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NCERT Solutions for Class 11 Biology Chapter 15 Body Fluids and Circulation
Edited By Irshad Anwar | Updated on Apr 14, 2025 03:36 PM IST
NCERT Solutions for Class 11 Biology Chapter 15 Body Fluids and Circulation describes the major functions of blood and lymph in the body. Blood is a red fluid that transports oxygen, nutrients, and waste through blood vessels. It consists of plasma, red blood cells, white blood cells, and platelets. The chapter further discusses how blood clots are formed and why blood groups are important.
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This Story also Contains
- NCERT Solutions For Class 11 Biology Body Fluids and Circulation - PDF Download
- Access Answers to Class 11 Biology Chapter 15 Body Fluids and Circulation
- Important Topics Biology Chapter 15 Body Fluids and Circulation
- Practice Questions for Class 11 NCERT Body Fluids and Circulation
- Important Diagram of Body Fluids and Circulation Chapter
- Tips for Answering Class 12 Biology Chapter 15 NCERT Exercises
- NCERT Solutions for Class 11 Biology - Chapter Wise
It also explains the human circulatory system, describing the heart structure and function, the cardiac cycle, and double circulation. The regulation of cardiac activity and disorders of the circulatory system give detailed knowledge of the transportation of nutrients and oxygen around the body. NCERT solutions provide clear explanations, helping students understand complex topics with ease.
The NCERT Solutions for Class 11 Biology explain concepts in a detailed and step-by-step way, providing students with an easy understanding of important concepts. The solutions include important concepts such as the composition of blood, pathways of circulation, and the working of the heart in a simple and organised way.
NCERT Solutions For Class 11 Biology Body Fluids and Circulation - PDF Download
Students can download the complete questions with detailed answers in a PDF of this chapter for better learning:
Also, Read
- NCERT Notes for Class 11 Biology Chapter 15 Body Fluids and Circulation
- NCERT Exemplar for Class 11 Biology Chapter 15 Body Fluids and Circulation
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Apply NowAccess Answers to Class 11 Biology Chapter 15 Body Fluids and Circulation
The detailed answers to all the questions in this chapter are given below:
Answer:
The following formed elements were discovered in the blood:
(1) Erythrocytes: The most prevalent type of red blood cells, erythrocytes are coloured red by the red pigment known as haemoglobin. Every part of the body receives oxygen from erythrocytes. Some body parts, like the marrow of long bones, ribs, etc., continuously produce these. Each cubic millimetre of blood contains roughly 4–6 million red blood cells.
(2) Leukocytes: These are colourless cells devoid of haemoglobin. They fall into two major categories and are the largest cells in the body.
(a) Granulocytes- These leukocytes have granules in their cytoplasm and include neutrophils, eosinophils, and basophils. Neutrophils are phagocytic cells that protect the body against various infecting agents. Eosinophils are associated with allergic reactions, while basophils are involved in inflammatory responses.
(b) Agranulocytes- Lymphocytes and monocytes are agranulocytes. Lymphocytes generate immune responses against infecting agents, while monocytes are phagocytic in nature.
(3) Platelets- These are small irregular bodies present in the blood. They contain essential chemicals that help in clotting. The main function of platelets is to promote clotting.
Q2 What is the importance of plasma proteins?
Answer:
About 55% of blood is made up of plasma, the colourless fluid. It facilitates the transportation of waste materials, salts, food, and carbon dioxide, among other things. Proteins like albumins, globulins, and fibrinogens make up around 6.8% of plasma. The liver produces the plasma glycoprotein fibrinogen. It contributes to blood coagulation. One of the main proteins in plasma, globulin, shields the body from pathogens. One of the main proteins in plasma that keeps the fluid volume in the vascular space constant is albumin.
Q3. Match Column I with Column II :
| Column I | Column II |
|---|---|
| (a) Eosinophils | (i) Coagulation |
| (b) RBC | (ii) Universal Recipient |
| (c) AB Group | (iii) Resist Infections |
| (d) Platelets | (iv) Contraction of Heart |
| (e) Systole | (v) Gas transport |
Answer:
The correct matching is a- iii, b- v, c- ii, d-i, e- iv
| Column I | Column II |
|---|---|
| (a) Eosinophils | (iii) Resist Infections |
| (b) RBC | (v) Gas transport |
| (c) AB Group | (ii) Universal Recipient |
| (d) Platelets | (i) Coagulation |
| (e) Systole | (iv) Contraction of Heart |
Q4. Why do we consider blood as a connective tissue?
