The supraneal, or adrenal, glands are a pair of glands that secrete hormones directly into the bloodstream. Each gland can be divided into two distinct organs. The outer region, the adrenal cortex, secretes hormones which have important effects on the way in which energy is stored and food is used, on chemicals in the blood, and on characteristics such as hairiness and body shape. The smaller, inner region — the adrenal medulla — is part of the sympathetic nervous system and is the body’s first line of defense and response to physical and emotional stresses.
The adrenal glands are shaped like the French Emperor Napoleon’s hat and, just as Napoleon’s three-cornered hat sat on his head, so each gland is perched on each of the kidneys. These glands are about one to two inches in length; they weigh only a fraction of an ounce each, yet are among the most productive of all of the body’s glands, secreting more than three dozen hormones. The adrenal cortex takes instruction from the pituitary gland and has important effects on physical characteristics, development and growth.
The adrenal gland has two parts:
- The cortex, or outer, yellow layer, takes its instructions from the pituitary hormone ACTH. The hormones secreted here are called steroids and have three main types: those which control the balance of sodium and potassium in the body; those which raise the level of sugar in the blood; and sex hormones.
- The inner, reddish brown layer of the adrenal gland (the adrenal medulla) makes two types of hormones; this part of the adrenal gland takes its instruction from the nervous system, producing chemicals which react to fear and anger and are sometimes called fight or flight hormones.