Question 46 of 782

Which of these products obtained from analyzing sweat from skin is not an excretory product?

  • A. water
  • B. Salts
  • C. Dust
  • D. Urea

Correct Answer: C

Explanation
The correct option is C. Dust. Detailed Explanation:
  1. Understanding Excretory Products:
  2. Excretory products are substances that are eliminated from the body as waste. The primary function of excretion is to remove harmful substances and maintain homeostasis (the balance of bodily functions).
  3. In humans, the main organs involved in excretion include the kidneys (which filter blood to produce urine), the lungs (which expel carbon dioxide), and the skin (which can excrete certain substances through sweat).
  4. Analyzing Sweat:
  5. Sweat is primarily composed of water (about 99%) and small amounts of salts (like sodium chloride), urea, and other substances. The primary purpose of sweating is thermoregulation (regulating body temperature) and, to a lesser extent, excretion.
  6. Evaluating Each Option:
  7. A. Water:
    • Water is a major component of sweat. While it is not a waste product in the traditional sense, it is excreted to help regulate body temperature and maintain fluid balance. However, it is not considered an excretory product in the context of waste removal.
  8. B. Salts:
    • Salts, particularly sodium chloride, are indeed excretory products. They are eliminated from the body through sweat, and their excretion helps maintain electrolyte balance and prevent dehydration.
  9. C. Dust:
    • Dust is not a product of the body; it is an external substance that can settle on the skin. While dust may be present on the skin's surface, it is not produced or excreted by the body. Therefore, it is not an excretory product.
  10. D. Urea:
    • Urea is a waste product formed from the breakdown of proteins in the liver. It is excreted in sweat, making it an excretory product. Urea helps in the removal of nitrogenous waste from the body.
  11. Why Other Options Are Incorrect:
  12. A. Water: While water is not a waste product in the same way as urea or salts, it is still excreted through sweat. However, it is not the primary focus of excretion; rather, it plays a role in thermoregulation.
  13. B. Salts: Salts are definitely excretory products, as they are eliminated from the body to help maintain electrolyte balance.
  14. D. Urea: Urea is a classic example of an excretory product, as it is a waste product of protein metabolism.
Summary of Key Points:
  • Excretory products are substances eliminated from the body to maintain homeostasis.
  • Sweat contains water, salts, and urea, all of which can be considered excretory products.
  • Dust is an external substance and not produced or excreted by the body, making it the correct answer to the question.
  • Understanding the distinction between excretory products and external substances is crucial for identifying what constitutes waste in biological systems.
Revision Summary:
  • Excretory products include substances like urea and salts, which are eliminated from the body.
  • Sweat is primarily composed of water, salts, and urea, all of which can be excretory.
  • Dust is not an excretory product; it is an external contaminant.
  • Recognizing the difference between internal waste and external materials is essential for understanding excretion.
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