Answer:
For the following reasons, we view blood as connective tissue:
- The body's other organs are held together, connected, or supported by connective tissues.
- They are the body's most prevalent and plentiful tissue.
- Gases, nutrients, and hormones are all transported by blood between the body's organs.
- It circulates throughout the body.
- Blood is, therefore, regarded as connective tissue.
Q5. What is the difference between lymph and blood?
Answer:
Blood
- Blood is a red colour connective tissue.
- It consists of hemoglobin, red blood cells, white blood cells, and platelets. It circulates via arteries, veins, and capillaries.
- Blood transports gases and nutrients to various parts of the body.
Lymph
- Lymph is a white-coloured fluid in the body.
- It has white blood cells known as lymphocytes and flows through vessels called lymph.
- The lymph system facilitates the interchange of gases and nutrients between the body's cells and blood.
Q6. What is meant by double circulation? What is its significance?
Answer:
Double circulation occurs when blood flows through the heart twice in a single cycle. Although it can be found in birds, mammals, amphibians, and reptiles, it is most noticeable in birds and mammals because of their four-chambered hearts:
- Atrium on the right
- The right ventricle
- Atrium on the left
- The left ventricle
The circulation of blood is separated into:
Systemic circulation: Blood that has been oxygenated leaves the left ventricle and travels to the aorta, then passes through arteries to reach bodily tissues before returning to the right atrium as deoxygenated blood.
Pulmonary circulation: Blood that has lost oxygen travels from the right ventricle to the lungs for oxygenation before returning to the left atrium.
By separating oxygenated and deoxygenated blood, double circulation guarantees an effective oxygen supply.
Q7. (1) Write the differences between Blood and Lymph
Answer:
Blood | Lymph |
| Red liquid connective tissue that circulates in blood vessels. | White tissue fluid that circulates in lymphatic vessels. |
| Red due to the presence of haemoglobin. | Colourless or pale yellow due to the absence of haemoglobin. |
| Contains red blood cells (RBCs), white blood cells (WBCs), platelets, plasma, and haemoglobin. | Contains white blood cells (mainly lymphocytes), proteins, and plasma but lacks RBCs and platelets. |
| Transports oxygen, nutrients, hormones, and waste products throughout the body. | Helps in immunity, removal of waste, and exchange of nutrients and gases between blood and cells. |
| Travels through arteries, veins, and capillaries. | Travels through lymphatic vessels. |
| Circulated by the heart. | Moves slowly without a central pump, relying on muscle movement and valves. |
Q7. (3) Write the differences between Systole and Diastole
Answer:
Systoles:
- It is the heart's chambers contracting.
- It raises the heart's internal blood pressure.
- When the chambers are in systole, blood is pumped out.
Diastole:
- It is the heart's chambers relaxing.
- The heart's blood pressure drops.
- The chambers in diastole receive blood.
Q7 (4) Write the differences between P-wave and T-wave
Answer:
P-Wave:
- P-wave represents the depolarisation or electrical excitation of atria.
- Blood is pumped into the ventricles.
T-Wave
- T-wave represents the repolarization of ventricles.
- Blood is received by the atria.
Q8 Describe the evolutionary change in the pattern of heart among the vertebrates.
Answer:
- In vertebrates, the heart has changed from having two chambers in fish to having four chambers in mammals and birds.
- In fish, deoxygenated blood is pumped to the gills for oxygenation by the heart's two chambers.
- Amphibians have three chambers, a ventricle, two atria, and a mixture of oxygenated and deoxygenated blood in the ventricle.
- In reptiles, blood mixing is decreased by an incomplete septum.
- The four-chambered hearts of crocodiles, birds, and mammals guarantee that oxygenated and deoxygenated blood are completely separated.
This development increases the availability of oxygen and effectively controls blood flow.
Q9. Why do we call our hearts myogenic?
Answer:
Because the cardiac impulse starts in the heart's muscles, the organ is known as myogenic. The heart beats as a result of impulses produced by the SA node, a specialized cardiac tissue, spreading throughout the heart walls.
"Genic" means coming from, and "myo" means muscle.
Q10. The sino-atrial node is called the pacemaker of the heart. Why?
Answer:
The sino-atrial node is referred to as the heart's pacemaker due to its ability to generate a cardiac impulse. The cardiac impulse and action potential are produced by the sinoatrial node. The atria and ventricles then contract or relax as a result of this cardiac impulse spreading throughout them.
The maximum number of action potentials that the SA node can produce is roughly 70–75 per minute. It also regulates the heart's rhythmic contractions.
