Selina Concise Solutions for ICSE Class 6 Biology Chapter 6 The Circulatory System

Multiple Choice Questions:

1. Put a tick mark (✓) against the correct alternative in the following statements:

(a) Function of WBCs is to
(i) Transport oxygen
(ii) Help in clotting of blood
(iii) Provide immunity
(iv) Provide storage of food.
Answer: (iii) Provide immunity
White blood cells act as the body's defense system by attacking harmful germs. They help keep us healthy by fighting off infections that enter our bloodstream.
Teacher's Tip: Remember "W" in WBC stands for "Warrior" because they fight germs.
Exam Tip: Always use the word "immunity" or "defense" when describing the function of WBCs.

(b) Blood Capillary is a
(i) Broad tube
(ii) Artery with thick wall
(iii) Vein with large lumen
(iv) Narrow tube made up of endothelium only.
Answer: (iv) Narrow tube made up of endothelium only.
Capillaries are the thinnest blood vessels and allow for the exchange of gases and nutrients. Their walls are only one cell thick to make this exchange very easy.
Teacher's Tip: Think of capillaries as tiny side-streets where goods are delivered to houses.
Exam Tip: Mention "one cell thick" to describe capillary walls for extra marks.

(c) Nucleus is absent in
(i) RBCs
(ii) VBCs
(iii) All blood cells
(iv) Liver cells.
Answer: (i) RBCs
Mature red blood cells lose their nucleus to create more space for carrying oxygen. This specialized shape helps them move through narrow blood vessels efficiently.
Teacher's Tip: RBCs are like "Empty Trucks" - they get rid of the driver's cabin (nucleus) to carry more cargo (oxygen).
Exam Tip: Specify that the nucleus is absent in "mature" RBCs for full marks.

(d) The only artery which carries deoxygenated blood is called,
(i) Hepatic artery
(ii) Pulmonary artery
(iii) Aorta
(iv) Renal artery
Answer: (ii) Pulmonary artery
While most arteries carry oxygen-rich blood, this specific artery takes "used" blood to the lungs. Once in the lungs, the blood picks up fresh oxygen to be sent back to the heart.
Teacher's Tip: "Pulmonary" always refers to the lungs, and this is the exception to the artery rule.
Exam Tip: In biology, "deoxygenated" means the blood is carrying more $CO_{2}$ than oxygen.

(e) Sphygmomanometer ni’sures
(i) Pulse rate
(ii) Heart beat
(iii) Blood pressure
(iv) Brain activity
Answer: (iii) Blood pressure
This instrument uses an inflatable cuff to measure the force of blood against the walls of your arteries. It is a vital tool for doctors to check your heart health.
Teacher's Tip: Break the long word down: Sphygmo-mano-meter.
Exam Tip: Practice the spelling of "Sphygmomanometer" as it is a common technical term in exams.

(f) Pulmonary vein carries
(i) Oxygenated blood
(ii) Deoxygenated blood
(iii) Glucose-rich blood
(iv) C02 laden blood
Answer: (i) Oxygenated blood
This vein brings fresh, oxygen-filled blood back to the heart from the lungs. It is the only vein in the human body that carries oxygen-rich blood.
Teacher's Tip: Veins usually go "TO" the heart, and this one brings the "Good" blood from the lungs.
Exam Tip: Remember that "Pulmonary" means "Lung-related" and indicates an exception to the normal blood vessel rule.

(g) The blood tastes saltish due to the dissolved:
(i) Sodium chloride
(ii) Potassium chloride
(iii) Ammonium nitrate
(iv) Sodium nitrate
Answer: (i) Sodium chloride
Sodium chloride is the common salt we use in food, and it is naturally found in our blood plasma. These minerals are important for maintaining the balance of fluids in our body.
Teacher's Tip: Think of "Sodium" as the saltiness in your sweat or tears.
Exam Tip: Chemical names like "Sodium Chloride" should be written clearly to avoid confusion with other salts.

Short Answer Questions:

1. Differentiate between the following pair of terms:

Question : Patelets and WBC
Answer:
Platelets
1. These are colourless, oval or round, cytoplasmic fragments found floating in the blood.
2. These play a major role in blood clotting.
3. Their life span is 3-5 days and it is called thrombocytes.
WBC
1. WBC are colourless and lack haemoglobin, larger in quantity, and have distinct oval and lobed nucleus.
2. They prevent body from disease causing germs by providing immunity
3. Their life span is short i.e. 5 to 20 days.
Platelets are essential for stopping bleeding when you get a cut by forming a scab. White blood cells are different because they actively fight off viruses and bacteria to keep you from getting sick.
Teacher's Tip: Platelets are the "Plaster" (clotting) and WBCs are the "Warriors" (fighting).
Exam Tip: Use the scientific names "Thrombocytes" and "Leukocytes" to show deeper knowledge.

