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

25. The Urinary System

The Nephron

Anatomy & Physiology

25. The Urinary System

The Nephron

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Multiple Choice

The descending limb of the nephron loop is impermeable to the movement of which substance out of the tubule?

Sodium ions

Urea

Glucose

Water

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Verified step by step guidance

Understand the structure and function of the nephron loop (loop of Henle). The nephron loop has two main segments: the descending limb and the ascending limb. Each segment has distinct permeability characteristics that are crucial for the kidney's ability to concentrate urine.

Recall that the descending limb of the nephron loop is highly permeable to water but impermeable to solutes, such as sodium ions (Na⁺), urea, and glucose. This allows water to leave the tubule by osmosis, concentrating the filtrate as it moves deeper into the medulla.

Eliminate options based on the permeability of the descending limb. Since the descending limb is impermeable to solutes, substances like sodium ions, urea, and glucose cannot move out of the tubule in this segment.

Focus on the specific question: Which substance is impermeable to movement out of the tubule in the descending limb? Water is not the correct answer because the descending limb is permeable to water. This leaves sodium ions, urea, and glucose as potential answers.

Conclude that the descending limb is impermeable to sodium ions, as it is a solute. This aligns with the physiological function of the nephron loop, where solutes are retained in the tubule during this segment, and water is reabsorbed into the surrounding medullary interstitium.