出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/11/14 17:38:08」(JST)
| Adrenal medulla | |
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Medulla labeled at bottom right.
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| Details | |
| Precursor | Neural crest |
| Artery | superior suprarenal artery, middle suprarenal artery, Inferior suprarenal artery |
| Vein | suprarenal veins |
| Nerve | celiac plexus, renal plexus |
| Lymph | lumbar glands |
| Identifiers | |
| TA | A11.5.00.008 |
| FMA | 15633 |
| Anatomical terminology
[edit on Wikidata]
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The adrenal medulla (Latin: medulla glandulae suprarenalis) is part of the adrenal gland. It is located at the center of the gland, being surrounded by the adrenal cortex. It is the innermost part of the adrenal gland, consisting of cells that secrete epinephrine (adrenaline), norepinephrine (noradrenaline), and a small amount of dopamine in response to stimulation by sympathetic preganglionic neurons.
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 (ANS). In fact, these adrenal medullary cells are modified postganglionic neurons, and preganglionic autonomic nerve fibers lead to them directly from the central nervous system. The adrenal medulla therefore affects available energy, heart rate, and metabolism.
Rather than releasing a neurotransmitter, the cells of the adrenal medulla secrete hormones.
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 epinephrine, norepinephrine, and dopamine.
Because the ANS, specifically the sympathetic division, exerts direct control over the chromaffin cells the hormone release can occur rather quickly. In response to stressors such as exercise or imminent danger, medullary cells release the catecholamines adrenaline and noradrenaline into the blood. Adrenaline composes about 85% of the released catecholamines, and noradrenaline the other 15%.[1]
Notable effects of adrenaline and noradrenaline include increased heart rate and blood pressure, blood vessel constriction in the skin and gastrointestinal tract, smooth muscle (bronchiole and capillary) dilation, and increased 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.
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 autonomic nervous system that have lost their axons and dendrites, receiving innervation from corresponding preganglionic fibers. The cells form clusters around large blood vessels.
As a cluster of neuron cell bodies, the adrenal medulla is considered a ganglion of the sympathetic nervous system.
Neoplasms include:[2]
The adrenal medulla may be poorly formed or absent in cases of absent adrenal gland. The deficiency in circulating catecholamines is mildly symptomatic due to compensation by the autonomous nervous system, except in episodes of hypoglycemia where glycogenolysis cannot be stimulated by circulating epinephrine .[2]
In dopamine beta hydroxylase deficiency, the entire body cannot efficiently produce epinephrine and norepinephrine from dopamine, this results in severe dysautonomia but most crucially due to autonomous nervous system failure which requires epinephrine and norepinephrine as neurotransmitters, dopamine being used in this pathology as an inadequate substitute.[2][3]
Anatomy of the endocrine system
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| Pituitary gland |
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| Thyroid gland |
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| Parathyroid gland |
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| Adrenal gland |
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| Gonads |
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| Islets of pancreas |
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| Pineal gland |
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| Other |
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| リンク元 | 「副腎髄質」「adrenomedullary」 |
| 拡張検索 | 「adrenal medulla scintigraphy」「function tests of the adrenal medulla」 |
| 関連記事 | 「adrenal」「medulla」 |