Adrenal gland

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Anatomy and physiology of the adrenal glands

The 2 adrenal glands are part of the body’s endocrine systemendocrine systemThe group of glands and cells in the body that make and release hormones (which control many functions such as growth, reproduction, sleep, hunger and metabolism) into the blood.. They are found just above each kidney, deep inside the upper part of the abdomen.


The adrenal glands are made up of 3 layers of tissue:

  • adrenal cortex
    • outer layer of the adrenal gland
    • made up of glandular (gland) tissue
    • has 3 layers (inner, middle and outer)
  • adrenal medulla
    • inner layer of the adrenal gland
    • made up of neural (nerve) tissue
  • capsule
    • outer covering of the adrenal gland
    • made of dense fibrous tissue


As part of the endocrine system, the adrenal glands produce hormoneshormonesA substance that regulates specific body functions, such as metabolism, growth and reproduction..

Adrenal cortex

The adrenal cortex produces several hormones. The most important are aldosterone (a mineralocorticoid), cortisol (a glucocorticoid), and androgen and estrogen (sex hormones). These hormones manage metabolism and body characteristics, such as hair growth and body shape.

  • aldosterone
    • helps the kidneys control the amount of salt in the blood and tissues of the body
  • cortisol (called hydrocortisone)
    • helps the body manage and use carbohydrates, protein and fat
    • causes changes in metabolismmetabolismThe chemical processes in the body that create and use energy. It includes breaking down food and transforming it into energy, eliminating wastes and toxins, breathing, circulating blood and regulating temperature. to help the body manage stress
    • suppresses the immune system
  • androgen (male sex hormone) and estrogen (female sex hormone)
    • more common for excess androgen to be produced than excess estrogen

The adrenal cortex is made up of inner, middle and outer layers. Aldosterone is produced in the outer layer. Cortisol, androgen and estrogen are produced in the inner layer (active zone) and stored in the middle layer (storage zone). In times of stress, the storage zone shrinks and the active zone thickens to secrete more hormones.

Adrenal medulla

The hormones produced by the adrenal medulla are called catecholamines. They act as hormones and as neurotransmitters (chemical messengers in the nervous system). They manage the body’s response to stress. The 2 more important catecholamines are:

  • epinephrine (adrenaline)
    • released during times of short-term stress (such as a sudden shock or fear)
    • increases heart rate, blood pressure and blood sugar level
  • norepinephrine (noradrenaline)
    • constricts blood vessels
    • like epinephrine, it increases heart rate, blood pressure and blood sugar levels

The adrenal medulla also produces the protein chromogranin A, which is stored and secreted with epinephrine and norepinephrine.


The capsule surrounds and protects the adrenal gland.


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