Question : Pulmonary artery and pulmonary vein
Answer:
Pulmonary artery
1. This involves circulation of blood from the heart to the lungs.
2. It carries deoxygenated blood.
Pulmonary vein
1. This involves circulation of blood to the heart from the lungs.
2. It carries oxygenated blood.
The pulmonary artery is unique because it takes "dirty" blood to the lungs to get cleaned. The pulmonary vein is special because it brings "clean," oxygen-rich blood back into the heart.
Teacher's Tip: "A" for Artery goes "Away" from the heart; "V" for Vein comes back to it.
Exam Tip: In a diagram, the pulmonary artery is usually colored blue, and the pulmonary vein is red.

Question : Vena Cava and Aorta
Answer:
Vena Cava
1. Vena Cava is a large vein.
2. It carries deoxygenated blood from the upper and lower parts of the body i.e. head and shoulders.
Aorta
1. Aorta is the large artery.
2. It carries oxygenated blood to all parts of the body through its branches.
The Vena Cava acts like a giant drain that collects blood from all over the body to bring it back to the heart. The Aorta is like a giant main pipe that pumps fresh blood out to every single cell in your body.
Teacher's Tip: Aorta is the "Almighty" biggest artery; Vena Cava is the "Very big" vein.
Exam Tip: Vena Cava consists of two parts: the superior and the inferior, which is good to mention.

Question : RBC and WBC
Answer:
RBC
1. They do not have nucleus at maturity.
2. They possess haemoglobin and are red.
3. They help in transport of respiratory gases.
WBC
1. They have a large characteristic nucleus.
2. They are colourless as they have no pigment.
3. They help in defence mechanism.
Red blood cells look like red discs and their main job is to deliver oxygen to your organs. White blood cells are often larger and have different shapes to catch and destroy invaders like bacteria.
Teacher's Tip: RBCs are the "Red Delivery Trucks" and WBCs are the "White Security Guards".
Exam Tip: Mention "haemoglobin" when talking about RBCs as it is the pigment that makes them red.

Question : Give any three differences between an artery and a vein:
Answer: Following are the differences between the artery and a vein:
Artery
1. Arteries carry blood from the heart to various body parts.
2. These carry oxygenated blood (except the pulmonary artery).
3. Blood flows with high speed and under high pressure.
Vein
1. Veins carry blood from different body parts to the heart.
2. These carry deoxygenatec blood (except the pulmonary vein).
3. Blood flows with low speech and under low pressure.
Arteries have thick, elastic walls because the heart pumps blood into them with great force. Veins have thinner walls and often contain valves to make sure blood only flows in one direction back to the heart.
Teacher's Tip: Feel your pulse on your wrist - that is the pressure of blood in an artery!
Exam Tip: Drawing a simple table for differences is the best way to get full marks for this question.

Question : Blood consists of two parts - a liquid part and a cellular part. Name these parts and briefly write about them.
Answer:
1. Plasma: The plasma is a light-yellow coloured, alkaline liquid which mainly consists of:
Water- 90-92%
Proteins - 7-8%
Inorganic salts - 1%
Other substances - traces
2. Cellular elements : These elements are of three categories:
Red blood cells (erythrocytes)
White blood cells (leukocytes)
Blood platelets (thrombocytes)
Plasma is the watery base that allows blood to flow smoothly through your vessels. The cellular elements are the solid parts floating in that liquid, each doing a specific job for your health.
Teacher's Tip: Think of blood like a soup: Plasma is the broth, and cells are the veggies and meat.
Exam Tip: Remember the percentages for Plasma components as they are frequently asked in short questions.

Question : What is the role of haemoglobin in the blood ?
Answer: The haemoglobin is the respiratory pigment which is formed of the iron containing part known as haemin and protein part known as globin. It helps to transport respiratory gases (oxygen).
Haemoglobin binds with oxygen molecules to carry them from the lungs to the rest of the body. Without enough iron to make haemoglobin, your body cannot get the oxygen it needs to function properly.
Teacher's Tip: Iron acts like a magnet for oxygen in your blood.
Exam Tip: Use the term "respiratory pigment" to define haemoglobin for a more professional answer.

Question : Fill in the blanks with suitable words given below:
1. The colour of a red blood cell is due to haemoglobin.
2. The two lower chambers of the heart are called ventricles.
3. The blood plasma contains a dissolved substance such as nutrient, proteins, waste products and harmones.
4. The pulmonary artery takes the blood from the ventricles to the lungs.
5. The instrument used to find out the blood pressure is known as sphygmomanometer.
6. The blood loaded with carbon dioxide from the body comes into the right auricle of the heart.
7. The oxygen-rich blood from the lungs comes into the left ventricle of the heart.
8. The oxygen-rich blood is pumped into different parts of the body through aorta.
9. The carbon dioxide loaded blood from right ventricle is pumped into the lungs through pulmonary artery.
10.The liquid part of coagulated blood is known as serum.
Answer: (As highlighted in the blanks above)
These key terms describe how the heart functions and how blood carries nutrients and waste. Knowing these specific names helps us understand the complex path blood takes through our body.
Teacher's Tip: Ventricles are at the "V" (bottom) of the heart, while Auricles/Atria are at the "A" (top).
Exam Tip: Be careful with the spelling of "Ventricle" and "Auricle" to avoid losing small marks.

