Selina Concise Solutions for ICSE Class 8 Biology Chapter 6 The Circulatory System

REVIEW QUESTIONS

Multiple Choice Questions:

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

(a) The only artery which carries deoxygenated blood is called,
1. Hepatic artery
2. Pulmonary artery
3. Aorta
4. Renal artery

Answer: 2. Pulmonary artery
While almost all arteries carry fresh oxygenated blood, this special artery carries blood to the lungs to get oxygen. It is the only exception to the rule that arteries carry bright red, oxygen-rich blood.
Teacher's Tip: Remember "A" for Artery and "Away" - it carries blood away from the heart.
Exam Tip: Always look for the word "only" or "except" when answering questions about the pulmonary vessels.

(b) Pulmonary vein carries
1. Oxygenated blood
2. Deoxygenated blood
3. Glucose-deficient blood
4. CO₂ laden blood

Answer: 1. Oxygenated blood
The pulmonary vein brings blood back from the lungs after it has picked up fresh oxygen. It is unique because it is the only vein in the body that carries oxygenated blood.
Teacher's Tip: Think of the "Pulmonary" vessels as a "U-turn" where the rules of arteries and veins swap roles.
Exam Tip: Mention the lungs as the source to explain why the blood in this vein is oxygenated.

(c) Function of WBCs is to
1. Transport oxygen
2. Help in clotting of blood
3. Provide immunity
4. Provide storage of food.

Answer: 3. Provide immunity
White Blood Cells act as the body's internal army, fighting off harmful bacteria and viruses. They seek out and destroy germs to prevent us from falling sick.
Teacher's Tip: Call WBCs the "Warrior Blood Cells" to remember their role in fighting germs.
Exam Tip: If the question asks for another term for immunity, you can use "defense mechanism."

(d) Blood Capillary is a
1. Broad tube
2. Artery with thick wall
3. Vein with large lumen
4. Narrow tube made up of endothelium only.

Answer: 4. Narrow tube made up of endothelium only.
Capillaries are the thinnest blood vessels, so thin that they are only one cell thick. This thinness allows oxygen and nutrients to pass through easily into the body tissues.
Teacher's Tip: Think of capillaries as tiny "filter bridges" connecting arteries to veins.
Exam Tip: Use the term "one cell thick" to describe the wall for extra marks.

(e) Nucleus is absent in
1. RBCs
2. WBCs
3. All blood cells
4. Liver cells.

Answer: 1. RBCs
Mature red blood cells lose their nucleus to create more room for carrying oxygen. This special disc shape helps them squeeze through the tiniest capillaries.
Teacher's Tip: RBC stands for "Roomy Blood Cells" because they ditch their nucleus to make room for oxygen.
Exam Tip: Specify "mature" RBCs if the question allows, as they have a nucleus when they are first formed.

(f) Sphygmomanometer measures
1. Pulse rate
2. Heart beat
3. Blood pressure
4. Brain activity

Answer: 3. Blood pressure
This medical tool uses an inflatable cuff to check how hard blood is pushing against your artery walls. Doctors use these readings to make sure your heart and vessels are healthy.
Teacher's Tip: The long name might be scary, but just link "manometer" with "pressure."
Exam Tip: Practice the spelling of "Sphygmomanometer" as it is a common technical term in exams.

(g) The blood tastes saltish due to the presence of dissolved:
1. Sodium chloride
2. Potassium chloride
3. Ammonium nitrate
4. Sodium nitrate

Answer: 1. Sodium chloride
Sodium chloride is the chemical name for common table salt, which is found naturally in our blood plasma. These minerals help maintain the fluid balance and help nerves send signals throughout the body.
Teacher's Tip: Just remember that blood and the ocean both contain salt (NaCl).
Exam Tip: Remember that minerals in the blood are often called "electrolytes."

Short Answer Questions:

Question 1: 1. Differentiate between the following pair of terms:
(a) Pulmonary artery and pulmonary vein.
(b) Vena cava and aorta.
(c) Platelets and WBC.
(d) RBC and WBC Ans.

Answer:
(a) Pulmonary artery and pulmonary vein.
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.

(b) Vena cava and Aorta
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.

