— .medulla central adrenomedullary vein also have a well-developed Golgi apparatus and numerous profiles of rER that may give a slight basophilia to some parts of the cytoplasm (Fig. 20.22). In general, however, the cytoplasm is acidophilic and contains numerous lipid droplets, although it usually appears vacuolated in routine histologic sections because of the extraction of lipid during dehydration. The lipid droplets contain neutral fats, fatty acids, cholesterol, and phospholipids that are precursors for the steroid hormones secreted by these cells.

The principal secretion of the zona fasciculata is glucocorticoids that regulate glucose and fatty acid metabolism

The zona fasciculata secretes glucocorticoids, so called because of their role in regulating gluconeogenesis (glucose synthesis) and glycogenesis (glycogen polymerization). One of the glucocorticoids secreted by the zona fasciculata, Cortisol (hydrocortisone), acts on many different cells and tissues to increase the metabolic availability of glucose and fatty acids, both of which are immediate sources of energy. Within this broad function, glucocorticoids may have different, even opposite effects in different tissues:

• In the liver, glucocorticoids stimulate conversion of amino acids to glucose, stimulate the polymerization of glucose to glycogen, and promote the uptake of amino acids and fatty acids.

• In adipose tissue, glucocorticoids stimulate the breakdown of lipids to glycerol and free fatty acids.

• In other tissues, they reduce the rate of glucose use and promote the oxidation of fatty acids.

• In cells such as fibroblasts, they inhibit protein synthesis and even promote protein catabolism to provide amino acids for conversion to glucose in the liver.

Glucocorticoids depress the immune and inflammatory responses and, as a result of the latter, inhibit wound healing. They depress the inflammatory response by suppress


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