Circulatory System

• Without Circulatory System

  • Hydras and Planarians; their gastrovascular cavity is lined with special cells that use diffusion to distribute nutrients to other cells.
• With an Open Circulatory System

  • Present in Arthropods and Mollusks (Insects, snails, etc).
  • Hemolymph is present instead of blood; heart to vessels to tissue spacces.
• With a Closed Circulatory System

  • Present in earthworms, squids, and octopuses.
  • Blood is present and hemoglobin is dissolved in the bloods
• Single-loop Circulatory Pathway

  • the heart has a single atrium and a single ventricle; the ventricle sends blood under pressure to the gills.
  • common in fishes.
• Double-loop Circulatory Pathways

  • has systemic and pulmonary circuits; present in 3 and 4-chambered hearts.