Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

26. Fluid and Electrolyte Balance, Acid Base Balance

Acid-Base Balance

Anatomy & Physiology

26. Fluid and Electrolyte Balance, Acid Base Balance

Acid-Base Balance

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5:24 minutes

Problem 24

Textbook Question

During a routine medical checkup, Shelby, a 26-year-old physiotherapy student, is surprised to hear that her blood pressure is 180/110. She also has a rumbling systolic and diastolic abdominal bruit (murmur) that is loudest at the mid-epigastric area. Her physician suspects renal artery stenosis (narrowing). She orders an abdominal ultrasound and renal artery arteriography, which confirm that Shelby has a small right kidney and the distal part of her right renal artery is narrowed by more than 70%. Her physician prescribes diuretics and calcium channel blockers as temporary measures, and refers Shelby to a cardiovascular surgeon. Explain the connection between Shelby's renal artery stenosis and her hypertension. Why is her right kidney smaller than her left? What would you expect Shelby's blood levels of K⁺, Na⁺, aldosterone, angiotensin II, and renin to be?

Verified step by step guidance

Step 1: Understand the connection between renal artery stenosis and hypertension. Renal artery stenosis reduces blood flow to the affected kidney, which is interpreted by the kidney as low blood pressure. This triggers the renin-angiotensin-aldosterone system (RAAS), leading to increased production of renin, angiotensin II, and aldosterone. These hormones cause vasoconstriction and sodium retention, raising systemic blood pressure.

Step 2: Explain why the right kidney is smaller than the left. Chronic reduced blood flow to the right kidney due to the stenosis leads to ischemia (lack of oxygen and nutrients). Over time, this can cause atrophy (shrinkage) of the kidney tissue, making the right kidney smaller than the left.

Step 3: Predict Shelby's blood levels of renin. Renin levels are expected to be elevated because the right kidney is sensing reduced blood flow and attempting to compensate by activating the RAAS.

Step 4: Predict Shelby's blood levels of angiotensin II and aldosterone. Angiotensin II levels would be elevated due to increased renin activity, and aldosterone levels would also be elevated as a downstream effect of angiotensin II, promoting sodium retention and contributing to hypertension.

Step 5: Predict Shelby's blood levels of K⁺ and Na⁺. Sodium (Na⁺) levels may be elevated due to aldosterone-induced retention, while potassium (K⁺) levels may be decreased because aldosterone promotes potassium excretion in the urine.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Renal Artery Stenosis

Renal artery stenosis is a condition characterized by the narrowing of one or both renal arteries, which supply blood to the kidneys. This narrowing can lead to reduced blood flow to the kidneys, triggering a series of physiological responses that often result in hypertension. The kidneys respond to perceived low blood flow by activating the renin-angiotensin-aldosterone system (RAAS), which increases blood pressure to restore perfusion, thus creating a direct link between renal artery stenosis and hypertension.

Kidney Size and Function

The size of the kidneys can be affected by various factors, including blood flow and overall function. In cases of renal artery stenosis, the affected kidney may receive less blood and oxygen, leading to atrophy or shrinkage over time. This phenomenon is known as renal hypoplasia, where the smaller kidney is often the one with compromised blood supply, while the other kidney may remain normal or hypertrophied due to compensatory mechanisms.

Hormonal Responses in Hypertension

In response to renal artery stenosis, the kidneys release renin, which catalyzes the production of angiotensin II, a potent vasoconstrictor. Angiotensin II stimulates the adrenal glands to secrete aldosterone, promoting sodium and water retention, which further elevates blood pressure. Consequently, in Shelby's case, we would expect elevated levels of renin and aldosterone, while potassium (K⁺) levels may be low due to the effects of diuretics, and sodium (Na⁺) levels may be high due to fluid retention.

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