ADRENAL GLAND SUPRARENAL GLANDS BY Mrs Gowri R
ADRENAL GLAND /SUPRARENAL GLANDS BY : Mrs. Gowri. R ASST. LECTURER BGI
Adrenal gland • Adrenal glands are the pair of endocrine glands , one each situated in relation to the upper pole of the kidneys. They lie retroperitoneally on each side of vertebral column in relation to posterior abdominal wall. They are golden yellow in color and weighs about 5 g. Shape : right gland is triangular or pyramidal in shape. Left suprarenal gland is semilunar in shape. Dimensions: • Ventrically: 3 cm • Breadth : 2 cm • Thickness: 1 cm
• Subdivision : Each gland has an outer cortex and inner medulla. They are entirely different in structure , function , and development. The cortex develops from mesoderm and medulla develops from neural crest.
Cortex cortex forms the main mass of the gland. It consists of the three cellular zones. • Zona glomerulosa : it consists of the small polyhedral cells arranged in rounded clusters. these cells secrete mineralocorticoids. • Zona fasciculata : it consists of large polyhedral cells with basophilic cytoplasm , arranged in straight column. These column have two cells width containing sinusoids between them. The cells of zona fasciculata secrete glucocorticoids. • Zona reticularis : this is the inner most part of the cortex. it consists of round cells , which forms a network. it secrete sex hormones
• Medulla it consists of chromaffin cells separated by wide venous sinusoids. they secrete adrenaline and noradrenaline. Blood supply : suprarenal is highly vascular gland. Each gland receives three sets of arteries : 1. Superior suprarenal arteries : branches of inferior phrenic arteries. 2. Middle suprarenal arteries : direct branches of abdominal aorta. 3. Inferior suprarenal arteries : arise from the renal arteries. These arteries pierce the capsule , supply the cortex and finally end in the medullary sinusoids. from the sinusoids , a single suprarenal veins comes out. On the right side , this veins ends in the inferior vena cava ; the left suprarenal veins ends in the left renal veins.
Lymphatic drainage : lymphatic drainage drains into the lateral aortic lymph nodes. MINERALOCORTICOIDS : ALDOSTERONE : aldosterone is the chief mineralocorticoid secreted from the zona glomerulosa of adrenal cortex. It has short half- life of 20 min. it metabolized in liver , kidneys and excreted in urine. Actions of aldosterone : Conversion of sodium and excretion of potassium : aldosterone acts on the distal convoluted tubules and collecting ducts of kidneys to increase the reabsorption of sodium in exchange of potassium. along with sodium , water is also reabsorbed leading to an increase in extracellular fluids (ECF). sodium reabsorption is also favoured in GI tract , salivary glands and sweat glands.
• Maintenance of ECF volume : Aldosterone helps in the reabsorption of water from the distal tubules of kidneys , along with sodium. It also plays the an important role in the long – term regulation of Bp , through ‘renin –angiotensin-aldosterone mechanism ‘. • Maintenance of acid –base balance : in case of metabolic acidosis , aldosterone stimulates sodium absorption in exchange for H ions thus, it helps in increasing the excretion of excess of acids. GLUCOCORTICOIDS : Glucocorticoids are the cortisol and corticosterone. They circulate in the blood by binding to corticosteroids-binding globulin, which is an alpha globulin present in plasma. the half –life of cortisol is 60 -90 min and corticosterone is 50 min/they are metabolized in liver. and excreted by urine.
Actions of glucocorticoids On metabolism of body 1. Effects n metabolism of carbohydrates : glucocorticoids tends to increase the blood sugar level by stimulating the gluconeogenesis and glycogenesis (synthesis of glycogen) in the liver and decreasing the peripheral utilization of glucose (anti – insulin effect ), they also decreases insulin sensitivity of the tissues. therefore , they may aggravate diabetes. 2. Effects on protein metabolism : glucocorticoids favour protein catabolism (protein breakdown )and decrease protein synthesis in extrahepatic tissues, especially skeletal muscle. as a results , there is a rise in plasma amino acids levels , which are diverted to form glucose(gluconeogenesis).
