The median eminence of the hypothalamus above continues down as an infundibular stalk that connects to the pituitary below in the sella turcica. Between these two parts is the pars intermedia that consists of small cystic structures lined by a cuboidal epithelium and containing pink proteinaceous material-and rarely Rathke's pouch remnants. The posterior pituitary (neurohypophysis, or pars nervosa) is derived from a downgrowth of neural tissue from the hypothalamus. Occasionally, remnants of Rathke's pouch persist between anterior and posterior pituitary that are nests of cells have a squamous appearance. The anterior pituitary (adenohypophysis, or pars distalis) is derived from an upward evagination of pharyngeal epithelium known as Rathke's pouch. The pituitary develops embryologically from two sources. Thus, endocrine glands are highly vascularized with many small capillaries among the nests of endocrine cells. Endocrine glands secrete directly into the bloodstream, not through a duct system. Thus, the hormones secreted by the endocrine glands enter the circulation and are carried throughout the body to act upon target cells located far away from the secreting glands. ![]() Įndocrine: the substance acts upon other cells at a distance.Paracrine: the substance acts upon other cells in the immediate vicinity-a localized effect Substances secreted by cells can have several actions:Īutocrine: the substance acts upon the cell that secreted it-an autofeedback mechanism Endocrine Organs Endocrine Organs Return to the Histology Tutorial menu.
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