Difference Between Open and Closed Circulatory System

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Difference Between Open and Closed Circulatory System

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A group of organs collectively referred to as the blood circulatory system, which includes the heart, blood vessels, and blood itself, circulates the entire body of a person or other animal. The cardiovascular system, commonly referred to as the vascular system, is composed mostly of the heart and blood arteries (from Greek kardia meaning heart, and from Latin vascula meaning vessels). The two components of the circulatory system are the systemic circulation or circuit and the pulmonary circulation or circuit. The cardiovascular system and vascular system are other names for the circulatory system. Large elastic arteries, large veins, other arteries, smaller arterioles, capillaries that connect to venules (small veins), and other veins make up the network of blood vessels that make up the vast vessels of the heart. In vertebrates, the circulatory system is closed, which implies that the blood never exits the system of blood vessels. Arthropods, for example, have an open circulatory system. Diploblasts without a circulatory system include sponges and comb jellies.

The fluid known as blood, which circulates throughout the body carrying nutrients and oxygen to the tissues as well as waste products, is made up of plasma, red blood cells, white blood cells, and platelets. The bloodstream also carries hormones, haemoglobin, gases like oxygen and carbon dioxide, and nutrients like proteins and minerals. These nutrients nourish the body, help the immune system fight disease, and support the body's capacity to maintain homeostasis by controlling pH and temperature.

In vertebrates, the lymphatic system is the circulatory system's opposite. This system returns excess plasma, which has been filtered from the body tissues' interstitial fluid by capillaries, to the blood circulation as lymph. Lymph takes far longer to go through the body than blood does.  Without the lymphatic system, a subsystem that is crucial to the blood circulatory system's operation, the blood would become dehydrated. The immune system and lymphatic system collaborate. The lymphatic system is an open system, in contrast to the closed circulatory system. It is referred to be a secondary circulatory system in certain publications. Numerous cardiovascular illnesses can have an impact on the circulatory system. Cardiothoracic surgeons specialize in operating on the heart and its surrounding parts, while cardiologists are medical specialists in the heart. Vascular surgeons concentrate on different circulatory system components.

The circulatory system, blood vessels, and heart all cooperate. All mammals have a cardiovascular system, which consists of the heart and blood arteries. Additional divisions of the circulatory system include pulmonary circulation and systemic circulation. Deoxygenated blood is transported from the right heart through the pulmonary circulation to the lungs, where it is given oxygen, and then returned to the left heart. Systemic circulation, a closed-loop system that sends oxygenated blood from the left heart to the rest of the body, returns deoxygenated blood to the right heart through the venae cavae. Microcirculation and microcirculation are two other ways to describe systemic circulation. A typical adult's blood volume ranges from five to six quarts (about 4.7 to 5.7 litres), or around seven per cent of their entire body weight. Red blood cells, white blood cells, platelets, and plasma all make up blood. The circulatory system and the digestive system collaborate to supply the body with the nutrition it needs to keep the heart beating. Additional circulatory pathways are connected, including coronary circulation, cerebral circulation, renal circulation, and bronchial circulation, which supply blood to the bronchi in the lungs as well as the heart itself.

Due to the closed nature of the human circulatory system, the blood is kept within the vascular system. To reach organs, nutrients must pass through the microcirculation's minuscule blood vessels. A network of lymphatic veins, lymph nodes, organs, tissues, and circulating lymph make up the lymphatic system, a crucial component of the circulatory system. An open system is this subsystem. One important job is to transport lymph, which drains and returns interstitial fluid to the lymphatic ducts, which then send it to the heart and the circulatory system. Working with the immune system to give defence against infections is another important job.

How Does the Circulatory System Work?

Your circulatory system functions because of the arteries, veins, and capillaries that make up your blood vessels. Your heart and lungs can continuously pump blood throughout your body thanks to these blood vessels. As follows:

  • The right ventricle, the lowest pumping chamber of the heart, delivers oxygen-poor blood to the lungs. Blood passes through the pulmonary trunk (the main pulmonary artery).
  • The blood cells in the lungs absorb oxygen.
  • Through pulmonary veins, the left atrium of the heart receives oxygenated blood from the lungs (upper heart chamber).
  • The left atrium sends oxygen-rich blood to the left ventricle (lower chamber). The muscular part of this heart pumps types of blood out to the body through the arteries.
  • As blood circulates throughout your body and organs, it absorbs and excretes nutrients, hormones, and waste products.
  • Carbon dioxide and deoxygenated blood are returned to the heart through the veins, where the heart then pumps the blood to the lungs.
  • The carbon dioxide leaves your lungs as you exhale.

Open vs. Closed Circulatory System

While the open circulatory system has open areas termed lacunae and sinuses, the closed circulatory system has closed blood channels called arteries and veins. This is the primary distinction between the open and closed circulatory systems. Arthropods and molluscs have an open circulatory system, whereas annelids and vertebrates have a closed circulatory system.

Difference Between Open and Closed Circulatory System in Tabular Form

Parameters of Comparison  Open Circulatory System  Closed Circulatory     system
Fluid Hemolymph is the name for the fluid that circulates in the open circulatory system.  Blood is the fluid that circulates in the body's closed circulatory system.
Flow Speed Hemolymph flows with a slow rate of motion. The blood is flowing with a quickening velocity.
Blood Veins The open circulatory system contains the dorsal blood vessel. The closed circulatory system has both ventral and dorsal blood vessels.
Nutrients The hemolymph and the tissues have a direct exchange of nutrients. The tissue fluid is the medium for the exchange of nutrients.
Organisms Arthropods and Mollusca both have an open circulatory system. Vertebrata and annelids have closed circulatory systems.

What is Open Circulatory System?

