Indeed, the adrenal medulla is an integral part of the sympathetic nervous system, a major subdivision of the autonomic nervous system ( see human nervous system). These cells migrate to the adrenal medulla from the embryonic neural crest and represent specialized neural tissue.

The adrenal medulla is composed of chromaffin cells that are named for the granules within the cells that darken after exposure to chromium salts. It is small, making up only about 10 percent of the total adrenal weight. The adrenal medulla is embedded in the centre of the cortex of each adrenal gland. In some vertebrates the cells of the two parts are interspersed to varying degrees. The adrenal glands vary in size, shape, and nerve supply in other animal species. The two parts differ in embryological origin, structure, and function. Each gland consists of two parts: an inner medulla, which produces epinephrine and norepinephrine (adrenaline and noradrenaline), and an outer cortex, which produces steroid hormones. In humans each adrenal gland weighs about 5 grams (0.18 ounce) and measures about 30 mm (1.2 inches) wide, 50 mm (2 inches) long, and 10 mm (0.4 inch) thick.

SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!Īdrenal gland, also called suprarenal gland, either of two small triangular endocrine glands one of which is located above each kidney.

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The adrenal glands are located