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Introduction to Body Fluids and Circulation

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What is Body Fluid?

Human circulatory system, or the cardiovascular system (along with body fluid), is of vital importance.  Together, they serve as a medium of transportation for oxygen, nutrients, hormones and other important substances. 


In this article, we will cover the different types of body fluids and circulation in brief. As a result, you will become familiar with the function and importance of body fluids in our system. 


Continue reading below to find more about body fluids and circulation Class 11!


Body fluids are several different types of liquids that are present inside the body. Generally, such fluids are either excreted out of the system or circulate within the body. 


In a broad sense, body fluids are classified as two intracellular fluid and extracellular fluid. In general, there are 7 body fluids, namely – blood, gastric juice, cerebrospinal fluid, saliva, semen, mucus and urine.  


On that note, let’s proceed to find out about the essential body fluids.


Types of Body Fluids

Undoubtedly blood and lymph are the most crucial body fluids. Human blood is a connective tissue fluid which comprises of white blood cells, red blood cells, plasma and platelets. 


Blood is red because of the presence of haemoglobin. Blood flows in two directions – from the heart to tissue and from tissues to heart. 


On the other hand, lymph is a transparent fluid which circulates inside lymphatic vessels and is also known as the tissue fluid and interstitial fluid. 


This image shows components of blood and lymph.


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Test Your Knowledge: 

Which of these is also known as RBC?

a) Leucocytes 

b) Erythrocytes 

c) Thrombocytes


Functions of Body Fluids

These are among a few functions of body fluids.

  1. Transportation of vital nutrients and oxygen to all essential organs.

  2. Removal of toxic waste.

  3. Regulation of body temperature.

  4. Regulation of metabolism.

DIY: Find out the largest lymphatic organ in the human body.


What is Circulation?

It is the flow of blood through blood vessels, which transport respiratory gases and nutrients. This movement is also responsible for removing waste from different body parts.


Other than these, the circulatory system is also responsible for transmitting hormones from endocrine glands to different organs. They also facilitate the destruction of pathogens and help to remove the body’s metabolic waste.


Notably, there are two types of circulatory systems – 

  1. Open circulatory system

  2. Closed circulatory system


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Mechanism of Circulation

In human beings, the heart is responsible for transporting blood all over the body. It comprises two upper chambers – atria or auricles and two lower chambers known as ventricles.


The arteries convey the oxygenated blood from the heart and other parts of the body. On the other hand, the veins send the deoxygenated blood to the heart from different organs.


However, there is an exception to it. To elaborate, the pulmonary vein supplies oxygen-rich blood to the heart, whereas the pulmonary artery takes deoxygenated blood away from it.


Maintenance of blood pressure and increased blood flow to tissues are among the most prominent advantages of double circulation. Also, it creates enough pressure to pump blood to the entirety of the system. 


Find more about the functioning of the heart by referring to quality body fluids and circulation NCERT notes and strengthen your knowledge further.


Disorders of the Circulatory System

These are some common disorders associated with this system –

  • Hypertension or high blood pressure.

  • Cardiac failure.

  • Angina.

  • Coronary Artery Disorder.

Learn more about circulation Chapter 12th from our subject experts by joining our live online classes. Also, by accessing our body fluids and circulation notes, you can improve your knowledge significantly. Likewise, if you are a NEET aspirant, you can access our body fluids and circulation NEET notes and boost your preparation significantly. 


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Body Fluids and Circulation - At A Glance

  • There are two types of circulatory systems prevalent in living beings, that is, the closed circulatory system and the open circulatory system.

  • The circulatory system consists of the heart, which is a muscular pump, blood vessels, and circulating fluid, that is, blood and lymph.

  • Blood is an essential body fluid that helps in the collection of wastes, transportation of gases, maintaining an optimum body temperature, and protecting the individual from diseases.

  • The wave of contraction in the heart travels from the S.A. node to the A.V. node followed by the bundle of HIS and finally to Purkinje fibres.

  • The main blood vessels that make a component of the circulatory system are arteries, veins, and capillaries.

