Nematode Respiratory System

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  • 0:00 What Are Nematodes?
  • 0:52 Diffusion
  • 1:41 Cuticle
  • 2:07 Nematode Respiration
  • 3:03 Lesson Summary
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Lesson Transcript
Instructor: Dominic Corsini
This lesson investigates the respiratory system of nematodes. It discusses how these organisms exchange gases with the atmosphere despite their lack of lungs, trachea, and other respiratory anatomy commonly found in other animals.

What Are Nematodes?

Many people have never heard of nematodes. Yet they are the most numerous multicellular organisms on the planet. So what are nematodes? They are microscopic worms that inhabit almost every ecosystem on Earth. In fact, even a single scoop of soil contains thousands of nematodes.

Like many living things, nematodes breathe, or exchange gases with the atmosphere. However, unlike many living things, nematodes lack a formal respiratory system responsible for performing gas exchange. In mammals and reptiles, this system consists of trachea, lungs, and bronchial tubes. In the respiratory system of fish, the dominant feature is gills. Nematodes do not possess any of these organs. Instead, nematode respiration works in a much more simplistic manner. We'll examine this in the next section.


Nematode respiration relies on a process called diffusion. Diffusion is when molecules, in this case gas molecules, move from an area of higher concentration into an area of lower concentration. For example, what would happen if you placed a drop of blue food coloring into a glass of water? Would the drop remain suspended in one location or would it slowly spread out? Yep, it would slowly spread throughout the glass until all the water was tinted blue. This simple example demonstrates diffusion in that the drop initially had a high concentration of blue dye, and the water had a low concentration. The blue dye then moved from the area of greater concentration (the drop) into an area of lower concentration (the water), thus precisely modeling our definition of diffusion.


Now let's look at how this concept applies to nematode respiration. We're primarily concerned with two gases: oxygen, the primary gas animals inhale for use in respiration, and carbon dioxide, a waste product and the primary gas animals exhale. The nematode takes in and expels out these gases through their outlet layer called a cuticle, which is essentially like an extra layer of skin that is semi-permeable.

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