Amphibians: Circulatory System

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  • 0:05 Purpose of a…
  • 0:36 Types of Circulatory Systems
  • 2:19 Amphibians and Circulation
  • 3:18 Amphibian Circulatory Pathway
  • 4:37 Lesson Summary
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Lesson Transcript
Instructor: Danielle Haak

Danielle has a PhD in Natural Resource Sciences and a MSc in Biological Sciences

Amphibians use a double circulation system, but what does that mean? As an organism suited to live both on land and in water, amphibians have unique ecological characteristics. Learn more in this lesson!

Purpose of the Circulatory System

What does a circulatory system do anyway, and why is it important enough to dedicate an entire lesson to? Well, the circulatory system is responsible for moving blood and nutrients around the body - that's a pretty important task! In fact, the circulatory system has two main jobs. First, it transports blood with oxygen and nutrients to cells all over the body. Second, it picks up waste products from the cells to be transported out of the body, and it takes the de-oxygenated blood back to the lungs so it can reload.

Types of Circulatory Systems

The animal kingdom is pretty diverse, but if we go back to the basics, we find two types of circulatory systems: open systems and closed systems. With an open circulatory system, blood and nutrients are not restricted to moving within blood vessels. Body fluids can be pumped right from the heart into the body cavity, where they cover the internal structures and the oxygen and nutrients needed are directly absorbed. This is common in invertebrates like crustaceans and insects.

Then, there is the closed circulatory system - this is the type vertebrates like fish, mammals, and amphibians have. With this type, the blood and other fluids stay inside a set of blood vessels and are never freely released into the body cavity. Blood vessels vary in size, and oxygen and nutrients are exchanged between blood vessels and tissues through the tiniest ones.

Looking closely at closed circulatory systems, they can actually categorize them further based on the path the blood takes through the body.

In some animals, like fish, blood takes a single path around the body and moves in one direction in a circuit called the systemic circuit. Because of this unidirectional path, or circuit, (also called single circulation) the heart of a fish only needs two chambers: one to receive blood and one to pump it back out again.

As animals evolved, the process of delivering blood and removing wastes became more efficient. Mammals, reptiles, and amphibians use a system called double circulation. This means that there are now two pathways, or circuits, for blood to move around the body.

  • The first circuit circulates blood between the heart and the oxygen source (typically the lungs) (this is called pulmonary circulation),
  • The second circuit circulates blood between the heart and the rest of the body (this is called systemic circulation).

Amphibians and Circulation

Amphibians are a pretty unique type of animal, and their circulatory system is adapted to fit their ecological traits. As juveniles, amphibians live entirely in water, breathing through gills and swimming with the help of a tail. After metamorphosis, they develop lungs and grow legs; adults split their time between land and water. What makes amphibians especially cool is that they breathe in two ways. First, they breathe through lungs, just like mammals and reptiles, but they also absorb oxygen through their skin!

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