Question : In which organ of our body does blood get oxygenated?
Answer: Blood becomes oxygenated in the lungs. The oxygenated blood is returned to left verticles by the pulmonary vein.
When we breathe in, oxygen enters the tiny air sacs in our lungs and moves into the blood. This process changes the "blue" deoxygenated blood into "red" oxygenated blood.
Teacher's Tip: Think of the lungs as the "Oxygen Refilling Station" for your blood.
Exam Tip: Mention the specific blood vessel (pulmonary vein) that carries this blood back to the heart.

Question : Which side of the heart (left or right) contains oxygenated blood?
Answer: The left side of the heart contains oxygenated blood.
The left side receives fresh blood from the lungs and pumps it out to the whole body. This is why the muscle on the left side of the heart is usually thicker and stronger.
Teacher's Tip: "L" for Left is for "L"ife-giving oxygen.
Exam Tip: Remember: Right side = deoxygenated (to lungs); Left side = oxygenated (to body).

Question : Name the disease in which the number of platelets reduces to 25,000 - 30,000 per cubic mm of blood. State its major symptoms.
Answer: Dengue fever is one such disease in which the number of platelets get reduced to as low as 25-30 thousands per cubic mm of blood. The major symptoms of dengue are high fever, rashes or red spots on body, nausea or vomiting, pain in abdomen, back, or back of the eyes and muscles.
When platelet levels drop this low, the blood cannot clot properly, which can lead to internal bleeding. It is important to rest and stay hydrated if someone is diagnosed with this mosquito-borne illness.
Teacher's Tip: Dengue is often called "Break-bone fever" because of the severe muscle and joint pain.
Exam Tip: Always list the "high fever" and "low platelet count" as the primary identifiers for Dengue.

Long answer Questions:

Question 1: Name the three kinds of blood vessels found in human beings. With the help of suitable diagrams, differentiate between them.
Answer: The three kind of blood vessels found in human beings are arteries, veins and capillaries.
1. Arteries are the blood vessels that carry blood from the heart to the various parts of the body.
2. Veins are the blood vessels that carry blood from the body parts to the heart.
Capillaries: These are the terminal branches of an artery, which rejoin to form a vein. A capillary is a very narrow tube whose walls have a single layer of cells with no muscles. Although the wall of a capillary is very thin, yet an exchange of nutrients, waste products and gases take place between the blood and the body fluids.
Differences:
Arteries
1. Carry blood away from the heart.
2. Have thick and more muscular walls.
3. Carry oxygenated blood (except pulmonary artery which carries deoxygenated blood).
4. The blood flows with jerks and under great force.
Veins
1. Carry blood towards the heart.
2. Have thin and less muscular walls.
3. Carry deoxygenated blood (except pulmonary vein which carries oxygenated blood).
4. The blood flows smoothly and under little pressure.
Capillaries:
1. Arteries after entering an organ divide into number of smaller branches called arterioles which further divide repeatedly to form a network of fine branches called capillaries.
2. The walls of the capillaries are very thin and are one cell deep.
3. The Capillaries after the metabolic exchange unite to form larger vessels called venules, which again unite to form a vein.
Each type of blood vessel is designed perfectly for its job, whether it's carrying high-pressure blood or allowing tiny nutrients to pass through. Together, they form a closed loop that keeps our whole body alive and nourished.
Teacher's Tip: Arteries = Away (High speed), Veins = Visit (Back to heart), Capillaries = Connect (Tiny bridges).
Exam Tip: For long answers, always use headings and numbered points to make your answer easy for the teacher to grade.

PQ. During surgical operations or during accidents, the patient may be given blood from outside to save his life. What is the technical name of this process ? Briefly explain the precautions to be taken in this process.
Answer: During surgical operation or an accident when excess of bleeding takes place, the patient may be given blood from outside to save his life. The transfer of blood from the donor to the recipient is called blood transfusion. The following precautions are taken before the blood is given to the needy person:
1. Matching of the donor’s blood with that of the recipient should be done.
2. It should be made sure clinically that blood of donor is free from any infection.
3. Sterilization of all the instruments to be used during the operation is must.
Giving the wrong type of blood can cause the blood to clump together, which is very dangerous for the patient. Testing for diseases like HIV or Hepatitis ensures that the donated blood is safe to use.
Teacher's Tip: Think of blood types like "matching keys to locks" - only the right fit works.
Exam Tip: Mention "Blood Matching" (cross-matching) as the most important step in the transfusion process.

