Class 10 Biology – Chapter 2: Circulatory System

Board: Federal Board (FBISE)

SECTION I: MULTIPLE CHOICE QUESTIONS

Q1. The heart’s upper chambers are called:

A) Ventricles
B) Atria

Correct Answer: B) Atria

Q2. Blood components that help the body to control bleeding are:

A) Platelets
B) Red blood cells
C) White blood cells
D) Haemoglobin

Correct Answer: A) Platelets

Q3. Bicuspid valve connects:

A) Left atrium and right atrium
B) Left atrium and left ventricle
C) Right atrium and left ventricle
D) Right atrium and right ventricle

Correct Answer: B) Left atrium and left ventricle

Note: The bicuspid (mitral) valve specifically connects the left atrium to the left ventricle. The original options contained a formatting error, so the scientifically correct connection is given above.

Q4. Which of the following chambers has the thickest walls in the human heart?

A) Left atrium
B) Right atrium
C) Left ventricle
D) Right ventricle

Correct Answer: C) Left ventricle

Q5. The left half of the human heart:

A) Has deoxygenated blood
B) Has oxygenated blood
C) Pumps blood to the lungs
D) Passes blood through the lungs

Correct Answer: B) Has oxygenated blood

Q6. The pulmonary arteries carry blood to the:

A) Brain
B) Heart
C) Liver
D) Lungs

Correct Answer: D) Lungs

Q7. Which one of the following helps to fight germs?

A) Red blood cells
B) White blood cells
C) Platelets
D) Plasma

Correct Answer: B) White blood cells

Q8. The blood vessels that carry blood from the heart to various parts of the body are called:

A) Septum
B) Arteries
C) Veins
D) Capillaries

Correct Answer: B) Arteries

Q9. Which one of the following is a double-membrane sac that covers the human heart?

A) Epicardium
B) Pericardium
C) Myocardium
D) Endocardium

Correct Answer: B) Pericardium

Q10. The alternating expansion and relaxation of the artery that you feel in your wrist is called:

A) Pulse
B) Coronary artery
C) Blood pressure
D) Plasma

Correct Answer: A) Pulse

Q11. Nutrients are exchanged between the blood and body cells in the:

A) Arteries
B) Capillaries
C) Veins
D) Aorta

Correct Answer: B) Capillaries

Q12. Which is the largest artery in the human body?

A) Pulmonary artery
B) Aorta
C) Common iliac artery
D) Femoral artery

Correct Answer: B) Aorta

Q13. What is the valve in the opening between the right atrium and the right ventricle called?

A) Pulmonary valve
B) Aortic valve
C) Tricuspid valve
D) Bicuspid valve

Correct Answer: C) Tricuspid valve

Q14. The human heart is:

A) Myogenic
B) Neurogenic
C) Cardiogenic
D) Digenic

Correct Answer: A) Myogenic

Q15. The pacemaker is situated in the heart:

A) In the wall of the right atrium
B) On the interauricular septum
C) On the interventricular septum
D) In the wall of the left atrium

Correct Answer: A) In the wall of the right atrium

SECTION II: SHORT ANSWER QUESTIONS

Q1. Write the functions of the following:

a. Pericardium

It encloses and protects the heart, reduces friction during heartbeats, and anchors the heart within the chest cavity.

b. Left atrium

It receives oxygenated blood from the lungs through the pulmonary veins and pumps it into the left ventricle.

c. Right atrium

It receives deoxygenated blood from the body through the superior and inferior vena cava and pumps it into the right ventricle.

d. Left ventricle

It pumps oxygenated blood at high pressure into the aorta to be distributed throughout the body.

e. Right ventricle

It pumps deoxygenated blood into the pulmonary trunk and pulmonary arteries toward the lungs for oxygenation.

f. Bicuspid valve (Mitral valve)

It prevents the backflow of blood from the left ventricle into the left atrium during ventricular systole.

g. Tricuspid valve

It prevents the backflow of blood from the right ventricle into the right atrium during ventricular contraction.

h. Semilunar valve

Semilunar valves are located at the bases of the aorta and pulmonary artery. They prevent blood from flowing back into the ventricles when they relax.

i. Septum

It is a muscular wall that separates the left and right sides of the heart, preventing the mixing of oxygenated and deoxygenated blood.

