Adrenal Medulla

Adrenal Medulla

The central part of the adrenal glands is called adrenal medulla. Its function is to synthesize and secrete catecholamines. Let us go into the details of this innermost part of the adrenal gland by scrolling down to the article below.
The endocrine glands that are present on the kidneys are called adrenal glands. These suprarenal glands or adrenal glands produce hormones when the body is under stress. They also affect the kidney function by secreting a hormone aldosterone. When we have a look at the adrenal gland anatomy, we find these glands are surrounded by adipose capsule and renal fascia. There are two distinct parts that make up the adrenal glands. These include the adrenal cortex and the adrenal medulla. Both these parts produce hormones. The adrenal cortex produces cortisol, aldosterone and androgen hormones. In this article, we focus on the functions of the adrenal medulla.

Overview

It forms the core of the adrenal glands. The adrenal cortex surrounds the medulla externally. The hormones of the gland include epinephrine, norepinephrine, as well as little amount of dopamine. These cells are irregularly shaped and connected to each other. These large columnar cells are called 'chromaffin cells'. A few ganglion cells are also seen in this region. This connection between cells is through sympathetic division of autonomic nervous system (ANS). These cells are modified neurons that have origins from the emryonic neural crest. These cells of the medulla are present in clusters surrounding the blood vessels. The blood from the adrenal gland is collected in the large medullary veins from where it flows out of the gland.

Hormones

The cells of adrenal medulla secrete epinephrine and norepinephrine. These hormones released into the blood stream bind to the adrenergic receptors present on the target cells. Thus, they have the same effect like the direct sympathetic nervous stimulation. The functions of these hormones are discussed below:

Epinephrine
  • This hormone helps the body prepare for 'fright, flight or fight' action
  • It helps in increasing heart rate
  • Increase in rate and depth of breathing
  • Increase in metabolic rate
  • Improvement in force of muscular contraction
  • Delay in onset of muscular fatigue
  • Reduction in blood supply to the bladder, intestines and causing their muscular walls to relax and contraction of the sphincters
Norepinephrine
  • Also called noradrenalin and has similar effects like adrenalin
  • It is a stress hormone that affects amygdala of the brain, the region where attention and responses are controlled
  • It also activates the 'fright, flight or fight' action within the body
  • It leads to constriction of blood vessels causing increase in blood pressure
  • Decrease in heart rate and increase in blood flow through coronary arteries
  • Increase in rate and depth of breathing
  • Helps smooth muscles of the intestinal walls relax
Disorders

The disorders affect the normal functioning of the adrenal gland and in turn the body. This leads to hypofunction or hyperfunction within the gland and body. These disorders occur either congenitally or are acquired. These disorders are very grave and hard to diagnose. If not treated on time, it could lead to life-threatening consequences. These disorders are enlisted below:
  • Pheochromocytoma (tumor of the chromaffin cells)
  • Cushing's Syndrome (adrenal gland producing excessive corticosteroids)
  • Pituitary adenoma (a disease that affects hormones regulating growth and activity of other glands in the body)
  • Hyperaldosteronism (condition that is related to high blood pressure)
  • Addison's disease (an autoimmune disorder causing failure of the gland to produce cortisol)
Neoplasm

Adrenal medulla is affected by a few neoplasms or tumors of the cells. These neoplasms are as follows:
  • Pheochromocytoma: A common neoplasm causing a tumor of the catecholamine secreating cells
  • Neuroblastoma: Neural crest tissues of the sympathetic nervous system are affected by a neuroendocrine tumor
  • Ganglioneuroma: A peripheral nervous system's nerve cell tumor
It is an important part of the adrenal gland and forms its core. Any disorder affecting the cells can cause disruption in normal functioning of the adrenal hormones. Hope, the above information has helped you understand about this important part of the adrenal gland.