- Slides: 36
THE ENDOCRINE GLANDS: HYPOPHYSIS Dr Iram Tassaduq
ENDOCRINE GLANDS v 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 q q q q q Hypophysis Pineal Thyroid & parathyroids Suprarenals Pancreas Testis Ovaries Kidneys Diffuse endocrine system
FEATURES OF ENDOCRINE GLANDS q Endocrine glands vary greatly in size. q The cells secreting the hormones (parenchyma) are epithelial, epithelioid, or neuronal. q 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. q However, the hormones pass from endocrine cells into intercellular spaces & the interstitium, from which they must diffuse to & enter the vascular system. q
HYPOPHYSIS n n n Located in SELLA TURCICA 1 cm in length Weighs 0. 5 -0. 6 gm
ORGANIZATION ADENOHYPOPHYSIS Pars tuberalis Pars distalis-pars anterior Pars intermedia NEUROHYPOPHYSIS Pars nervosa Infundibulum (infundibular stem & median eminence )
PARS DISTALIS q 75% of the mass of the hypophysis q Common stains allow recognition of 3 cell types o o Chromophobes 2 types of chromophils • • Acidophils Basophils
PARS DISTALIS n At higher magnifications the dark staining chromophils ( A) and the very light staining chromophobes (B) are easily distinguished.
CHROMOPHOBES n n Small rounded polygonal cells Have little cytoplasm devoid of granules Appear in groups They were called reserve cells in past
ACIDOPHILS q Larger than chromophobes q Further divided into two types q Somatotrophs and mamotrophs
BAOPHILS n n Larger than acidophils Granules less in number and smaller in size Best stained with PAS Subdivided into beta and delta cells
BAOPHILS n Beta cells secrete TSH n Larger in size n Granules concentrated at periphery n Delta cells include Gonadotropic and coticotropic
PARS TUBERALIS n n 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 q Parenchyma surround colloid filled follicles q Pars intermedia contains basophils and chromophobes q Basophils secrete MSH q Poorly developed in humans q
PARS NERVOSA q Extension of CNS that stores and releases secretory products from hypothalamus q Three types of neurosecretory vesicles
NEURO SECRETORY VESICLES q Herring bodies ranging 10 -30 nm contain oxytocin or ADH q Vesicles containing acetylcholine and adrenergic nerve endings
NEUROHYPOTHYSIS - PARS NERVOSA q This region of the pituitary is non secretory. Its cells are neuroglial-like pituicytes (C).