The zona fasciculata (ZF ) consists of radially oriented cords and sheets of cells, usually two cells in width, that extend toward the medulla. The cells of the outer part of the zona fasciculata are generally larger than those of the inner portion of this zone and typically stain poorly because of the large number of lipid droplets that they contain. The cells of the zona reticularis (ZR) are relatively small and contain little or no lipid droplets and, consequently, stain prominently with eosin. Because of their small size, the nuclei are in close proximity to one another, much like the cells of the zona glomerulosa.
Typically, the cells in this part of the zona fasciculata are filled with lipid droplets, thus, the very poor staining characteristic of their cytoplasm. Delicate connective tissue trabeculae (arrows) extend from the capsule to surround the glomerular groups of cells and extend between the cords of cells in the zona fasciculata. Capillaries and arterioles are located within the connective tissue trabeculae. Usually, the capillaries are collapsed and, without the presence of red blood cells in their lumina, are thus difficult to identify.
Cortex, adrenal gland, human, H&E ×245. in cords and contain lipid droplets, though in lesser amounts. The cells of This is a higher magnification of the area inscribed by the right the zona reticularis (ZR) are arranged in irregular anastomosing cords and rectangle in figure above. This deep portion of the zona fascic-contain at best only a small amount of lipid and, consequently, their cyto ulata (ZF) reveals smaller cells, although they are still arranged plasm stains with eosin.
KEY A, arteries AT, adipose tissue BV, blood vessels Cap, capsule Cort, cortex Med, medulla ZF, zona fasciculata ZG, zona glomerulosa ZR, zona reticularis arrows, connective tissue trabeculae dashed line, corticomedullary boundary
The cells of the adrenal medulla develop from the same source as the postganglionic cells of the sympathetic nervous system. They are directly innervated by preganglionic cells of the sympathetic system and may be regarded as modified postganglionic cells that are specialized to secrete. These cells produce the catecholamines epinephrine and norepinephrine. The adrenal medulla receives its blood supply via two routes: by arterioles that pass through the cortex and by capillaries that continue from the cortex, a type of portal circulation. Thus, some of the blood supplying the medulla contains cortical secretions that regulate medullary function. Blood leaves the medulla via the central adrenomedullary vein. Its structure is unusual in that the tunica media of the vessel contains prominent bundles of longitudinally oriented smooth muscle, the contraction of which facilitates rapid outflow of blood when medullary cate-cholamines are released.
Medulla, adrenal gland, human, H&E ×175; inset ×250.
This moderately low power photomicrograph shows the cells of the adrenal medulla. The medullary cells are organized in ovoid groups and short interconnecting cords. The cytoplasm of the medullary cells may stain with different intensity. The cytoplasm of some cells is very poorly stained, appearing almost clear, whereas others show greater intensity of eosin
Central adenomedullary vein, adrenal gland, human, H&E ×350.