Class 8 :: Biology :: Human Body – II: The Circulatory System

 

Human Body – II: The Circulatory System

✅ SECTION I

A. Choose the correct option.

1. Which of the following blood groups does a universal recipient have?
a. AB b. A c. B d. O
Answer: a. AB

2. Valves are present in …………………….
a. arteries b. veins c. heart d. both veins and heart
Answer: d. both veins and heart

3. The largest veins in the body are the …………………….
a. superior and inferior vena cava
b. aorta
c. pulmonary veins
d. cardiac veins
Answer: a. superior and inferior vena cava

4. The largest artery in the body is the …………………….
a. pulmonary artery b. aorta c. renal artery d. coronary artery
Answer: b. aorta

5. The rhythmic contraction and relaxation of chambers of the heart is:
a. heart rate b. heart attack c. heartbeat d. pulse
Answer: c. heartbeat

6. The circulation of lymphatic fluid increases due to:
P. Heartbeat
Q. Pumping of heart
R. Muscular activity of lymph vessels
S. Exercise

a. Only P
b. Only Q and R
c. Only R and S
d. Only P, Q, and S

Answer: c. Only R and S

7. What is the correct sequence of blood being pumped from lungs to heart?
a. Lungs → Pulmonary Artery → Left Ventricle
b. Lungs → Pulmonary Artery → Left Atrium
c. Lungs → Pulmonary Vein → Left Atrium
d. Lungs → Pulmonary vein → Right Atrium

Answer: c. Lungs → Pulmonary Vein → Left Atrium

8. Rishabh’s father has to undergo a major heart surgery. The doctor advises Rishabh to make prior arrangement of blood that would be required for transfusion during the surgery. His father’s blood group is A. What is the compatible blood group that Rishabh needs to arrange from the blood donors?
P. AB
Q. O
R. A

a. Only P
b. Only Q
c. Only P and Q
d. Only Q and R

Answer: d. Only Q and R

9. Which of the following is the feature of an artery?
a. Wider cavity b. Thin wall c. One layer d. Thick wall
Answer: d. Thick wall

10. In ……………………. circulation, blood is transported from the heart, through the lungs, and then back to the heart.
a. systemic b. double c. pulmonary d. coronary
Answer: c. pulmonary

 

✅ B. Assertion and Reasoning Questions

1. Assertion (A): A person with the blood group O is called a universal donor.
Reason (R): Blood group O has no antibody.
a. Both A and R are True.
b. Both A and R are False.
c. A is True and R is False.
d. A is False and R is True.

Answer: c. A is True and R is False

2. Assertion (A): The white blood cells act as soldiers and fight against germs.
Reason (R): The white blood cells are components of plasma.

a. Both A and R are True.
b. Both A and R are False.
c. A is True and R is False.
d. A is False and R is True.

Answer: c. A is True and R is False

✅ C. Name the following.

1. The fluid matrix in blood
Answer: Plasma

2. Structure present in the heart, responsible for initiating heartbeat
Answer: Pacemaker (Sinoatrial node – SAN)

3. Distributing chambers of the heart
Answer: Ventricles

4. Blood vessel carrying blood to the left atrium
Answer: Pulmonary vein

5. The blood group of a universal donor
Answer: O

✅ D. Write True or False. Correct the false statements by changing the first or last word/s.

1. The largest artery in the human body is the pulmonary artery.
Answer: False — The largest artery is the aorta.

2. Pacemaker is responsible for initiating the heartbeat.
Answer: True

3. Tricuspid valve lies between the left atrium and left ventricle.
Answer: False — It lies between the right atrium and right ventricle.

4. Lymph is transported to body parts due to pumping action of the heart.
Answer: False — It moves due to muscular movement.

