Table of contents

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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

Which choice describes the countercurrent mechanism of the nephron loop?

It is the process by which the distal convoluted tubule secretes ions into the collecting duct.

It involves the exchange of substances between the descending and ascending limbs of the loop of Henle, creating a concentration gradient in the medulla.

It refers to the filtration of blood in the glomerulus and the reabsorption of water in the proximal convoluted tubule.

It describes the active transport of sodium ions from the collecting duct into the renal pelvis.

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Verified step by step guidance

Understand the structure of the nephron, particularly the loop of Henle, which consists of descending and ascending limbs.

Recognize that the countercurrent mechanism is crucial for concentrating urine and involves the exchange of substances between these limbs.

Identify that the descending limb is permeable to water but not to solutes, allowing water to leave the limb and enter the medulla, increasing the concentration of solutes inside the limb.

Note that the ascending limb is impermeable to water but actively transports sodium ions out into the medulla, decreasing the concentration of solutes inside the limb.

Realize that this exchange creates a concentration gradient in the medulla, which is essential for the kidney's ability to concentrate urine and conserve water.