Types of the Circulatory System

The circulatory system in animals can be broadly classified into two types: open circulatory system and closed circulatory system. Each type has its own characteristics and is found in different groups of animals.

 

Open Circulatory System

Definition: In an open circulatory system, blood is pumped by the heart into an aorta, which then branches into arteries. These arteries open into a series of interconnected spaces called haemocoel, which collectively make up the body cavity. Blood does not stay confined within vessels, hence the term 'open' is used.

Examples of Animals: Open circulatory system is observed in animals belonging to phylum Arthropoda, such as crustaceans (e.g. crabs), spiders, and insects, as well as phylum Mollusca, such as snails and clams, and a group of protochordates called tunicates.

Characteristics: Blood under low pressure: In an open circulatory system, blood moves slowly between the tissues under low pressure, as there are no closed vessels to maintain high pressure.

Poorly controlled blood distribution: The distribution of blood to the tissues is not well-controlled, as the blood percolates back into the heart through open-ended veins gradually.

 

Closed Circulatory System

Definition: In a closed circulatory system, blood is confined to a single set of branching vessels, through which it is moved under pressure by one or more hearts. The blood flows in a circuit, following the same pathway repeatedly as it is pumped through the body. The blood flows from arteries to veins through capillaries, and the blood vessels are distinct and separate from the body cavity.

Examples of Animals: Closed circulatory system is observed in animals belonging to Annelids, such as earthworms, cephalopods, such as squids and octopuses, echinoderms, and vertebrates, including fishes, amphibians, reptiles, birds, and mammals.

CHARACTERISTICS

Greater efficiency: Closed circulatory system is considered more advanced as it allows for more efficient delivery of oxygen and nutrients to tissues and organs due to the higher pressure and control over blood flow.

Maintenance of blood pressure: The closed circulatory system allows for better maintenance of blood pressure throughout the body, as the blood is pumped under pressure by the heart.

Economy of blood volume: Closed circulatory system also allows for economy of blood volume, as the blood is contained within vessels and does not mix with body fluids, reducing the overall volume of blood needed to circulate.

Animals exhibit two distinct types of blood vascular systems: open circulatory system and closed circulatory system. The open circulatory system is characterized by blood flowing through interconnected spaces and is observed in certain arthropods and mollusks, while the closed circulatory system is characterized by blood flowing through distinct vessels and is observed in annelids, cephalopods, echinoderms, and vertebrates. The closed circulatory system is considered more advanced, as it provides greater efficiency, better control of blood pressure, and economy of blood volume.