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The Adrenal Glands

Anatomy of the adrenal glands

Adrenal glands, which are also called suprarenal glands, are small, triangular glands located on top of both kidneys. An adrenal gland is made of two parts--the outer region is called the adrenal cortex and the inner region is called the adrenal medulla.

Function of the adrenal glands

The adrenal glands work interactively with the hypothalamus and pituitary gland. For example, for the adrenal cortex to produce corticosteroid hormones:

  • The hypothalamus produces corticotropin-releasing hormones that stimulate the pituitary gland.
  • The pituitary gland, in turn, produces corticotropin hormones that stimulates the adrenal glands.
  • The adrenal glands makes and releases corticosteroid hormones.

Both parts of the adrenal glands--the adrenal cortex and the adrenal medulla--perform very separate functions.

What is the adrenal cortex?

The adrenal cortex, the outer portion of the adrenal gland, secretes hormones that have an effect on the body's metabolism, on chemicals in the blood, and on certain body characteristics. The adrenal cortex secretes corticosteroids and other hormones directly into the bloodstream. The hormones produced by the adrenal cortex include:

  • Corticosteroid hormones:
    • Hydrocortisone (cortisol). This hormone helps control the body's use of fats, proteins, and carbohydrates.
    • Corticosterone. This hormone, together with hydrocortisone, suppresses inflammatory reactions in the body and also affects the immune system.
  • Aldosterone. This hormone regulates the level of sodium excreted into the urine, maintaining blood volume and blood pressure.
  • Androgenic steroids (androgen hormones). These hormones are converted elsewhere in the body to female hormones (estrogens) and male hormones (androgens); however, these steroid hormones are produced in much larger amounts by the ovaries in women and testes in men.

What is the adrenal medulla?

The adrenal medulla, the inner part of the adrenal gland, is not essential to life, but helps a person in coping with physical and emotional stress. The adrenal medulla secretes the following hormones:

  • Epinephrine (also called adrenaline). This hormone helps the body respond to a stressful situation by increasing the heart rate and force of heart contractions, facilitates blood flow to the muscles and brain, causes relaxation of smooth muscles, helps with conversion of glycogen to glucose in the liver, and other activities.
  • Norepinephrine (also called noradrenaline). This hormone has little effect on smooth muscle, metabolic processes, and cardiac output, but has strong vasoconstrictive effects, thus increasing blood pressure.

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