Adrenal glands

The adrenal glands (glandulae suprarenales) are paired endocrine glands located at the upper poles of the kidneys. Each adrenal gland weighs only 5-7g but produces over 50 different hormones critical for survival.

Building

The adrenal gland consists of two fundamentally different parts:

Cortical substance (bark) - 80% of the mass, of mesodermal origin. Three zones:

• Zona glomerulosa - mineralocorticoids (aldosterone)
• Zona fasciculata - glucocorticoids (cortisol)
• Reticular zone - sex hormones (androgens)

Medulla - 20% of the mass, neuroectodermal origin. Contains chromaffin cells that secrete catecholamines (adrenaline and norepinephrine).

Cortex hormones

Cortisol is the main stress hormone:

• Increases blood glucose levels
• Suppresses inflammation and immune response
• Mobilizes fats and proteins for energy
• Maximum secretion - at 6–8 am (circadian rhythm)

Aldosterone - regulates water-salt metabolism:

• Retains sodium and water in the kidneys
• Removes potassium
• Regulates blood pressure

Androgens (DHEA, androstenedione) - in women, this is the main source of androgens necessary for libido and hair growth.

Adrenaline and stress

Adrenaline - the “fight or flight” hormone:

• Increases heart rate to 180–200 beats/min
• Expands the bronchi
• Increases blood pressure
• Dilates pupils
• Redirects blood flow to muscles
• Released into the bloodstream in fractions of a second

Norepinephrine is a mediator of alertness: it increases blood pressure, constricts blood vessels, and increases attention.

Diseases

• Cushing's syndrome - excess cortisol: obesity, stretch marks, osteoporosis, diabetes
• Addison's disease - cortical failure: weakness, hyperpigmentation, hypotonia
• Pheochromocytoma - brain tumor: crises with a sharp increase in pressure
• Congenital hyperplasia - impaired cortisol synthesis, excess androgens

Without adrenal glands, a person dies within a few days - their hormones are so important for maintaining life.

In 3D atlas Humio, you can view the adrenal glands in the context of surrounding structures - the kidneys, aorta and inferior vena cava - and understand their topography.