Anatomy of the Adrenal Gland

Structure of the Adrenal Gland

• The adrenal gland is pyramidal on the right and semilunar on the left.
• It consists of two parts: cortex and medulla.

Position and Relations of the Adrenal Gland

• The adrenal gland is a yellowish retroperitoneal organ lying on the superomedial aspect of the kidney.
• It is surrounded by a capsule and renal fascia, but is separated from the kidneys by the perirenal fat.
• Right adrenal gland relations:
  • Anteriorly: Liver and Inferior Vena Cava
  • Posteriorly: Diaphragm
• Left adrenal gland relations:
  • Anteriorly: Posterior surface of the stomach
  • Posteriorly: Diaphragm

Nerve Supply and Blood Supply

• Nerve supply: Preganglionic sympathetic fibers derived from the splanchnic nerves
• Most of the nerves end in the medulla
• Blood supply: Three arteries supply each gland (inferior phrenic artery, aorta, and renal artery)
• A single vein emerges from the hilum of each gland and drains into the inferior vena cava on the right and into the renal vein on the left

Development of Adrenal Glands

• The cortex forms from two waves of mesoderm proliferation
• The first wave forms the fetal cortex
• The second wave surrounds the fetal cortex and forms the adult cortex
• The medulla forms from neural crest cells, which migrate to the fetal cortex and differentiate into chromaffin cells

Histology of the Adrenal Gland

• Each gland has two concentric regions: adrenal cortex and adrenal medulla
• The adrenal cortex and medulla can be considered two different organs with distinct embryonic origins, functions, and morphologic characteristics
• Adrenal cortex cells have characteristic features of steroid-secreting cells
• The adrenal cortex has three concentric zones:
  • Zona glomerulosa: synthesizes aldosterone
  • Zona fasciculata: synthesizes glucocorticoids, especially cortisol, and small amounts of weak androgens
  • Zona reticularis: synthesizes small amounts of weak androgens

Regulation of Glucocorticoids and Mineralocorticoids

• Glucocorticoid secretion is regulated by the hypothalamic anterior pituitary adrenal cortex axis
• The axis exerts its effect through corticotropin-releasing hormone (CRH)