Question

What is the function of RAAS in the human excretory system

Answer 1

When the plasma sodium concentration is lower than normal or the renal blood flow is reduced, the juxtaglomerular cells in the kidneys convert prorenin (an intracellular protein) into renin, which is then secreted directly into thecirculation. Plasma renin then cuts a short, 10 amino acid long, peptide off a plasma protein known asangiotensinogen. The short peptide is known as angiotensin I. Angiotensin I is then converted, by the removal of 2 amino acids, to form an octapeptide known as angiotensin II, by the enzyme angiotensin-converting enzyme (ACE) found in the endothelial cells of the capillaries throughout the body, within the lungs and the epithelial cells of the kidneys. Angiotensin II is a potent vaso-active peptide that causes arterioles to constrict, resulting in increased arterial blood pressure. Angiotensin II also stimulates the secretion of the hormone aldosterone from the adrenal cortex.Aldosterone causes the tubular epithelial cells of the kidneys to increase the reabsorption of sodium ions from the tubular fluid back into the blood, while at the same time causing them to excrete potassium ions into the tubular fluid which will become urine.