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 Weigh s gm

ORGANIZATIONADENOHYPOPHYSIS Pars tuberalis Pars distalis- 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 o2 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 beta  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 4 th 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