Class 6 Human Circulatory System MCQ with Answers

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Practice Class 6 Human Circulatory System MCQs with answers.
Learn the heart, blood, blood vessels, circulation, and lymph - with instant answers and performance report.

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Quick Revision: Human Circulatory System

Human Circulatory system Diagram
  • Circulatory System: Transports oxygen, nutrients, hormones, and waste products throughout the body. Comprises the heart, blood vessels, and blood.
  • Heart: A muscular pumping organ about the size of a fist, located in the chest cavity slightly to the left. Beats about 72 times per minute.
  • Heart Chambers: Four chambers — Right Atrium (receives deoxygenated blood), Right Ventricle (pumps blood to lungs), Left Atrium (receives oxygenated blood from lungs), Left Ventricle (pumps oxygenated blood to the body).
  • Heartbeat: The rhythmic contraction and relaxation of heart muscles (lub-dub sound). The number of heartbeats per minute is called the pulse rate.
  • Blood Vessels — Arteries: Carry blood away from the heart. Thick, elastic walls. Carry oxygenated blood (except pulmonary artery).
  • Blood Vessels — Veins: Carry blood towards the heart. Thin walls with valves to prevent backflow. Carry deoxygenated blood (except pulmonary vein).
  • Blood Vessels — Capillaries: Extremely thin vessels connecting arteries and veins. Site of exchange of oxygen, nutrients, and waste between blood and body cells.
  • Blood — Plasma: Pale yellow liquid, about 55% of blood. Transports nutrients, hormones, and waste proteins.
  • Blood — Red Blood Cells (RBCs): Contain haemoglobin (iron-rich protein) that carries oxygen. Disc-shaped, no nucleus. Produced in bone marrow.
  • Blood — White Blood Cells (WBCs): Fight infections and provide immunity. Larger than RBCs, have a nucleus. Produced in bone marrow and lymph nodes.
  • Blood — Platelets: Tiny cell fragments that help in blood clotting (coagulation) at injury sites, preventing excessive blood loss.
  • Double Circulation: Pulmonary circulation — blood flows between heart and lungs. Systemic circulation — blood flows between heart and the rest of the body.
  • Oxygenated vs Deoxygenated Blood: Oxygenated blood is bright red (rich in Oâ‚‚, carried by arteries except pulmonary artery). Deoxygenated blood is dark red (rich in COâ‚‚, carried by veins except pulmonary vein).
  • Lymphatic System: A network of lymph vessels that collects excess fluid (lymph) from tissues and returns it to the blood. Lymph nodes filter out germs.
  • Lymph: A pale yellow fluid similar to plasma but with fewer proteins. Contains WBCs (lymphocytes) that fight infection.
  • Spleen: An organ that filters blood, removes old RBCs, and helps produce WBCs.
  • Bone Marrow: Soft tissue inside bones where RBCs, WBCs, and platelets are produced.
  • Blood Groups: A, B, AB, and O (based on antigens on RBCs). Rh factor (+ or -) is also important for blood transfusion compatibility.
  • Common Circulatory Disorders: Anaemia (low haemoglobin/RBCs), High Blood Pressure (hypertension), Heart Attack (blocked coronary artery), Stroke (blocked blood vessel in brain).

Human Circulatory System Class 6 Questions and Answers (FAQ)

What is the human circulatory system and how does it work for Class 6 students?
The human circulatory system is a network of organs and vessels that transports oxygen, nutrients, hormones, and waste products throughout the body. It consists of three main parts: (1) The Heart - a four-chambered muscular pump that beats about 72 times per minute to push blood around the body; (2) Blood Vessels - arteries carry blood away from the heart, veins carry blood back to the heart, and capillaries connect them and allow exchange of materials with body cells; (3) Blood - the fluid that carries everything, made of plasma, red blood cells, white blood cells, and platelets. Together, they ensure every cell in the body gets oxygen and nutrients.
What are the four chambers of the heart and their functions?
The human heart has four chambers: (1) Right Atrium - receives deoxygenated blood (blood low in oxygen) from the body; (2) Right Ventricle - pumps deoxygenated blood to the lungs for oxygenation; (3) Left Atrium - receives oxygenated blood (blood rich in oxygen) from the lungs; (4) Left Ventricle - pumps oxygenated blood to the entire body. The left ventricle has the thickest wall because it has to pump blood to the whole body, while the right ventricle only pumps to the nearby lungs.
What is the difference between arteries and veins?
Arteries and veins have opposite functions and structures: (1) Arteries carry blood AWAY from the heart, while veins carry blood TOWARDS the heart. (2) Arteries have thick, elastic walls (because blood flows with high pressure), while veins have thinner walls. (3) Arteries carry oxygenated blood (except the pulmonary artery), while veins carry deoxygenated blood (except the pulmonary vein). (4) Veins have valves to prevent backflow of blood, while arteries do not need valves. (5) Blood in arteries is bright red, while blood in veins is dark red.
What are the components of blood and their functions?
Blood has four main components: (1) Plasma - the pale yellow liquid (about 55% of blood) that carries nutrients, hormones, and waste products; (2) Red Blood Cells (RBCs) - contain haemoglobin (an iron-rich protein) that carries oxygen from the lungs to all body cells; they are disc-shaped and have no nucleus; (3) White Blood Cells (WBCs) - fight infections and provide immunity; they are larger than RBCs and have a nucleus; (4) Platelets - tiny cell fragments that help in blood clotting when you get an injury, preventing excessive blood loss.
What are common circulatory disorders and how can we keep our heart healthy?
Common circulatory disorders include: (1) Anaemia - low haemoglobin or RBC count, causing tiredness and weakness; (2) High Blood Pressure (Hypertension) - heart has to work harder to pump blood; (3) Heart Attack - blockage of a coronary artery stops blood supply to part of the heart; (4) Stroke - blockage of a blood vessel in the brain. To keep the heart healthy, we should: eat a balanced diet low in fat and salt, exercise regularly, maintain a healthy weight, avoid smoking and alcohol, manage stress, get enough sleep, and get regular health checkups. A healthy lifestyle is the best way to prevent heart disease.

Chapter Summary: Human Circulatory System

The human circulatory system transports oxygen, nutrients, hormones, and waste products throughout the body. It consists of the heart (a four-chambered muscular pump), blood vessels (arteries, veins, capillaries), and blood. The heart has two atria and two ventricles — the right side pumps deoxygenated blood to the lungs (pulmonary circulation), while the left side pumps oxygenated blood to the body (systemic circulation). Arteries carry blood away from the heart (usually oxygenated), veins carry blood towards the heart (usually deoxygenated), and capillaries are the sites of exchange between blood and body cells.

Blood consists of plasma (liquid carrier), RBCs (oxygen transport via haemoglobin), WBCs (immunity and infection fighting), and platelets (blood clotting). The lymphatic system collects excess tissue fluid (lymph) and returns it to the bloodstream, filtering germs through lymph nodes. The pulse rate corresponds to heartbeats (about 72 per minute), and blood groups (A, B, AB, O with Rh factor) are crucial for safe transfusions. Common disorders include anaemia, high blood pressure, and heart disease. The circulatory system works continuously to maintain oxygen and nutrient supply to every cell in the body.

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