Human Anatomy & Physiology (9th Edition)

Published by Pearson
ISBN 10: 0321743261
ISBN 13: 978-0-32174-326-8

Chapter 26 - Fluid, Electrolyte, and Acid-Base Balance - Review Questions - Critical Thinking and Clinical Application Questions - Page 1016: 5

Answer

Candace is a 26 year old female. Her blood pressure should be about 120 systolic/80 mm Hg diastolic. Therefore, she has high blood pressure HBP-- 180/110 mm Hg. Her signs and symptoms (SS) diagnosed by her doctor include: By auscultation: Cardiovascular murmurs (bruits) in the epigastric region of the abdomen. By imaging: Narrowed distal right renal artery Small right kidney Explanation: Candace's small right kidney is due to prolonged hypo-perfusion of that kidney secondary to the stenosis of the right renal artery. The cause of the renal artery stenosis could be atherosclerosis, fibromuscular dysplasia (FMD) in the renal artery, or to one of several uncommon genetic diseases. Because of the patient's age and sex the cause is most likely FMD. The juxtaglomerular apparatus of Candace's right kidney will sense the decrease in perfusion as a decrease in ECF Na+ ions and decrease in water (fluid). The kidney will respond by reabsorbing more sodium-- water will follow the sodium(Na+) ions. As a consequence, the osmolarity and blood volume will increase, and these effects will raise the blood pressure. At the same time, the kidney tubules will be stimulated to increase potassium excretion , so in this condition there will be lowered blood levels of potassium (K+)--hypokalemia. The hormonal interactions by which these effects are procured involve actions of renin, angiotensin I angiotensin II, and aldosterone ( adrenal corticosteroid). Lab tests of Candace's blood will show increased levels of renin, angiotensin I, and angiotensin II. Angiotensinogen will be lower than normal because of it's continual conversion to angiotensin I by angiotensin converting enzyme (ACE).

Work Step by Step

Prolonged hypotension causes the JGA to secrete renin. Prolonged kidney hypo-perfusion (ischemia) caused the kidney (right kidney) to develop scar tissue and atrophy. Angiotensinogen is produced by the liver and is always present in the blood. When renin reacts with angiotensinogen it converts the latter to the inactive hormone angiotensin I. Angiotensin I is converted to the active hormone angiotensin II by the action of angiotensin converting enzyme (ACE). Among other effects, angiotensin II stimulates the secretion of aldosterone by the zona glomerulosa cells of the adrenal glands. Some effects of aldosterone is to increase the reabsorption of sodium (Na+) and increase the excretion of potassium(K+) --hence the hypernatremia and hypokalemia in extracellular fluids --including the blood.
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