(c) Blood platelets and WBC.
Platelets: 1. These are colourless, oval or round, cytoplasmic fragments. 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.

(d) RBC and WBC
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.
Differences help us understand how each part of the blood has a specific, specialized job to do. For example, while RBCs focus on transport, WBCs focus on protecting the body from invaders.
Teacher's Tip: Use a table format for all "differentiate" questions to make your comparisons crystal clear.
Exam Tip: For full marks, always give at least two points of difference for each pair.

Question 2: 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 deoxygenated blood (except the pulmonary vein). 3. Blood flows with low speed and under low pressure.
Arteries act like high-pressure pipes delivering fresh supplies, while veins act like low-pressure return pipes. This is why arteries have much thicker, more elastic walls than veins.
Teacher's Tip: Arteries = Away from heart (oxygen rich); Veins = Visit the heart (oxygen poor).
Exam Tip: Mention the "exception" (Pulmonary vessels) to show the examiner you know the full picture.

Question 3: Fill in the blanks with suitable words given below:
Answer:
a. The two lower chambers of the heart are called ventricles.
b. The pulmonary artery takes the blood from the ventricles to the lungs.
c. The blood loaded with carbon dioxide from the body comes into the right auricle of the heart.
d. The oxygen-rich blood from the lungs comes into the left ventricle of the heart.
e. The oxygen-rich blood is pumped into different parts of the body through aorta.
f. The carbon dioxide loaded blood from right ventricle is pumped into the lungs through pulmonary artery.
g. The instrument used to find out the blood pressure is known as sphygmomanometer.
h. The colour of a red blood cell is due to haemoglobin.
i. The blood plasma contains a dissolved substance called fibrinogen.
j. The liquid part of coagulated blood is known as serum.
Completing these blanks helps build a step-by-step map of how blood travels through the heart. Each term represents a vital part of our life-support system.
Teacher's Tip: Think of auricles as "entry doors" and ventricles as "exit pumps."
Exam Tip: Read the entire sentence carefully before filling the blank to ensure the scientific logic holds up.

Question 4: 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.
This process happens in tiny air sacs where carbon dioxide is traded for oxygen from the air we breathe. Once the blood is oxygenated, it becomes a bright red color.
Teacher's Tip: Remember the lungs as the "oxygen gas station" for your blood.
Exam Tip: Mention the specific blood vessel involved (pulmonary vein) to give a complete answer.

Question 5: Which side of the heart (left or right) contains oxygenated blood?
Answer: The left side of the heart contains oxygenated blood.
The left side is more muscular because it has to pump this oxygen-rich blood to the entire body. The right side only needs enough strength to send blood to the nearby lungs.
Teacher's Tip: Left = Life-giving (oxygenated).
Exam Tip: Always remember that the heart is a "double pump" with two separate sides.

Question 6: 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 in the lungs and releases them into tissues that need energy. It is what gives our blood its characteristic red color.
Teacher's Tip: Think of haemoglobin as a "magnetic taxi" that picks up oxygen passengers.
Exam Tip: Mention that it is an "iron-containing protein" for more precise marks.

Question 7: 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.
Platelets are needed for clotting, so having such a low number is dangerous as it can lead to internal bleeding. Doctors monitor platelet counts closely to treat patients with this mosquito-borne illness.
Teacher's Tip: Associate Dengue with "Dangerously low platelets."
Exam Tip: List at least three distinct symptoms to provide a thorough answer.

Long Answer Questions:

Question 1: 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 type 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?
Answer:
1. Left pulmonary artery
2. Superior vena cava
3. Left pulmonary vein
4. Right auricle
5. Left auricle
6. Left ventricle
(a) Deoxygentated blood.
(b) Aortic arch (Aorta).
(c) Right Atrium
Labeling a diagram helps visualize how the heart is divided into rooms and hallways for the blood to flow through. The superior vena cava is one of the main return pipes bringing "used" blood back to the heart.
Teacher's Tip: Practice drawing the heart and labeling it; it's a favorite diagram for teachers to include in tests!
Exam Tip: Make sure your label lines are straight and point precisely to the correct chamber or vessel.

