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What is the significance of juxtaglomerular apparatus (JGA) in kidney function?

             Juxtaglomerular apparatus (JGA) is a complex structure made up of a few cells of glomerulus, distal tubule, and afferent and efferent arterioles. It is located in a specialised region of a nephron, wherein the afferent arteriole and the distal convoluted tubule (DLT) come in direct contact with each other.
            The juxtaglomerular apparatus contains specialised cells of the afferent arteriole known as juxtaglomerular cells. These cells contain the enzyme renin that can sense blood pressure. When glomerular blood flow (or glomerular blood pressure or glomerular filtration rate) decreases, it activates juxtaglomerular cells to release renin.
           Renin converts the angiotensinogen in blood into angiotensin I and further into angiotensin II. Angiotensin II is a powerful vasoconstrictor that increases the glomerular blood pressure and filtration rate. Angiotensin II also stimulates the adrenal cortex of the adrenal gland to produce aldosterone. Aldosterone increases the rate of absorption of sodium ions and water from the distal convoluted tubule and the collecting duct. This also leads to an increase in blood pressure and glomerular filtration rate. This mechanism, known as renin-angiotensin mechanism, ultimately leads to an increased blood pressure.

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JGR plays important role in maintaining and regulation of kidney functioning by hormonal feedback mechanism, involving hypothalamus and to a certain extent, the heart
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The significant of jga: the jga play a complex regulatory role. A fall in glomerular blood flow /glomerular blood pressure/ GFR can activate the JG cells to release renin which convert angiotensin in blood to angiotensin l and further to angiotensin ll
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The juxtaglomerular apparatus is a specialised sensitive region that is formed by the cellular modifications in the distal convoluted tubule and the afferent arteriole at the location of their contact. Significance Its mechanism is via the renin-angiotensin-aldosterone system (RAAS). When the glomerular filtration rate dips, the juxtaglomerular apparatus stimulates, causing the secretion of renin. This renin converts a protein into a peptide, i.e., angiotensinogen, to angiotensin. Angiotensin is a hormone that elevates the GFR and the flow of blood in these three ways: Narrowing the efferent arterioles causes an increase in glomerular pressure. Triggering the walls of the PCT in order to reabsorb more water and NaCl. Triggers the adrenal gland to secrete aldosterone that facilitates reabsorption of water and NaCl in the DCT. The volume of blood and blood pressure thereby increases. The hypertonic urine and urine volume decreases.
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