Adrenal glands and pancreas

There is one adrenal gland on top of each kidney. Each has an inner part, the adrenal medulla, and an outer part, the adrenal cortex, which has three layers (from inside out: zona reticularis, zona fasciculata and zona glomerulosa).

The adrenal medulla makes adrenaline (epinephrine) and noradrenaline (norepinephrine), together called catecholamines. They are released fast in any emergency or stress, so they are called the fight or flight hormones. They make you alert, widen the pupils, raise the hairs on the skin (goosebumps), cause sweating, make the heart beat faster and stronger, speed up breathing, and break down glycogen, fats and proteins to give quick energy.

The adrenal cortex makes hormones called corticoids:

• Glucocorticoids, mainly cortisol: they make new glucose (gluconeogenesis), break down fats and proteins, reduce inflammation (anti-inflammatory), suppress the immune response, and increase red blood cell production.
• Mineralocorticoids, mainly aldosterone: they make the kidney reabsorb Na⁺ and water and get rid of K⁺ and phosphate, controlling the body's salt and water balance.
• Small amounts of androgens (male hormones).

If the cortex makes too little, the result is Addison's disease.

The pancreas is both an exocrine gland (making digestive juice) and an endocrine gland. Its hormones come from 1 to 2 million small clusters of cells, the Islets of Langerhans, which make up only 1-2% of the pancreas.

• α-cells make glucagon. It makes the liver break down glycogen (glycogenolysis) and make new glucose (gluconeogenesis), so it raises blood sugar: it is hyperglycemic.
• β-cells make insulin. It helps the liver and fat cells take up glucose and store it as glycogen (glycogenesis), so it lowers blood sugar.

If blood sugar stays high for a long time, the result is diabetes mellitus: glucose and harmful ketone bodies appear in the urine. It is treated with insulin.