3. Effects of fat metabolism : glucocorticoids favour mobilization and utilization of fat from the adipose tissues , thereby increasing plasma free fatty acids levels. Excess cortisol causes redistribution of fat in the body , especially in the face and shoulder. 4. Effects on electrolyte and water metabolism : cortisol causes retention of Na and excretion of K. Cortisol maintains ECF volume by providing an adequate glomerular filtration rate. SYSTEMIC ACTION : 1. Effects on blood cells and lymphoid tissues : cortisol decreases number of circulating basophils , eosinophils and lymphocytes. it reduces the size of lymph nodes and cause atrophy of thymus. but it increases the number of neutrophils and RBCs.
2. antiallergic reaction : high levels glucocorticoids in plasma prevents histamine release. Hence , they are very useful in allergic reaction condition and delayed hypersensitivity reaction. they also relax bronchial smooth muscles , reduce the inflammatory changes and mucosal edema , therefore used in the treatment of bronchial asthma. 3. Immunosuppressive effect : cortisol inhibits the formation of lymphocytes and plasma cells and therefore , suppress immunity. this action occurs only after prolonged therapeutic use of glucocorticoids. 4. Effects of central nervous system : cortisol produces a sense of well being. in deficiency , there are personality changes. Irritability, apprehension and inability to concentrate.
5. actions on bone : glucocorticoids favour the osteoclastic activity and reduce the osteoblastic activity in bones. this leads to destruction of bones and osteoporosis. 6. effects on gastric secretions : glucocorticoids increases pepsin and HCl secretions in the stomach. hence , prolonged steroid therapy can cause peptic ulcer. ADRENAL ANDROGENS : Dehydroepiandrosterone is the principal sex hormone secreted from the adrenal cortex. It is secreted in both males and females and has weak androgenic activity. Large amounts secreted during foetal life , which forms precursors for the synthesis of oestrogen by placenta. In adult female , it contributes to increased muscle mass , growth of pubic and axillary hair , acne , etc. Its action in male is overshadowed by testicular testosterone.
HORMONES OF ADRENAL MEDULLA The hormones of adrenal medulla are the catecholamines they are : • Epinephrine (adrenaline) • Norepinephrine (noradrenaline) • Dopamine epinephrine is the predominant hormone. dopamine is a precursor of norepinephrine and epinephrine. Adrenal medullary hormone are synthesized from the amino acids phenylalanine and tyrosine(for the steps of catecholamine synthesis ) Norepinephrine is also found at the sympathetic nerve ending.
Actions of epinephrine and norepinephrine • Effects on CVS : increased heart rate , force of contraction leading to increase in cardiac output and SBP. Produce vasoconstriction except in skeletal muscle and liver where their action causes vasodilatation. • Metabolic effects : increase blood sugar levels by stimulating glycogenolysis in liver and muscles. also decrease insulin secretion, increase free fatty acids mobilization by stimulating lipases in adipose tissues and muscle. This provides energy to kidneys and cardiac muscle. Increase the BMR.
Effects on CNS Increase anxiety , restlessness Increase alertness response Others actions Decrease GI tract motility , Relax detrusor muscle and contract urinary sphincter , cause urinary continence • Stimulate sweating • Produce bronchodilation • Responsible for pupil dilatation and relaxation of accommodation ( ciliary muscle )of eye for far vision. • • •
TERMINOLOGY • Addison’s diseases : in this conditions of the deficiency of the both glucocorticoids and mineralocorticoids. • Cushing syndrome : is a condition occurs due to excess cortisol in the body due to prolonged use of high doses of steroids. • Hormones of adrenal cortex ØGlucocorticoids ØMineralocorticoid ØSex steroids Androgens: are group of hormones that play a role in male are testosterone.
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