Chapter 35, Problem 1FIB

Summary Introduction

Introduction:

The urinary system is a part of the organ system that participates in the formation of urine and the elimination of waste material from the body. Urine constitutes the waste products, foreign substances, and some ions and nutrients in excess of the body demands. The urinary system plays important role in eliminating cellular wastes and maintaining the homeostasis of the body.

Answer to Problem 1FIB

Correct answer:

Fill in the urinary organ of the following animals: earthworm: nephridia; insects: Malpighian tubules; flatworms: protonephridia. Which of these organs most closely resembles the nephrons of vertebrates? Nephridia.

Explanation of Solution

The lower organisms such as sponges and cnidarians do not contain urinary systems and they excrete their wastes with the help of diffusion and active transport through cell membranes. The structure and organization of urinary system vary among vertebrates and invertebrates. Earthworms have a tubular structure that constitutes the urinary system called nephridia. Freshwater flatworms have protonephridia as their urinary system which branches throughout the body within the interstitial fluid. Insects urinary system consists of small tubules called Malpighian tubules. The urinary system of annelids that is nephridia most closely resemble the nephrons of vertebrates.

Conclusion

The main function of the urinary system is to eliminate the cellular waste and maintain homeostasis.