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  • Structure And Function Of Adrenal Gland In Animal – Animal Husbandry Notes – For W.B.C.S. Examination.

    Adrenal gland, also called suprarenal gland, either of two small triangular endocrine glands one of which is located above each kidney.Continue Reading Structure And Function Of Adrenal Gland In Animal – Animal Husbandry Notes – For W.B.C.S. Examination.

    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.

    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. The two parts differ in embryological origin, structure, and function. The adrenal glands vary in size, shape, and nerve supply in other animal species. In some vertebrates the cells of the two parts are interspersed to varying degrees.

    Adrenal Medulla

    The adrenal medulla is embedded in the centre of the cortex of each adrenal gland. It is small, making up only about 10 percent of the total adrenal weight. The adrenal medulla is composed of chromaffin cells that are named for the granules within the cells that darken after exposure to chromium salts.

    These cells migrate to the adrenal medulla from the embryonic neural crest and represent specialized neural tissue. 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). The sympathetic nervous system and the adrenal medulla are collectively known as the sympathoadrenal system.

    The chromaffin granules contain the hormones of the adrenal medulla, which include dopamine, norepinephrine, and epinephrine. When stimulated by sympathetic nerve impulses, the chromaffin granules are released from the cells and the hormones enter the circulation, a process known as exocytosis. Thus, the adrenal medulla is a neurohemal organ.

     
    Adrenal Cortex

    Cells of the adrenal cortex synthesize and secrete chemical derivatives (steroids) of cholesterol. While cholesterol can be synthesized in many body tissues, further modification into steroid hormones takes place only in the adrenal cortex and its embryological cousins, the ovaries and the testes. In adult humans the outer cortex comprises about 90 percent of each adrenal gland.

    It is composed of three structurally different concentric zones. From the outside in, they are the zona glomerulosa, zona fasciculata, and zona reticularis.

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