Adrenal Gland
The pair of adrenal glands are located close to the kidneys on either side. Each gland lies cranially and medially to the corresponding kidney. When sectioned the adrenal gland can be seen to comprise an obvious cortex and medulla.
The cortex comprises three zones. The outer zone is the zona glomerulosa, the middle zone is the zona fasciculata and the inner zone is the zona reticularis. The cortex produces steroid hormones - mineralocorticoids (e.g. aldosterone), glucocorticoids (cortisol and cortisone) and androgens.The functions of the cortical hormones are as follows:
• Mineralocorticoids: regulation of blood pressure and concentration of electrolytes
• Glucocorticoids: regulation of metabolism and suppression of the immune system
• Androgens: production of steroids that are turned into sex hormones in the gonads.
The chromaffin cells of the adrenal medulla produce the catecholamines adrenaline and noradrenaline. The adrenal medulla is innervated by sympathetic preganglionic neurones and releases the hormones into the bloodstream (see Section 11.4.3).
12.6.1 The blood supply of the adrenal gland
The adrenal gland receives a rich blood supply via the suprarenal arteries. These arteries are branches of the phrenicoabdominal (see Section 8.1.3), aortic and renal arteries. In addition, variable arteries arising from the cranial mesenteric and coeliac arteries may be present.