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Wize University Biology Textbook > Animal Physiology

Circulation

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Circulation

  • Every cell must get rid of CO2 and receive O2
  • Circulatory Systems: connect the gas-exchange surfaces to the body
  • Allows organisms to grow larger

Circulatory systems


Three Main Components

  • Circulatory Fluid: fluid that transports O2 and CO2 Examples: Hemolymph, Blood
  • Vessels: structure that allows the hemolymph to move throughout the body Example: Blood veins
  • Muscular Pump: contracts to pump the hemolymph Example: Heart

Open vs Closed Circulatory systems

  • Open Circulatory System: hemolymph pools in body cavity and contacts organs directly
  • Hemolymph is pumped from the sinuses through the heart
  • Hemolymph is not always in vessels! Examples: Arthropods, Clams
  • Closed Circulatory System: blood remains in vessels, does not surround organs Examples: Cephalopods, all vertebrates



Photo by Tomas Kebert | CC BY

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Vertebrate Circulatory Systems

  • Cardiovascular system: a name for the circulatory system in humans and vertebrates
  • Three types of blood vessels
  • Arteries: carry blood from heart to organs
  • Capillaries: thin branching veins that allow blood to enter tissues and organs
  • Veins: carry blood from organs to heart
  • Hearts
  • Atria: chamber the receives blood into heart
  • Ventricle: larger, muscular chamber, pumps blood out of heart



Photo by Gccwang | CC BY

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Single vs Double Circulation



  • Single Circulation:
  • Heart has only 1 Atrium and 1 Ventricle
  • Blood only enters heart ONCE per cycle
  • Blood travels
  • Heart > Gills > Body (Organs) > Heart Examples: Fish and Sharks


Photo by Lennert B. | CC BY


  • Double Circulation:
  • Heart has 2 Atria and 2 Ventricles
  • Blood enters the heart TWICE per cycle
  • Blood travels
  • Heart > Lungs > Heart > Body > Heart Examples: Humans and Amphibians








Photo by Gccwang | CC BY
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What are the three main components of the circulatory system?
What type of blood vessels contact the organs directly?
checklist
Mark Yourself Question
  1. Grab a piece of paper and try this problem yourself.
  2. When you're done, check the "I have answered this question" box below.
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Describe the main difference between Single Circulation and Double Circulation systems.