Online Self Test
Learn & Practice Quizzes & Challenges Competitive Exams
 

Body Fluids and Circulation – CBSE NCERT Study Resources

Previous ChapterNext Chapter
Previous Chapter Next Chapter

Study Materials

11th

11th - Biology

Body Fluids and Circulation

Jump to Question Sets

Overview of the Chapter

This chapter explores the concepts of body fluids and circulation, focusing on the composition and functions of blood, lymph, and the circulatory system in humans. It covers the structure of the heart, blood vessels, and the mechanism of blood circulation, along with common disorders related to the circulatory system.

Body Fluids: The liquids present in the body that are essential for transporting nutrients, gases, and waste products. These include blood and lymph.

Blood

Blood is a specialized connective tissue composed of plasma and formed elements (RBCs, WBCs, and platelets). It plays a crucial role in transportation, defense, and homeostasis.

Plasma: The liquid matrix of blood, containing water, proteins, hormones, and waste products.

Formed Elements

  • Erythrocytes (RBCs): Carry oxygen via hemoglobin.
  • Leukocytes (WBCs): Provide immunity against pathogens.
  • Thrombocytes (Platelets): Assist in blood clotting.

Lymph (Tissue Fluid)

Lymph is a colorless fluid derived from blood plasma that circulates in the lymphatic system. It transports nutrients, hormones, and immune cells while draining excess tissue fluid.

Circulatory System

The human circulatory system consists of the heart, blood vessels (arteries, veins, capillaries), and blood. It functions as a double circulation system (pulmonary and systemic).

Structure of the Heart

The heart is a muscular organ with four chambers (two atria and two ventricles). Valves prevent backflow of blood.

Blood Vessels

  • Arteries: Carry oxygenated blood away from the heart (except pulmonary artery).
  • Veins: Carry deoxygenated blood toward the heart (except pulmonary vein).
  • Capillaries: Facilitate exchange of materials between blood and tissues.

Cardiac Cycle

The cardiac cycle involves rhythmic contraction (systole) and relaxation (diastole) of the heart chambers, regulated by the sinoatrial node (pacemaker).

Disorders of the Circulatory System

  • Hypertension: High blood pressure leading to cardiovascular risks.
  • Coronary Artery Disease (CAD): Reduced blood flow to the heart due to plaque buildup.
  • Heart Failure: Inability of the heart to pump blood efficiently.

All Question Types with Solutions – CBSE Exam Pattern

Explore a complete set of CBSE-style questions with detailed solutions, categorized by marks and question types. Ideal for exam preparation, revision and practice.

Very Short Answer (1 Mark) – with Solutions (CBSE Pattern)

These are 1-mark questions requiring direct, concise answers. Ideal for quick recall and concept clarity.

Question 1:
Define plasma in blood.
Answer:

Plasma is the liquid part of blood containing water, proteins, and salts.

Question 2:
Name the iron-containing pigment in RBCs.
Answer:

Hemoglobin.

Question 3:
What is the function of platelets?
Answer:

Platelets help in blood clotting.

Question 4:
Which blood group is a universal donor?
Answer:

O negative.

Question 5:
What is lymph?
Answer:

Lymph is a colorless fluid containing WBCs and drained from tissues.

Question 6:
Name the largest artery in the human body.
Answer:

Aorta.

Question 7:
What is the normal blood pressure range in humans?
Answer:

120/80 mmHg.

Question 8:
Define cardiac cycle.
Answer:

The cardiac cycle is the sequence of events in one heartbeat.

Question 9:
Which heart valve prevents backflow into the left atrium?
Answer:

Bicuspid (mitral) valve.

Question 10:
What is the role of SA node?
Answer:

SA node initiates the heartbeat.

Question 11:
Name the blood vessel carrying oxygenated blood to the heart.
Answer:

Pulmonary vein.

Question 12:
What causes systolic pressure?
Answer:

Systolic pressure is caused by ventricular contraction.

Question 13:
Which blood cells produce antibodies?
Answer:

B-lymphocytes (B-cells).

Question 14:
What is erythropoiesis?
Answer:

Erythropoiesis is the formation of RBCs.

Question 15:
Define plasma in the context of body fluids.
Answer:

Plasma is the liquid component of blood, making up about 55% of its volume. It is a straw-colored fluid that contains water, proteins, salts, hormones, and dissolved gases, serving as a medium for transporting nutrients and waste.

Question 16:
What is the function of hemoglobin in RBCs?
Answer:

Hemoglobin is a iron-containing protein in RBCs that binds with oxygen to form oxyhemoglobin, facilitating oxygen transport from the lungs to tissues. It also helps in carrying some carbon dioxide back to the lungs.

Question 17:
Name the blood cells involved in immune response.
Answer:

The white blood cells (WBCs), specifically lymphocytes and phagocytes, are responsible for immune responses by identifying and destroying pathogens.

Question 18:
What is the role of platelets in blood?
Answer:

Platelets (thrombocytes) are tiny cell fragments that help in blood clotting by forming a plug at injury sites and releasing clotting factors to prevent excessive bleeding.

Question 19:
Differentiate between arteries and veins based on wall thickness.
Answer:

Arteries have thicker, muscular walls to withstand high blood pressure, while veins have thinner walls with valves to prevent backflow of blood.

Question 20:
What is the significance of the SA node in the heart?
Answer:

The SA node (sinoatrial node) acts as the natural pacemaker of the heart, generating electrical impulses that initiate rhythmic contractions, setting the heart rate.

Question 21:
Explain the term double circulation.
Answer:

Double circulation refers to the two separate pathways of blood flow in mammals:
1. Pulmonary circulation (heart to lungs and back)
2. Systemic circulation (heart to body and back).

Question 22:
What is lymph and its primary function?
Answer:

Lymph is a colorless fluid derived from tissue fluid. It transports nutrients, hormones, and waste, and plays a key role in immune defense via lymph nodes.

Question 23:
Why is the left ventricle wall thicker than the right?
Answer:

The left ventricle has a thicker muscular wall to pump oxygenated blood at high pressure to the entire body, whereas the right ventricle only pumps blood to the lungs.

