Adrenal Glands

The adrenal glands are small yellowish, triangular-shaped glands located on top of each kidney. They are part of the endocrine system and play a crucial role in producing hormones that regulate various bodily functions, including metabolism, immune response, blood pressure, and stress response.
Each adrenal gland consists of two main parts: the outer cortex and the inner medulla.
The cortex is divided into three layers:

• Zona glomerulosa: The outermost layer, responsible for producing mineralocorticoids, such as aldosterone. Aldosterone acts on the kidneys, more specifically on the distal tubules and collecting ducts, where it promotes sodium retention (and with that water reabsorption) and potassium excretion. This leads to an increase in blood volume and thus a higher blood pressure.
• Zona fasciculata: The middle layer, produces glucocorticoids, such as cortisol. Cortisol is secreted in response to stress and low blood-glucose levels, and it has several important functions, including increasing blood sugar through gluconeogenesis (in the liver), suppressing the immune system (anti-inflammatory effects), and aids in fat, protein, and carbohydrate metabolism. Too much cortisol can lead to Cushing's syndrome, while too little can cause Addison's disease.
• Zona reticularis: The innermost layer, responsible for producing androgens, mainly dehydroepiandrosterone (DHEA) and androstenedione. These hormones are than converted into more potent androgens, such as testosterone, and estrogens in the gonads and other tissues. Androgens play a role in the development of secondary sexual characteristics and influence libido.

The adrenal medulla is responsible for producing catecholamines, including:

• Adrenaline (epinephrine): This hormone is released in response to stress and helps prepare the body for a "fight or flight" response by increasing heart rate, blood pressure, and blood flow to muscles. It also helps increase blood sugar levels by promoting glycogenolysis in the liver.
• Noradrenaline (norepinephrine): This hormone works alongside adrenaline to increase heart rate and blood pressure, and it also helps regulate blood vessel constriction.