j. Aorta

It is the largest artery in the body. It carries oxygenated blood away from the left side of the heart to the systemic circulation.

k. Pulmonary artery

It transports deoxygenated blood from the right ventricle to the lungs.

l. Pulmonary vein

It carries oxygenated blood from the lungs back to the left atrium of the heart.

m. Plasma

It is the liquid portion of blood. It transports nutrients, hormones, waste products, and proteins throughout the body.

n. Red blood cells (Erythrocytes)

They contain haemoglobin, which transports oxygen from the lungs to body tissues and carries away some carbon dioxide.

o. White blood cells (Leukocytes)

They defend the body against pathogens, infections, and foreign substances as part of the immune system.

p. Platelets (Thrombocytes)

They play an important role in blood clotting and haemostasis, preventing excessive bleeding from injuries.

Q2. Differentiate between the following:

a. Serum and Blood

b. Artery and Vein

c. Tricuspid and Bicuspid Valve

d. Systole and Diastole

Q3. Why is a circulatory system necessary?

A circulatory system is necessary because complex multicellular organisms are too large for diffusion alone to supply nutrients and remove wastes efficiently. It ensures the rapid transport of oxygen, nutrients, hormones, and immune cells to all body tissues. It also removes metabolic wastes, such as carbon dioxide and urea.

Q4. Name the three circuits of the circulatory system.

1. Pulmonary Circuit: Carries blood between the heart and the lungs.

2. Systemic Circuit: Carries blood between the heart and the rest of the body tissues.

3. Coronary Circuit: Supplies blood specifically to the heart muscle tissue itself.

Q5. Describe the coronary circuit.

The coronary circuit is a network of blood vessels that delivers oxygenated blood and nutrients to the myocardium (heart muscle) and removes metabolic waste products.

It consists of coronary arteries, which branch off the base of the aorta, and cardiac veins, which drain into the right atrium through the coronary sinus.

Q6. Write the six functions of blood.

1. Transportation of respiratory gases: Blood carries oxygen from the lungs to body tissues and carbon dioxide back to the lungs.

2. Transport of nutrients and wastes: It distributes digested food molecules and carries metabolic wastes to excretory organs.

3. Defence against infection: White blood cells and antibodies protect the body against pathogens.

4. Clotting (Haemostasis): Platelets and clotting factors prevent blood loss from injured blood vessels.

5. Regulation of body temperature: Blood absorbs and redistributes heat throughout the body.

6. Maintenance of pH and osmotic balance: Buffer systems maintain a stable acid-base balance and osmotic pressure.

Q7. What are the organs that are connected to the circulatory system?

The key organs connected to the circulatory system include:

• Heart: Acts as the central pump of the circulatory system.

• Lungs: Carry out gas exchange.

• Kidneys: Filter blood and remove waste products.

• Liver: Processes nutrients and detoxifies blood.

• Gastrointestinal tract: Absorbs nutrients into the blood.

Q8. Name the types of blood vessels.

1. Arteries

2. Arterioles

3. Capillaries

4. Venules

5. Veins

Q9. What are the types of white blood cells? Why are they called white blood cells?

White blood cells are broadly classified into two groups:

1. Granulocytes:

• Neutrophils

• Eosinophils

• Basophils

2. Agranulocytes:

• Lymphocytes

• Monocytes

Reason for the name: They are called white blood cells (leukocytes) because they lack haemoglobin and appear colourless or white when viewed under a microscope compared with red blood cells.

Q10. In what ways does the pulmonary artery differ from all other arteries?

Unlike most other arteries in the body, which carry oxygenated blood, the pulmonary artery carries deoxygenated blood from the right ventricle of the heart directly to the lungs for oxygenation.

Q11. How are the valves of the human heart important?

Heart valves act as one-way gates that ensure blood flows in only one direction through the heart, from the atria to the ventricles and then into the arteries. They prevent the backward flow of blood.

Q12. Suggest why an injury that cuts open an artery is much more dangerous than an injury to a vein.

Arteries carry blood directly from the heart under high pressure. Therefore, an injured artery may cause blood to spurt out rapidly, resulting in massive blood loss in a short time. Veins carry blood under much lower pressure, so bleeding is generally slower.

Q13. Why are valves present in veins but not in arteries?