Question 24:
Name the blood group known as the universal donor.
Answer:

Blood group O negative is called the universal donor because its RBCs lack A, B, and Rh antigens, minimizing rejection in transfusions.

Question 25:
What causes heart sounds 'lub' and 'dub'?
Answer:

The 'lub' sound is due to the closure of atrioventricular valves (tricuspid and mitral), while the 'dub' sound results from the closure of semilunar valves (aortic and pulmonary).

Question 26:
How does hypertension affect the circulatory system?
Answer:

Hypertension (high blood pressure) strains artery walls, increasing risks of atherosclerosis, heart attacks, and strokes due to reduced blood flow efficiency.

Very Short Answer (2 Marks) – with Solutions (CBSE Pattern)

These 2-mark questions test key concepts in a brief format. Answers are expected to be accurate and slightly descriptive.

Question 1:
Define plasma and list its two major components.
Answer:

Plasma is the liquid part of blood that carries cells and proteins. Its two major components are:

  • Water (90-92%)
  • Proteins (e.g., albumin, globulin, fibrinogen)

Question 2:
Name the blood cells involved in immune response and their role.
Answer:

White Blood Cells (WBCs) like lymphocytes and phagocytes are involved.

  • Lymphocytes produce antibodies.
  • Phagocytes engulf pathogens.

Question 3:
Explain the term double circulation in humans.
Answer:

Double circulation involves two pathways:

  • Pulmonary circulation (heart to lungs and back)
  • Systemic circulation (heart to body and back)
This ensures efficient oxygen supply.

Question 4:
Why are platelets essential for blood clotting?
Answer:

Platelets release thromboplastin, which triggers the clotting cascade to form a fibrin mesh, sealing wounds and preventing blood loss.

Question 5:
What is lymph? State its primary function.
Answer:

Lymph is a colorless fluid derived from tissue fluid. Its primary function is to:

  • Transport nutrients and hormones
  • Remove waste and pathogens via lymph nodes

Question 6:
Describe the cardiac cycle in one sentence.
Answer:

The cardiac cycle is the sequence of atrial and ventricular contraction (systole) and relaxation (diastole) that completes one heartbeat.

Question 7:
How does blood pressure differ in arteries and veins?
Answer:

Arteries have higher pressure (120/80 mmHg) due to direct pumping by the heart, while veins have lower pressure and rely on valves and muscle contractions for blood flow.

Question 8:
Name the blood groups in the ABO system and their antibodies.
Answer:

  • A: Anti-B antibodies
  • B: Anti-A antibodies
  • AB: No antibodies
  • O: Anti-A and Anti-B antibodies

Short Answer (3 Marks) – with Solutions (CBSE Pattern)

These 3-mark questions require brief explanations and help assess understanding and application of concepts.

Question 1:
Explain the role of lymph in the human circulatory system.
Answer:

Lymph is a colorless fluid that plays a crucial role in the immune system and nutrient transport. It is derived from tissue fluid and contains lymphocytes, which help fight infections.

Its functions include:

  • Returning proteins and excess interstitial fluid to the bloodstream.
  • Transporting fats from the intestine to the blood in the form of chylomicrons.
  • Filtering and destroying pathogens via lymph nodes.

Question 2:
Differentiate between open and closed circulatory systems with examples.
Answer:

Open Circulatory System: Blood is not confined to vessels and flows freely in body cavities. Hemolymph bathes tissues directly. Example: Arthropods (e.g., insects) and Mollusks (e.g., snails).

Closed Circulatory System: Blood flows in enclosed vessels (arteries, veins, capillaries). Example: Vertebrates (e.g., humans, fish).

Key difference: Open systems lack capillaries, while closed systems ensure efficient oxygen delivery.

Question 3:
Describe the significance of the SA node in heart function.
Answer:

The SA node (Sinoatrial node) is the natural pacemaker of the heart.

It generates electrical impulses that initiate each heartbeat, ensuring rhythmic contractions.

Located in the right atrium, it sets the heart rate (70-75 beats/min) and coordinates atrial contraction.

Without the SA node, the heart would lose its automaticity, leading to irregular rhythms.

Question 4:
How does blood clotting prevent excessive blood loss? Explain the process briefly.
Answer:

Blood clotting (coagulation) is a defense mechanism to seal wounds.

Steps:

  • Injury triggers platelet aggregation at the site.
  • Platelets release clotting factors, activating prothrombin to thrombin.
  • Thrombin converts fibrinogen to fibrin, forming a mesh to trap blood cells.
This prevents further blood loss and infection.

Question 5:
What is erythropoiesis? State the hormone regulating it and its site of production.
Answer:

Erythropoiesis is the process of red blood cell (RBC) formation in bone marrow.

The hormone erythropoietin (EPO), produced by the kidneys, regulates it.

EPO stimulates marrow stem cells to differentiate into RBCs, ensuring oxygen transport efficiency. Low oxygen levels (e.g., at high altitudes) increase EPO secretion.

Question 6:
Why are veins equipped with valves, whereas arteries are not?
Answer:

Veins carry deoxygenated blood at low pressure back to the heart.

Valves prevent backflow of blood, especially in limbs where gravity opposes flow.

Arteries lack valves because their high-pressure flow (from heart contractions) naturally prevents backflow.

Example: Leg veins rely on valves during standing to avoid pooling.

Question 7:
Explain the role of lymph in the human body.
Answer:

Lymph is a colorless fluid that plays a crucial role in the immune system and fluid balance.

1. It transports white blood cells (lymphocytes) to fight infections.
2. It returns interstitial fluid (excess fluid from tissues) back to the bloodstream.
3. It absorbs and transports fatty acids and glycerol from the digestive system via lacteals.

Question 8:
Differentiate between arteries and veins based on their structure and function.
Answer:

Arteries and veins differ in structure and function:

  • Structure: Arteries have thick, muscular walls to withstand high pressure, while veins have thinner walls with valves to prevent backflow.
  • Function: Arteries carry oxygenated blood (except pulmonary artery) away from the heart, whereas veins carry deoxygenated blood (except pulmonary vein) towards the heart.

