NCERT Class 11 Biology Biology: Chapter 15 — Body Fluids and Circulation
This chapter, 'Body Fluids and Circulation,' from NCERT Class 11 Biology, details the essential transport mechanisms in living organisms. It explains how simple organisms use water circulation while complex ones rely on specialized body fluids like blood and lymph. The chapter elaborates on the composition of blood, a vital connective tissue comprising plasma and formed elements (erythrocytes, leucocytes, and platelets). Plasma, the fluid matrix, contains water, proteins (fibrinogen, globulins, albumins), minerals, and nutrients. Formed elements, making up about 45% of blood, include RBCs for oxygen transport, WBCs for defense, and platelets for clotting. Understanding these components and their functions is crucial for comprehending human physiology and the circulatory system within the CBSE curriculum.
Quick info
| Board | CBSE / NCERT |
|---|---|
| Class | Class 11 |
| Subject | Biology |
| Book | Biology |
| Chapter | Chapter 15 — Body Fluids and Circulation |
| Language | English |
| PDF type | NCERT Textbook |
| Session | CBSE 2026 |
| Reading time | 4 minutes |
| Word count | 642 |
Learning outcomes
- Understand the necessity of efficient transport systems in living organisms.
- Identify and describe the composition of blood, including plasma and formed elements.
- Explain the functions of erythrocytes, leucocytes, and platelets.
- Differentiate between granulocytes and agranulocytes and their specific roles.
- Recognize the importance of blood and lymph in maintaining homeostasis.
Vocabulary
| Word | Meaning |
|---|---|
| Plasma | The fluid matrix of blood, containing water, proteins, minerals, and nutrients. |
| Erythrocytes | Red blood cells (RBCs), responsible for transporting respiratory gases. |
| Leucocytes | White blood cells (WBCs), involved in the body's defense mechanisms. |
| Platelets | Thrombocytes, essential for blood clotting. |
| Fibrinogen | A protein in plasma essential for blood clotting. |
| Globulins | Proteins in plasma primarily involved in defense mechanisms. |
| Albumins | Proteins in plasma that help maintain osmotic balance. |
| Haemoglobin | An iron-containing protein in RBCs that transports oxygen. |
| Phagocytic | Cells capable of engulfing and destroying foreign particles or pathogens. |
| Histamine | A compound released by basophils involved in inflammatory responses. |
| Serotonin | A neurotransmitter and vasoconstrictor, also found in blood. |
| Heparin | An anticoagulant secreted by basophils. |
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Practice questions
- What are the main components of blood? Answer: Blood consists of a fluid matrix called plasma and formed elements: erythrocytes, leucocytes, and platelets.
- What is the primary function of erythrocytes? Answer: Erythrocytes (RBCs) are primarily responsible for the transport of respiratory gases like oxygen.
- Name the different types of leucocytes. Answer: Leucocytes include granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes).
- Which plasma protein is essential for blood clotting? Answer: Fibrinogen is the plasma protein essential for blood clotting.
- What is the role of albumins in plasma? Answer: Albumins help in maintaining the osmotic balance of the blood.
Frequently asked questions
What is the main function of blood in the human body?
Blood transports essential substances like nutrients and oxygen to cells and removes waste products, playing a vital role in maintaining homeostasis.
What percentage of blood is plasma?
Plasma constitutes approximately 55 per cent of the blood.
What are the three main types of formed elements in blood?
The three main types of formed elements are erythrocytes (RBCs), leucocytes (WBCs), and platelets.
Which cells are known as phagocytic cells?
Neutrophils and monocytes are phagocytic cells that engulf foreign organisms.
What is the average lifespan of RBCs?
The average lifespan of RBCs is about 120 days.
What is serum?
Serum is plasma without the clotting factors.
Related resources
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Topics covered
NCERT Class 11 Biology — Biology — Chapter 15 — Body Fluids and Circulation. Verified by NCERT Help Editorial Team. Reviewed on 29 Jul 2026. Last updated 10 Aug 2026.