ABSTRACT
This chapter describes the adrenal gland. The adrenal or suprarenal glands lie on top of the upper poles of the kidneys and play a key role in the synthesis of corticosteroids and catecholamines. The adrenal glands are at the level of the twelfth thoracic vertebra. Anatomically, the adrenal gland is divided into two distinct areas: an outer cortex and inner medulla. The hypothalamus secretes corticotrophin-releasing hormone (CRH), which stimulates release of adrenocorticotropic hormone (ACTH) from the anterior pituitary. ACTH stimulates cortisol secretion from the zona fasciculata of the adrenal cortex. Cortisol exerts its effects by binding to glucocorticoid receptors and promoting specific enzyme synthesis. The glucocorticoids works in many ways to provide resistance to ‘stress’, having effects on metabolism, immune function and vascular reactivity. Cortisol is essential in maintaining vascular reactivity to noradrenaline. Catecholamines are synthesised in the chromaffin cells of the adrenal medulla.
