THE ENDOCRINE GLANDS: HYPOPHYSIS Dr Iram Tassaduq ENDOCRINE GLANDS An endocrine gland is one whose product passes by way of the blood vascular system to other cells in the body, where it elicits a specific response. COMPONENTS OF THE ENDOCRINE SYSTEM Discrete endocrine glands The endocrine components of the glands with both exocrine & endocrine functions Scattered cells with endocrine functions ENDOCRINE GLANDS OF THE BODY Hypophysis Pineal Thyroid & parathyroids Suprarenals Pancreas Testis Ovaries Kidneys Diffuse endocrine system FEATURES OF ENDOCRINE GLANDS Endocrine glands vary greatly in size. The cells secreting the hormones (parenchyma) are epithelial, epithelioid, or neuronal. The glands are richly vascularized by highly permeable capillaries. FEATURES OF ENDOCRINE GLANDS Endocrine glands either lack ducts or the ducts do not communicate with the endocrine cells. However, the hormones pass from endocrine cells into intercellular spaces & the interstitium, from which they must diffuse to & enter the vascular system. HYPOPHYSIS Located in SELLA TURCICA 1cm in length Weighs gm ORGANIZATION ADENOHYPOPHYSIS Pars tuberalis Pars distalis-pars anterior Pars intermediaNEUROHYPOPHYSIS Pars nervosa Infundibulum (infundibular stem & median eminence ) ADENOHYPOPHYSIS PARS DISTALIS 75% of the mass of the hypophysis Common stains allow recognition of 3 cell types o Chromophobes o 2 types of chromophils Acidophils Basophils PARS DISTALIS At higher magnifications the dark staining chromophils ( A) and the very light staining chromophobes (B) are easily distinguished. CHROMOPHOBES Small rounded polygonal cells Have little cytoplasm devoid of granules Appear in groups They were called reserve cells in past CHROMOPHILS ACIDOPHILS Larger than chromophobes Further divided into two types Somatotrophs and mamotrophs BAOPHILS Larger than acidophils Granules less in number and smaller in size Best stained with PAS beta Subdivided into beta and delta cells BAOPHILS Beta cells secrete TSH Larger in size Granules concentrated at periphery Delta cells include Gonadotropic and coticotropic PARS TUBERALIS Funnel shaped region Surrounding the infundibulum. Most of the cells secrete gonadotropins and are arranged in cords along blood vessels PARS INTERMEDIA Surrounds a series of small cavities Parenchyma surround colloid filled follicles Pars intermedia contains basophils and chromophobes Basophils secrete MSH Poorly developed in humans PARS INTERMEDIA PARS NERVOSA Extension of CNS that stores and releases secretory products from hypothalamus Three types of neurosecretory vesicles NEURO SECRETORY VESICLES Herring bodies ranging 10-30nm contain oxytocin or ADH Vesicles containing acetylcholine and adrenergic nerve endings NEUROHYPOTHYSIS - PARS NERVOSA This region of the pituitary is non secretory. Its cells are neuroglial-like pituicytes (C).