There are no blood arteries in the open circulatory system, and the organs and tissues are entirely covered in hemolymph (tissue fluid). Snails and insects (arthropods) are examples of species with this type of circulatory system (molluscs). In these kinds of animals, the core body cavity is known as the hemocoel. Blood circulates through the open areas known as lacunae and sinuses in the open circulatory system. Hemolymph, the flowing fluid, and hemocoel, the open cavity, are both medical terms. Since there are no closed blood arteries, the organs are entirely batched in the hemolymph. Arthropods and molluscs have this kind of circulatory system.

The blood is pumped directly into the bodily cavity in the open circulatory system. Only the dorsal blood arteries are visible, and there is no capillary system can be seen. The exchange of nutrients between the fluid and the tissue occurs directly because the hemolymph is in direct touch with the tissues. In comparison to a closed circulatory system, an open circulatory system has a slower rate of fluid flow. Additionally, there are no respiratory pigments present, and blood volume cannot be regulated. In comparison to a closed circulatory system, an open circulatory system is less effective. The latter is preferable for the movement of blood in large creatures, which is why octopuses, despite belonging to the mollusc family, have a closed circulatory system. Open circulatory systems are ones where blood permeates the body and may even be exposed to the outside world in places like the digestive tract, as opposed to being tightly enclosed in arteries and veins. Hemolymph is used in open circulatory systems in place of blood. The tasks of blood, lymph, and intestinal fluid—three distinct, highly specialized fluids in animals with closed circulatory systems—are carried out by this "hemolymph."

Organisms with open circulatory systems possess a "hemocoel" in place of a complicated and closed system of veins and arteries. Most invertebrate creatures have a central body cavity in which the circulatory and digestive systems are combined. Even though this hemocoel has "arteries" that allow blood to get to tissues, these arteries are not closed and do not circulate blood as quickly as closed, muscle-assisted arteries. The hemolymph directly absorbs nutrients from food and oxygen from the lungs or the hemocoel's breathing holes. Immune cells are present in hemolymph even though it lacks red blood cells as our own do. In organisms with open circulatory systems, oxygen is transported throughout the body by blue or yellow-green pigments instead of haemoglobin. Many animals with open circulatory systems only use their hearts to circulate hemolymph to specific compartments inside the hemocoel. Blood from these branches of the central body cavity must enter the tissues and subsequently return to the heart without the use of highly specialized pathways or muscle-assisted arteries like those seen in vertebrates.

What is Closed Circulatory System?

There are different blood vessels known as arteries and veins in the closed-type circulatory system. Blood travels through these closed blood arteries, as opposed to the open circulatory system, and carries nutrition, oxygen, hormones, etc. to various organs and tissues. Vertebrate species like humans have closed circulatory systems. Blood passes through the closed blood vessels known as arteries and veins in the closed circulatory system. In a closed circulatory system, the interstitial fluid, lymphatic fluid, and blood are different from one another. Vertebrates and annelids both have this kind of circulatory system.

The closed circulatory system of the body is powered by the heart, and every tissue and organ receives blood via the veins. This type of circulatory system includes the capillary system as well as the dorsal and ventral blood vessels. Because the blood travels through closed blood vessels, the tissues are not in direct contact with the blood. The volume of blood in a closed circulatory system can be controlled by the blood vessels' contraction and relaxation. Respiratory pigments are also found. Since a closed circulatory system operates at significantly higher blood pressure than an open circulatory system does, distribution happens much more swiftly as a result.

The blood is contained within blood vessels in a closed circulatory system. Blood is kept apart from bodily tissues in this way. The heart of this system continuously circulates blood through a pumping action. As a result, the blood is often pumped with more pressure. Blood does not fill bodily cavities in species with closed circulatory systems. Many animals, including humans, have a secondary system called the lymphatic system in addition to a circulatory system known as the cardiovascular system. Consider an elephant against a grasshopper as an example of an animal having a closed circulatory system versus an open circulatory system. In contrast to the open circulatory system, this type of circulation may provide blood to the extremities while maintaining greater blood pressure.

There are several heart arrangements for animals with closed circulatory systems. The four-chambered hearts of most mammals distinguish between oxygenated and deoxygenated blood. The two-chambered heart of a fish pumps blood directly to the gills, where it is oxygenated before travelling to the rest of the body. In the three-chambered hearts of frogs, oxygenated and deoxygenated blood can mingle before being pumped into the body.

Difference Between Open and Closed Circulatory System In Points

  • The open areas in the open circulatory system are referred to as lacunae and sinuses, whereas the closed blood vessels in the closed circulatory system are known as arteries and veins.
  • The words for the fluids that circulate through the open and closed circulatory systems, respectively, are haemolymph and blood.
  • Haemolymph flow in the open circulatory system is slow compared to the speed of blood in the closed circulatory system.
  • The closed circulatory system has both the dorsal and ventral blood vessels, whereas the open circulatory system only has the dorsal blood vessel.
  • The haemolymph and the tissues directly exchange nutrients in the open circulatory system. Contrarily, in a closed circulatory system, nutrients are exchanged through tissue fluid.


Although the open and closed circulatory systems differ greatly from one another, they both carry out the same task of transferring nutrients and moving fluid. Haemolymph is the flowing fluid in an open circulatory system, which lacks closed blood vessels. In contrast, blood is the flowing fluid in a closed circulatory system, which has arteries and veins. Any organism's circulatory system's primary job is to transport nutrients and oxygen to different organs and tissues while also removing waste products from them. The lymphatic system, which is part of the circulatory system and is responsible for circulating lymph, moves much more slowly than blood does.


  1. https://www.hindawi.com/journals/ijz/2009/301284/
  2. https://www.journals.uchicago.edu/doi/abs/10.1086/physzool.23.2.30152069


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