5. The right ventricle pumps blood to the lungs.
Answer: True

✅ E. Match the items

Column A	Column B
1. Bicuspid valve	d. Between left atrium and left ventricle
2. Ventricles	e. Lower chambers of the heart
3. Pericardium	b. Double-layered sac
4. Antigen	f. Protein substance on the surface of RBC
5. Systemic circulation	a. From heart to body parts and back to heart

 

🔹 F. Choose the odd one out from the following terms and name the category to which the others belong.

1. Blood, Lymph, Heart, Blood vessels
Answer:
Odd one: Lymph
Category of others: Components of the circulatory (cardiovascular) system

2. Valves in veins, Aortic semilunar valves, Tricuspid valve, Bicuspid valve
Answer:
Odd one: Valves in veins
Category of others: Valves present in the heart

3. RBC, SAN, WBC, Platelet
Answer:
Odd one: SAN
Category of others: Components of blood

4. Lymphatic vessel, Lymph, Blood, Lymph node
Answer:
Odd one: Blood
Category of others: Components of the lymphatic system

5. Palpitation, Congestion, Hypertension, Heart Attack
Answer:
Odd one: Congestion
Category of others: Conditions related to improper functioning of the heart

 

🔹 G. Choose between the two options to answer the questions specified in brackets.

1. Arteries or veins (Which of these carries blood towards the heart?)
Answer: Veins

2. Aortic semilunar valve or pulmonary semilunar valve (Which of these is located on the right side?)
Answer: Pulmonary semilunar valve

3. Systole or diastole (Which of these is the contraction phase of chambers of heart?)
Answer: Systole

4. Blood or lymph (Which of these fluids is devoid of RBC?)
Answer: Lymph

5. Pulmonary circulation or systemic circulation (Which of these takes a longer route?)
Answer: Systemic circulation

 

✅ SECTION II

H. Give reasons for the following.

1. Ventricles have thicker walls as compared to auricles.
Answer: Because ventricles pump blood with greater force to long distances.

2. Valves are present in veins.
Answer: To prevent backflow of blood.

3. Double circulation is an efficient way of blood circulation in humans.
Answer: Because it keeps oxygenated and deoxygenated blood separate.

4. A person with blood group O is called a universal donor.
Answer: Because it has no antigens.

5. A person with blood group A cannot donate blood to a recipient having blood group B.
Answer: Because antibodies in B react with antigen A.

 

✅ I. Differentiate between the following pairs of words based on the terms given in brackets.

1. Left auricle vs Right ventricle (organ/s that send blood to them)

Left auricle (Left atrium)	Right ventricle
Receives blood from the lungs (via pulmonary veins)	Receives blood from the right atrium
Gets oxygenated blood from lungs	Gets deoxygenated blood from right atrium

 

2. Bicuspid vs Tricuspid valve (function)

Bicuspid valve (Mitral valve) Tricuspid valve Prevents backflow of blood from left ventricle to left atrium Prevents backflow of blood from right ventricle to right atrium Ensures one-way flow of oxygenated blood on the left side Ensures one-way flow of deoxygenated blood on the right side

3. Heart vs Blood vessels (location)

Heart	Blood vessels
Located in the chest cavity between the lungs	Located throughout the entire body
Lies slightly towards the left side of the body	Spread from the heart to all body parts forming a network

 

4. Antigen A vs Antigen B (their complementary antibodies)

Basis	Antigen A	Antigen B
Complementary antibody present in plasma	Anti-B antibody	Anti-A antibody

 

5. Platelets vs White Blood Cells (functions)

Platelets	White Blood Cells
Clot blood	Fight infection

✅ J. Mention exact location

1. Pericardium → Around the heart
2. Aorta → Leaves left ventricle
3. Pulmonary semilunar valve → Between right ventricle & pulmonary artery
4. SAN → Upper right atrium
5. Haemoglobin → In RBC

 

🔹 K. Differentiate between the following.

