The inner part of the adrenals, derived embryonically from spinal nerve precursors, they secrete epinephrine, norepinephrine and dopamine; used locally as neurotransmitters, sensitive receptors can be mobilized totally by the adrenal medullas.
Structure Each suprarenal gland has an enveloping layer of ?brous tissue. Within this, the gland shows two distinct parts: an outer, ?rm, deep-yellow cortical (see CORTEX) layer, and a central, soft, dark-brown medullary (see MEDULLA) portion. The cortical part consists of columns of cells running from the surface inwards, whilst in the medullary portion the cells are arranged irregularly and separated from one another by large capillary blood vessels.
Functions Removal of the suprarenal glands in animals is speedily followed by great muscular prostration and death within a few days. In human beings, disease of the suprarenal glands usually causes ADDISON’S DISEASE, in which the chief symptoms are increasing weakness and bronzing of the skin. The medulla of the glands produces a substance – ADRENALINE – the effects of which closely resemble those brought about by activity of the SYMPATHETIC NERVOUS SYSTEM: dilated pupils, hair standing on end, quickening and strengthening of the heartbeat, immobilisation of the gut, increased output of sugar from the liver into the bloodstream. Several hormones (called CORTICOSTEROIDS) are produced in the cortex of the gland and play a vital role in the metabolism of the body. Some (such as aldosterone) control the electrolyte balance of the body and help to maintain the blood pressure and blood volume. Others are concerned in carbohydrate metabolism, whilst others again are concerned with sex physiology. HYDROCORTISONE is the most important hormone of the adrenal cortex, controlling as it does the body’s use of carbohydrates, fats and proteins. It also helps to suppress in?ammatory reactions and has an in?uence on the immune system.... adrenal glands
It can be acute or chronic.
Adrenal failure may be caused by a disorder of the adrenal glands, in which case it is called Addison’s disease, or by reduced stimulation of the adrenal cortex by ACTH, a hormone produced by the pituitary gland.... adrenal failure
A genetic defect causes congenital adrenal hyperplasia, in which the adrenal cortex is unable to make sufficient hydrocortisone and aldosterone, and androgens are produced in excess. In adrenal failure, there is also deficient production of hormones by the adrenal cortex; if due to disease of the adrenal glands, it is called Addison’s disease. Adrenal tumours are rare and generally lead to excess hormone production.
In many cases, disturbed activity of the adrenal glands is caused, not by disease of the glands themselves, but by an increase or decrease in the blood level of hormones that influence the action of the adrenal glands. For example, hydrocortisone production by the adrenal cortex is controlled by ACTH, which is secreted by the pituitary gland. Pituitary disorders can disrupt production of hydrocortisone.... adrenal gland disorders
In severe cases, the disorder is apparent soon after birth. In milder cases, symptoms appear later, sometimes producing premature puberty in boys and delayed menstruation, hirsutism, and potential infertility in girls.
Congenital adrenal hyperplasia is confirmed by measuring corticosteroid hormones in blood and urine. Treatment is by hormone replacement. If this is started early, normal sexual development and fertility usually follow.... adrenal hyperplasia, congenital
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