Question 9:
Describe the significance of the SA node in the cardiac cycle.
Answer:

The SA node (Sinoatrial node) is the natural pacemaker of the heart.

1. It generates electrical impulses that initiate each heartbeat.
2. It ensures rhythmic and coordinated contraction of the atria.
3. It regulates the heart rate based on signals from the autonomic nervous system.

Question 10:
What is the function of platelets in blood clotting?
Answer:

Platelets (thrombocytes) are essential for hemostasis (blood clotting).

1. They adhere to damaged blood vessel walls and form a temporary plug.
2. They release chemicals like serotonin to constrict blood vessels.
3. They activate clotting factors to form a fibrin mesh, sealing the wound permanently.

Question 11:
Explain the term double circulation and its importance in mammals.
Answer:

Double circulation refers to the two separate pathways of blood flow in mammals:

1. Pulmonary circulation: Blood is pumped to the lungs for oxygenation.
2. Systemic circulation: Oxygenated blood is delivered to body tissues.

Importance: It ensures efficient oxygenation and maintains high blood pressure for rapid nutrient delivery.

Question 12:
How does hemoglobin assist in oxygen transport in the blood?
Answer:

Hemoglobin is a respiratory pigment in red blood cells.

1. It binds with oxygen in the lungs to form oxyhemoglobin.
2. It releases oxygen in tissues where partial pressure is low.
3. It also carries a small amount of carbon dioxide back to the lungs.

Long Answer (5 Marks) – with Solutions (CBSE Pattern)

These 5-mark questions are descriptive and require detailed, structured answers with proper explanation and examples.

Question 1:
Explain the double circulation mechanism in humans and its significance. Highlight the role of pulmonary and systemic circulation.
Answer:
Theoretical Framework

Double circulation ensures blood passes through the heart twice per cycle, optimizing oxygen delivery. It consists of pulmonary circulation (heart-lungs) and systemic circulation (heart-body).

Evidence Analysis
  • Pulmonary circulation: Deoxygenated blood → right ventricle → lungs → oxygenated.
  • Systemic circulation: Oxygenated blood → left ventricle → body organs → deoxygenated.
Critical Evaluation

Our textbook shows this separation prevents oxygen-rich and poor blood mixing, enhancing efficiency. Example: Athletes benefit from rapid oxygen supply during exercise.

Future Implications

Understanding this aids in treating congenital heart defects, like ventricular septal defects.

Question 2:
Describe the cardiac cycle with reference to systole and diastole. How does it maintain blood pressure?
Answer:
Theoretical Framework

The cardiac cycle includes systole (contraction) and diastole (relaxation) phases, completing in 0.8 seconds.

Evidence Analysis
  • Atrial systole: Blood enters ventricles (0.1 sec).
  • Ventricular systole: Blood pumps to arteries (0.3 sec).
  • Diastole: Chambers relax and refill (0.4 sec).
Critical Evaluation

We studied that rhythmic pressure changes maintain BP. Example: Hypertension occurs if diastolic pressure exceeds 80 mmHg.

Future Implications

Research on arrhythmias uses this to design pacemakers.

Question 3:
Compare open and closed circulatory systems. Provide two examples of organisms for each type.
Answer:
Theoretical Framework

Open systems (blood directly bathes tissues) lack vessels, while closed systems confine blood in vessels.

Evidence Analysis
  • Open: Insects (e.g., cockroach), mollusks (e.g., snail).
  • Closed: Humans, earthworms.
Critical Evaluation

Our textbook shows closed systems are more efficient for larger organisms due to higher pressure. Example: Earthworms survive better in moist soils.

Future Implications

Studying these helps in biomimicry for fluid transport designs.

Question 4:
Analyze the electrocardiogram (ECG) and its importance in diagnosing heart conditions. Label the P, QRS, and T waves.
Answer:
Theoretical Framework

ECG records electrical activity of the heart via P-wave (atrial depolarization), QRS complex (ventricular depolarization), and T-wave (repolarization).

Evidence Analysis
  • P-wave: Atria contract.
  • QRS: Ventricles contract.
  • T-wave: Ventricles recover.
Critical Evaluation

We studied abnormal ECGs detect arrhythmias or myocardial infarction. Example: Flat T-wave indicates potassium deficiency.

Future Implications

Portable ECGs revolutionize remote cardiac monitoring.

Question 5:
Discuss the lymphatic system and its role in immunity. How does it differ from blood circulation?
Answer:
Theoretical Framework

The lymphatic system transports lymph, a fluid containing WBCs, and drains excess tissue fluid.

Evidence Analysis
  • Lymph nodes filter pathogens (e.g., swollen nodes during infection).
  • No pump; relies on muscle movement.
Critical Evaluation

Our textbook highlights its immunity role via lymphocytes. Example: Vaccines exploit lymphatic memory cells.

Future Implications

Research targets lymphedema treatments post-cancer surgery.

Question 6:
Explain blood clotting (coagulation) with reference to platelets and fibrin. Why is it vital?
Answer:
Theoretical Framework

Coagulation prevents blood loss via a cascade converting fibrinogen to fibrin threads, trapping platelets.

Evidence Analysis
  • Platelets adhere to wounds (e.g., cut finger).
  • Calcium and vitamin K are essential cofactors.
Critical Evaluation

We studied deficiencies cause hemophilia. Example: Aspirin inhibits clotting, risking hemorrhage.

Future Implications

Artificial clotting agents are being developed for trauma care.

Question 7:
Explain the double circulation mechanism in humans and its significance. How does it differ from single circulation?
Answer:
Theoretical Framework

Double circulation involves two pathways: pulmonary (heart-lungs-heart) and systemic (heart-body-heart). Our textbook shows it ensures efficient oxygen delivery.

Evidence Analysis
  • Oxygenated and deoxygenated blood remain separate, preventing mixing.
  • Example: Left ventricle pumps oxygen-rich blood to the body, while right ventricle sends deoxygenated blood to lungs.
Critical Evaluation

Unlike single circulation (e.g., fish), double circulation supports higher metabolic demands in mammals.

Future Implications

Research explores its role in adapting to high-altitude hypoxia.

