What is the Difference Between Excretion and Osmoregulation

The main difference between excretion and osmoregulation is that excretion is the process of removing waste products and toxic substances from the body, whereas osmoregulation is the process of maintaining a constant osmotic pressure within the body fluids. Furthermore, the three events in excretion are exhalation, defecation, and urination, while the two events of osmoregulation are endosmosis and exosmosis. 

Excretion and osmoregulation are two processes of the body. Generally, they help to maintain a constant environment in the body. 

Key Areas Covered 

1. What is Excretion
     – Definition, Types, Importance
2. What is Osmoregulation
     – Definition, Types, Importance
3. What are the Similarities Between Excretion and Osmoregulation
     – Outline of Common Features
4. What is the Difference Between Excretion and Osmoregulation
     – Comparison of Key Differences

Key Terms 

Excretion, Kidney, Lungs, Nephridia, Osmoregulation, Osmosis

Difference Between Excretion and Osmoregulation - Comparison Summary

What is Excretion 

Excretion is the process of eliminating metabolic wastes from the body. In vertebrates, the three main organs that take part in excretion are the lungs, kidneys, and the lower parts of the digestive system. Therefore, the three main events of excretion are exhalation, defecation, and urination. Lungs are responsible for the elimination of carbon dioxide from the body during exhalation.

Moreover, the lower parts of the digestive system collect and eliminate undigested materials from the body through defecation. Kidneys, on the other hand, remove excess water and electrolytes as well as metabolic products such as urea and uric acid from body fluids. It is also the main process of osmoregulation. Additionally, our skin removes a small amount of metabolic wastes and electrolytes from the body. 

Excretion vs Osmoregulation

Figure 1: Functional Unit of Kidney

Furthermore, in invertebrates, the main organs involved in excretion are nephridia. When considering the plants, the green plants produce two respiratory by-products: carbon dioxide and water. During photosynthesis, they also produce oxygen as a byproduct. However, the main route of elimination of these byproducts is the stomata in plants. Here, the elimination occurs in the gaseous form. Moreover, the removal of excess water in the form of water vapour occurs by means of transpiration or guttation.  

What is Osmoregulation 

Osmoregulation is the process of balancing salt and water inside the body. In other words, it regulates the osmotic balance across membranes. Therefore, it is the process of maintaining homeostasis of the water content. Generally, osmotic pressure is the tendency of water to move from one to another fluid by osmosis, which is the diffusion of water across a semipermeable membrane in response to an imbalanced osmotic pressure. Moreover, there are two processes of osmosis: exosmosis, which moves water out, and endosmosis, which takes water in.

Difference Between Excretion and Osmoregulation

Figure 2: Osmoregulation in Water

Furthermore, the two components dissolved in water are electrolytes and non-electrolytes, influencing the osmotic pressure of a particular fluid. Generally, electrolytes dissociate into ions during dissolution in the water while non-electrolytes do not dissociate into ions. Moreover, the main types of fluids that occur in the animal body are the cytosol of the cell, interstitial fluid that occurs in between cells, and blood plasma. Basically, kidneys are responsible for the removal of excess water and ions from blood plasma.  

Meanwhile, animals that maintain constant osmotic pressure inside the body independently from the outside environment are osmoregulators. In contrast, some euryhaline organisms can match the osmotic pressure of the body to the osmotic pressure to the outside environment. Thus, this tremendous ability to have variable osmotic pressures in the body allows these animals to live in different salinities during their lifetime. They are known as osmoconformers 

Similarities Between Excretion and Osmoregulation 

  • Excretion and osmoregulation are two mechanisms that help to control a constant internal environment inside animals. 
  • Therefore, they are features of homeostasis. 
  • In higher animals, kidneys are the organs responsible for both excretion and osmoregulation. 

Difference Between Excretion and Osmoregulation 

Definition 

Excretion refers to the process by which metabolic waste is eliminated from an organism, while osmoregulation refers to the process of regulating water potential to keep fluid and electrolyte balance within an organism. 

Significance 

The main difference between excretion and osmoregulation is that excretion is a process of eliminating unwanted substances from the body, while osmoregulation is the process of balancing intake and loss of water from the body. 

Events 

The three events in excretion are exhalation, defecation, and urination, while the two events of osmoregulation are endosmosis and exosmosis. 

Organs 

Kidneys, as well as the respiratory and digestive systems, are responsible for the excretion while kidneys are the organs responsible for osmoregulation. 

Conclusion 

Excretion is the process of removing mainly metabolic wastes from the body. Moreover, during excretion, the elimination of excess ions and toxins from the body occurs as well. The three main organs and organ systems that take part in excretion are kidneys, lungs, and rectum. On the other hand, osmoregulation is the process of regulating water balance inside the body. The main organ that takes part in osmoregulation is the kidney. It regulates a constant osmotic pressure inside the body. Therefore, the main difference between excretion and osmoregulation is the type of process. 

References:

1. “Excretion: In Plants and Animals, Human Excretory System with Examples.” Toppr, 26 Sept. 2018, Available Here.
2. “Osmoregulation and Osmotic Balance|Boundless Biology.” Lumen, Available Here.

Image Courtesy:

1. “Physiology of Nephron” By Madhero88 – Own workReferenceshere (CC BY 3.0) via Commons Wikimedia   
2. “Figure 41 01 02ab” By CNX OpenStax (CC BY 4.0) via Commons Wikimedia   

About the Author: Lakna

Lakna, a graduate in Molecular Biology & Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things

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