Adrenal Medulla: Structure, Function and Disorders

Adrenal glands are small triangular glands present on top of both kidneys. They are also known as suprarenal glands. The adrenal gland is divided into an adrenal medulla and adrenal cortex. The adrenal medulla is the innermost layer of the adrenal glands, surrounded by the adrenal cortex. The medulla produces a variety of hormones that help in non-essential functions.

Structure

  • It is embedded in the centre of the adrenal gland and weighs about 10% of the total gland weight.
  • It consists of chromaffin cells which secrete hormones.
  • It is made up of irregularly shaped cells around the blood vessels.
  • These cells are a connection between the medulla and autonomic nervous system.

Hormones of Adrenal Medulla

  1. Epinephrine: Also known as adrenaline, it is released as a result of stress in our body. It increases the heart rate, rushes blood to muscles and the brain, and spikes our blood sugar.
  2. Norepinephrine: Also known as nor-adrenaline, it works in conjunction with epinephrine in response to stress. It constricts the blood vessels causing high blood pressure.
  3. Dopamine: Dopamine is a neurotransmitter released in small amounts from the adrenal medulla. It is the precursor of norepinephrine.

Functions of Adrenal Medulla

  • It releases hormones in fight and flight responses after getting signals from the nervous system.
  • It is the site of the conversion of amino acid tyrosine to epinephrine and norepinephrine.

Disorder of Adrenal Medulla

  • Pheochromocytoma: Only one disorder of the adrenal medulla is known. It is a tumour of the chromaffin cells leading to excess secretion of epinephrine and norepinephrine. The chief symptom of the disorder is hypertension.

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Frequently Asked Questions

What controls the adrenal medulla?

The adrenal medulla is controlled by the fibres of the sympathetic nervous system.

How is adrenal medulla stimulated?

The adrenal medulla is stimulated by the preganglionic fibres of the sympathetic nervous system.

What is primarily produced in the adrenal medulla?

The adrenal medulla primarily produces catecholamines that include epinephrine, norepinephrine and small traces of dopamine.

What is the difference between the adrenal cortex and adrenal medulla?

The main difference between the adrenal cortex and adrenal medulla is in the hormones they secrete, and secondly, the medulla is the innermost layer of the adrenal gland, while the cortex is the layer covering the medulla.

Why is the adrenal medulla not essential for life?

Adrenal medulla releases hormones in response to stress which is not an essential part of life.

What is the name of the cells producing the hormone in the adrenal medulla?

Chromaffin cells produce the hormones in the adrenal medulla.

What is the difference between epinephrine and norepinephrine?

Epinephrine and norepinephrine are very similar hormones released from the adrenal medulla in response to stress. The chief difference between the two lies in their use as a drug. While epinephrine is used as an antihistamine for treating asthma shocks, norepinephrine is used to modulate the blood pressure.

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