Answer:
The atrioventricular node and atrioventricular bundle are important for the heart's operation because:
- The SA node sends the cardiac impulse to the atrioventricular node.
- The cardiac impulse is sent farther toward the ventricle walls by the atrioventricular bundle, which emerges from the AV node.
Q12. Define the cardiac cycle and the cardiac output.
Answer:
The cardiac cycle
- The alternating contraction and relaxation of the heart chambers, which is also referred to as diastole and systole, is what causes the blood to circulate in the heart.
- There is a relaxation or expansion phase (diastole) after each contraction phase (systole).
- The cardiac cycle, which lasts 0.8 seconds, is the sequence of events that take place during a single heartbeat.
Heart Output - The cardiac output is the volume of blood pumped by each ventricle in a minute.
Q13. Explain heart sounds
Answer:
Every heartbeat is followed by a series of heart sounds.
- Every cardiac cycle produces the sounds "lub" and "dub."
- The first low-pitched sound, "lub," is produced when the tricuspid and bicuspid valves close.
- The second high-pitched sound, "dub," is produced when the semi-lunar valves close.
- For the diagnosis of heart-related conditions, these sounds are important.
Q14. Draw a standard ECG and explain the different segments in it.
Answer:
The heart's activity during a cardiac cycle is represented graphically by an ECG. Electrocardiograph, or ECG. Assume that a patient has three electrical leads attached to the device—one to the left ankle and one to each wrist—and that the device is continuously monitoring the patient's heart activity. Several leads are connected to the chest area for a thorough assessment of the heart's performance.
Every ECG peak is denoted by a letter, ranging from P to T, which represents a distinct electrical activity of the heart.
The P-wave is a representation of the electrical excitation (or depolarization) of the atria, which causes both atria to contract.
The QRS complex stands for the ventricles' depolarization, which starts the ventricular contraction. Shortly after, the contraction begins.
T-wave symbolizes the ventricles' repolarization or transition from an excited to a normal state.
The systole ends when the T-wave ends. Naturally, one can calculate a person's heartbeat rate by counting the number of QRS complexes that occur in a specific amount of time. For a given lead configuration, the ECGs from different people have a similar shape, so any deviation from this shape suggests a potential abnormality or illness. It is, therefore, very important from a clinical standpoint.
Important Topics Biology Chapter 15 Body Fluids and Circulation
The important topics and subtopics of body fluids and circulation are given below:
| Section | Topic |
|---|---|
| 15.1 | Blood |
| 15.1.1 | Plasma |
| 15.1.2 | Formed Elements |
| 15.1.3 | Blood Groups |
| 15.1.3.1 | ABO Grouping |
| 15.1.3.2 | Rh Grouping |
| 15.1.4 | Coagulation of Blood |
| 15.2 | Lymph (Tissue Fluid) |
| 15.3 | Circulatory Pathways |
| 15.3.1 | Human Circulatory System |
| 15.3.2 | Cardiac Cycle |
| 15.3.3 | Electrocardiograph (ECG) |
| 15.4 | Double Circulation |
| 15.5 | Regulation of Cardiac Activity |
| 15.6 | Disorders of the Circulatory System |
Types of Body Fluids in Chapter 15 Class 11 Biology Solutions
In this chapter, we learn two key body fluids:
- Blood – A connective tissue that is used in transportation.
- Lymph – A fluid that facilitates immunity and transportation of fat.
Knowledge of these fluids is significant for learning the NCERT Solutions for Class 11 concepts.
Components of Blood
The blood contains:
- Plasma: A fluid that carries nutrients and hormones.
- Formed Elements: Includes Red Blood Cells (RBCs), White Blood Cells (WBCs), and Platelets.
All these components play a major role in circulatory functions in Chapter 15, Class 11 Biology Solutions.
Blood Groups and Their Importance in Class 11 Biology: Body Fluids and Circulation
The solutions involve the discussion of blood groups:
- ABO Blood Group System: Divides blood into A, B, AB, and O groups.
- Rh Factor: Specifies if the blood group is Rh-positive or Rh-negative.
Types of Circulatory Systems
The class 11 biology topic body fluids and circulation states:
- Open Circulatory System – Arthropods and molluscs have it.
- Closed Circulatory System – Vertebrates have it, with the blood flowing through vessels.
Organisation of the Human Heart in Body Fluids and Circulation
The heart is the main organ of circulation. Important points are:
- Four Chambers: Right atrium, right ventricle, left atrium, and left ventricle.
