Define open and closed type of circulatory systems.

OPEN CIRCULATORY SYSTEM:

• The blood is pumped by the heart and passes through the large vessels into large cavities or sinuses.
• The blood comes in direct contact with the tissue cells.
• Blood capillaries are absent.
  
• The blood is called haemolymph and the tissues through which the blood flows is called haemocoel.
• This type of circulatory system is found in arthropods and many molluscs.
  

CLOSED CIRCULATORY SYSTEM:

• The blood is pumped by the heart and circulated through closed network of blood vessels.
• The blood does not come in direct contact with the tissue cells.
• Blood capillaries are present.
• This type of circulatory system is found in annelids such as Pheretima, and many chordates.