ADRENAL (Suprarenal) GLANDS
Slide # 199 - Your slide made also include a section of kidney, easily identified by presence of glomeruli. Note that the adrenal gland is closely associated with the kidney. Observe the prominent fibroelastic capsule investing the adrenal gland. The gland is divided into an outer cortex and an inner medulla , each displaying distinct cell morphology and H & E staining characteristics. This is because the cortical cells produce steroids and the medullary cells secrete neuropeptides. Remember that the cortical and medullary cells derive from different embryologic origins .
The adrenal medulla can generally be recognized by its more basophilic cells, which are arranged in round clusters or short cords. The medulla is also characterized by numerous large veins, culminating in the suprarenal vein. Recall that the adrenal medulla is fed by a portal blood supply that first percolates through the cortex. Capillaries are fenestrated with diaphragms. The adrenal medullary cells synthesize and store epinephrine and norepinephine in granules for immediate release upon triggering by preganglionic sympathic fibers that innervate adrenal medullary cells. Catecholamine-secreting cells have a high affinity for chromium salts; thus, adrenal medullary cells are also called "chromaffin cells".
The adrenal cortex is divided structurally and functionally into 3 major areas, although cells in all 3 areas have characteristics of steroid-secreting cells. (1) The zona glomerulosa , the narrow outermost layer located just under the capsule, contains arching cords of cells. The predominant hormone secreted is aldosterone. Glomerulosa cells can be distinguished from fasciculata cells by their small size (due to less cytoplasm) and strongly stained nuclei. (2) The zona fasciculata , the middle and widest cortical layer, is characterized by long, parallel columns of cells that appear pale and vacuolated or "spongy". These cells contain abundant SER and many lipid droplets. The predominant product of the zona fasciculata in humans is cortisol. (3) The zona reticularis , the narrow innermost layer adjacent to the adrenal medulla secretes low levels of adrenal androgens, as well as cortisol. Cells in the zona reticularis appear to be arranged in twisted cords and also have a vacuolated appearance. Adrenal cortical cells produce and secrete steroid hormones as needed; the hormones are not stored in the cortex. Review the regulation of cortical hormones by the hypothalamic-pituitary-adrenocortical axis.