Question 2: State briefly, the difference between white blood cells and the red blood cells.
Answer: Difference between white blood cells and the red blood cells
RBC
1. They do not have nucleus atmaturity.
2. They possess haemoglobin and are red.
3. They help in transport of respiratory gases.
4. Life span is 120 days.
5. They are about 5 million/$mm^{3}$ of blood.
6. In the embryonic stage the RBC are formed in the liver and spleen. But after birth, they are formed in the red bone marrow.
WBC
1. They have a large characteristic nucleus.
2. They are colourless as they have no pigment.
3. They help in defence mechanism.
4. WBC have a short life.span of 5 to 20 days.
5. They are about 7000/$mm^{3}$ of blood.
6. WBC are formed in the red bone marrow.
RBCs are much more numerous because every cell in the body needs a constant supply of oxygen to survive. WBCs are fewer in number but increase rapidly whenever your body is trying to fight off an illness.
Teacher's Tip: Use the numbers to remember: millions of RBCs, but only thousands of WBCs.
Exam Tip: Including the "life span" in your comparison table shows you have studied the topic thoroughly.

Question 3: You can see some blood vessels on the outside of the hands specially in older people. Are those veins or arteries ? How can you confirm your answer ?
Answer: In older persons the skin becomes loose as the fat below becomes less with age and the vessels passing through these areas especially on the outside of the hands become prominent. These are veins as they flow superficially. The veins are thin and less muscular. These carry the blood to the heart veins are placed superficially so they are easily visible to the eye and are prominent. The blood in the veins will be carrying $CO_{2}$ and will have many substances like sugar, amino acids, chemicals and bacteria.
Veins are located closer to the surface of the skin, which is why we can see them, whereas arteries are buried deep to keep them safe. You can confirm they are veins because they don't have a strong pulse like the arteries do.
Teacher's Tip: If the vessel looks blue or green through your skin, it is a vein!
Exam Tip: Use the word "superficial" to describe the location of veins near the skin's surface.

Question 4: Given alongside is a diagram of human heart showing its internal structures. Label the parts marked 1 to 6, and answer the following questions.
(a) Which types of blood is carried by the blood vessel marked 2?
(b) Name the main artery which takes the blood from heart to different parts of the body?
(c) Which chamber of the heart receives deoxygenated blood from the body?
(d) Which chamber of the heart receives oxygenated blood from the lungs ?
Answer:
1. Left pulmonary artery
2. superior vena cava
3. Left pulmonary vein
4. Right auricle
5. Left auricle
6. Left ventricle
(a) Deoxygenated blood.
(b) Aortic arch (Aorta).
(c) Right Atrium.
(d) Left Atrium
This diagram shows how the heart is divided into sections to keep "clean" and "used" blood from mixing. Labeling these parts helps us trace the exact path blood takes as it flows in and out of the heart.
Teacher's Tip: Always remember that in diagrams, "Left" and "Right" are reversed because you are looking at someone else's heart.
Exam Tip: Practice drawing this diagram and labeling the four main chambers (auricles and ventricles) first.

ADDITIONAL QUESTIONS

I. Multiple choice questions. Tick ( ✓ ) the correct choice:

1. Human heart has
(a) one auricle and one ventricle.
(b) two auricles and one ventricle.
(c) two auricles and two ventricles.
(d) one auricle and two ventricles.
Answer: (c) two auricles and two ventricles.
The four-chambered heart is very efficient for mammals because it completely separates oxygen-rich and oxygen-poor blood. This allows us to have a high level of energy and maintain our body temperature.
Teacher's Tip: Imagine a 4-room apartment: 2 rooms on top (auricles) and 2 rooms on the bottom (ventricles).
Exam Tip: Mention the number "4" if you are ever asked how many chambers the human heart has.

2. The blood vessels in which blood goes away from the heart to different body parts are
(a) arteries
(b) capillaries
(c) veins
(d) both arteries and veins.
Answer: (a) arteries
Arteries are the high-pressure "delivery" tubes that branch out from the heart like roots of a tree. They carry the oxygen and food that every part of your body needs to grow.
Teacher's Tip: "A" for Artery = "A"way from the heart.
Exam Tip: Do not confuse this with veins, which always bring blood back to the heart.

3. The heartbeat is measured by an instrument called
(a) thermometer
(b) sphygmomanometer
(c) stethoscope
(d) none of the above
Answer: (c) stethoscope
A stethoscope amplifies the "lub-dub" sounds of the heart valves closing as they pump blood. Doctors use it to listen for any unusual sounds that might indicate a problem with the heart.
Teacher's Tip: The stethoscope makes your heartbeat sound much louder so it's easier to count.
Exam Tip: If the question asks about "Blood Pressure," the answer is sphygmomanometer, but for "Heartbeat," it's a stethoscope.

4. The blood cells which protect the body from infection are
(a) RBCs
(b) platelets
(c) WBCs
(d) all the above
Answer: (c) WBCs
White Blood Cells are specialized to recognize foreign invaders like germs and neutralize them. They are like a mobile security team that patrols your entire body through the blood vessels.
Teacher's Tip: WBCs are the "Protectors" of the body.
Exam Tip: Identify WBCs as "Leukocytes" in advanced biology questions for extra points.