- Valves: Prevent the backward flow of blood.
- Cardiac Cycle: Includes systole and diastole.
Blood Circulation in Chapter 15 Biology Class 11
Blood flows through:
- Pulmonary Circulation – between lungs and heart.
- Systemic Circulation – between body tissues and heart.
Both are important for the supply of oxygen and nutrients.
Lymphatic System in Class 11 Biology: Body Fluids and Circulation
The lymphatic system is a component of immunity and fluid balance. It comprises:
- Lymph Nodes
- Lymphatic Vessels
- Lymph Fluid
Disorders of the Circulatory System in Body Fluids and Circulation
Some of the common disorders are:
- Hypertension (High Blood Pressure)
- Coronary Artery Disease
- Anemia
- Hemophilia
NCERT Solutions for Class 11 Subject wise
Practice Questions for Class 11 NCERT Body Fluids and Circulation
Given below are some important practice questions from this chapter to help you revise and test your understanding effectively.
Question 1 :
Which of the following correctly explains a phase/ event in the cardiac cycle in a standard electrocardiogram?
(a) QRS complex indicates atrial contraction.
(b) QRS complex indicates ventricular contraction.
(c) The time between S and T represents atrial systole.
(d) P-wave indicates the beginning of ventricular contraction.
Answer:
The answer is option (b). The QRS complex indicates ventricular contraction
Explanation: The QRS wave starts with a downward deflection and continues as an upright triangular wave with downward waves as its base. It indicates ventricular depolarization or contraction.
Question 2 :
The instrument used for measuring blood pressure is called .......................
Answer:
The instrument used for measuring blood pressure is called a Sphygmomanometer.
Question 3 :
The walls of ventricles are much thicker than atria. Explain.
Answer:
The walls of ventricles are much thicker as they exert more pressure in the pumping of blood to most of the body parts. The left ventricle has three times thicker walls than the right. The atria is a collecting chamber and is thus thin-walled.
Question 4:
Explain different types of blood groups and donor compatibility by making a table.
Answer:
Blood group | Antigens | Antibodies | Can receive blood from Donor group | Can give blood to |
A | A | Anti-B | A, O | A and AB |
B | B | A | B, O | B and AB- |
AB (Universal Recipient) | A, B | Nil | A, B, AB, O | AB Only |
O (Universal Donor) | Nil | A, B | O Only | A, AB, B, and O |
Question 5:
Define cardiac cycle.
Answer:
The sequence of events that takes place during the completion of one heartbeat is known as the cardiac cycle. The human heart beats at a rate of 75 beats per minute in normal conditions.
The cardiac cycle consists of four main events: atrial systole, atrial diastole, ventricular systole, and ventricular diastole.
Question 6 :
Differentiate between arteries and veins.
| Arteries | Veins |
| Arteries are those blood vessels that carry blood away from the heart. | Veins are those blood vessels that carry blood in the direction of the heart. |
| Have more elastic tissues. | Have less elastic tissues. |
| Arteries have smaller lumen relative to diameter. | Veins have larger lumen relative to diameter. |
Question 7 :
Describe the structure of the human heart.
Answer:
In humans, the heart is situated between the two lungs and behind the sternum in the thorax.
1- Chambers: The human heart consists of four chambers- two atria and two ventricles. The right atrium receives Deoxygenated blood from the circulation of the body while the left atrium receives oxygenated blood from the lungs. The ventricles, on the other hand, are thickly muscular structures. The Right ventricle receives Deoxygenated blood from the right atrium and the left ventricle oxygenates blood from the left atrium.
2- The heart valves: Each layer between atrium and th corresponding ventricle remains guarded by an atrioventricular valve(AV). The right AV valve consists of three cups, whereas the left consists of two cups known as tricuspid and bicuspid valves respectively.
3- Sinoatrial and atrioventricular node (SAN and AVN) : Within the right atrium, near the opening of the superior vena cava, a small structure, called sinoatrial node is located. Similarly, near the tricuspid valve, within the right atrium, on the interatrial septum, another small structure atrioventricular node (AVN) is present.
Important Diagram of Body Fluids and Circulation Chapter
The human heart is a muscular organ that pumps oxygenated and deoxygenated blood throughout the body. It is made up of four chambers — two atria and two ventricles — along with related valves that facilitate unidirectional blood flow. Accurate labelling of the structures of the heart aids in understanding its role in circulation and the coordination of the cardiac cycle.