Question 2: 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 CO₂ and will have many substances like sugar, amino acids, chemicals and bacteria.
Veins are easier to see because they are located closer to the skin, while arteries are buried deep within muscles for protection. You can tell they are veins because they often appear blue or green through the skin and do not have a strong pulse.
Teacher's Tip: Veins are "visible," arteries are "anchored" deep.
Exam Tip: Use the word "superficially" to describe the location of veins near the skin surface.

Question 3: Give the functions of lymph. Differentiate between Blood and the lymph.
Answer: Functions of lymph are:
1. Nutritive: It supplies nutrition and oxygen to those parts where blood cannot reach.
2. Drainage: It drains away excess tissue fluid and metabolites and returns proteins to the blood from tissue spaces.
3. Absorption: It absorbs the fats from the intestine through lymphatics.
4. Defence: Lymphocytes and monocytes of the lymph function to protect the body. The lymphatics also remove bacteria from the tissues.
Lymph acts like a secondary drainage and security system for the body. It picks up what the blood leaves behind and cleans it up before returning it to the main circulation.
Teacher's Tip: Think of lymph as the "cleaning crew" that follows the blood supply.
Exam Tip: Be sure to mention "fat absorption" as a unique function of the lymphatic system.

Difference between Blood and Lymph
Answer:
Lymph: 1. It contains blood plasma without blood proteins and some RBC. 2. They are light yellow in colour and does not contain RBC and haemoglobin. 3. It doesnot carry Oxygen. 4. It is the part of open circulatory system.
Blood: 1. It contains blood plasms with proteins and all three types of blood cells namely RBC, WBC and blood platelets. 2. They are red in colour due to presence of haemoglobin in RBC. 3. It carries oxygen in the body. 4. It is the part of closed circulatory system.
Blood is the primary transport system, while lymph is a specialized fluid for defense and drainage. The lack of RBCs in lymph is why it is clear or pale yellow instead of red.
Teacher's Tip: Lymph is basically blood plasma that has leaked out of capillaries and lost its red cells.
Exam Tip: Focus on the presence or absence of "Haemoglobin" to explain the color difference.

Question 4: Name any two heart conditions that occur commonly. Briefly explain each of them.
Answer:
1. Palpitations: Sometimes, one may experience the heart beating too hard or too fast or sometimes even skipping a beat. This can be frightening, but not serious or harmful and often this condition goes away on its own. Most of the time it is caused by stress or anxiety. Sometimes certain types of food may also cause palpitations. In rare cases, palpitations may be an indication of a more serious heart condition, specially if it is accompanied by shortness of breath, dizziness or chest pain.
2. Hypertension: This is a condition that occurs in a person when blood flows through the blood vessels with a force greater than normal. This is also called High Blood Pressure. Hypertension can strain the heart, damage blood vessels and increase the risk of a heart attack or stroke.
These conditions show how lifestyle and stress can directly affect the way our heart works. Understanding them helps people take better care of their cardiovascular health.
Teacher's Tip: Palpitations = irregular rhythm; Hypertension = high pressure.
Exam Tip: Provide both the common name (High Blood Pressure) and the scientific name (Hypertension).

Question 5: 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 observed and 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.
Transfusion is a lifesaving procedure that requires extreme care to ensure the donor's blood is safe and compatible. Giving the wrong blood type can cause a dangerous reaction in the patient.
Teacher's Tip: Think of a transfusion as "donating life" through the blood.
Exam Tip: "Blood Group Matching" is the most important precaution to mention for this answer.

Question 6: 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 at maturity. 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/mm³ 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/ mm³ of blood. 6. WBC are formed in the red bone marrow.
RBCs are the "freight trains" carrying oxygen, while WBCs are the "soldiers" protecting the body. Because we need oxygen constantly, there are far more RBCs in the blood than WBCs.
Teacher's Tip: Remember RBCs live for months (120 days), but WBCs usually live for only a few days.
Exam Tip: Use numerical data (like life span or count) to make your differences more scientific.

