Why Body Fluids and Circulation Are Vital for Living Organisms
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.
Transportation of vital nutrients and oxygen to all essential organs.
Removal of toxic waste.
Regulation of body temperature.
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 –
Open circulatory system
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.
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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).
FAQs on Body Fluids and Circulation: Types, Functions & Mechanism
1. What are body fluids and why is circulation essential for living organisms?
Body fluids are the liquids originating from inside the bodies of living organisms that are essential for transport and maintaining homeostasis. The most common body fluid is blood. Circulation is the process by which these fluids move throughout the body. This process is vital because it transports essential substances like oxygen, nutrients, and hormones to the cells, and simultaneously removes waste products like carbon dioxide and urea, ensuring the survival and proper functioning of every cell.
2. What are the main components of blood in the human body?
Blood is a specialised connective tissue consisting of a fluid matrix, plasma, and formed elements. The main components are:
- Plasma: A straw-coloured, viscous fluid constituting nearly 55% of the blood. It is primarily water (90-92%) but also contains proteins (Fibrinogen, Globulins, Albumins), glucose, amino acids, and electrolytes.
- Formed Elements: These constitute the remaining 45% of the blood and include:
- Erythrocytes (Red Blood Cells): Responsible for transporting oxygen.
- Leucocytes (White Blood Cells): Part of the immune system, they fight infections.
- Thrombocytes (Platelets): Cell fragments that help in blood clotting.
3. What is the difference between an open and a closed circulatory system?
The primary difference lies in how blood is circulated. In an open circulatory system, found in arthropods and molluscs, blood pumped by the heart passes through large vessels into open spaces or body cavities called sinuses. The blood flows slowly and directly bathes the tissues. In a closed circulatory system, found in vertebrates, the blood is always confined within a network of blood vessels (arteries, veins, and capillaries). This allows for more rapid and efficient transport of substances as the blood flows at a higher pressure.
4. Why is the human circulatory system considered a "double circulation" system, and what is its main advantage?
The human circulatory system is called double circulation because blood passes through the heart twice for each complete circuit of the body. It involves two distinct pathways: the pulmonary circulation (heart to lungs and back) and the systemic circulation (heart to the rest of the body and back). The primary advantage of this system is the complete segregation of oxygenated and deoxygenated blood. This ensures a highly efficient supply of oxygen to the body tissues, which is necessary to support the high metabolic rate of mammals and birds.
5. How does the human heart function as a pump? Explain the path of blood through its chambers.
The human heart acts as a muscular pump to propel blood. The path is as follows:
- Deoxygenated blood from the body enters the right atrium.
- It flows into the right ventricle, which pumps it to the lungs for oxygenation.
- Oxygenated blood from the lungs returns to the left atrium.
- It then flows into the left ventricle, the strongest chamber, which pumps it through the aorta to the rest of the body.
Valves between the chambers and in the major arteries ensure that blood flows in only one direction.
6. How do the structures of arteries, veins, and capillaries relate to their specific functions in circulation?
The structure of each blood vessel is perfectly adapted to its function:
- Arteries: Have thick, muscular, and elastic walls to withstand the high pressure of blood being pumped away from the heart.
- Veins: Have thinner walls as the blood pressure is much lower. They also contain valves to prevent the backflow of blood as it returns to the heart against gravity.
- Capillaries: Are extremely narrow and have walls that are only one-cell thick. This minimal thickness provides a very short diffusion path, facilitating the efficient exchange of gases, nutrients, and waste products between the blood and the body's cells.
7. What is the importance of blood groups in the context of blood transfusions?
Blood groups (like the ABO and Rh systems) are classifications of blood based on the presence or absence of specific inherited antigens on the surface of red blood cells. Their importance in transfusions is critical to prevent an immune reaction. If a patient receives blood from an incompatible group, their immune system will produce antibodies that attack the foreign antigens on the transfused red blood cells. This can lead to agglutination (clumping) of blood cells, which can block blood vessels and be fatal. Therefore, proper blood matching is essential for safe transfusions.
8. How is the normal rhythmic activity of the human heart regulated?
The human heart's rhythmic activity is auto-regulated or myogenic, meaning it can generate its own electrical impulses. This is controlled by specialised nodal tissue. The sino-atrial (SA) node, often called the pacemaker, initiates the impulse, causing the atria to contract. This impulse travels to the atrioventricular (AV) node, which, after a slight delay, relays it to the ventricles via the bundle of His and Purkinje fibres, causing them to contract. While the heart is auto-rhythmic, its rate can be moderated by neural signals from the brain and by hormones to meet the body's changing demands.
9. What are some common disorders of the circulatory system mentioned in the NCERT syllabus?
According to the CBSE/NCERT syllabus for the 2025-26 session, some common circulatory disorders include:
- Hypertension (High Blood Pressure): A condition where the pressure of the blood against the artery walls is consistently too high.
- Coronary Artery Disease (CAD): Often referred to as atherosclerosis, it affects the vessels that supply blood to the heart muscle. It is caused by the deposition of calcium, fat, and cholesterol, which narrows the lumen of the arteries.
- Angina: A type of chest pain caused by reduced blood flow to the heart muscle.
- Heart Failure: A condition where the heart muscle doesn't pump blood as well as it should.
10. How is lymph formed and why is the lymphatic system sometimes called the body's "second circulatory system"?
Lymph is formed when blood flows through capillaries. The high pressure forces some water and small solutes from the blood plasma out into the spaces between cells. This fluid is called interstitial fluid or tissue fluid. Most of this fluid returns to the capillaries, but some of it, along with proteins and other substances, enters a network of tiny vessels called lymphatic capillaries, at which point it is known as lymph. The lymphatic system is called a "second circulatory system" because it collects this excess fluid and returns it to the bloodstream, maintaining fluid balance. It also plays a crucial role in the immune system by transporting white blood cells and filtering pathogens at lymph nodes.
