21.15: Anatomy of the Adrenal Glands
The adrenal or supra-renal glands, situated above the kidneys and aligned with the twelfth rib, are paired pyramid-shaped structures crucial for the body's stress response. During stress, these glands secrete hormones vital for adaptive physiological reactions.
These glands possess a distinctive yellow tinge due to the stored cholesterol and fatty acids required for hormone synthesis. They are encased in a fibrous capsule and cushioned by fat.
The adrenal gland comprises two distinct regions with specialized functions. The outer layer, the adrenal cortex, constitutes most of the gland and synthesizes corticosteroids. These hormones produced by the zona glomerulosa, zona fasciculata, and zona reticularis regions facilitate prolonged responses to stress.
Encapsulated by the cortex, the interior layer is the adrenal medulla, composed of nervous tissue. This region houses spherical chromaffin cells surrounding capillaries. Chromaffin cells play a pivotal role in synthesizing catecholamines, such as adrenaline and noradrenaline. These hormones induce immediate and brief effects, precipitating the well-known fight-or-flight response during stressful situations.
In summary, the adrenal glands are crucial in orchestrating both immediate and protracted physiological responses to stress, ensuring the body's adaptability and survival in challenging situations.
