2. Anatomy
External environmental changes can create scenarios that the human
brain interprets as dangerous or stressful. The body can be equipped to face
these changes under the influence of the adrenal glands, also known as
the suprarenal glands.
The left and right suprarenal glands differ slightly in their shape and location on
top of their respective kidneys. The right gland is more pyramidal and sits on top
of the upper pole of the kidney, while the left gland is more crescenteric and
hangs more over the medial side of the left kidney, superior to the hilum.
3. The adrenal gland is divided into an outer cortex and an inner medulla
The adrenal cortex is subdivided into
the zona glomerulosa
the zona fasciculata
zona reticularis.
4. The zona glomerulosa is comprised of small rounded cells that are responsible for
secreting mineralocorticoids such as aldosterone.
Aldosterone regulates the uptake of water in the distal convoluted tubules and collecting
ducts, which consequently alters the body’s blood pressure.
Mainly through increasing the absorption of sodium and chloride back into the blood in
exchange for potassium and hydrogen into the urine.
The net result of the aldosterone release is to increase blood volume and blood
pressure.
5. Zona fasciculata is significantly thicker than the other two cortical layers. It is
made up of pale staining vacuolated cells arranged in parallel rows.
This layer is responsible for secreting glucocorticoids (cortisol and cortisone) to
increase the overall blood glucose level in an effort to provide more energy for a system
under stress.
Result in gluconeogenesis from non sugar sources such as amino acids and lactic
acids
They also result in increasing the rate at which adipose tissue breaks down triglycerides
into fatty acids and glycerol.
They also decrease protein synthesis
And decrease the effectiveness of our immune system.
6. Zona reticularis consists of smaller cells that stain darker relative to cells of the
aforementioned layers. Here, suprarenal androgens are produced, which serve as
precursors for testosterone.
These represent a small portion of the sex hormones.
7. At the center of the organ is a thin, grey medulla. Residing here are chromaffin
cells, splanchnic nerves and dilated capillaries.
The chromaffin cells are responsible for the production of catecholamines, namely
epinephrine (adrenaline), norepinephrine (noradrenaline) and
dopamine. Epinephrine is released directly into the medullary capillaries and
carried to their site of action via systemic circulation.
The physiological effect it has is dependent on the neuroreceptors present at the
site at which the chemical acts.
8.
9. Control of adrenal gland
The hypothalamus secretes corticotropin releasing factors which then acts on the
anterior pituitary gland to release Adrenocorticotropic hormone (ACTH).
ACTH will act on the adrenal cortex to release the required hormone which in turn
will exert a negative feedback on the pituitary gland.
The adrenal medulla is under the influence of the nervous system.
10. Cushing syndrome
Pituitary adenomas can result in a hypersecretion of ACTH.
The excess ACTH will overstimulate the suprarenal cortex, resulting in hypercortisolism,
or Cushing syndrome.
The disease is more predominant in women in the young adult age group. Immunosuppression,
muscular atrophy, weight gain and hyperglycaemia are some of the clinical manifestations of
the disease. Both medical and surgical options can be implemented to correct this disorder.
11. Pheochromocytoma
Pheochromocytoma (PCC) is the primary neoplasm of the suprarenal medulla.
These tumors are rare and may precipitate life threatening hypertension.
The neoplasms can also affect extra-adrenal chromaffin tissue.
The lesion results in a hyper production of catecholamines, which consequently results
in an overactive sympathetic response.