Question 7: Answer very briefly, the following:
(a) Red Blood cells have no nucleus, then why do we call them cells?
(b) Why is it necessary to know The blood groups of the donor as well as the recipient ?
(c) Why should the blood going away from the stomach and intestines pass through the liver and not directly to heart?
Answer:
(a) RBC are formed in the liver and spleen when the organisjn is foetus. After birth these are formed in the red bone marrow. At the time of formation of RBC’s they have nucleus but later on they loose nucleus. Those enucleated cells perform all the functions of a cell so these are called cells. RBC’s are surrounded by semipermeable plasma membrane. It contains homogenous cytoplasm and it is without the nucleus, endoplasmic reticulum, mitochondria, ribosomes and centrioles. RBC’s get advantage due to this condition. Corpuscles have more space to hold haemoglobin. It can as well give more oxygen by the haemoglobin to the tissue cells. So the enucleated condition is more useful to the tissue cells. The necessity of work has made them without nucleus and perform all the functions of the cells so they are called cells.
(b) Before transfusion of blood, it is most essential to determine the blood group of the donor and the recipient. The blood group of the donor and the recipient must match with each other, otherwise the RBC’s will stick to each other and thus the life of a recipient may be in danger as the blood groups are different. The sticking is due to the antigens (proteins) found in the blood of the donor and the antibodies found in the blood of the recipient.
(c) The blood from the stomach and the intestine goes to liver before going to the heart. Liver monitors the substances before passing into the body. Excess of glucose is retained by the liver in the form of glycogen and the excess amino acids are broken down by the liver. Harmful chemicals are detoxified and bacteria are destroyed and excess minerals, water and vitamins are stored in the liver.
These answers explain the amazing efficiency and safety checks built into our bodies. From RBCs giving up their nucleus to save space, to the liver acting as a "security filter" for our food, everything has a purpose.
Teacher's Tip: Think of the liver as the "Customs Officer" checking all blood coming from the stomach.
Exam Tip: For part (a), focus on the "enucleated" state being an adaptation for carrying more oxygen.

Question 8: 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.
3. 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 veiy 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 vessel is designed for a specific level of pressure and flow. Arteries must be tough to handle the heart's pumping, while capillaries must be thin to allow things to pass through.
Teacher's Tip: Remember: Thick Arteries (high pressure), Thin Veins (valves needed), Thinnest Capillaries (exchange).
Exam Tip: Include a small diagram of each vessel type to illustrate the difference in wall thickness.

ADDITIONAL QUESTIONS

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

1. Human heart has
1. one auricle and one ventricle.
2. two auricles and one ventricle.
3. two auricles and two ventricles.
4. one auricle and two ventricles.

Answer: 3. two auricles and two ventricles.
This four-chambered design ensures that oxygenated and deoxygenated blood never mix. This efficiency allows humans to maintain a constant body temperature and be active.
Teacher's Tip: Just think "Four Rooms for Life" when remembering the human heart chambers.
Exam Tip: The upper rooms are auricles (atria) and the lower rooms are ventricles.

2. The blood vessels in which blood goes away from the heart to different body parts are
1. arteries
2. capillaries
3. veins
4. both arteries and veins.

Answer: 1. arteries
Arteries are the high-speed delivery roads that start at the heart and fan out across the body. Their thick, elastic walls expand and contract with every heartbeat.
Teacher's Tip: Remember: Artery = Away.
Exam Tip: If the question asks about returning to the heart, the answer would be veins.

3. The heartbeat is measured by an instrument called
1. thermometer
2. sphygmomanometer
3. stethoscope
4. none of the above

Answer: 3. stethoscope
The stethoscope amplifies the sounds made by the heart valves as they open and close. These "lub-dub" sounds tell doctors if the heart is pumping correctly.
Teacher's Tip: The stethoscope "listens," while the sphygmomanometer "squeezes."
Exam Tip: Be sure not to mix up the names of these two common medical instruments.

4. The blood cells which protect the body from infection are
1. RBCs
2. platelets
3. WBCs
4. all the above

Answer: 3. WBCs
White Blood Cells are specialized to recognize and attack foreign invaders like bacteria. They are the core of our immune system's defense strategy.
Teacher's Tip: Think of WBCs as "Bodyguards."
Exam Tip: If asked to describe them, note that they are larger than RBCs but fewer in number.

