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Each adrenal gland is located above the kidney and comprises two endocrine organs.
Medial medulla of the adrenal gland is mainly involved, in response to nerve
impulses, in the secretion of catecholamine adrenaline (epinephrine), noradrenaline
(norepinephrine), and dopamine, which are transmitted through the preganglionic
sympathetic nerve. Outer part of cortex releases glucocorticoids, sex hormones, steroid hormones, and mineralocorticoids. Two different embryological origins are
involved in adrenal cortex and adrenal medulla. Chromaffin ectodermal cells of
neural crest are responsible for derivation of medulla oblongata, that cleave from
sympathatic ganglion cells, while coelomic mesothelium is in derivation of adrenal
cortex. Blood vessels of adrenal gland are much strong, and arterial blood comes
from branches of the phrenic arteries and aorta as well as from kidneys. The medulla
takes blood from cortex bearing enough corticosteroids that controls formation of
enzymes responsible for conversion of noradrenaline to adrenaline. Venous blood
drains mainly into renal vein or inferior vena cava through the large adrenal vein [1].
Adrenal Medulla
Adrenal medulla is an altered sympathetic ganglion consisting of dense innervated
granules containing cells, accounting for approximately 30% of the adrenal structure. About ten percent of the cells are responsible for noradrenaline secretion,
while 90% are chiefly epinephrine secreting cells. It is not clear which kind of cells
involved in dopamine release. A little portion of chromaffin cells are also positioned
outer side of the medulla, generally next to the sympathetic ganglion chain [6].
Catecholamines
Epinephrine, norepinephrine, and dopamine are packed in membrane bound granules; their emission is triggered by the secretion of acetylcholine from sympathetic
nerve fibers which propagate into splanchnic nerves. The half-life of catecholamines
in plasma is very short, ≥2 min. Removal from bloodstream includes absorption of
both neuronal as well as non-neuronal tissues in which their degradation or recycling by catechol-O-methyltransferase or monoamine oxidase occurs. Approximately
fifty percent of the released catecholamines are present in the urine as free or bound
meta-adrenalines and normetadrenalines, while approximately 35% of the vanillylmandelic acid (VMA) form appears. Catecholamine’s release is lower in the basal
state but it is further reduced during nap. Sympathetic activity controlled by the
hypothalamus is involved in their secretion and happens in order to respond to
excitement, hypoglycemia, hypovolemia, anxiety, and pain. You get diffuse medullary discharges through an emergency stimulus, making patients to combat or evasive reactions. The effects of noradrenaline and adrenaline are various and
complicated, depending on their bounding with alpha (α1, α2) and beta (β1, β2)
adrenergic receptors, whereas dopamine also has effect on particular dopaminergic
receptors. They mimic action of noradrenergic nerve discharge, stimulate the
A. Ahsan et al.
Each adrenal gland is located above the kidney and comprises two endocrine organs.
Medial medulla of the adrenal gland is mainly involved, in response to nerve
impulses, in the secretion of catecholamine adrenaline (epinephrine), noradrenaline
(norepinephrine), and dopamine, which are transmitted through the preganglionic
sympathetic nerve. Outer part of cortex releases glucocorticoids, sex hormones, steroid hormones, and mineralocorticoids. Two different embryological origins are
involved in adrenal cortex and adrenal medulla. Chromaffin ectodermal cells of
neural crest are responsible for derivation of medulla oblongata, that cleave from
sympathatic ganglion cells, while coelomic mesothelium is in derivation of adrenal
cortex. Blood vessels of adrenal gland are much strong, and arterial blood comes
from branches of the phrenic arteries and aorta as well as from kidneys. The medulla
takes blood from cortex bearing enough corticosteroids that controls formation of
enzymes responsible for conversion of noradrenaline to adrenaline. Venous blood
drains mainly into renal vein or inferior vena cava through the large adrenal vein [1].
Adrenal Medulla
Adrenal medulla is an altered sympathetic ganglion consisting of dense innervated
granules containing cells, accounting for approximately 30% of the adrenal structure. About ten percent of the cells are responsible for noradrenaline secretion,
while 90% are chiefly epinephrine secreting cells. It is not clear which kind of cells
involved in dopamine release. A little portion of chromaffin cells are also positioned
outer side of the medulla, generally next to the sympathetic ganglion chain [6].
Catecholamines
Epinephrine, norepinephrine, and dopamine are packed in membrane bound granules; their emission is triggered by the secretion of acetylcholine from sympathetic
nerve fibers which propagate into splanchnic nerves. The half-life of catecholamines
in plasma is very short, ≥2 min. Removal from bloodstream includes absorption of
both neuronal as well as non-neuronal tissues in which their degradation or recycling by catechol-O-methyltransferase or monoamine oxidase occurs. Approximately
fifty percent of the released catecholamines are present in the urine as free or bound
meta-adrenalines and normetadrenalines, while approximately 35% of the vanillylmandelic acid (VMA) form appears. Catecholamine’s release is lower in the basal
state but it is further reduced during nap. Sympathetic activity controlled by the
hypothalamus is involved in their secretion and happens in order to respond to
excitement, hypoglycemia, hypovolemia, anxiety, and pain. You get diffuse medullary discharges through an emergency stimulus, making patients to combat or evasive reactions. The effects of noradrenaline and adrenaline are various and
complicated, depending on their bounding with alpha (α1, α2) and beta (β1, β2)
adrenergic receptors, whereas dopamine also has effect on particular dopaminergic
receptors. They mimic action of noradrenergic nerve discharge, stimulate the
A. Ahsan et al.