1. Arteries and veins.

Answer:

Arteries	Veins
Carry blood away from the heart	Carry blood towards the heart
Usually carry oxygenated blood (except pulmonary artery)	Usually carry deoxygenated blood (except pulmonary vein)
Thick, elastic and muscular walls	Thin and less elastic walls
Narrow lumen	Wider lumen
Blood flows at high pressure	Blood flows at low pressure
No valves present	Valves present to prevent backflow
Located deeper in the body	Often located closer to the skin
Pulse can be felt	No pulse can be felt

2. Bicuspid valve and tricuspid valve.

Answer:

Bicuspid valve (Mitral valve)	Tricuspid valve
Located between left atrium and left ventricle	Located between right atrium and right ventricle
Present on the left side of the heart	Present on the right side of the heart
Has two flaps (cusps)	Has three flaps (cusps)
Prevents backflow of blood into left atrium	Prevents backflow of blood into right atrium
Handles oxygenated blood	Handles deoxygenated blood
Experiences higher pressure	Experiences lower pressure

3. Systole and diastole.

Answer:

Systole	Diastole
Contraction phase of the heart	Relaxation phase of the heart
Blood is pumped out of the heart	Chambers fill with blood
Pressure in arteries increases	Pressure in arteries decreases
Occurs when ventricles contract	Occurs when ventricles relax
Shorter duration	Longer duration
Represents active phase	Represents resting phase

4. Blood and lymph.

Answer:

Blood	Lymph
Red in colour	Pale yellow or colourless
Contains RBCs, WBCs, platelets, plasma	Mainly contains WBCs and plasma
Transports oxygen, nutrients and wastes	Transports fats and fights infection
Flows through arteries and veins	Flows through lymph vessels
Pumped by the heart	Moves due to muscle movement
Faster circulation	Slower circulation
Contains haemoglobin	Does not contain haemoglobin

5. Pulmonary circulation and systemic circulation.

Answer:

Pulmonary circulation	Systemic circulation
Between heart and lungs	Between heart and body parts
Carries deoxygenated blood to lungs and brings oxygenated blood back	Carries oxygenated blood to body and returns deoxygenated blood
Shorter route	Longer route
Right ventricle → lungs → left atrium	Left ventricle → body → right atrium
Helps in oxygenation of blood	Supplies oxygen to body tissues
Lower pressure	Higher pressure

 

🔹 L. Short answer questions

1. Name the three components of the cardiovascular system?
Answer:
The three components of the cardiovascular system are blood, heart and blood vessels.

2. What are the different blood groups identified by the ABO blood grouping system?
Answer:
The different blood groups identified by the ABO blood grouping system are A, B, AB and O.

3. Name the four chambers of the heart.
Answer:
The four chambers of the heart are right atrium, left atrium, right ventricle and left ventricle.

4. What are blood vessels? Name the different types of blood vessels found within the human body.
Answer:
Blood vessels are tube-like structures that transport blood throughout the body.
The different types of blood vessels are arteries, veins and capillaries.

5. What causes hypertension?
Answer:
Hypertension is caused due to factors such as high intake of salty and fatty food, stress, lack of physical activity, smoking and obesity.

6. What is the value of normal blood pressure for an adult?
Answer:
The normal blood pressure for an adult is 120/80 mm Hg.

7. Cardiac arrest is a serious health issue. Justify.
Answer:
Cardiac arrest is a serious health issue because the heart suddenly stops pumping blood, which stops the supply of oxygen to the brain and other organs. This can lead to loss of consciousness and may cause death if not treated immediately.

🔹 M. Long answer questions

1. Describe the internal structure of the human heart.
Answer:
The human heart is a muscular organ about the size of a clenched fist, located in the chest cavity between the lungs. It is enclosed in a double-walled sac called the pericardium, which contains pericardial fluid to reduce friction.

The heart has four chambers: two upper chambers called atria (auricles) and two lower chambers called ventricles.

• The right atrium receives deoxygenated blood from the body through 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 through the pulmonary veins.
• The left ventricle pumps oxygenated blood to the body through the aorta.