5. The four blood groups in humans are
(a) A, B, C and D
(b) A, B, AB and C
(c) A, B, AB and O
(d) A, B, AB and OO
Answer: (c) A, B, AB and O
Blood groups are determined by specific markers on the surface of your red blood cells. Knowing your blood group is essential if you ever need to receive blood from someone else.
Teacher's Tip: Just remember the first two letters of the alphabet (A, B), their combo (AB), and the letter "O".
Exam Tip: Group 'O' is the universal donor, and 'AB' is the universal recipient.

II. Fill in the blanks.
1. In human body, heart is located on the left side of the chest cavity.
2. The blood vessels which carry blood from the heart to different parts of the body are called arteries.
3. Arteries carry pure blood.
4. The red-coloured pigment present in RBCs is called Haemoglobin.
5. The fluid part of blood is called plasma.
Answer: (As highlighted in the blanks above)
These basic facts form the foundation of how our circulatory system works every day. Each blank represents a major component or location that keeps our blood moving.
Teacher's Tip: "Pure" blood is another name for oxygenated blood.
Exam Tip: When filling blanks, ensure your spelling is 100% correct to avoid losing easy marks.

III. Which of the following statements are true (T) and which ones are false (F)? Mark T or F:
1. Platelets help in clotting of blood. True.
2. The four blood groups in human beings are A, B, AB and AO. False. (The four blood groups are A, B, AB and O.)
3. People with blood group ‘O’ are called universal recipients. False. (People with blood group ‘O’ are called universal donors.)
4. Blood group A has antigen A. True.
5. Impure blood is received by the right auricle. True.
Answer: (As indicated after each statement)
Understanding these true/false points helps clarify common misunderstandings about blood groups and heart function. For example, knowing that "O" is a donor rather than a recipient is a life-saving piece of information.
Teacher's Tip: "O" looks like a zero - zero antigens, so anyone can take it! (Universal Donor).
Exam Tip: If a statement is False, always try to write the correct statement next to it to show you understand why it is wrong.

IV. Match the statements in Column A with those in Column B:
Column A
1. Heart
2. Food and oxygen
3. Carrier of oxygen
4. Circulation
5. Arteries and veins
Column B
(a) Movement of materials
(b) Channels for transport in man
(c) A living pump
(d) Materials needed by every living being
(e) Red blood cells
Answer:
1. Heart - (c) A living pump
2. Food and oxygen - (d) Materials needed by every living being
3. Carrier of oxygen - (e) Red blood cells
4. Circulation - (a) Movement of materials
5. Arteries and veins - (b) Channels for transport in man
This matching exercise shows how different parts of our body work like a delivery system. The heart powers the system, the vessels are the roads, and the blood carries the vital supplies.
Teacher's Tip: Match the "Action" (Circulation) with the "Result" (Movement).
Exam Tip: Use a ruler to draw neat lines or write the corresponding letters clearly in the margin.

V. Describe the functions of the:
1. Heart
2. Blood vessels
3. Red blood cells
4. White blood cells
5. Platelets
6. Blood
Answer:
1. Heart: The heart is a muscular organ that pumps blood to all the cells in our body through a network of blood vessels. It pumps the blood and hence helps in circulating oxygen and nutrients to all body parts. The heart pumps deoxygenated blood to the lungs and oxygenated blood to the rest of the body.
2. Blood vessels: Blood vessels are a necessaiy part of the body’s circulatory system. The blood vessels carry blood throughout the body. Three types of blood vessels are : (1) Arteries: They carry oxygenated blood from the heart to all parts of the body. (2) Veins: They carry deoxygenated blood from the body cells to the heart. (3) Capillaries: They form the connection between the arteries and the veins where exchange of substances takes place.
3. Red blood cells: Red blood cells (RBCs) contain haemoglobin which carries oxygen throughout the body. It also transports nutrients to cells.
4. White blood cells: White blood cells (WBCs) help in fighting infection as they destroy the germs.
5. Platelets: The platelets help in clotting of blood, whenever there is a blood flow due to some injury.
6. Blood: Blood circulates throughout the body and performs the following functions: (1) It carries or transports food and oxygen to each body cell. (2) It carries away waste products to organs (like kidneys, lungs and intestine) from where they are excreted out of the body. (3) It protects the body against infection by destroying germs. (4) It helps in blood clotting, thereby preventing excessive blood loss. (5) It regulates body temperature.
Each component of the circulatory system has a specific, vital role in keeping our body balanced and alive. From the powerful pumping of the heart to the tiny platelets sealing a wound, every part is necessary.
Teacher's Tip: Think of the whole system as a "Delivery and Trash Pickup" service for your body.
Exam Tip: When describing "Blood," list at least 3-4 different functions to get full marks.

VI. Define the:
1. Circulatory system
2. Arteries
3. Veins
Answer:
1. Circulatory system: Circulatory system is a transport system moving substances throughout our body with the help of blood.
2. Arteries: Arteries are the blood vessels in which oxygenated blood is going away from the heart to all parts of the body.
3. Veins: Veins are the blood vessels which carry deoxygenated (impure) blood from the body cells to the heart.
These definitions capture the core purpose of each part of the system. In simple terms, they are the "what" and the "how" of blood movement in humans.
Teacher's Tip: Learn these definitions word-for-word as they are "Standard Definitions".
Exam Tip: Always specify the "direction" of blood flow when defining arteries and veins.

