8 Difference Between Single And Double Circulation With Examples

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What Is Single Circulation?

Single circulation is a circulation in which blood flows once through the heart in one complete cycle of the body with the blood being pumped through the capillaries of the gills and on to the capillaries of the body tissues.

In an open circulatory system, blood vessels transport all fluids into a cavity. When the organism moves, the blood inside the cavity moves freely around the body in all directions. The blood bathes the organs directly thus supplying oxygen and removing waste from the organs. In this circulatory system, blood flows at a very slow speed due to the absence of smooth muscles.

 Single circulatory system is found in typical fish species and reptiles. The heart pumps deoxygenated blood to the gills where it is oxygenated. Also most invertebrates (crabs, insects, snails e.t.c) have open circulatory system.

What You Need To Know About Single Circulation

  1. A circulatory system in which blood flows once through the heart in one complete cycle of the body is referred to as Single circulation.
  2. Single circulatory system is found in typical fish species and reptiles. The heart pumps deoxygenated blood to the gills where it is oxygenated.
  3. Organisms that possess a single circulatory system have a double chambered heart.
  4. These circulatory system is referred to as ‘’single’’ circulatory because it is made up of only one circuit referred to as systemic circulatory system.
  5. Only venous blood passes through the heart.
  6. Single circulation is less efficient as gill capillaries slow down the blood flow; hence the body receives blood at a low pressure which decreases the rate of oxygen supply to the cells.
  7. In single circulation, the circulatory fluid is referred to as hemolymph (haemolymph).
  8. In single circulation, haemolymph is constrained within heart, gills and body tissues.

What Is Double Circulation?

Double circulation is a circulatory system in which blood flows twice through the heart in one complete cycle of the body. Most mammals including humans have a double circulatory system. This system is referred to as ‘’double’’ because they are made up of two circuits referred to as pulmonary and systemic circulatory systems.

Animals with double circulatory system have a four-chambered heart. The heart consists of left atria, right atria, left ventricles and right ventricles. The right atrium receives deoxygenated blood from the body and the right ventricle sends it to the lungs to be oxygenated. The left atrium receives oxygenated blood from the lungs and the left ventricle sends it to the rest of the body.

Through the systemic circulatory system, oxygenated blood travels from the left side of the heart to the other areas of the body. At various organ sites, exchange of gases, nutrients and waste through lymph occurs. This deoxygenated blood again goes back to the right side of the heart.

The pulmonary circulatory system or pathway carries the deoxygenated blood from the right side of the heart to the lungs. Exchange of oxygen and carbon dioxide takes place in the lungs and the blood is now oxygenated.

What You Need To Know About Double Circulation

  1. A circulatory system in which blood flows twice through the heart in one complete cycle of the body is referred to as double circulation.
  2. Occurs in all other vertebrates which include mammals and humans.
  3. Animals with double circulatory system have a four-chambered heart. The heart consists of left atria, right atria, left ventricles and right ventricles.
  4. These circulatory system is referred to as ‘’double’’ circulatory system because it is made up of two circuits referred to as the pulmonary and systemic circuits. The pulmonary circuit is between the heart and lungs whereas the systemic circuit is between the heart and the other organs.
  5. Mixed or oxygenated or venous blood passes through the heart.
  6. Double circulation is more efficient as blood at higher pressure especially in humans and mammals. This increases the rate of supply of glucose and oxygen to the cell and also rapid removal of wastes from them.
  7. In double circulation, the circulatory fluid is referred to as blood.
  8. In double circulation, blood is constrained within the heart and blood vessels.

Also Read: Difference Between Open And Closed Circulatory System

Difference Between Single And Double Circulation In Tabular Form

BASIS OF COMPARISON SINGLE CIRCULATION DOUBLE CIURCULATION
Description A circulatory system in which blood flows once through the heart in one complete cycle of the body.   A circulatory system in which blood flows twice through the heart in one complete cycle of the body.  
Occurrence Single circulatory system is found in typical fish species and reptiles. Occurs in all other vertebrates which include mammals and humans.  
Occurrence Organisms that possess a single circulatory system have a double chambered heart.   Animals with double circulatory system have a four-chambered heart.
Number Of Pulmonary Circuits These circulatory system is referred to as ‘’single’’ circulatory because it is made up of only one circuit referred to as systemic circulatory system.   These circulatory system is referred to as ‘’double’’ circulatory system because it is made up of two circuits referred to as the pulmonary and systemic circuits.
Heart Blood flow   Only venous blood passes through the heart.   Mixed or oxygenated or venous blood passes through the heart.  
Efficiency Single circulation is less efficient as gill capillaries slow down the blood flows; hence the body receives blood at a low pressure which decreases the rate of oxygen supply to the cells.   Double circulation is more efficient as blood at higher pressure especially in humans and mammals. This increases the rate of supply of glucose and oxygen to the cell and also rapid removal of wastes from them.  
Circulatory Fluid In single circulation, the circulatory fluid is referred to as hemolymph (haemolymph).   In single circulation, the circulatory fluid is referred to as hemolymph (haemolymph).  
Circulatory Fluid Path In double circulation, blood is constrained within the heart and blood vessels.   In single circulation, haemolymph is constrained within heart, gills and body tissues.