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NEET Biology
Circulation of Blood

Frequently Asked Questions

Blood circulation is the process by which the heart pumps blood through a network of arteries, veins, and capillaries to deliver oxygen and nutrients to the body and remove waste products like carbon dioxide.

Pulmonary circulation: Carries deoxygenated blood from the right side of the heart to the lungs for oxygenation, then returns oxygenated blood to the left side of the heart. Systemic circulation: Distributes oxygenated blood from the left side of the heart to the rest of the body, and returns deoxygenated blood to the right side of the heart.

Blood enters the right atrium from the body through the vena cava, moves into the right ventricle, and is pumped to the lungs via the pulmonary artery. After being oxygenated in the lungs, blood returns to the left atrium, moves into the left ventricle, and is pumped out through the aorta to the rest of the body.

Arteries carry oxygen-rich blood away from the heart to various tissues of the body. The largest artery is the aorta, which distributes blood from the heart to the body.

Veins carry deoxygenated blood from the body back to the heart. The largest veins are the superior and inferior vena cava, which transport blood to the right atrium of the heart.

Capillaries are tiny blood vessels that connect arteries to veins. They are the site of gas, nutrient, and waste exchange between blood and tissues.

Oxygenated blood is rich in oxygen and is transported from the lungs to the heart and then to the body. Deoxygenated blood has low oxygen content and is carried from the body back to the heart and lungs for reoxygenation.

The heart acts as a pump, propelling blood throughout the body. It maintains two separate circuits: pumping deoxygenated blood to the lungs (pulmonary circulation) and oxygenated blood to the rest of the body (systemic circulation).

The cardiac cycle refers to the sequence of events that occur during one complete heartbeat. It includes systole (contraction of the heart chambers) and diastole (relaxation of the chambers), which ensure continuous blood flow through the heart and body.

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Circulation of Blood

The circulation of blood is a vital process in which the heart pumps blood throughout the body, delivering oxygen and nutrients to cells and removing waste products like carbon dioxide. This circulatory system is composed of two main circuits: the pulmonary circulation and the systemic circulation. 

1.0Circulatory System Anatomy

  • The human circulatory system consists of a network of arteries, veins, and capillaries, with the heart pumping blood through it. 
  • Its primary role is to provide essential nutrients, minerals, and hormones to various parts of the body. 
  • Alternatively, the circulatory system is also responsible for collecting metabolic waste and toxins from the cells and tissues to be purified or expelled from the body.  

2.0Organs of Circulatory System 

  • The human circulatory system comprises 4 main organs that have specific roles and functions. 
  • The vital circulatory system organs include:  
  • Heart  
  • Blood (technically, blood is considered a tissue and not an organ)  
  • Blood Vessels  Lymphatic system 

Heart 

  • The heart is a muscular organ located in the chest cavity, right between the lungs. 
  • It is positioned slightly towards the left in the thoracic region and is enveloped by the pericardium. 
  • The human heart is separated into four chambers; namely, two upper chambers called atria (singular: atrium), and two lower chambers called ventricles. 

Also Read: Coagulation of blood

3.0Types of Circulation

There are two types of circulation of blood taking place in the human heart. 

  • Pulmonary Circulation 
  • Systemic Circulation

4.0Pulmonary Circulation

  • The deoxygenated blood pumped into the pulmonary artery is passed on to the lungs from where the oxygenated blood is carried by the pulmonary veins into the left atrium. 
  • This pathway constitutes the pulmonary circulation. 

Significance of Pulmonary Circulation 

  • Supply deoxygenated blood to lungs for oxygenation and collect oxygenated blood from lungs.

Pulmonary Circulation flow chart

5.0Systemic Circulation 

The oxygenated blood entering the aorta is carried by a network of arteries, arterioles and capillaries to the tissues from where the deoxygenated blood is collected by a system of venules, veins and vena cava and emptied into the right atrium. This is the systemic circulation. 

Significance of Systemic circulation 

Supply oxygen and nutrients to various parts of the body and collect carbon dioxide and waste materials from different parts of the body. 

Systemic circulation flow chart

6.0Double Circulation 

  • Pulmonary circulation and Systemic circulation collectively called "Double circulation".
  • In double circulation, blood has to pass through the heart twice once in right part of the heart then goes to lungs for oxygenation and come back to the left side of the heart.

Double circulation

On the basis of supply to the organ circulation is of various types

  • For Brain – Cerebral Circulation 
  • For Kidneys – Renal Circulation 
  • For Heart – Coronary Circulation 
  • For liver – Hepatic Circulation
  • Coronary Circulation : A special coronary system of blood vessels is present in our body exclusively for the circulation of blood to and from the cardiac musculature.

Double circulation through different channels

Also Read:

Coronary artery disease

Body Fluids and Circulation

Cardiac Cycle

Blood Groups

Composition of blood

Functions of Blood

Lymphatic System

Pulmonary Artery

Double Circulation

Table of Contents


  • 1.0Circulatory System Anatomy
  • 2.0Organs of Circulatory System 
  • 3.0Types of Circulation
  • 4.0Pulmonary Circulation
  • 5.0Systemic Circulation 
  • 6.0Double Circulation