VII. Answer the following questions:

Question 1: Name the main parts of the circulatory system.
Answer: The main parts of the circulatory system are: 1. Heart, 2. Blood vessels and 3. Blood.
These three parts work together like an engine, pipes, and fuel to keep the body running. Without any one of these, the transport of oxygen and nutrients would stop immediately.
Teacher's Tip: It's a "Trinity" - Heart, Vessels, Blood.
Exam Tip: List them clearly in a numbered format for better readability.

Question 2: Name the organ from which oxygenated blood goes into the heart.
Answer: Lungs.
The lungs are where blood picks up oxygen from the air we breathe. This oxygen-rich blood then travels through the pulmonary vein to reach the heart's left side.
Teacher's Tip: Breathing and Blood are best friends - the lungs do the work and blood does the transport.
Exam Tip: Just writing "Lungs" is correct, but adding "via the pulmonary vein" shows you know more.

Question 3: Describe, in brief, the circulatory system in human beings.
Answer: The circulatory system in human beings consists of heart, blood vessels (arteries, veins and capillaries) and blood. Blood circulates throughout the body in blood vessels by the pumping action of the heart. The impure blood is carried by veins from all parts of the body to the heart. The heart pumps it into the lungs where blood is oxygenated and carried back to the heart. From heart, the oxygenated (pure) blood is pumped to all parts of the body through arteries. Thus, the circulatory system forms the transport system carrying food, oxygen, waste products, nutrients etc. throughout the body.
This description summarizes how blood makes a continuous loop through our body every few minutes. It is a highly organized system that ensures every cell, from your brain to your toes, gets what it needs to survive.
Teacher's Tip: Imagine a figure-8 shape: Heart to lungs, back to heart, then heart to body, and back to heart.
Exam Tip: Use the terms "oxygenated" and "deoxygenated" to describe the types of blood being moved.

Question 4: Draw the structure of human heart and label its parts
Answer: (As shown in the provided heart diagram with labels: Superior Vena Cava, Right Auricle, Right Ventricle, Aorta, Pulmonary Artery/Veins, Left Auricle, Left Ventricle).
A good diagram of the heart should clearly show the four chambers and the main entrance/exit tubes. Labeling the valves is also important because they act like one-way doors for blood flow.
Teacher's Tip: Practice drawing the heart as a simplified "box" with four rooms first.
Exam Tip: Use a sharp pencil and always point your labeling lines exactly to the part you are naming.

Question 5: Why is a person having blood group AB called universal recipient and a person with blood group O called a universal donor?
Answer: People with blood group O are called universal donors because they can donate blood to all the blood groups. Their red blood cells (RBCs) have no antigens and so cannot be stuck by blood of any other group. People with blood group AB are called universal recipients because they can receive blood from all 4 blood groups. The red cells in them have no antibodies and therefore it does not stick with blood from other groups.
This special chemistry is why blood banks always need more "O" type blood, as it can save almost anyone in an emergency. On the other hand, "AB" individuals are lucky because they can safely receive almost any type of blood donation.
Teacher's Tip: "O" has zerrr-O antigens. "AB" has Both antigens.
Exam Tip: Use the words "antigens" and "antibodies" in your explanation to get full technical credit.

Question 6: Name the instruments used for measuring: 1. pulse and 2. blood pressure.
Answer: 1. Stethoscope. 2. Sphygmomanometer
These two tools are basics in any doctor's medical kit. One listens to the "sound" of the heart, while the other measures the "force" of the blood.
Teacher's Tip: Pulse can also be measured by hand, but doctors use a stethoscope for accuracy.
Exam Tip: Make sure you link the right instrument to the right measurement; don't swap them!

Question 7: Name the following: 1. Components of blood, 2. Different blood groups
Answer: 1. Components of blood are: liquid part called plasma, The cells or corpuscles which are further of three types: RBC (red blood cell), WBC (white blood cell), platelets. 2. The four blood groups in humans are A, B, AB and O.
Knowing these components and groups helps doctors treat patients for many different illnesses. Whether someone needs more iron (RBC) or a blood transfusion, these names are the key.
Teacher's Tip: Remember: 1 liquid part + 3 types of cells = Blood.
Exam Tip: If asked to list "cells," don't forget the scientific names (Erythrocytes, Leukocytes, Thrombocytes) if you can remember them.

Question 8: Differentiate between arteries and veins.
Answer: Arteries
1. They carry blood away from the heart to all parts of the body.
2. They carry oxygenated blood (except pulmonary artery).
3. They are usually deep seated in the tissues.
4. Blood flows with jerks and under high pressure.
5. Valves are absent.
6. Thick elastic walls present.
Veins
1. They carry blood into the heart from all parts of the body.
2. They carry deoxygenated blood (except pulmonary vein).
3. They lie closer to skin surface.
4. Blood flows smoothly and under low pressure.
5. Valves are present.
6. Walls thinner than arteries present
Arteries need thick walls because the heart acts like a high-power pump pushing blood into them. Veins have valves that work like little check-gates to prevent blood from falling backward due to gravity.
Teacher's Tip: Arteries = Deep and Muscular; Veins = Surface and Valved.
Exam Tip: Mentioning "Valves" is a very important distinction that teachers look for in your answer.

