Adrenal and Parathyroid

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ENDOCRINE GLANDSADRENAL (SUPRARENAL ) GLANDLies on upper pole of each kidneyComprised of two zones outer cortex inner medullaDevelops from intermediate mesoderm and neural crest cells

INTRODUCTIONThe adrenal gland is encased in a connective tissue capsule that extends septae into the substance of the gland. The organ is richly vascularized and capsular blood vessels, nerves and lymphatics penetrate along with the connective tissue septae.

CORTEXzona glomerulosa - thin, outermost zone zona fasiculata - thick, middle zone zona reticularis - thin, inner zone

ZONA GLOMERULOSA Composed of columnar or pyramidal cells arranged as rounded or arched cordsOccupy 15% of gland volume

ZONA GLOMERULOSA ZONA FASICULATACells are arranged in straight cords. 1-2 cells thickCords run at right angles to the surface of organ and have capillaries between themOccupy 65% of gland volume

ZONA FASICULATAZONA RETICULARISPolyhedral cells with lipid dropletsForm 7% of glandAppears vacuolated in histological preparations Cells are smallest in size

ZONA RETICULARIS

ADRENAL MEDULLAComposed of cords or clumps of cells called chromaffin cells. These can acquire brown colour which is due to oxidation of catecholaminesModified postganglionic sympathetic neurons

ADRENAL MEDULLAFUNCTIONS OF ADRENAL GLAND

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 GLANDBegins to develop during 4th week of gestation from a primordium originating as an endodermal thickening of floor of primitive pharynxSTRUCTURAL UNIT OF THYROID GLAND ----- THYROID FOLLICLE

FOLLICULAR EPITHELIUM

Follicular cellsPara follicular cellsFOLLICULAR CELLSPRINCIPAL/ CHIEF CELLSResponsible for the production of T3 & T4Vary in size & shapeSlightly basophilic in H & E stained slidesLipid droplets

COLLOIDInactive storage form of thyroid hormoneConstituentsPrincipal component is thyroglobulin (large iodinated glycoprotein)EnzymesGlycoproteinsStaining with both acidic & basic dyes. Strongly with PAS

PARAFOLLICULAR CELLSC CELLS/ CALCITONIN CELLSLocated in periphery of follicular epitheliumNo exposure to lumen In H & E stained slides appear as pale staining cellsSecrete calcitonin

FUNCTION OF THYROID GLAND

PARATHYROID GLANDTwo pairs in mammalsEmbedded within thyroid gland substanceC.T. capsule is thin

PRINCIPAL CELLS/ CHIEF CELLSMore numerous of parenchymal cellsSmall, polyhedral cells, of 7-10 um in diameterRounded, vesicular nucleiResponsible for secretion of PTH

chief cells

OXYPHILL CELLSConstitute a minor portion of parenchymaFound singly or in clustersMore rounded & larger than principal cellsDistinctly acidophilic cytoplasmNo secretory activity