The adrenal gland consists of two endocrine tissues, the cortex and medulla, that are functionally distinct. The glandular epithelia of the adrenal cortex are arranged in small clusters (zona glomerulosa and reticularis) or cords (zona fasciculata) with closely associated capillaries. Cells of the cortex have features common to steroid producing cells, such as abundant smooth endoplasmic reticulum and lipid droplets, giving the cytoplasm of these cells a “foamy appearance.” The adrenal medulla contains clusters of chromaffin cells, a type of neurosecretory cell, and parasympathetic ganglion cells. The adrenal medulla also contains a central adrenal medullary vein, a distinctive blood vessel with longitudinal bundles of smooth muscle in its wall. Review the table below describing the features and functions of the adrenal glands.

• Examine the images below and these three slides of adrenal gland (sample 1, sample 2, sample 3). The adrenals are flattened glands with concentric layers of secretory tissue. In the distinct capsule associated with adipose tissue, notice the small arteries entering the gland and the vascular plexus just inside the capsule.
• On these two slides (sample 1, sample 2), examine the cortex. Identify the three layers or zones in which the steroid-secreting cells have slightly different arrangements, with groups of cells separated by fine, well-vascularized connective tissue septa. The outermost zona glomerulosa has cells secreting mineralocorticoids arranged in irregular clusters ("glomeruli"). The middle and widest layer, the zona fasciculata, has cells secreting glucocorticoids arranged in strands ("fascicles"). The innermost layer, the zona reticularis, shows irregular, branching ("reticular") cords of cells secreting small quantities of weak androgens.
• Examine the medulla, noting the clusters of chromaffin cells, scattered ganglion cells, and the central adrenomedullary vein.

Clinical note: Addison’s disease is an adrenal insufficiency caused by infection or autoimmune destruction of the adrenal cortex. Fatigue, low blood pressure, nausea and other symptoms of the disorder suggest failure of secretion of both glucocorticoids and mineralocorticoids.

Now try this self-assessment quiz, no one sees the score but you.

Now for specialized sensory organs .