ENDOCRINE GLANDS

ADRENAL (SUPRARENAL ) GLAND Lies on upper pole of each kidney Comprised of two zones outer cortex inner medulla Develops from intermediate mesoderm and neural crest cells

INTRODUCTION The 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.

CORTEX zona 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 cords Occupy 15% of gland volume

ZONA GLOMERULOSA

ZONA FASICULATA Cells are arranged in straight cords. 1-2 cells thick Cords run at right angles to the surface of organ and have capillaries between them Occupy 65% of gland volume

ZONA FASICULATA

ZONA RETICULARIS Polyhedral cells with lipid droplets Form 7% of gland Appears vacuolated in histological preparations Cells are smallest in size

ZONA RETICULARIS

ADRENAL MEDULLA Composed of cords or clumps of cells called chromaffin cells. These can acquire brown colour which is due to oxidation of catecholamines Modified postganglionic sympathetic neurons

ADRENAL MEDULLA

FUNCTIONS 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 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

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

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

FUNCTION OF THYROID GLAND

PARATHYROID GLAND Two pairs in mammals Embedded within thyroid gland substance C.T. capsule is thin

PRINCIPAL CELLS/ CHIEF CELLS More numerous of parenchymal cells Small, polyhedral cells, of 7-10 um in diameter Rounded, vesicular nuclei Responsible for secretion of PTH chief cells

OXYPHILL CELLS Constitute a minor portion of parenchyma Found singly or in clusters More rounded & larger than principal cells Distinctly acidophilic cytoplasm No secretory activity