Question

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

Answer 1

• The juxtaglomerular apparatus (JGA) is a complex structure made up of a few cells of the 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 into 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, which 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 the 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 the renin-angiotensin mechanism, ultimately leads to increased blood pressure.

Answer 2

• A unique sensitive area known as the juxta glomerular apparatus (JGA) is created when cellular changes occur at the point of contact between the afferent arteriole and the distal convoluted tubule. JGA has a complicated regulatory function.
• Angiotensinogen in the blood is converted to angiotensin I and then angiotensin II by renin, which is released by the JG cells in response to a decrease in glomerular blood flow, glomerular blood pressure, or GFR.
• Due to its potent vasoconstrictor properties, angiotensin II raises GFR by raising glomerular blood pressure. Adrenal cortex activation by angiotensin II results in the release of aldosterone.
• Water and Na⁺ are reabsorption from the distal tubule by aldosterone. Additionally, this raises GFR and blood pressure.