Question 8:
Describe the cardiac cycle with reference to systole and diastole. How does the ECG correlate with these phases?
Answer:
Theoretical Framework

The cardiac cycle includes systole (contraction) and diastole (relaxation). We studied its regulation via SA node impulses.

Evidence Analysis
  • Atrial systole (P-wave on ECG) fills ventricles; ventricular systole (QRS complex) pumps blood.
  • Example: T-wave marks ventricular repolarization during diastole.
Critical Evaluation

ECG abnormalities (e.g., arrhythmias) disrupt timing, reducing cardiac output.

Future Implications

Wearable ECG monitors enable early detection of cycle disorders.

Question 9:
Analyze the role of lymphatic system in immune response and fluid balance. Provide two examples of its dysfunction.
Answer:
Theoretical Framework

The lymphatic system returns interstitial fluid to blood and houses lymphocytes for immunity.

Evidence Analysis
  • Lymph nodes filter pathogens; Example: Swollen nodes during infection indicate immune activation.
  • Lymphedema (e.g., post-surgery) disrupts fluid balance, causing swelling.
Critical Evaluation

Dysfunction increases infection risk, as seen in elephantiasis (parasitic blockage).

Future Implications

Research focuses on lymphatic regeneration therapies.

Question 10:
Compare open and closed circulatory systems using arthropods and annelids as examples. Why is blood pressure higher in closed systems?
Answer:
Theoretical Framework

Open systems (e.g., arthropods) lack vessels; hemolymph directly bathes tissues. Closed systems (e.g., annelids) use confined blood vessels.

Evidence Analysis
  • Example: Earthworms (closed) show rapid nutrient delivery due to higher pressure.
  • Grasshoppers (open) have low-pressure hemolymph, limiting oxygen transport.
Critical Evaluation

Closed systems support larger body sizes and activity levels.

Future Implications

Biomimicry studies explore hybrid systems for medical devices.

Question 11:
Explain the structure and function of the human heart with a labeled diagram.
Answer:

The human heart is a muscular organ that pumps blood throughout the body via the circulatory system. It is located in the thoracic cavity, slightly tilted to the left.

Structure:

  • The heart has four chambers: two atria (upper chambers) and two ventricles (lower chambers).
  • The right atrium receives deoxygenated blood from the body via the superior and inferior vena cava.
  • The right ventricle pumps this blood to the lungs through the pulmonary artery.
  • The left atrium receives oxygenated blood from the lungs via the pulmonary veins.
  • The left ventricle pumps this oxygenated blood to the body through the aorta.
  • Valves like the tricuspid and bicuspid prevent backflow of blood.

Function:

The heart ensures continuous circulation of blood, supplying oxygen and nutrients to tissues while removing waste products like CO2. The rhythmic contraction (systole) and relaxation (diastole) maintain blood pressure.

Diagram: (Draw a neat, labeled diagram of the human heart showing all chambers, valves, and major blood vessels.)

Question 12:
Describe the composition and functions of blood in the human body.
Answer:

Blood is a specialized connective tissue composed of plasma and formed elements (RBCs, WBCs, and platelets).

Composition:

  • Plasma (55%): A yellowish fluid containing water (90%), proteins (albumin, globulin, fibrinogen), hormones, and waste products.
  • Red Blood Cells (RBCs): Contain hemoglobin for oxygen transport.
  • White Blood Cells (WBCs): Provide immunity (e.g., lymphocytes, neutrophils).
  • Platelets: Assist in blood clotting.

Functions:

  • Transportation: Carries O2, CO2, nutrients, hormones, and waste.
  • Defense: WBCs fight infections; antibodies neutralize pathogens.
  • Homeostasis: Regulates body temperature and pH.
  • Clotting: Prevents excessive blood loss via fibrin formation.

Blood also maintains osmotic balance and acts as a buffer to stabilize pH.

Question 13:
Differentiate between open and closed circulatory systems with examples.
Answer:

Open Circulatory System:

  • Blood is not confined to blood vessels; it flows freely in body cavities (hemocoel).
  • Low-pressure system; less efficient for oxygen delivery.
  • Found in arthropods (e.g., insects) and mollusks (e.g., snails).

Closed Circulatory System:

  • Blood circulates within a network of vessels (arteries, veins, capillaries).
  • High-pressure system; ensures precise nutrient and gas exchange.
  • Found in vertebrates (e.g., humans) and some annelids (e.g., earthworms).

Key Differences:

  • Open systems lack capillaries; closed systems have them for efficient exchange.
  • Closed systems allow faster blood flow and better regulation.
  • Open systems are simpler but limit body size and activity levels.
Question 14:
Explain the structure and function of the human heart with a well-labeled diagram. Discuss how the double circulation system ensures efficient oxygen supply to the body.
Answer:

The human heart is a muscular organ located in the thoracic cavity, slightly tilted to the left. It is enclosed in a protective sac called the pericardium. The heart has four chambers: two atria (upper chambers) and two ventricles (lower chambers). The right atrium receives deoxygenated blood from the body via the superior and inferior vena cava, while the left atrium receives oxygenated blood from the lungs through the pulmonary veins. The ventricles pump blood out of the heart—the right ventricle sends blood to the lungs via the pulmonary artery, and the left ventricle pumps oxygenated blood to the body through the aorta.

The double circulation system consists of two pathways: pulmonary circulation (heart to lungs and back) and systemic circulation (heart to body and back). This ensures efficient oxygen supply because:

  • Oxygenated and deoxygenated blood do not mix, maintaining high oxygen delivery to tissues.
  • The heart pumps blood at high pressure to systemic circulation, ensuring rapid oxygen transport.
  • Pulmonary circulation allows blood to be oxygenated before redistribution.

Here’s a simple labeled diagram of the heart:

[Diagram: Label the four chambers, major blood vessels, and direction of blood flow.]

Question 15:
Describe the composition and functions of blood. How does it differ from lymph? Provide a comparative analysis.
Answer:

Blood is a specialized connective tissue composed of plasma (55%) and formed elements (45%). Plasma contains water, proteins (albumin, globulins, fibrinogen), salts, and hormones. The formed elements include:

  • Erythrocytes (RBCs): Transport oxygen via hemoglobin.
  • Leukocytes (WBCs): Provide immunity.
  • Platelets: Aid in blood clotting.

