adrenal Gland
Our body has one pair of adrenal glands, one at the anterior part of eachkidney (Figure 22.4 a). The gland is composed of two types of tissues.The centrally located tissue is called the adrenal medulla, and outsidethis lies the adrenal cortex (Figure 22.4 b).Underproduction of hormones by the adrenal cortex alterscarbohydrate metabolism causing acute weakness and fatigue leadingto a disease called Addison’s disease The adrenal medulla secretes two hormones called adrenaline orepinephrine and noradrenaline or norepinephrine. These arecommonly called as catecholamines. Adrenaline and noradrenaline arerapidly secreted in response to stress of any kind and during emergencysituations and are called emergency hormones or hormones of Fightor Flight. These hormones increase alertness, pupilary dilation,piloerection (raising of hairs), sweating etc. Both the hormones increasethe heart beat, the strength of heart contraction and the rate of respiration.Catecholamines also stimulate the breakdown of glycogen resulting in an increased concentration of glucose in blood. In addition, they alsostimulate the breakdown of lipids and proteins.The adrenal cortex can be divided into three layers, called zonareticularis (inner layer), zona fasciculata (middle layer) and zonaglomerulosa (outer layer). The adrenal cortex secretes many hormones,commonly called as corticoids. The corticoids, which are involved incarbohydrate metabolism are called glucocorticoids. In our body, cortisolis the main glucocorticoid. Corticoids, which regulate the balance of waterand electrolytes in our body are called mineralocorticoids. Aldosterone isthe main mineralocorticoid in our body.Glucocorticoids stimulate gluconeogenesis, lipolysis and proteolysis;and inhibit cellular uptake and utilisation of amino acids. Cortisol is alsoinvolved in maintaining the cardio-vascular system as well as the kidneyfunctions. Glucocorticoids, particularly cortisol, produces anti-inflammatory reactions and suppresses the immune response. Cortisolstimulates the RBC production. Aldosterone acts mainly at the renaltubules and stimulates the reabsorption of Na+ and water and excretionof K+ and phosphate ions. Thus, aldosterone helps in the maintenance ofelectrolytes, body fluid volume, osmotic pressure and blood pressure.Small amounts of androgenic steroids are also secreted by the adrenalcortex which play a role in the growth of axial hair, pubic hair and facialhair during puberty.
Our body has one pair of adrenal glands, one at the anterior part of eachkidney (Figure 22.4 a). The gland is composed of two types of tissues.The centrally located tissue is called the adrenal medulla, and outsidethis lies the adrenal cortex (Figure 22.4 b).Underproduction of hormones by the adrenal cortex alterscarbohydrate metabolism causing acute weakness and fatigue leadingto a disease called Addison’s disease The adrenal medulla secretes two hormones called adrenaline orepinephrine and noradrenaline or norepinephrine. These arecommonly called as catecholamines. Adrenaline and noradrenaline arerapidly secreted in response to stress of any kind and during emergencysituations and are called emergency hormones or hormones of Fightor Flight. These hormones increase alertness, pupilary dilation,piloerection (raising of hairs), sweating etc. Both the hormones increasethe heart beat, the strength of heart contraction and the rate of respiration.Catecholamines also stimulate the breakdown of glycogen resulting in an increased concentration of glucose in blood. In addition, they alsostimulate the breakdown of lipids and proteins.The adrenal cortex can be divided into three layers, called zonareticularis (inner layer), zona fasciculata (middle layer) and zonaglomerulosa (outer layer). The adrenal cortex secretes many hormones,commonly called as corticoids. The corticoids, which are involved incarbohydrate metabolism are called glucocorticoids. In our body, cortisolis the main glucocorticoid. Corticoids, which regulate the balance of waterand electrolytes in our body are called mineralocorticoids. Aldosterone isthe main mineralocorticoid in our body.Glucocorticoids stimulate gluconeogenesis, lipolysis and proteolysis;and inhibit cellular uptake and utilisation of amino acids. Cortisol is alsoinvolved in maintaining the cardio-vascular system as well as the kidneyfunctions. Glucocorticoids, particularly cortisol, produces anti-inflammatory reactions and suppresses the immune response. Cortisolstimulates the RBC production. Aldosterone acts mainly at the renaltubules and stimulates the reabsorption of Na+ and water and excretionof K+ and phosphate ions. Thus, aldosterone helps in the maintenance ofelectrolytes, body fluid volume, osmotic pressure and blood pressure.Small amounts of androgenic steroids are also secreted by the adrenalcortex which play a role in the growth of axial hair, pubic hair and facialhair during puberty.
