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Article Topic: adrenals
In mammals, the adrenal glands (also known as suprarenal glands) are the triangular-shaped endocrine glands that sit on top of the kidneys. They are chiefly responsible for releasing hormones in conjunction with stress through the synthesis of corticosteroids and catecholamines, including cortisol and adrenaline (epinephrine), respectively. Anatomically, the adrenal glands are located in the retroperitoneum situated atop the kidneys, one on each side. They are surrounded by an adipose capsule and renal fascia. In humans, the adrenal glands are found at the level of the 12th thoracic vertebra. Each adrenal gland is separated into two distinct structures, the adrenal cortex and medulla, both of which produce hormones. The cortex mainly produces cortisol, aldosterone, and androgens, while the medulla chiefly produces epinephrine and norepinephrine. The average combined weight of the adrenal glands in an adult is 7 to 10 grams.[1] The adrenal cortex is devoted to the synthesis of corticosteroid hormones from cholesterol. Some cells belong to the hypothalamic-pituitary-adrenal axis and are the source of cortisol and corticosterone synthesis. Under normal unstressed conditions, the human adrenal glands produce the equivalent of 35–40&_160;mg of cortisone acetate per day.[2] Other cortical cells produce androgens such as testosterone, while some regulate water and electrolyte concentrations by secreting aldosterone. In contrast to the direct innervation of the medulla, the cortex is regulated by neuroendocrine hormones secreted by the pituitary gland and hypothalamus, as well as by the renin-angiotensin system. The adrenal cortex comprises three zones, or layers. This anatomic zonation can be appreciated at the microscopic level, where each zone can be recognized and distinguished from one another based on structural and anatomic characteristics.[3] The adrenal cortex exhibits functional zonation as well by virtue of the characteristic enzymes present in each zone, the zones produce and secrete distinct hormones.[3]
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