Functions of blood:

  • Transport of gases, nutrients, and waste.
  • Regulation of body temperature and pH.
  • Protection via immune responses and clotting.

Lymph is a colorless fluid derived from tissue fluid. Unlike blood, it lacks RBCs and platelets but contains lymphocytes. Key differences:

  • Composition: Blood has RBCs; lymph does not.
  • Circulation: Blood flows in vessels; lymph moves through lymphatic vessels.
  • Function: Blood transports gases; lymph maintains fluid balance and immunity.
Question 16:
Explain the double circulation of blood in humans. Why is it more efficient than single circulation?
Answer:

In humans, double circulation refers to the pathway where blood passes through the heart twice during one complete cycle—once through the pulmonary circulation (to the lungs) and once through the systemic circulation (to the body). Here's how it works:


1. Pulmonary Circulation: Deoxygenated blood from the body enters the right atrium, flows to the right ventricle, and is pumped to the lungs via the pulmonary artery. In the lungs, blood gets oxygenated and returns to the left atrium via the pulmonary vein.


2. Systemic Circulation: Oxygenated blood from the left atrium moves to the left ventricle and is pumped to the body via the aorta. After supplying oxygen, deoxygenated blood returns to the heart through the vena cava.


Advantage over Single Circulation: Double circulation ensures higher pressure and efficient oxygen delivery to tissues, as blood is pumped separately to the lungs and body. In single circulation (e.g., fish), blood pressure drops after passing through the gills, reducing efficiency.

Question 17:
Describe the lymphatic system and its role in circulation. How does it maintain fluid balance in the body?
Answer:

The lymphatic system is a network of lymph vessels, lymph nodes, and organs (like the spleen) that work alongside the circulatory system. Its primary roles are:


1. Fluid Balance: Excess interstitial fluid (leaked from blood capillaries) is collected by lymph capillaries and returned to the bloodstream as lymph, preventing swelling (edema).


2. Immunity: Lymph nodes filter lymph, trapping pathogens and activating lymphocytes (white blood cells) to fight infections.


3. Fat Absorption: In the small intestine, lacteals (lymph capillaries) absorb dietary fats and transport them to the bloodstream.


Mechanism of Fluid Balance: When blood pressure forces plasma out of capillaries, ~90% is reabsorbed, while the remaining 10% enters lymph vessels. This ensures no fluid accumulates in tissues, maintaining homeostasis.

Question 18:
Explain the process of double circulation in humans and its significance. How does it differ from single circulation?
Answer:

The double circulation system in humans involves two distinct pathways: pulmonary circulation and systemic circulation.

Process:
1. Pulmonary Circulation: Deoxygenated blood from the right ventricle is pumped to the lungs via the pulmonary artery. In the lungs, blood picks up oxygen and releases carbon dioxide, becoming oxygenated.
2. Systemic Circulation: Oxygenated blood returns to the left atrium via the pulmonary veins, then moves to the left ventricle, which pumps it to the entire body through the aorta.

Significance:
- Ensures efficient oxygenation of blood by separating oxygenated and deoxygenated blood.
- Maintains higher blood pressure in systemic circulation, enabling faster nutrient and oxygen delivery to tissues.

Difference from Single Circulation:
In single circulation (e.g., fish), blood passes through the heart once per cycle, while in double circulation, blood passes through the heart twice, improving efficiency.

Question 19:
Describe the composition and functions of lymph. How does it contribute to immunity and fluid balance in the body?
Answer:

Lymph is a colorless fluid derived from tissue fluid (interstitial fluid) that plays a vital role in immunity and homeostasis.

Composition:
- Water, ions, and small proteins (similar to plasma but fewer proteins).
- Lymphocytes (white blood cells) for immune response.
- Fats absorbed from the intestines (in lacteals).

Functions:
1. Immunity: Lymph transports lymphocytes and antigens to lymph nodes, where pathogens are filtered and destroyed.
2. Fluid Balance: It returns excess interstitial fluid and proteins to the bloodstream, preventing edema.
3. Nutrient Transport: Carries absorbed fats from the intestines to the blood.

Contribution to Immunity:
Lymph nodes act as checkpoints where pathogens are trapped and destroyed by immune cells, preventing infections.

Question 20:
Explain the double circulation of blood in humans with a well-labeled diagram. Highlight the significance of this process.
Answer:

In humans, double circulation refers to the passage of blood twice through the heart to complete one full cycle: once through the pulmonary circulation (heart to lungs and back) and once through the systemic circulation (heart to body and back).

Steps:
1. Deoxygenated blood from the body enters the right atrium via the vena cava.
2. It flows to the right ventricle and is pumped to the lungs via the pulmonary artery for oxygenation.
3. Oxygenated blood returns to the left atrium through the pulmonary veins.
4. It moves to the left ventricle and is pumped to the body via the aorta.

Significance:
- Ensures efficient oxygenation by separating oxygenated and deoxygenated blood.
- Maintains high blood pressure for systemic circulation, ensuring rapid nutrient and gas exchange.
- Supports high metabolic demands of humans.

Diagram: (Draw a labeled heart with arrows showing pulmonary and systemic circulation pathways.)

Question 21:
Describe the composition and functions of lymph. How does it differ from blood?
Answer:

Composition of Lymph:
- A clear, colorless fluid derived from tissue fluid.
- Contains lymphocytes (WBCs), proteins, fats (absorbed from intestines), and cellular debris.
- Lacks RBCs and platelets.

Functions:
1. Immunity: Transports lymphocytes to fight pathogens.
2. Fat Absorption: Carries digested fats from the intestines.
3. Fluid Balance: Returns excess tissue fluid to the bloodstream.
4. Waste Removal: Eliminates metabolic waste and toxins.

Differences from Blood:

  • Color: Lymph is colorless; blood is red due to hemoglobin.
  • Cells: Lymph lacks RBCs and platelets.
  • Circulation: Lymph flows unidirectionally (tissues → veins), while blood circulates in a closed loop.
  • Proteins: Lymph has lower protein content than blood plasma.