Tips for Answering Class 12 Biology Chapter 15 NCERT Exercises
Listed below are some important tips that students must follow to understand the concepts clearly and solve their questions skillfully:
Firstly, it's important to understand the basics of this chapter, like plasma, RBCs, WBCs, platelets, and double circulation, before going towards the questions.
Read the NCERT textbook carefully, line by line, and try to understand and visualize how the circulatory system works.
After reading, it's mandatory to make notes in your own words that can be used in the future also. Create short notes in your own words and highlight important definitions and diagrams.
Practice the diagrams like the heart, blood vessels, and circulatory routes to increase your understanding.
After that, try to solve all NCERT exercise questions without any help to test whether you have understood the chapter or not.
Try to revise the chapter regularly, and if you have any doubts, you can go through the NCERT Solutions.
NCERT Solutions for Class 11 Biology - Chapter Wise
Below mentioned are the Chapter-wise solutions:
The NCERT Solutions for Class 11 Biology Chapter 15, Body Fluids and Circulation, help students understand how blood and lymph work in the body. This chapter explains the structure and function of the heart, blood vessels, and circulatory system. It also covers important topics like blood groups, blood clotting, and heart disorders. These solutions make learning easier by providing clear answers and step-by-step explanations. By studying this chapter, students can understand how nutrients, oxygen, and waste are transported in the body.
Also, check NCERT Books and NCERT Syllabus here :
Frequently Asked Questions (FAQs)
1. What are the important topics covered in NCERT Solutions for Class 11 Biology Chapter 15?
Important Topics Covered:
- Blood composition
- Human circulatory system
- Heart structure and function
- Blood groups and clotting
- Double circulation
- Oxygen and carbon dioxide transport
- Lymph and its functions
- Heart disorders
2. How do NCERT solutions explain the composition of blood in Class 11 Biology?
Blood has plasma, red blood cells (RBCs), white blood cells (WBCs), and platelets.
3. What is the function of plasma according to NCERT Class 11 Biology Chapter 15?
The liquid part of blood called plasma transports waste materials, hormones, and nutrients.
Additionally, it has proteins that support immunity and coagulation.
4. How do RBCs and WBCs differ in their functions as per NCERT solutions?
Red blood cells, or RBCs, use hemoglobin to carry oxygen and return carbon dioxide to the lungs.
White blood cells, or WBCs, protect the body from foreign substances and infections.
5. What is the significance of the human circulatory system in Class 11 NCERT Biology?
- It delivers hormones, nutrients, and oxygen to body cells.
- It eliminates waste products like urea and carbon dioxide.
- It aids in preserving the pH balance and body temperature.
6. How is oxygen transported in the blood as per NCERT Class 11 solutions?
Hemoglobin in red blood cells binds to oxygen, which is then carried by arteries.
Carbon dioxide is returned to the lungs while oxygen is released for cellular respiration in tissues.
7. What is double circulation, and why is it important according to NCERT?
- In a single circulation cycle, the blood goes through the heart twice.
- Transporting deoxygenated blood to the lungs for oxygenation is known as pulmonary circulation.
- Systemic Circulation delivers blood enriched with oxygen to the body's organs.
- This separation keeps oxygenated and deoxygenated blood from mixing and guarantees an effective oxygen supply.
8. How does the heart function as per NCERT Class 11 Biology Chapter 15?
- The sinoatrial (SA) node produces the electrical impulses that cause the heart to beat.
- Systole, or contraction, and diastole, or relaxation, are the rhythmic contractions that it uses to pump blood.
- The heart's valves guarantee that blood only flows in one direction.
9. What are the different types of blood groups explained in NCERT Class 11 Biology?
- Based on the presence of antigen on RBCs, there are four primary types A, B, AB, and O.
- The O group is a universal donor, and the AB group is a universal recipient.
10. What are the differences between open and closed circulatory systems in NCERT solutions?
- Open Circulatory System: Blood circulates freely within bodily cavities (in insects, for example).
- Closed Circulatory System: Humans and other animals can be transported efficiently because blood is contained within vessels.
11. How is lymph different from blood as explained in NCERT Class 11 Biology?
- A colourless substance called lymph aids in immunity and removes extra fluid from tissues.
- Blood contains platelets, plasma, RBCs, and WBCs that transport nutrients and oxygen.
12. What is the cardiac cycle, and how is it explained in NCERT solutions?
One heartbeat, lasting roughly 0.8 seconds, is included.
- Systole: The contraction stage during which blood is expelled.
- Diastole: The relaxation stage during which blood fills the heart.
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