5. The four blood groups in humans are
1. A, B, C and D
2. A, B, AB and C
3. A, B, AB and O
4. A, B, AB and OO

Answer: 3. A, B, AB and O
Blood groups are determined by proteins called antigens on the surface of our Red Blood Cells. Knowing your group is vital for safe medical treatments.
Teacher's Tip: There is no "C" in blood types!
Exam Tip: "O" is often referred to as the universal donor type.

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: Fill in the underlined words as shown above.
These facts cover the basic anatomy and chemistry of the circulatory system. Understanding these helps explain how our bodies transport essential supplies to every single cell.
Teacher's Tip: Remember "Plasma" is mostly water but holds all the important "passengers" like cells and food.
Exam Tip: Use scientific terms like "Haemoglobin" instead of just saying "red pigment."

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 in human beings 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: Follow the T/F markers and corrections provided above.
These True/False statements test your understanding of blood group compatibility and heart function. For example, knowing that "O" is a donor and not a recipient is critical in transfusion science.
Teacher's Tip: "O" = Open to give (donors). "AB" = All blood (recipients).
Exam Tip: If a statement is false, always write the correct version to show your understanding.

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: Column A Column B
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

V. Describe the functions of the following:
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 necessary 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: • It carries or transports food and oxygen to each body cell. • It carries away waste products to organs (like kidneys, lungs and intestine) from where they are excreted out of the body. • It protects the body against infection by destroying germs. • It helps in blood clotting, thereby preventing excessive blood loss. • It regulates body temperature.
The circulatory system works as a team where every part has a specific role to keep us alive. Without the heart's pump or the blood's transport cells, our body would not receive the energy it needs to function.
Teacher's Tip: Think of the heart as the "Motor," blood vessels as "Roads," and blood as the "Delivery Truck."
Exam Tip: Use bullet points for functions of "Blood" to make your answer organized and high-scoring.

VI. Define the following:
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.
Definitions provide a precise way to describe how materials move from point A to point B in the body. Arteries and veins are the primary roads for this biological transit system.
Teacher's Tip: Always mention "direction" and "blood type" when defining arteries and veins.
Exam Tip: For "Circulatory system," emphasize the word "transport" as it is the system's main purpose.

VII. Answer the following questions:

Question 1: Name the main parts of the circulatory system.
Answer: The main parts of the circulatory system are: • Heart • Blood vessels and • Blood.
These three components work together to form a complete network for survival. The heart provides the power, the vessels provide the path, and the blood carries the cargo.
Teacher's Tip: Think of this as the "Triad of Life."
Exam Tip: List all three parts to get full credit for this "naming" question.

Question 2: Name the organ from which oxygenated blood goes into the heart.
Answer: Lungs.
The lungs are where the blood trades harmful carbon dioxide for fresh oxygen. This refreshed blood then travels back to the heart to be sent out to the rest of the body.
Teacher's Tip: The lungs are the only place blood gets "recharged."
Exam Tip: Be sure not to say "nose" or "mouth"; the gas exchange happens specifically in the lungs.

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 system is like a continuous loop that never stops as long as we are alive. It ensures that every part of the body, from the brain to the toes, gets exactly what it needs to stay healthy.
Teacher's Tip: Imagine a highway loop where trucks (blood) never stop moving.
Exam Tip: Use the terms "oxygenated" and "deoxygenated" to describe the types of blood being moved.

Question 4: Draw the structure of a human heart and label its parts.
Answer: Refer to the diagram titled "Internal structure of the human heart" (Page 13).
The heart diagram shows how the four chambers and major vessels are connected. Labeling correctly helps you understand the path of "Double Circulation."
Teacher's Tip: The right side of the heart is shown on the left of your paper diagram.
Exam Tip: Practice labeling the valves as they are the "one-way doors" of the heart.

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 compatibility is why blood grouping is so important in hospitals. If the antigens and antibodies don't match, the blood will clump together, which is very dangerous.
Teacher's Tip: O = "Oh, I can give to anyone!" AB = "All Blood is welcome here!"
Exam Tip: Use the scientific terms "antigen" and "antibody" to explain why clumping does or doesn't happen.