Question 9: Write in brief about the following: 1. Blood groups and 2. Blood transfusion
Answer: 1. The four types of blood in humans are called blood groups. These are A, B, AB and O. The blood is determined by the antigens present on the RBCs. RBCs also contain antibodies in the plasma. 2. Transfer of blood from one person to another is called blood transfusion. Ill or seriously injured people may need it. But compatibility of the blood groups is checked first. People with blood group AB are called universal recipients and people with blood group O are called universal donors.
Blood groups are like genetic ID cards that tell us which blood is safe for our body. A transfusion is a medical procedure that must be done carefully to ensure the donor's blood is a perfect match for the patient.
Teacher's Tip: Transfusion is like "Trans-ferring" "Fusion" (joining) of blood.
Exam Tip: Be sure to mention that "compatibility" is checked before any transfusion begins.

10. Find the odd one out, giving reason:
1. Arteries, capillaries, blood, veins
Ans. Blood.
Reason: Arteries, veins and capillaries are types of blood vessels whereas blood is a constituent of circulatory system.
2. RBC, platelets, anti-A, WBC
Ans. Anti-A.
Reason: RBC, platelets and WBC are three types of blood cells whereas anti-A is a type of antibody present in the blood plasma.
Answer: (As provided in the reasons above)
This type of question tests if you really understand the categories of the circulatory system. One group is about the "containers" (vessels), while the other is about the "contents" (blood and its parts).
Teacher's Tip: Always look for the "Category" - is it a cell, a vessel, or a chemical?
Exam Tip: In "Odd One Out" questions, the "Reason" is usually worth more marks than just identifying the word.

Question 11: What is the rate of heartbeat in normal adult human being?
Answer: 70-72 per minute.
This rate can go up if you are exercising or if you are excited or scared. A steady resting heart rate is a sign that your heart muscle is strong and healthy.
Teacher's Tip: Your heart beats about once every second!
Exam Tip: Mention the range "70-72" rather than just a single number for a more accurate answer.

Question 12: Name the main artery which carries blood to different parts of the body.
Answer: Aorta.
The Aorta is the largest artery in your body and it starts right at the left ventricle of your heart. It curves around and branches off into smaller arteries that reach every organ.
Teacher's Tip: The Aorta is like the "Main Highway" for oxygenated blood.
Exam Tip: Capitalize the word "Aorta" as it is a specific anatomical name.

Question 13: What is the difference between pulmonary circulation and systemic circulation?
Answer: Pulmonary circulation
1. This involves circulation of blood between the heart and the lungs.
2. It is the function of the right side of the heart.
3. It carries deoxygenated blood to the lungs to receive oxygen.
4. It begins on the right ventricle and ends on left auricle.
5. It returns oxygenated blood back to the heart.
Systemic circulation
1. This involves circulation of blood between the heart and body organs (except lungs).
2. It is the function of the left side of the heart.
3. It carries oxygenated blood to the body organs.
4. It starts at left ventricle and ends at the right auricle.
5. It returns deoxygenated blood back to the heart.
Pulmonary circulation is the shorter trip that blood takes just to get fresh oxygen. Systemic circulation is the much longer journey that blood takes to deliver that oxygen to every part of the body.
Teacher's Tip: Pulmonary = Heart to Lungs; Systemic = Heart to System (Body).
Exam Tip: Using a flow chart with arrows is a great way to show you understand these two loops.

Question 14: Blood in the human body circulates twice for making one complete round through the body. Explain.
Answer: The circulation of blood through the human heart takes place twice making one complete round through the body. This is called double circulation. The impure blood (deoxygenated blood) is collected from different body organs through two major veins (vena cava). The two veins empty blood into the right auricle. From here, it enters the right ventricle and is carried to lungs by pulmonary artery. Exchange of gases takes place in the lungs. Pulmonary vein then carries the pure (oxygenated) blood to the left auricle. From here, it enters the left ventricle and is then carried by an artery called aorta to all parts of the body.
Double circulation is efficient because it ensures that only blood with high oxygen levels gets sent out to the body. By separating the two loops, the heart can pump blood at different pressures for the delicate lungs and the large body.
Teacher's Tip: Think of it like a "double-loop" roller coaster that always passes through the station (the heart).
Exam Tip: Always use the term "Double Circulation" when explaining why blood passes through the heart twice.

Question 15: How many litres of blood does an adult human body have?
Answer: 5.5 litres of blood.
This amount can vary slightly depending on a person's size and weight. This blood is constantly moving, completing a full circuit through your body in about one minute.
Teacher's Tip: That is about the same as eleven 500ml water bottles!
Exam Tip: Remember the unit "litres" - just writing "5.5" is incomplete.