Case-based Questions (4 Marks) – with Solutions (CBSE Pattern)

These 4-mark case-based questions assess analytical skills through real-life scenarios. Answers must be based on the case study provided.

Question 1:
A patient has low hemoglobin levels and complains of fatigue. Analyze how this affects oxygen transport and suggest two dietary changes to improve the condition.
Answer:
Case Deconstruction

Low hemoglobin reduces oxygen-carrying capacity, leading to fatigue due to inadequate tissue oxygenation.

Theoretical Application
  • Hemoglobin binds O2 in lungs; deficiency disrupts this process.
  • Iron-rich foods (spinach, lentils) can boost hemoglobin synthesis.
Critical Evaluation

Our textbook shows vitamin C enhances iron absorption, so citrus fruits should accompany iron sources. Example: Paleness in anemia confirms poor O2 delivery.

Question 2:
During an ECG, a student observes an irregular QRS complex. Link this observation to possible cardiac arrhythmia and explain its impact on circulation.
Answer:
Case Deconstruction

Irregular QRS indicates abnormal ventricular depolarization, suggesting arrhythmia.

Theoretical Application
  • Arrhythmia disrupts heart's pumping efficiency, causing uneven blood flow.
  • Example: Ventricular fibrillation can lead to stroke due to clot formation.
Critical Evaluation

We studied that prolonged arrhythmia reduces cardiac output, evidenced by dizziness in patients. Beta-blockers may stabilize rhythm.

Question 3:
Compare open and closed circulatory systems using two organisms. How does a four-chambered heart provide an evolutionary advantage?
Answer:
Case Deconstruction

Insects (open) lack vessels, while humans (closed) have precise blood flow control.

Theoretical Application
  • Closed systems enable higher metabolic rates.
  • Four chambers separate oxygenated/deoxygenated blood completely.
Critical Evaluation

Our textbook shows crocodiles’ four-chambered hearts support diving by reducing O2 wastage. Example: Mammals thrive due to efficient circulation.

Question 4:
A blood report shows high LDL cholesterol. Predict its effect on atherosclerosis and propose two lifestyle modifications to mitigate risks.
Answer:
Case Deconstruction

LDL deposits cholesterol in arteries, narrowing them and causing atherosclerosis.

Theoretical Application
  • Plaque buildup increases hypertension risk.
  • Example: Mediterranean diet reduces LDL levels.
Critical Evaluation

We studied that aerobic exercise (e.g., cycling) raises HDL, which removes LDL. Statins are pharmaceutical options.

Question 5:
Explain why lymphatic drainage is crucial post-surgery. How does it relate to edema prevention? Support with a clinical example.
Answer:
Case Deconstruction

Lymph vessels remove excess interstitial fluid; blockage causes swelling (edema).

Theoretical Application
  • Post-mastectomy patients wear compression sleeves to aid drainage.
  • Example: Lymphedema in filariasis shows system failure.
Critical Evaluation

Our textbook highlights manual lymph drainage therapy as evidence-based. Proteins in lymph prevent fluid retention.

Question 6:
A patient reports fatigue and shortness of breath. Blood tests reveal low hemoglobin and decreased RBC count. Analyze the condition and explain how it affects oxygen transport.
Answer:
Case Deconstruction

The patient likely has anemia, characterized by reduced hemoglobin and RBCs. Hemoglobin binds oxygen, so its deficiency impairs oxygen delivery.

Theoretical Application
  • Low hemoglobin reduces blood's oxygen-carrying capacity.
  • Tissues receive less oxygen, causing fatigue and breathlessness.
Critical Evaluation

Our textbook shows that anemia can result from iron deficiency or blood loss. Severe cases may require supplements or transfusions.

Question 7:
An athlete's ECG shows an abnormal QRS complex. Relate this to possible cardiac arrhythmia and its impact on blood circulation.
Answer:
Case Deconstruction

An irregular QRS complex suggests ventricular arrhythmia, disrupting the heart's electrical activity.

Theoretical Application
  • Abnormal rhythms reduce cardiac output.
  • Blood flow to organs becomes inefficient, risking fainting or organ damage.
Critical Evaluation

We studied that arrhythmias may stem from electrolyte imbalances. Treatments include medications or pacemakers.

Question 8:
Compare open and closed circulatory systems using examples from arthropods and humans. Highlight one evolutionary advantage of each.
Answer:
Case Deconstruction

Arthropods have open systems where hemolymph directly bathes tissues. Humans have closed systems with blood confined to vessels.

Theoretical Application
  • Open systems (e.g., insects) are energy-efficient for small bodies.
  • Closed systems (e.g., humans) enable precise oxygen delivery.
Critical Evaluation

Our textbook shows closed systems support higher metabolic rates, crucial for active organisms.

Question 9:
A blockage in the coronary artery reduces blood supply to the heart. Predict two consequences and explain how angioplasty addresses this.
Answer:
Case Deconstruction

Blocked coronary arteries cause ischemia, starving heart muscles of oxygen.

Theoretical Application
  • Consequences: Chest pain (angina) or heart attack.
  • Angioplasty uses a stent to widen the artery, restoring blood flow.
Critical Evaluation

We studied that timely angioplasty prevents tissue death, but lifestyle changes are needed to avoid recurrence.

Question 10:
A patient reports fatigue and shortness of breath. Blood tests reveal low hemoglobin and decreased RBC count. Analyze the possible condition and its impact on oxygen transport.
Answer:
Case Deconstruction

The patient likely has anemia, where reduced hemoglobin impairs oxygen binding. Our textbook shows hemoglobin carries O2, so deficiency causes hypoxia.

Theoretical Application
  • Low RBCs reduce blood’s oxygen-carrying capacity.
  • Tissues receive less O2, causing fatigue.
Critical Evaluation

Example: Iron-deficiency anemia disrupts heme synthesis. Severe cases may require transfusions, as per recent studies.

Question 11:
During an ECG, a student observes an irregular QRS complex. Link this abnormality to cardiac arrhythmia and its physiological consequences.
Answer:
Case Deconstruction

Irregular QRS indicates ventricular arrhythmia, where abnormal electrical signals disrupt heart rhythm.

