Circulation

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

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

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

• 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

Example: Single vs. Double Circulation