Difference Between Open and Closed Circulatory Systems

Introduction

All living organisms need to be provided with essential nutrients, O and other important substances and other harmful substances should be continuously removed from the body. This is achieved with the help of the circulatory system present in almost all multicellular organisms.

Mostly two types of circulatory systems exist namely −

• Open circulatory system - Blood flows through a large vessel in open spaces. The network of vessels is absent in this system.

• Closed circulatory system - Blood flows through a defined path with the help of a well-developed vessel system.

Features of circulatory system

• Circulatory system comprises blood (specialized connective tissue), heart, a network of vessels and capillaries, and lymph.

• Most invertebrates possess an open circulatory system.

• Blood, the major body fluid flows through circulatory pathways.

• A network of arteries, capillaries, and veins helps in the exchange of substances between cells with help of blood.

Different types of Heart

• Fishes possess 2 chambered heart. It has one atrium and one ventricle. Deoxygenated blood flows through the heart and gets oxygenated with the help of diffusion by gills and supplied to other body parts and again cycle repeats. Thus it is called single circulation.

• Reptiles and amphibians (except crocodiles) possess 3 chambered heart with 2 atria and 1 ventricle. Blood gets mixed in ventricles thus it is called incomplete double circulation.

• In humans and crocodiles, 4 chambered heart is present with 2 atrium and 2 ventricles. Here no mixing of blood takes place. Oxygenated and deoxygenated blood are well separated. Thus it is called double circulation.

• Lymph system is a well-developed system that is also an important component of circulatory pathways.

Open circulatory system

• This type of system is mainly present in invertebrates.

• It includes members of phylum Arthropoda, phylum Mollusca (non-cephalopods), phylum Echinodermata, phylum Hemichordata and Tunicata.

• In this system the blood flows from the heart into the haemocoel. The blood is called haemolymph in such a case.

• The blood freely flows and there is no proper network of vessels.

• The organ and tissues of the organism are directly bathed in blood because of which there is no substantial difference between body fluid and interstitial fluid.

Closed circulatory system

• This type of system is mainly present in vertebrates. It is also present in a few invertebrates.

• It includes members of phylum Annelida, phylum Mollusca (Cephalopoda), and phylum Chordata.

• In this system the blood is pumped by the heart through a proper blood vessel network.

• The blood does not freely flow and the exchange of material takes place between cells through the network of capillaries.

Human circulatory system

• Humans have a closed type of circulatory system.

• They possess 4 chambered heart with 2 auricles and 2 ventricles.

• The human circulatory system comprises of the heart, blood vessels, lymphatic system, and blood.

• Chambers are well separated and mixing of oxygenated and deoxygenated blood does not take place. Thus it is very efficient.

• Complete double circulation takes place in humans one for oxygenated and the other for deoxygenated blood. It provides a steady supply of oxygenated blood throughout the body.

• It possesses an elaborate network of blood vessels and capillaries spread throughout the body.

• Blood vessels form a network through which blood travels throughout the body.

• Veins and arteries are the blood vessels found in the body.

• Oxygenated blood from the heart to other organs is carried through arteries. Deoxygenated blood from various body parts to the heart is carried through veins.

• Lumen of arteries is smaller than that of veins. It helps to maintain blood pressure throughout the body.

• Heart in humans is a muscular organ of the size of a fist present in the chest cavity and tilted a little towards the left side. It pumps blood throughout the body.

• Blood is the fluid connective tissue which is a vital part of the human circulatory system. It consists of plasma and formed elements. Its main function is to circulate various essential components throughout the body and helps in the removal of harmful metabolic products out of the body.

• Plasma is the fluid portion of blood and consists of 90 per cent of water. It also contains various factors required for the clotting of blood.

• Blood has 3 types of blood cells namely- leucocytes (WBC), erythrocytes (RBC), and platelets.

• Respiratory pigment Haemoglobin is present in erythrocytes. It is an iron compound which gives the characteristic red colour to blood and plays a major role in oxygen transport in our body.

Differences between open and closed circulatory systems

Open circulatory system	Closed circulatory system
Tissues and organs are directly bathed in blood.	Tissues and organs receive blood through a network of capillaries.
Fluid is called haemolymph.	Fluid is called blood.
Blood pumped in the haemocoel.	Blood is pumped by the heart through vessels.
Direct exchange of nutrients.	The exchange of nutrients takes place with help of tissue fluid.
Less developed.	More developed.
Low pressure of blood flow.	High pressure of blood flow.
Slower	Faster
Consumes less energy.	Consumes more energy.
Blood volume cannot be controlled.	Blood volume can be controlled.
The respiratory pigment is usually absent.	The respiratory pigment is usually present.
No transport of gases.	Transport of gases takes place.
Dorsal blood vessels are present.	Both dorsal and ventral blood vessels are present.
Example- Cockroach, spider, etc.	Example- Humans, Octopus, Earthworm, etc.

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Conclusion

Open and closed circulatory systems are two types of circulatory systems. The closed circulatory system has a network of capillaries through which blood flows and is more efficient and elaborate whereas in an open circulatory system blood is pumped in open cavities and is comparatively less developed. Different components of the closed circulatory system includes the heart, blood, arteries, veins, and capillaries.

FAQ’S

Q1. In which phyla is the open circulatory system present?

Ans. In phylum Arthropoda, phylum Mollusca (non-cephalopods), phylum Echinodermata, and phylum Hemichordata open circulatory system is present.

Q2. In which phyla is the closed circulatory system present?

Ans. In phylum Annelida, phylum Mollusca (cephalopods), and phylum Chordata closed circulatory system is present.

Q3. What is a fluid called in case of an open circulatory system?

Ans. The body fluid in case of an open circulatory system is called hemolymph.

Q4. Which circulatory system consumes more metabolic energy- open or closed?

Ans. The closed circulatory system consumes more metabolic energy than the open circulatory system.

Q5. What are open spaces called in the open circulatory system?

Ans. The open spaces in the open circulatory system are known as sinuses or lacunae.

Q6. Lumen of which is narrower according to the human circulatory system- arteries or veins and why?

Ans. The lumen of arteries is narrower than veins in the human circulatory system so as to maintain blood pressure throughout the body.