Presentation on theme: "Histology of endocrine glands"— Presentation transcript:
1 Histology of endocrine glands Dr Abubakr H MossaMBBS, 8&11 /3/12
2 Outline Endocrine tissues/glands in the body Basic structure of endocrine glandsPituitary glandAdenohypophysisNeurohypophysisThyroid glandParathyroid glandsAdrenal glandsCortexMedullaIslets of Langerhans (pancreas)
4 Endocrine tissues/glands in the body Endocrine gland produces/secretes hormones to control or alter the function of other cells/tissue/organsEndocrine function can be carried out by:Glands like: pituitary, thyroid, parathyroid, adrenal and pineal glandsClusters of cells in larger organs: ovarian follicles cells, islets of pancreas, Leydig cells of testes…Scattered Single cells: enteroendocrine cells (GIT)..
5 Basic structure of endocrine glands Endocrine glands have:Parenchyma (cells): polyhedral, arranged in cords or plates, contain secretory vesiclesBlood vessels and capillaries: plenty, to convey the hormones and meet the high metabolic demand, in close relation to the cellsLittle CT
6 Pituitary glandFound in the ……….. of sphenoid bone at the base of brain (hypothalamus)Master glandHas two parts with different embryological originsAdenohypophysis (anterior pituitary)Neurohypophysis (posterior pituitary)
10 Adenohypophysis In pars distalis: Cells which take the stain are called chromophils:These are divided into acidophils (red) (A) & basophils (blue) (B)Cells which do not stain are called chromophobes (C)
11 Adenohypophysis Pars intermedia: Pars tuberalis: Contains mainly basophilsFunction in humans not clearly knownProduces melanocytes stimulating hormonesPars tuberalis:Wraps partially the infundibulumHighly vascularNo specific hormones secreted here in humans
13 NeurohypophysisNo production of hormones takes place here, only release of hormones form the nerve endingsThe cell bodies of these neurons are in the hypothalamus (supraoptic & paraventricular nuclei)The nerve endings contain secretory vesicles which are known as Hering’s (or neurosecretory) bodies (NB)Contain ADH & oxytocinThe other type of cells in posterior pituitary is called pituicytes (P)which are glial cells sheathing the unmyelinated axons
14 Control of pituitary gland: vascular & neural connection to hypothalamus
15 Thyroid gland In the anterior aspect of the neck Has Isthmus & 2 lobes Covered by pretracheal fasciaDivided into lobules by the CT septaEach lobule contains follicles, parafollicular cells & capillariesFollicles; sac like structureEach follicle is surrounded by a basal lamina and reticular fibersThe follicle is lined by a simple cuboidal epitheliumThe follicular cells secrete thyroxine T4 & T3The height of the cells depends on the activity of the cellsLow or squamous: inactive or restingHigh or columnar: active or secretoryThe cavity of the follicle is full of colloid (acidophilic gel-like substance) for the storage of hormone-bound thyroglobulinParafollicular cells :lie between follicles, pale cells with round nucleus, secrete calcitonin
18 Parathyroid glands 4 in number, 2 superior & 2 inferior Lie posterior to the thyroid glandHave two types of cells:Chief (principal cells):most numerous,acidophilic cytoplasm with round nucleus,secretes parathyroid hormone (PTH) which increase blood calciumOxyphil cells:less in number andhave deeply acidophilic cytoplasmic granules
22 Adrenal cortex; Has three layers (zones) which are not well demarcated Zona glomerulosa: (mineralocorticoids; aldosterone)Thin layerCells are arranged in circles or archesDark nucleus & acidophilic cytoplasm with few lipid dropletsSinusoids present between cellsZona Fasciculata: (glucocorticoids: cortisol)Widest zoneCells arranged in columns or cordsLarge cells with pale staining nuclei and acidophilic cytoplasm containing plenty of lipid dropletsZona reticularis: (androgens, estrogen)Thin zone near the medullaCells are deeply staining with network like arrangement
24 Adrenal medullaCells here are large & arranged in groups or short cords with sinusoids in betweenThe cytoplasm of medullary cells is clear or light basophilic in H & E stainThese cells are called also chromaffin cells as they stain with dicromate salt in a reaction called chromaffin reaction (catecholamine containing cells take this stain). So these cells secrete adrenalin and nor adrenalin.They are derived from the neural crest cells and respond directly to sympathetic nerve endings. So they are considered as postganglionic cells.Other cells in medulla are the few but large parasympathetic ganglionic cells.
27 Islets of Langerhans This is the endocrine part of pancreas Oval or round cluster of endocrine cells with plenty of capillaries in betweenHas many types of cells1 million islet and most are in the tail region