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

Renal Physiology: Regulation of Glomerular Filtration

Anatomy & Physiology

25. The Urinary System

Renal Physiology: Regulation of Glomerular Filtration

Previous problemNext problem

Problem 30

Textbook Question

Mannitol is a sugar that is filtered, but not reabsorbed, by the kidneys. What effect would drinking a solution of mannitol have on the volume of urine produced?

Verified step by step guidance

Understand the role of mannitol: Mannitol is an osmotic diuretic, meaning it increases the osmolarity of the filtrate in the kidneys, preventing water reabsorption in the nephron.

Identify the mechanism of action: Mannitol is filtered by the glomerulus but is not reabsorbed in the renal tubules. This creates an osmotic gradient that pulls water into the tubules, increasing urine volume.

Consider the physiological impact: Drinking a solution of mannitol would lead to an increase in the osmolarity of the blood plasma, which would then be filtered into the kidneys, enhancing the osmotic effect in the renal tubules.

Relate to urine production: The increased osmotic gradient in the renal tubules reduces water reabsorption in the collecting ducts, leading to a higher volume of urine being excreted.

Summarize the outcome: Drinking a solution of mannitol would result in increased urine production due to its osmotic diuretic properties, which prevent water reabsorption in the kidneys.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Play a video:

Was this helpful?

Key Concepts

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

Osmotic Diuresis

Osmotic diuresis occurs when substances that are not reabsorbed by the kidneys, like mannitol, increase the osmolarity of the renal tubules. This leads to an increase in urine production as water is drawn into the tubules to balance the osmotic gradient, resulting in a higher volume of urine.

Renal Filtration

Renal filtration is the process by which the kidneys filter blood to remove waste products and excess substances. Mannitol, being a small sugar molecule, is freely filtered at the glomerulus but is not reabsorbed in the renal tubules, which is crucial for understanding its diuretic effect.

Fluid Balance

Fluid balance refers to the homeostasis of body fluids, which is regulated by the kidneys. When mannitol is ingested, it disrupts this balance by increasing urine output, leading to potential dehydration if fluid intake is not maintained, highlighting the importance of monitoring fluid levels during osmotic diuresis.