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Adrenal medulla: Wikis

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Adrenal medulla
Gray1185.png
Medulla labeled at bottom right.
Gray's subject #277 1280
Artery superior suprarenal artery, middle suprarenal artery, Inferior suprarenal artery
Vein suprarenal veins
Nerve celiac plexus, renal plexus
Lymph lumbar glands
Precursor Neural crest
Medullary part of the adrenal gland (on the pointer).

The adrenal medulla is part of the adrenal gland. It is located at the center of the gland, being surrounded by the adrenal cortex.

Contents

Basic

The adrenal medulla consists of irregularly shaped cells grouped around blood vessels. These cells are intimately connected with the sympathetic division of the autonomic nervous system. In fact, these adrenal medullary cells are modified postganglionic neurons, and postganglionic autonomic nerve fibers lead to them directly from the central nervous system.

Function

Composed mainly of hormone-producing chromaffin cells, the adrenal medulla is the principal site of the conversion of the amino acid tyrosine into the catecholamines adrenaline (epinephrine), noradrenaline (norepinephrine), and dopamine.

In response to stressors such as exercise or imminent danger, medullary cells release catecholamines into the blood in a 17:3 ratio of adrenaline to noradrenaline.[1]

Notable effects of adrenaline and noradrenaline include increased heart rate and blood pressure, blood vessel constriction in the skin and gastrointestinal tract, blood vessel dilation in skeletal muscles, bronchiole dilation, and decreased metabolism, all of which are characteristic of the fight-or-flight response. Release of catecholamines is stimulated by nerve impulses, and receptors for catecholamines are widely distributed throughout the body.

Origin

Medullary cells are derived from the embryonic neural crest and, as such, are simply modified neurons.

In particular, they are modified postganglionic cells of the sympathetic nervous system that have lost their axons and dendrites, receiving innervation from corresponding preganglionic fibers.

Moreover, as the synapses between pre- and postganglionic fibers are called ganglia, the adrenal medulla is actually a ganglion of the sympathetic nervous system.

Pathology

Neoplasms including:

See also

References

External links

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