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ENDOCRINE GLANDS 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 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. HYPOPHYSIS • Located in SELLA TURCICA • 1cm in length • 1-1.3cm in width • Weighs 0.5-0.6 gm ORGANIZATION ADENOHYPOPHYSIS Pars tuberalis Pars distalisPars intermedia NEUROHYPOPHYSIS 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. ACIDOPHILS Larger than chromophobes Cells taking OrangeG stain are alpha acidophils Also called somatotrophs Contain extensive RER ACIDOPHILS Carminophils stain intensely with azocarmine Also called mamotrophs Cytoplasmic granules are larger in size and are scattered BASOPHILS Larger than acidophils Best stained with PAS Subdivided into beta and delta cells BASOPHILS Beta cells secrete TSH Larger in size Granules concentrated at periphery Delta cells include Gonadotrophs and coticotrophs CHROMOPHOBES Small rounded polygonal cells Have little cytoplasm devoid of granules Appear in groups They were called reserve cells in past 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 NEUROHYPOPHYSIS - PARS NERVOSA This region of the pituitary is non secretory Its cells are neuroglial-like pituicytes (C). NEURO SECRETORY VESICLES Herring bodies ranging 10-30nm contain oxytocin or ADH Vesicles containing acetylcholine approx 30nm in size Vesicles ranging 50-80nm resembling vesicles of adrenal medulla containing adrenergic nerve endings THYROID GLAND C.T. sheath formed by deep cervical fascia Extremely labile gland & varies in size & structure Three dimensional view of thyroid follicles DEVELOPMENT OF THYROID GLAND Begins to develop during 4th week of gestation from a primordium originating as an endodermal thickening of floor of primitive pharynx STRUCTURAL UNIT OF THYROID GLAND ----- THYROID FOLLICLE FOLLICULAR EPITHELIUM Follicular cells Para follicular cells FOLLICULAR CELLS PRINCIPAL/ CHIEF CELLS Responsible for the production of T3 & T4 Vary in size & shape Slightly basophilic in H & E stained slides Lipid droplets & PAS positive droplets COLLOID Inactive storage form of thyroid hormone Constituents Principal component is thyroglobulin (large iodinated glycoprotein) Enzymes Glycoproteins Staining with both acidic & basic dyes. Strongly with PAS FUNCTION OF THYROID GLAND PARAFOLLICULAR CELLS C CELLS/ CALCITONIN CELLS Located in periphery of follicular epithelium No exposure to lumen In H & E stained slides appear as pale staining cells Secrete calcitonin