  • The superior vena cava and the inferior vena cava collect blood from all parts of the body and bring it to the heart whereas pulmonary veins take the blood from the heart and give it to the aorta for distribution in all parts of the body.

  • The process by which blood is produced is known as hemopoiesis that occurs in the bone marrow of a human body.

  • The main components that make up the blood are plasma and cell components (RBCs, WBCs, and blood platelets).

  • A healthy individual has a normal blood pressure of 120/75 mm of mercury, though it can decrease or increase by 5 mm of mercury depending upon the person. The blood pressure of a human being is measured by a device known as a sphygmomanometer.

  • The colourless fluid that moves out of the capillary wall is known as lymph.

  • The ability by which the body protects itself from harmful substances is known as immunity and any disorders in this system lead to disorders like AIDS (caused by HIV virus) and SCID (an immunodeficiency disorder).

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FAQs on Introduction to Body Fluids and Circulation

1. How many types of body fluids are there?

Any fluid that is produced by a living organism is referred to as body fluid. These body fluids can be with extracellular fluid or intracellular fluid. Extracellular fluid refers to the fluid which is located outside the cells of the body, for example, lymph, intravascular fluid, transcellular fluid, and interstitial fluid. The water, dissolved ions, and molecules present inside a cell denote the intracellular fluid. Extracellular fluid constitutes 26% of the total body water composition whereas intracellular fluid constitutes 67% of the total body water composition. There are 7 types of body fluids, namely – blood, gastric juices, mucus, cerebrospinal fluid, saliva, semen and urine.  Body fluids and circulation are related, through circulation fluids help to regulate body temperature and water content, facilitates digestion, etc.

2. What is the significance of double circulation?

The circulatory path refers to the path that blood takes while travelling through different tissues and organs of the body to supply them with nutrients and oxygen. Since, in humans the blood comes back to the heart twice before completing one cycle, it is known as double circulation. Double circulation is an extremely important and efficient mode of circulation of blood. It ensures proper blood circulation within the body without getting oxygen-rich blood mixed with the deoxygenated one. Furthermore, this separation between the two types of blood supplies oxygen to blood cells and increases blood flow.

3. What are the components of the circulatory system?

Its major components include – heart, lungs, veins, arteries, portal vessels and coronary. If these components are broadly classified, then their components will be the heart, the blood vessels, and the blood. The heart refers to the main organ of the circulatory system that pumps blood into different parts of the body. The blood vessels that are a part of the circulatory system are arteries, veins, and capillaries. The arteries are the blood vessels that carry blood from the heart to other parts of the body, that is, away from the heart, while veins are the blood vessels that bring blood from all parts of the body to the heart, that is, towards the heart and capillaries are the smallest blood vessels which help in distributing the body fluid to all the parts of the body, that is, to each cell and tissue.

4. What are the different types of circulatory systems used for the circulation of body fluids?

The circulatory system of living beings is broadly divided into the open circulatory system and the closed circulatory system. When the blood flows through lacunae, sinuses, and large open spaces then that mode of circulation is known as the open circulatory system found in higher invertebrates like prawns and insects. The blood in the open circulatory system flows at very low pressure. Therefore, a direct exchange of nutrients and gases occurs between the blood and the tissues. The circulatory system in which blood does not come in direct contact with the tissue, and flows at very high pressure through the arteries, veins, and capillaries. This type of circulation is found in all vertebrates and also in echinoderms and molluscs. The closed circulatory system is a very efficient and rapid way of circulating body fluids.

5. What is the composition of body fluids and why is their circulation important?

There are three major types of body fluids in a human body, that is, extracellular body fluids, intracellular body fluids, and transcellular fluids. The extracellular body fluids are composed of cations and anions while the intracellular fluids are composed of 70% water and the rest are ions and molecules. The transcellular body fluid is composed of electrolytes like bicarbonates, sodium, and chlorides. The main functions of the body fluid in a human body include the facilitation of the transportation of nutrients and oxygen throughout the body, removal of waste from the body, regulation of body temperature, and maintaining an efficient metabolism in the body.

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