Question 6: Name the instruments used for measuring – (i) pulse and (ii) blood pressure.
Answer: (i) Stethoscope. (ii) Sphygmomanometer.
The stethoscope lets a doctor hear the heart's rhythm, while the sphygmomanometer measures the strength of the blood flow. Together, they provide a snapshot of a person's cardiovascular health.
Teacher's Tip: Pulse can also be felt with fingers, but the stethoscope is the formal instrument.
Exam Tip: Spell "Stethoscope" correctly; don't forget the 'h'.

Question 7: Name the following: (a) Components of blood (b) Different blood groups
Answer: (a) Components of blood are: 1. liquid part called plasma 2. The cells or corpuscles which are further of three types: (a) RBC (red blood cell), (b) WBC (white blood cell), (c) platelets. (b) The four blood groups in humans are A, B, AB and O.
Blood is not just a red liquid; it is a complex mixture of cells floating in a watery base. Each of these components has a specialized job, such as transport, defense, or repair.
Teacher's Tip: Think of plasma as the "soup" and the blood cells as the "ingredients."
Exam Tip: List both the cellular parts and the fluid part (plasma) for a full answer.

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 are designed to handle the forceful "pump" of the heart, while veins have valves to prevent blood from flowing backward on its slow trip back. This structural difference is why arteries pulsate and veins do not.
Teacher's Tip: The "jerky" flow in arteries is what we feel as our pulse.
Exam Tip: Mentioning the "valves" in veins is a very important point for getting full marks.

Question 9: Write in brief about the following: (a) Blood groups and (b) Blood transfusion
Answer:
(a) 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. (Follow table for antigens/antibodies).
(b) 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.
Knowing blood groups ensures that medical treatments like transfusions are safe and successful. Antigens and antibodies must match properly to prevent the blood from clumping together.
Teacher's Tip: Blood groups are like "id tags" on our cells.
Exam Tip: For part (b), always define "transfusion" first before explaining the details.

Question 10: Find the odd one out, giving reason:
Answer:
(i) Arteries, capillaries, blood, veins.
Ans. Blood.
Reason: Arteries, veins and capillaries are types of blood vessels whereas blood is a constituent of circulatory system.
(ii) 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.
Finding the odd one out tests your ability to categorize parts of a system correctly. In these cases, we distinguish between "containers" (vessels) and "contents" (blood), and between "cells" and "antibodies."
Teacher's Tip: Always look for the shared "family" name of the other three items.
Exam Tip: Be sure to write the full "reason" to get the extra point for your answer.

Question 11: What is the rate of heartbeat in normal adult human being?
Answer: 70-72 per minute.
This rate can speed up when we exercise or feel excited, and slow down when we are resting. It reflects how often the heart needs to pump to keep oxygen moving through the body.
Teacher's Tip: Check your own pulse for 15 seconds and multiply by 4 to see your current rate!
Exam Tip: Provide the range (70-72) rather than just a single number.

Question 12: Name the main artery which carries blood to different parts of the body.
Answer: Aorta.
The aorta is the largest artery in the human body, thick as a garden hose. It branches out into smaller and smaller arteries to reach every single organ.
Teacher's Tip: The Aorta is the "Superhighway" of blood leaving the heart.
Exam Tip: It is located leaving the "Left Ventricle."

Question 13: What is the difference between pulmonary circulation and systemic circulation?
Answer:
Pulmonary circulation: (i) This involves circulation of blood between the heart and the lungs. (ii) It is the function of the right side of the heart. (iii) It carries deoxygenated blood to the lungs to receive oxygen. (iv) It begins on the right ventricle and ends on left auricle. (v) It returns oxygenated blood back to the heart.
Systemic circulation: (i) This involves circulation of blood between the heart and body organs (except lungs). (ii) It is the function of the left side of the heart. (iii) It carries oxygenated blood to the body organs. (iv) It starts at left ventricle and ends at the right auricle. (v) It returns deoxygenated blood back to the heart.
Pulmonary circulation is the "cleaning loop" for the blood, while systemic circulation is the "delivery loop." Together, they make up the complete double circulation system.
Teacher's Tip: Think: Pulmonary = Lungs; Systemic = System (whole body).
Exam Tip: Use the terms "Right side" and "Left side" to show which part of the heart handles each circulation.