Veins transport blood back to the heart under low pressure, often against gravity. Therefore, they contain pocket-like valves to prevent blood from flowing backward.

Arteries carry blood under high pressure generated by the heart, which helps maintain forward blood flow without the need for valves along their length.

Q14. Why are the walls of the atria thinner than the walls of the ventricles?

Atria only need to pump blood a short distance into the adjacent ventricles, requiring less muscular force. In contrast, ventricles must pump blood to the lungs or the entire body, requiring greater force and thicker muscular walls.

Q15. Why is the muscle of the left ventricle thicker than that of the right ventricle?

The left ventricle must pump blood through the extensive systemic circuit to the entire body against higher resistance. The right ventricle only pumps blood through the shorter pulmonary circuit to the lungs. Consequently, the left ventricle requires more muscle mass and has a thicker wall.

SECTION III: EXTENSIVE ANSWER QUESTIONS

Q1. Describe the pulmonary and systemic circuits of the circulatory system.

Pulmonary Circuit

1. Deoxygenated blood returns from body tissues to the right atrium.

2. It passes through the tricuspid valve into the right ventricle.

3. The right ventricle pumps blood into the pulmonary trunk and pulmonary arteries.

4. These arteries branch into the left and right lungs, where carbon dioxide is released and oxygen is absorbed through the alveolar capillaries.

5. Oxygen-rich blood returns to the left atrium through four pulmonary veins, completing the pulmonary circuit.

Systemic Circuit

1. Oxygenated blood moves from the left atrium through the bicuspid (mitral) valve into the left ventricle.

2. The left ventricle contracts and forces blood through the aortic valve into the aorta.

3. The aorta distributes blood through systemic arteries to all body organs and tissues.

4. In tissue capillaries, oxygen and nutrients are delivered to cells, while carbon dioxide and other wastes are collected.

5. Deoxygenated blood is collected by venules and veins and eventually drains into the superior and inferior vena cava.

6. The vena cava empties the blood back into the right atrium.

Q2. How are materials transported through the blood?

Materials are transported through blood in two main ways:

1. Through Plasma (Liquid Medium)

• Nutrients: Glucose, amino acids, and lipids absorbed from the digestive tract are transported in plasma to body cells.

• Wastes: Metabolic waste products, such as urea, uric acid, and excess ions, are carried in plasma to the kidneys for excretion.

• Hormones: Chemical messengers secreted by endocrine glands travel through plasma to their target organs.

• Carbon Dioxide: A significant portion of carbon dioxide is transported in the form of dissolved bicarbonate ions \(\mathrm{HCO_3^-}\) in plasma.

2. Through Cellular Components

– Oxygen: It is transported primarily by binding reversibly to haemoglobin inside red blood cells to form oxyhaemoglobin.

Q3. What are the organs connected to the blood circulatory system? Explain.

1. Heart

The heart acts as the central muscular pump that drives blood through blood vessels.

2. Lungs

The lungs facilitate external respiration by oxygenating deoxygenated blood and removing carbon dioxide.

3. Kidneys

The kidneys filter blood, remove nitrogenous wastes, regulate blood volume, and maintain ionic balance.

4. Liver

The liver processes absorbed nutrients, regulates blood glucose levels, synthesizes plasma proteins, and breaks down toxins.

5. Intestines

The intestines absorb digested food materials directly into capillary networks connected to the hepatic portal system.

Q4. What are the components of blood?

Blood consists of two main fractions:

1. Plasma (Approximately 55%)

Plasma is a pale-yellow aqueous solution containing:

• Water

• Dissolved proteins, including albumin, globulins, and fibrinogen

• Electrolytes

• Nutrients

• Hormones

• Waste products

2. Formed Elements / Blood Cells (Approximately 45%)

These include:

• Red Blood Cells (Erythrocytes): Biconcave cells specialized for oxygen transport. In mammals, they lack a nucleus, while in many other vertebrates they are nucleated.

• White Blood Cells (Leukocytes): Nucleated cells involved in immunity and defence against infections.

• Platelets (Thrombocytes): Small cell fragments that play an important role in blood clotting.

Q5. Describe the cell types found in blood.

Blood contains three main types of formed elements:

1. Erythrocytes (Red Blood Cells)

• They are biconcave disc-shaped cells packed with haemoglobin.