The right and left sides are separated by a muscular wall called the septum, which prevents mixing of oxygenated and deoxygenated blood.

2. Draw labelled diagrams to show the internal structure of an artery and a vein.
Answer:

Artery (cross-section):

Thick outer layer
Thick muscular middle layer
Narrow lumen
No valves

Vein (cross-section):

Thin outer layer
Thin muscular layer
Wide lumen
Valves present

(Arteries have thick walls and narrow lumen, while veins have thin walls and valves.)

3. Mention the location and function of the valves present inside the heart.
Answer:

• Tricuspid valve
  Location: Between right atrium and right ventricle
  Function: Prevents backflow of blood into the right atrium
• Bicuspid (mitral) valve
  Location: Between left atrium and left ventricle
  Function: Prevents backflow into the left atrium
• Semilunar valves
  Location: At the openings of the aorta and pulmonary artery
  Function: Prevent backflow of blood into the ventricles

All valves ensure that blood flows in one direction only.

4. Give a brief account of the lymphatic system.
Answer:
The lymphatic system consists of lymphatic vessels, lymph nodes and lymph, a fluid present in the body.

It runs parallel to the circulatory system. Lymph is a pale yellow fluid containing lymphocytes (white blood cells).

Functions of the lymphatic system:

• Helps in fighting infections
• Transports fats and absorbed nutrients
• Drains excess fluid from tissues
• Maintains fluid balance in the body

The movement of lymph is due to muscle contraction, not by the heart.

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5. Describe the antigen and antibody compositions of the four types of blood groups. Why are blood groups O and AB called universal donor and universal recipient, respectively?
Answer:

Blood Group	Antigen on RBC	Antibody in Plasma
A	Antigen A	Antibody b
B	Antigen B	Antibody a
AB	Antigen A and B	None
O	None	Antibody a and b

• Blood group O is called the universal donor because it has no antigens, so it can be given to any blood group.
• Blood group AB is called the universal recipient because it has no antibodies, so it can receive blood from any group.

 

✅ Picture Study Answers

 

1.

a. Which chambers of the heart are contracting?
Answer: Ventricles

b. Label parts 1–5:

1. Right ventricle
2. Left ventricle
3. Pulmonary artery
4. Aorta
5. Left atrium

c. Distributing chambers:
Answer: Ventricles → arteries

d. Function of SAN:
Answer: Starts heartbeat; located in right atrium

1e. Vessel supplying heart muscles:
Answer: Coronary artery

✅ Diagram Question 2

a. Type: Double circulation
Routes: Pulmonary & Systemic

b. Labels:

1. Vena cava
2. Aorta
3. Pulmonary vein
4. Pulmonary artery

✅ Diagram Question 3

a. Name the blood vessels 1–3 in the diagram.
Answer:
1 – Artery
2 – Vein
3 – Capillaries

b. Which blood vessel is provided with valves?
Answer:
The blood vessel provided with valves is the vein (2).

c. Which blood vessel carries blood away from the heart?
Answer:
The blood vessel that carries blood away from the heart is the artery (1).

d. Give the name of the blood vessel responsible for exchange of substances between blood and cells in the body.
Answer:
The blood vessel responsible for exchange of substances is the capillaries (3).

e. Which is the only artery carrying deoxygenated blood? Why is it called an artery?
Answer:
The only artery carrying deoxygenated blood is the pulmonary artery.
It is called an artery because it carries blood away from the heart, even though the blood is deoxygenated.

 

🔹 My Learning Corner

A. Think about

1. Why are valves present in veins and not in arteries? (Hint: What is the function of valves?)
Answer:
Valves are present in veins to prevent the backflow of blood and ensure that blood flows only in one direction towards the heart. Blood in veins flows at low pressure, so there is a chance of it flowing backward, especially against gravity (like from legs to heart).
In arteries, blood flows at high pressure directly from the heart, so there is no need for valves.