Theoretical Application
  • Mismatched ventricular contractions reduce cardiac output.
  • Example: In ventricular fibrillation, blood flow becomes erratic.
Critical Evaluation

Our textbook shows arrhythmias may cause stroke. Immediate defibrillation is critical, as per 2023 clinical guidelines.

Question 12:
Compare open and closed circulatory systems using arthropods and humans as examples. Highlight one adaptive advantage of each.
Answer:
Case Deconstruction

Arthropods have open systems where hemolymph directly bathes organs. Humans use closed systems with confined blood vessels.

Theoretical Application
  • Open: Energy-efficient for small bodies (e.g., insects).
  • Closed: Enables higher pressure (e.g., human aortic circulation).
Critical Evaluation

Closed systems support endothermy, as seen in mammals. Recent studies confirm their role in sustained activity.

Question 13:
A thrombus blocks a coronary artery. Explain how this leads to myocardial infarction and two compensatory mechanisms the body might employ.
Answer:
Case Deconstruction

The thrombus restricts blood flow, causing ischemia and heart muscle death (infarction).

Theoretical Application
  • Compensation: Collateral circulation develops.
  • Increased heart rate to maintain output.
Critical Evaluation

Example: STEMI patients show elevated troponin. Our textbook notes timely angioplasty can restore perfusion.

Question 14:
A patient reports symptoms of fatigue, shortness of breath, and pale skin. Upon diagnosis, the doctor suspects anemia. Based on the NCERT chapter Body Fluids and Circulation, explain how a deficiency in hemoglobin affects oxygen transport in the body.
Answer:

Hemoglobin is a crucial protein in RBCs that binds with oxygen in the lungs and transports it to tissues. In anemia, the hemoglobin levels drop, reducing the oxygen-carrying capacity of blood.


This leads to:

  • Decreased oxygen supply to cells, causing fatigue.
  • Compensatory increase in breathing rate (shortness of breath) to meet oxygen demand.
  • Pale skin due to reduced oxygen saturation in blood.
Question 15:
A person suffers from a blocked coronary artery. Using NCERT concepts, explain how this condition disrupts double circulation and affects heart function.
Answer:

In double circulation, the heart pumps oxygenated blood (systemic circulation) and deoxygenated blood (pulmonary circulation) separately. A blocked coronary artery restricts blood supply to the heart muscles.


Consequences include:

  • Reduced oxygen delivery to cardiac tissues, impairing contraction.
  • Potential myocardial infarction (heart attack) due to tissue damage.
  • Disruption in systemic circulation, affecting overall body function.
Question 16:
During intense exercise, a runner's heart rate increases significantly. Referring to NCERT, describe the role of SA node and adrenaline in regulating this response.
Answer:

The SA node (pacemaker) initiates cardiac impulses, increasing heart rate to meet oxygen demand during exercise. Adrenaline (hormone) enhances this effect by:


  • Stimulating the SA node to fire faster.
  • Increasing cardiac output by strengthening ventricular contractions.
  • Dilating blood vessels in muscles for better oxygen supply.
Question 17:
A blood report shows elevated WBC count in a patient. Relate this observation to the defense mechanism of the body as per NCERT.
Answer:

Leukocytosis (high WBC count) indicates an immune response. WBCs protect the body by:


  • Phagocytosis: Neutrophils/macrophages engulf pathogens.
  • Antibody production: Lymphocytes (B-cells and T-cells) neutralize infections.
  • Inflammation: Basophils/eosinophils combat allergens/parasites.

Elevated count suggests ongoing infection or immune activity.

Question 18:

A patient was admitted to the hospital with symptoms of fatigue, shortness of breath, and pale skin. Upon examination, the doctor diagnosed the patient with anemia. Based on this case:

  • Explain the role of hemoglobin in oxygen transport.
  • How does a deficiency in hemoglobin affect the circulatory system?
Answer:

Hemoglobin is a respiratory pigment found in red blood cells (RBCs) that binds with oxygen in the lungs and transports it to tissues. It consists of four heme groups, each containing an iron atom that binds one oxygen molecule.


In anemia, the hemoglobin levels drop, reducing the oxygen-carrying capacity of blood. This leads to:

  • Reduced oxygen delivery to tissues, causing fatigue and shortness of breath.
  • The heart compensates by pumping faster (tachycardia), increasing cardiac workload.
  • Pale skin occurs due to decreased oxygen saturation in peripheral tissues.

Thus, hemoglobin deficiency disrupts efficient oxygen transport, affecting overall body function.

Question 19:

A student observed that during intense exercise, their heart rate increased significantly. Answer the following based on this scenario:

  • Name the autonomic nervous system division responsible for increasing heart rate.
  • Explain how this response helps in meeting the body's oxygen demand during exercise.
Answer:

The sympathetic nervous system (a division of the autonomic nervous system) increases heart rate during exercise by releasing adrenaline (epinephrine).


This response helps in:

  • Enhancing cardiac output: Faster heart rate pumps more blood per minute, supplying oxygenated blood to muscles.
  • Improving oxygen delivery: Increased blood flow ensures active muscles receive sufficient oxygen and nutrients.
  • Removing waste: Faster circulation helps remove carbon dioxide and lactic acid produced during exercise.

Thus, the sympathetic response optimizes circulation to meet heightened metabolic demands.

Question 20:

Rahul, a 16-year-old boy, experienced severe fatigue and shortness of breath during his morning run. Upon medical examination, his hemoglobin level was found to be 8 g/dL (normal range: 12-16 g/dL). The doctor diagnosed him with anemia.

(a) Explain how low hemoglobin affects oxygen transport in the body.

(b) Suggest two dietary changes Rahul should adopt to improve his condition.

Answer:

(a) Hemoglobin is the iron-containing protein in red blood cells (RBCs) responsible for binding and transporting oxygen. A low hemoglobin level reduces the oxygen-carrying capacity of blood, leading to:

  • Decreased oxygen delivery to tissues, causing fatigue and shortness of breath.
  • Compromised cellular respiration, as cells receive insufficient oxygen for ATP production.