Question 16: Write a short note on human heart.
Answer: The heart is a pump that circulates blood to all parts of the body. It is about the size of a human fist and located to the left in chest cavity. It has four chambers – two upper chambers called auricles or atria and two lower chambers called ventricles. The auricles receive blood from different body parts and ventricles pump the blood out of the heart. The valves between auricle and ventricle on each side allow blood to flow in one direction only. Heart acts as a double pump. The right side of the heart carries deoxygenated blood to the lungs to be oxygenated. The left side of the heart pump oxygenated blood to the body.
The heart is made of special "cardiac muscle" that never gets tired throughout your whole life. Its rhythmic beating is essential for maintaining life by ensuring every cell gets its supply of nutrients.
Teacher's Tip: Your heart is the only muscle that works 24/7 without a break!
Exam Tip: Mentioning the "fist size" and "left side location" are great descriptive details for a short note.

Question 17: What are seen as greenish blue lines in our hands and legs?
Answer: Veins.
These lines appear greenish because of how light interacts with our skin and the blood inside. Since veins carry blood that has already delivered its oxygen, it is often darker in color.
Teacher's Tip: If you see a "blue" vessel on your wrist, you are looking at a vein!
Exam Tip: Don't say the blood is actually green; explain that it's a vein visible through the skin.

Question 18: Name the iron containing protein present in RBC of blood.
Answer: Haemoglobin.
This protein is what gives red blood cells their color and their ability to carry oxygen. Eating iron-rich foods like spinach and meat helps your body make enough haemoglobin.
Teacher's Tip: Iron is the "glue" that holds oxygen to the RBC.
Exam Tip: Correct spelling of "Haemoglobin" is crucial; some books use "Hemoglobin" (American), but "Haemoglobin" is common in Indian textbooks.

Question 19: Define pulse.
Answer: Pulse is the throbbing of the arteries due to the movement of blood in them.
Every time the heart's left ventricle contracts, it sends a wave of pressure through the arteries. You can feel this wave most easily at your wrist or on the side of your neck.
Teacher's Tip: Your pulse rate is exactly the same as your heart rate.
Exam Tip: Use the word "throbbing" or "expansion" when defining pulse.

Question 20: Define heartbeat.
Answer: The sound or movement of the heart as it sends blood around the body is called heartbeat. Every heartbeat causes a pulse in the arteries.
A single heartbeat includes the contraction of the heart muscle followed by its relaxation. This rhythmic cycle is what keeps the blood moving in a steady flow.
Teacher's Tip: Think of it as a "Lub-Dub" cycle.
Exam Tip: Remember that the heartbeat originates in the heart, while the pulse is felt in the arteries.

Question 21: What is stethoscope? Explain.
Answer: The pulse in humans can be measured by using an instrument called stethoscope. It is a device that amplifies the sound of a heartbeat and is used to hear heartbeats in the chest. It consists of three parts: 1. A chest piece, which is sensitive to heartbeats. 2. Two earpieces. 3. A tube joining the chest piece and the earpieces.
The chest piece has a thin membrane called a diaphragm that vibrates when it picks up sound. These vibrations travel through the air-filled tubes directly into the doctor's ears.
Teacher's Tip: A stethoscope works like a "Megaphone" but for small, quiet sounds.
Exam Tip: Listing the three main parts of the stethoscope is often required in description questions.

Question 22: What is a stroke? What causes it?
Answer: A disabling attack or loss of consciousness by an interruption in the flow of blood to the brain is called a stroke. Constant high blood pressure puts a strain on the heart and can also cause an artery to burst open. If this happens in the brain, it causes stroke.
When brain cells are deprived of oxygen-rich blood, they begin to die very quickly. This can happen because of a blockage in an artery or because a vessel has ruptured.
Teacher's Tip: Think of a stroke as a "Brain Attack" - it's just as serious as a heart attack.
Exam Tip: Mention "High Blood Pressure" (Hypertension) as a primary cause of stroke.

Question 23: What is blood pressure? When does it rise?
Answer: The pressure of the blood in the arteries caused by pumping of heart is called blood pressure. It rises if we do activities like running, cycling etc. or if the arteries become narrower.
Blood pressure is measured with two numbers: systolic (when the heart beats) and diastolic (when it rests). It is normal for it to change throughout the day based on your activity level and stress.
Teacher's Tip: Think of BP like the "Water Pressure" in the pipes of your house.
Exam Tip: Stress and exercise are the most common reasons for a temporary rise in blood pressure.

Question 24: What are antigens and antibodies?
Answer: Antigens are foreign substances in the body which stimulate the production of antibodies. Antibodies are chemical substances made by the body in response to foreign substances (antigens). They destroy antigens.
Antigens act like an "alarm" that tells the immune system there is an intruder. Antibodies are the "specialized weapons" created to specifically target and remove that exact intruder.
Teacher's Tip: Antigens = The Bad Guys; Antibodies = The Good Guys' Weapons.
Exam Tip: Remember that antibodies are "Specific" - one antibody usually only works against one type of antigen.