Adrenal Cortex of the Dog (Canis familiaris): I. Histomorphologic Changes during Growth,Maturity, and Aging1

The adrenal glands of 56 dogs ranging in age from birth to 13.6 years were examined for a determination of normal zonal and cellular morphology patterns throughout development, maturity and aging. Routine light microscopic techniques as well as lipid and cholesterol staining were used. The zona arcuata is described as developing between the fibrous and cellular layers of the capsule forming the cortical blastema layer, a zona biproliferativa. It is proposed that both centrifugal and centripetal migration of cortical parenchyma can result. The formation of accessory nodules is described as compensatory hyperplasia. Histomorphometric analysis revealed growth in the zona fasciculata to be by hyperplasia and the zonal volume percentages to be arcuata, 27%; fasciculata, 50%; reticularis, 23%.