The adrenal medulla is the central part of the adrenal gland, surrounding by the cortex. The medulla dram a really important duty in homeostasis: it serves to secrete adrenaline and also noradrenaline. This post will covering the structure, function and clinical relevance of the adrenal medulla.

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Structure

The adrenal glands, likewise known as supra-renal glands, are found automatically superior to the kidneys. They room retroperitoneal structures and also composed of two major regions: the outer adrenal cortex and the inside adrenal medulla.

The main secreting cell of the adrenal medulla are referred to as chromaffin cells, which space neuroendocrine cells that are modified sympathetic ganglia. The chromaffin cells are neural crest cell derivatives. Adrenaline is released in an answer to activation that the sympathetic nervous system, fibres of which are brought to the adrenal medulla by the thoracic splanchnic nerves.


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Fig 1 – Histology the the adrenal gland.


Function

The adrenal medulla is mostly responsible because that the synthesis of the catecholamines, adrenaline and also noradrenaline, but additionally has other secretory attributes such as the production of dopamine. Both adrenaline and noradrenaline are created from the amino mountain tyrosine, through multiple reactions.

The synthesised adrenaline is stored in vesicles prior to being released right into the blood stream. Adrenaline is mainly associated with the “fight or flight response“, and noradrenaline also plays a function in the activation that the sympathetic nervous mechanism as a neurotransmitter in post-ganglionic synapses.

It exhibits its actions with α and β adrenoreceptors (G protein coupled receptors), both in the main nervous system and also in the periphery. The “fight or trip response” is a key survival mechanism, and causes a variety of physiological changes, such together increased cardiac output and also increased glycogenolysis in liver and also muscle tissue.


Clinical relevance – Phaeochromocytoma

A Phaeochromocytoma is a neuroendocrine tumour the the adrenal medulla, particularly the chromaffin cell which secrete adrenaline as disputed previously. This leader to an overabundance of adrenaline, and leads to constant activation the the “flight or fight response”. Hence, this deserve to lead come symptoms together as:

TachycardiaHypertensionAnxietyPalpitationsWeight lossHyperglycaemia

In some instances it can lead to a hypertensive crisis. Whilst the above symptoms room all possible, the most usual presentation is intermittent assaults of headaches, excessive sweating and also tachycardia.

These patients present with very high blood pressures, typically higher than 180/120 mmHg. Hypertension deserve to lead to enhanced pressure in vital circulations, such together in the brain and in the kidney, which can be lethal.

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Typically, treatment requires surgical resection that the tumour, however alpha adrenoceptor blockers regularly need come be offered prior to surgical procedure to minimize complications.


By Michael Feldman, MD, PhD university of Pennsylvania college of medicine , via Wikimedia Commons