• Their shape provides a large surface area for gas exchange.

• They transport oxygen from the lungs to body tissues.

• Their average lifespan is about 120 days.

2. Leukocytes (White Blood Cells)

White blood cells are divided into two main groups:

a. Granulocytes

• Neutrophils: Engulf and destroy bacteria through phagocytosis.

• Eosinophils: Help combat parasites and participate in allergic reactions.

• Basophils: Release histamine during inflammatory responses.

b. Agranulocytes

• Lymphocytes: Produce antibodies and play an important role in adaptive immunity.

• Monocytes: Can differentiate into macrophages, which engulf pathogens and cellular debris.

3. Thrombocytes (Platelets)

• They are tiny cell fragments derived from bone marrow megakaryocytes.

• They gather at sites of blood vessel injury to form a platelet plug.

• They help initiate the blood-clotting process.

Q6. Draw and describe the structure of the human heart.

Structure of the Human Heart

The human heart is a four-chambered muscular organ with the following structures:

1. Chambers

The heart consists of four chambers:

• Two thin-walled upper chambers called atria.

• Two thick-walled lower chambers called ventricles.

2. Septum

A thick internal muscular partition divides the heart into left and right halves. It prevents the mixing of oxygenated and deoxygenated blood.

3. Valves

The heart contains two main types of valves:

• Atrioventricular valves: The tricuspid valve is present between the right atrium and right ventricle, while the bicuspid (mitral) valve is present between the left atrium and left ventricle.

• Semilunar valves: These are present at the bases of the aorta and pulmonary artery. They maintain one-way blood flow.

4. Pericardium

It is a protective double-layered sac that encloses the heart.

5. Blood Supply

The heart muscle receives oxygenated blood through the coronary artery network.

Diagram requirement: Draw a labelled diagram of the human heart showing the four chambers, septum, major blood vessels, and valves.

Q7. Explain the circulation of blood through the human heart.

1. Deoxygenated blood from the body enters the right atrium through the superior and inferior vena cava.

2. From the right atrium, blood flows through the tricuspid valve into the right ventricle.

3. The right ventricle contracts and pumps deoxygenated blood through the pulmonary semilunar valve into the pulmonary artery toward the lungs.

4. In the lungs, blood releases carbon dioxide and absorbs oxygen.

5. Oxygenated blood returns to the left atrium through the pulmonary veins.

6. Blood flows through the bicuspid valve into the left ventricle.

7. The left ventricle contracts and pushes oxygenated blood through the aortic semilunar valve into the aorta for distribution throughout the body.

Q8. Discuss the following heart diseases in humans.

a. Coronary Heart Disease

Coronary heart disease occurs when the coronary arteries become narrowed or blocked by atherosclerotic plaques, which are fatty deposits containing cholesterol. This reduces blood flow and oxygen supply to the heart muscle. It may lead to chest pain (angina) or a heart attack.

b. Myocardial Infarction (Heart Attack)

A myocardial infarction occurs when a coronary artery becomes completely blocked, often by a blood clot. This cuts off the blood supply to a region of the myocardium, causing damage or death of heart muscle tissue (necrosis).

c. Angina (Angina Pectoris)

Angina is a type of chest pain or discomfort that occurs when the heart muscle does not receive enough oxygen-rich blood. It is typically triggered by physical exertion or emotional stress and may be relieved by rest or medication.

Q9. Explain the harmful effects of smoking related to heart diseases.

1. Promotion of Atherosclerosis

Chemicals in tobacco smoke, such as nicotine and carbon monoxide, damage the inner lining of blood vessels (endothelium). This promotes the buildup of fatty plaques in arteries.

2. Increased Heart Rate and Blood Pressure

Nicotine stimulates the sympathetic nervous system, causing the heart to beat faster and blood pressure to rise. This increases the workload of the heart.

3. Blood Clot Formation

Smoking increases blood viscosity and platelet stickiness, raising the risk of dangerous blood clots that can trigger heart attacks and strokes.

4. Reduced Oxygen-Carrying Capacity

Carbon monoxide in cigarette smoke binds preferentially to haemoglobin instead of oxygen. This reduces the amount of oxygen delivered to the heart muscle and other body tissues.

Notes by Sir Dilawar
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