Body Fluids and Circulation NCERT Textbook PDF

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Body Fluids and Circulation NCERT Textbook With Solutions PDF Free Download

Chapter 18: Body Fluids and Circulation

You have learned that all living cells have to be provided with nutrients, O2, and other essential substances. Also, the waste or harmful substances produced, have to be removed continuously for the healthy functioning of tissues.

It is, therefore, essential to have efficient mechanisms for the movement of these substances to the cells and from the cells.

Different groups of animals have evolved different methods for this transport. Simple organisms like sponges and coelenterates circulate water from their surroundings through their body cavities to facilitate the cells to exchange these substances.

More complex organisms use special fluids within their bodies to transport such materials. Blood is the most commonly used body fluid by most of the higher organisms including humans for this purpose.

Another body fluid, lymph, also helps in the transport of certain substances. In this chapter, you will learn about the composition and properties of blood and lymph (tissue fluid), and the mechanism of circulation of blood is also explained herein.

18.1 BLOOD

Blood is a special connective tissue consisting of a fluid matrix, plasma, and formed elements.

18.1.1 Plasma

Plasma is a straw-colored, viscous fluid constituting nearly 55 percent of the blood. 90-92 percent of plasma is water and proteins contribute 6-8 percent of it. Fibrinogen, globulins, and albumins are the major proteins.

Fibrinogens are needed for clotting or coagulation of blood. Globulins primarily are involved in the defense mechanisms of the body and the albumins help in osmotic balance.

Plasma also contains small amounts of minerals like Na+ , Ca++, Mg++, HCO3 – , Cl– , etc. Glucose, amino acids, lipids, etc., are also present in the plasma as they are always in transit in the body.

Factors for coagulation or clotting of blood are also present in the plasma in an inactive form. Plasma without the clotting factors is called serum.

18.1.2 Formed Elements

Erythrocytes, leukocytes, and platelets are collectively called formed elements (Figure 18.1) and they constitute nearly 45 percent of the blood. Erythrocytes or red blood cells (RBC) are the most abundant of all the cells in the blood.

A healthy adult man has, on average, 5 million to 5.5 million RBCs mm–3 of blood. RBCs are formed in the red bone marrow in adults. RBCs are devoid of nuclei in most of the mammals
and are biconcave in shape.

They have a red-colored, iron-containing complex protein called hemoglobin, hence the color and name of these cells. A healthy individual has 12-16 gms of hemoglobin in every 100 ml of blood.

These molecules play a significant role in the transport of respiratory gases. RBCs have an average life span of 120 days after which they are destroyed in the spleen (the graveyard of RBCs). Leucocytes are also known as white blood cells (WBC) as they are colorless due to the lack of hemoglobin.

They are nucleated and are relatively lesser in number which averages 6000-8000 mm–3 of blood. Leucocytes are generally short-lived. We have two main categories of WBCs – granulocytes and agranulocytes.

Neutrophils, eosinophils, and basophils are different types of granulocytes, while lymphocytes and monocytes are the agranulocytes.

Neutrophils are the most abundant cells (60-65 percent) of the total WBCs and basophils are the least (0.5-1 percent) among them.

Neutrophils and monocytes (6-8 percent) are phagocytic
cells that destroy foreign organisms entering the body. Basophils secrete histamine, serotonin, heparin, etc., and are involved in inflammatory reactions.

Language English
No. of Pages12
PDF Size2.6 MB

NCERT Solutions Class 11 Biology Chapter 18 Body Fluids and Circulation

1. Name the components of the formed elements in the blood and mention one major function of each of them.


The components of the formed elements in blood are as follows:

  • Erythrocytes or Red blood cells – They carry oxygen and contain the pigment, hemoglobin. Hemoglobin reacts with oxygen to form Oxyhaemoglobin which carries oxygen to areas that are deprived of oxygen in the body.
  • Leucocytes or white blood cells – Lymphocytes are known to synthesize antibodies that neutralize or kill germs. Neutrophils act as a defense mechanism against bacteria known as phagocytosis.
  • Thrombocytes or blood platelets – They aid in the coagulation of blood

2. What is the importance of plasma proteins?


Significance of plasma proteins:

Some of the plasma proteins are

  • Globulins – They are involved in the defense mechanism of the body, and are also referred to as immunoglobulins
  • Albumins –They aid in maintaining the osmotic balance of the body
  • Fibrinogens – it plays a significant role in blood coagulation

3. Why do we consider blood as a connective tissue?


Blood is a connective tissue as it is mesodermally derived and contains an extra-cellular matrix known as plasma.

It is abundant and a widely distributed tissue in the body. Connective tissues link and bind, providing support to other organs of the body thereby transporting oxygen and other nutrients within the body, eliminating waste products from the body and flowing throughout the body. Hence, it is considered as connective tissue.

4. What is meant by double circulation? What is its significance?


Double circulation, as the name suggests, is where the blood circulates twice in the heart. Double circulation is possible as the heart is divided into four chambers, the right and the left halves by the atrioventricular septum.

The two circulations are:

  1. Pulmonary circulation
    • Blood in the right ventricle is pumped into the pulmonary arteries
    • For oxygenation, these pulmonary arteries transport deoxygenated blood to the lungs
    • The oxygenated blood is then sent to the left atrium from the lungs through the pulmonary veins
    • This type of circulation of blood is referred to as pulmonary circulation where blood is pumped via pulmonary blood vessels.
  2. Systemic circulation
    • It is a term used to refer to the major circulation of the body
    • Oxygenated blood is pumped from the left ventricle into the aorta
    • Furthermore, it is carried by the arteries, arterioles and the linkage of blood capillaries
    • Simultaneously, deoxygenated blood is accumulated in the right atrium through the inferior and superior vena cava
    • This circulation supplies nutrients and oxygen and carries away carbon dioxide and other toxic substances for elimination

Importance of double circulation:

  • This type of circulation checks and prevents the mixing of oxygenated and deoxygenated blood
  • In double circulation, oxygen is utilized efficiently

NCERT Class 11 Biology Textbook Chapter 18 Body Fluids and Circulation With Answer PDF Free Download

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