2. Does sudden cardiac arrest differ from heart attack? What medical care can be provided for such emergency situations?
Answer:
Yes, sudden cardiac arrest and heart attack are different.

• A heart attack occurs when blood flow to a part of the heart is blocked.
• A cardiac arrest occurs when the heart suddenly stops beating.

Medical care for such emergencies includes:

• Immediate CPR (Cardiopulmonary Resuscitation)
• Use of a defibrillator to restore heartbeat
• Quick medical attention and hospitalization

B. Try out

1. Visit a pathologist and find out how blood tests can reveal the presence of infection and other diseases such as diabetes. Write a report for your class based on it and present it in your class. (English)

Answer (Sample Report):

Title: How Blood Tests Help Detect Diseases

Blood tests are very useful in diagnosing diseases. A pathologist examines blood samples to detect abnormalities.

• Infections:
  When a person has an infection, the number of white blood cells (WBCs) increases. This helps doctors identify bacterial or viral infections.
• Diabetes:
  Blood tests measure the level of glucose (sugar) in the blood. High glucose levels indicate diabetes.
• Haemoglobin levels:
  Low haemoglobin indicates anaemia, which causes weakness.
• Platelet count:
  Helps in detecting blood clotting problems.

Thus, blood tests provide important information about a person’s health and help in early diagnosis and treatment of diseases.

 

🔹 2. A Physical Education teacher wanted to investigate the heart rate of students, aged 16–18 years, after they performed different types of activities for about 10 mins. The results have been represented below in the form of a bar graph. (Mathematics)

a. Which activity gave the lowest pulse rate?
Answer: The activity that gave the lowest pulse rate is Rest.

b. What is the normal rate of heartbeat in an adult? Is it the same as the pulse rate?
Answer:
The normal rate of heartbeat in an adult is about 72 beats per minute.
Yes, the heartbeat rate is generally the same as the pulse rate, because pulse is the result of the heartbeat.

c. According to the bar graph, which activity consumed the greatest number of calories?
Answer: The activity that consumed the greatest number of calories is Run, as it shows the highest pulse rate.

d. Which activities would you suggest to a 12-year-old obese child for reducing weight?
Answer: Activities like running, dancing and swimming should be suggested, as they increase heart rate and help burn more calories.

e. How does exercise improve the health of the heart?
Answer:
Exercise improves heart health by:

• Strengthening the heart muscles
• Increasing blood circulation
• Improving oxygen supply to body cells
• Reducing the risk of heart diseases

🔹 3. Create a working model of the human heart to demonstrate how it works. You can use materials like plastic balls, balloons, plastic tubes, tapes, blue and red coloured plasticine, small bulbs in red and blue, wires, or any other material of your choice. Use your creative imagination to make the model.

Answer:
A working model of the human heart can be made using:

• Balloons to represent heart chambers
• Plastic tubes as blood vessels
• Red and blue colours to show oxygenated and deoxygenated blood
• A pump or squeezing mechanism to demonstrate blood flow

This model helps to show how blood flows through different chambers and vessels of the heart.

🔹 Self-Assessment (Answers / What you should know)

1. Name the components of the cardiovascular system.
Answer: Blood, heart and blood vessels

2. Differentiate between artery and vein.
Answer:

• Artery: carries blood away from heart, thick walls
• Vein: carries blood towards heart, valves present

3. Name the great vessels entering and leaving heart and state their functions.
Answer:

• Vena cava: brings deoxygenated blood to heart
• Pulmonary artery: carries blood to lungs
• Pulmonary vein: brings oxygenated blood to heart
• Aorta: carries oxygenated blood to body

4. Define double circulation of blood.
Answer:
Double circulation means blood passes through the heart twice in one complete cycle — pulmonary and systemic circulation.

5. Define hypertension and explain how it can be managed.
Answer:
Hypertension is high blood pressure.
It can be managed by:

• Healthy diet (low salt and fat)
• Regular exercise
• Avoiding stress
• Avoiding smoking and alcohol

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