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 can be summarised as:
1. Circulation of blood between the heart and the lungs is called pulmonary circulation. In this, the blood flows as follows: Right ventricle → lungs → left auricle (through pulmonary veins)
2. Circulation of blood between the heart and body organs (except lung) is called systemic (body) circulation. Blood flows as following: Left ventricle → body organs → right auricle (through vena cava)
Double circulation is efficient because it ensures oxygenated blood reaches body tissues at high pressure. It prevents the mixing of pure and impure blood, which is vital for warm-blooded animals like us.
Teacher's Tip: Think of it as two separate "loops" connected by the heart's "station."
Exam Tip: Use the flow-chart style (Right ventricle \rightarrow lungs \rightarrow left auricle) to make your explanation easy to follow.

Question 15: How many litres of blood does an adult human body have?
Answer: 5.5 litres of blood.
This volume can vary slightly based on a person's size and health. This amount is constantly being recycled and cleaned throughout our lifetime.
Teacher's Tip: That's about the same as 11 large water bottles!
Exam Tip: Remember this specific number (5.5) as it is a common fact-based question.

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 a tireless muscle that beats over 100,000 times a day without ever resting. Its "valves" are crucial because they stop blood from going the wrong way, keeping the flow efficient.
Teacher's Tip: Close your fist—that's how big your heart is right now!
Exam Tip: Mention the "four chambers" and "double pump" function to get the best marks.

Question 17: What are seen as greenish blue lines in our hands and legs?
Answer: Veins.
These lines appear greenish-blue because of how light reflects through the skin and the deoxygenated blood inside. They are returning blood to the heart at a low pressure.
Teacher's Tip: If you look at your wrist, those are the veins you see!
Exam Tip: Note that veins are "closer to the skin surface" compared to arteries.

Question 18: Name the iron containing protein present in RBC of blood.
Answer: Haemoglobin.
Iron is what allows haemoglobin to grab onto oxygen molecules in the lungs. This is why having enough iron in your diet is so important for energy.
Teacher's Tip: Think "Hemo" for blood and "Globin" for protein.
Exam Tip: Remember that iron deficiency can lead to a condition called anemia.

Question 19: Define pulse.
Answer: Pulse is the throbbing of the arteries due to the movement of blood in them.
Each "throb" you feel corresponds to one contraction of the heart's left ventricle. It is a direct way to measure how fast your heart is beating.
Teacher's Tip: Your pulse is basically your heart's "beat" reaching your wrist.
Exam Tip: Use the word "throbbing" in your definition for accuracy.

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 chambers followed by a brief period of relaxation. This rhythmic cycle keeps blood moving in a steady flow.
Teacher's Tip: Listen for the "Lub-Dub" sound – that's the valves closing during a beat.
Exam Tip: Note the connection between heartbeat and pulse to show a deeper understanding.

Question 21: What is stethoscope? Explain.
Answer: The pulse in humans can be n. ;asured by using an instrument called stethoscope. It is a de’ cejhat amplifies the sound of a heartbeat and is used to sear 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 captures small vibrations from the heart valves and sends them up the tube to the doctor's ears. It helps medical professionals check for any abnormal sounds or rhythms.
Teacher's Tip: Think of a stethoscope as a "magical hearing aid" for your internal organs.
Exam Tip: Be sure to list the "three parts" as it is often a specific sub-question.

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.
A stroke happens when brain cells die because they aren't getting enough oxygen from the blood. It can be caused by a blockage in an artery or a leak from a broken vessel.
Teacher's Tip: Think of a stroke as a "brain attack."
Exam Tip: Mention "interruption of blood flow" and "brain" as the two key components of the definition.

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.
It is the force that keeps blood moving through the miles of vessels in our bodies. While it rises during exercise, having a high resting pressure (hypertension) can be bad for your health.
Teacher's Tip: Think of blood pressure like the water pressure in your house's pipes.
Exam Tip: Mention that exercise is a "normal" reason for pressure to rise to show contrast with medical conditions.

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 are like the "enemy's uniform" that helps your immune system recognize a germ. Antibodies are the "smart missiles" your body creates specifically to target and destroy those enemies.
Teacher's Tip: Antigens = Attackers; Antibodies = Army.
Exam Tip: Use the word "stimulate" when describing how antigens cause the body to react.