(b) Dietary changes for Rahul:

  • Increase intake of iron-rich foods like spinach, lentils, and red meat to boost hemoglobin synthesis.
  • Consume vitamin C-rich foods (e.g., citrus fruits) to enhance iron absorption in the gut.
Question 21:

During a lab activity, students observed a blood smear under a microscope and identified different cells. One student noted a cell with a bilobed nucleus and granular cytoplasm.

(a) Identify the cell and state its function.

(b) How does this cell contribute to the body's defense mechanism?

Answer:

(a) The observed cell is an eosinophil, a type of white blood cell (WBC). Its functions include:
1. Combating parasitic infections by releasing toxic granules.
2. Modulating allergic reactions by neutralizing histamine.

(b) Eosinophils defend the body by:
1. Phagocytosis: Engulfing pathogens like parasites.
2. Releasing enzymes (e.g., peroxidase) to destroy foreign particles.
3. Regulating inflammation during allergies by controlling chemical mediators.

Question 22:
A patient was admitted to the hospital with symptoms of fatigue, shortness of breath, and pale skin. Upon examination, the doctor diagnosed him with anemia. Based on the case, answer the following:
(a) Explain the role of hemoglobin in the transport of oxygen in the body.
(b) How does a deficiency of hemoglobin lead to the symptoms observed in the patient?
Answer:

(a) Hemoglobin is an iron-containing protein present in red blood cells (RBCs). It binds with oxygen in the lungs to form oxyhemoglobin, which is transported to tissues via blood circulation. In tissues, oxygen is released due to lower oxygen concentration, allowing it to be utilized for cellular respiration.


(b) A deficiency of hemoglobin reduces the oxygen-carrying capacity of blood, leading to hypoxia (low oxygen levels in tissues). This causes:

  • Fatigue – Due to insufficient oxygen for energy production.
  • Shortness of breath – As the body tries to compensate by increasing breathing rate.
  • Pale skin – Due to reduced oxygen supply to skin tissues.

Question 23:
A student observed that after vigorous exercise, his heart rate increased significantly. Analyze the physiological changes that occur in the cardiovascular system during exercise and explain how they help meet the body's increased oxygen demand.
Answer:

During exercise, the cardiovascular system undergoes the following changes to meet oxygen demand:

1. Increased Heart Rate – The SA node (pacemaker) accelerates impulses, raising heart rate to pump more blood.
2. Enhanced Cardiac Output – More blood is ejected per beat, supplying oxygen faster.
3. Vasodilation – Blood vessels in muscles widen, improving oxygen delivery.
4. Redistribution of Blood – Blood is diverted from less active organs (e.g., digestive system) to muscles.

These changes ensure sufficient oxygen reaches muscles for aerobic respiration, preventing fatigue and maintaining performance.

Question 24:
A patient was diagnosed with anaemia and showed symptoms like fatigue and pale skin. Upon examination, his RBC count was found to be significantly low. Explain the role of erythropoietin in such a condition and how the body compensates for the reduced oxygen-carrying capacity.
Answer:

In cases of anaemia, the oxygen-carrying capacity of blood decreases due to a low RBC count. The kidneys release a hormone called erythropoietin in response to low oxygen levels in tissues. This hormone stimulates the bone marrow to produce more RBCs, helping restore oxygen transport.

The body compensates by:
1. Increasing heart rate to pump blood faster.
2. Enhancing breathing rate to absorb more oxygen.
3. Redirecting blood flow to vital organs like the brain and heart.

Additionally, erythropoietin ensures that new RBCs mature properly, improving oxygen delivery over time.

Question 25:
During a lab experiment, a student observed that a blood sample clotted faster when mixed with calcium ions and platelet factors. Explain the coagulation cascade and the significance of these components in blood clotting.
Answer:

The coagulation cascade is a series of reactions that lead to blood clot formation to prevent excessive bleeding. Calcium ions (Ca²⁺) and platelet factors play crucial roles:

  • Calcium ions act as cofactors for several clotting factors, such as Factor IV, ensuring proper activation of enzymes like prothrombinase.
  • Platelet factors (e.g., PF3) provide a surface for clotting factors to assemble, speeding up reactions.

The process involves:
1. Vasoconstriction to reduce blood flow.
2. Platelet plug formation to seal the injury.
3. Activation of the coagulation cascade to form a fibrin mesh, stabilizing the clot.

Without these components, clotting would be delayed, risking excessive blood loss.

Question 26:
A patient was diagnosed with anaemia and reported symptoms like fatigue and pale skin. Upon examination, the doctor found a reduced hemoglobin count. Explain the role of hemoglobin in oxygen transport and how its deficiency affects the body.
Answer:

Hemoglobin is an iron-containing protein in red blood cells (RBCs) responsible for transporting oxygen from the lungs to body tissues and carrying carbon dioxide back to the lungs for exhalation. It binds oxygen in the lungs to form oxyhemoglobin, which releases oxygen in tissues with low oxygen concentration.

In anaemia, reduced hemoglobin levels impair oxygen delivery, leading to:

  • Fatigue – Due to insufficient oxygen supply for cellular respiration.
  • Pale skin – Caused by reduced oxygenated blood flow.
  • Shortness of breath – As the body compensates for low oxygen levels.

Severe deficiency can also affect heart function, as it works harder to pump oxygen-deprived blood.

Question 27:
During a lab experiment, a student observed that a drop of human blood mixed with an anticoagulant separated into distinct layers. Identify these layers and explain their composition and functions.
Answer:

When blood is centrifuged with an anticoagulant, it separates into three layers:

  • Plasma (Top layer, ~55%) – A yellowish fluid containing water (90%), proteins (albumin, globulins, fibrinogen), hormones, and waste products. It transports nutrients, gases, and regulates pH.
  • Buffy coat (Middle layer, <1%) – Comprises white blood cells (WBCs) for immunity and platelets for clotting.
  • Red blood cells (Bottom layer, ~45%) – Contain hemoglobin for oxygen transport.

This separation helps diagnose conditions like infections (high WBCs) or polycythemia (excess RBCs).

Chat on WhatsApp