:Meninges / Q000166:cytology*; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D051381:Rats; D011919:Rats, Inbred Strains