RBSE Solutions For Class 12 Biology Chapter 24: Blood Circulatory System of Human | Textbook Important Questions & Answers

RBSE Class 12 Biology Chapter 24- Blood circulatory system of Human, provides complete information related to the circulatory system, heart, parts of heart, functions of heart, mechanism of heart, circulation of blood, the external and internal structure of the human heart, heartbeat, different types of blood cells, its functions, types of the circulatory system, functions of lymph, hemostasis, pulse rate, cardiovascular disease and a lot more.

These important questions help students to perform exceptionally well in their exams. By practising these important questions, students can analyze their preparation, get a thorough knowledge about all the important terminologies and perform their best in the examinations.

RBSE Solutions for Class 12 are the best study material for both class assignments and other board examinations. By practising these important questions, students can gain deep knowledge about the topics explained in this chapter and also help them to be well prepared for their upcoming examinations.

RBSE Class 12 Biology Chapter 24 Important Questions

RBSE Biology Chapter 24: MCQ Type Questions

Q.1.The human heart is developed from ________.

(a) Endoderm.

(b) Mesoderm.

(c) Exoderm.

(d) Endomesoderm.

Sol: (b) Mesoderm.

Q.2. Which of the following statements is true about the blood?

(a) Blood is a tissue.

(b) Blood is not a tissue.

(c) Blood is a liquid tissue.

(d) Blood is a fluid connective tissue.

Sol: (d) Blood is a fluid connective tissue.

Q.3. At higher altitude, red blood cells will________.

(a) Increase in number.

(b) Increase in its size.

(c) The decrease in its shape.

(d) The decrease in the number.

Sol: (a) Increase in number.

Q.4. Contraction of the heart starts from________.

(a) Left ventricle.

(b) Right auricle.

(c) Left auricle.

(d) Right ventricle.

Sol: (b) Right auricle.

Q.5. Which of the following blood cells play an important role in blood clotting?

(a) Neutrophils.

(b) Thrombocytes.

(c) Erythrocytes.

(d) Monocytes.

Sol: (b) Thrombocytes.

Q.6.Ventricular contraction is under the control of________.

(a) AVN.

(b) SAN.

(c) Purkinje fibres.

(d) Papillary muscles.

Sol: SAN.

Q.7. Which of the following ions plays an important role in Blood clotting?

(a) K+.

(b) Na+.

(c) Fe2+.

(d) Ca2+.

Sol: (d) Ca2+.

Q.8.Which of the following is the function of lymph?

(a) Provide oxygen to the brain.

(b) Transport of carbon dioxide.

(c) Provide liquid to blood.

(d) Returning of WBC to Lymph nodes.

Sol: (c) Provide liquid to blood.

Q.9. The normal Blood pressure of a human is________.

(a) 140/90.

(b) 120/80.

(c) 110/70

(d) 130/60.

Sol: (b) 120/80.

Q.10. A human heart has ______ chambers

(a) Two.

(b) Three.

(c) Four.

(d) Eight.

Sol: (c) Four.

RBSE Biology Chapter 24:Short Answer Type Questions.

Q.1. What is blood? Where are red blood cells formed?

Sol. Blood is the fluid connective tissue and it is one of the most important components of life as it is involved in delivering oxygen and nutrients to various cells and tissues. RBC – Red Blood Corpuscles are formed in the red bone marrow of bones.

Q.2.Which blood group is known as Universal donor and Universal acceptor?

Sol: O blood group is called the Universal donor because a person born with this blood group can donate blood to all other blood groups – A, B, and AB.

AB blood group is called the Universal acceptor, because a person born with this blood group can receive blood from A, B, and O.

Q.3. Which protein is important for blood clotting?

Sol: Fibrinogen is a glycoprotein complex, which plays an important role in the clotting of blood. These protein molecules are produced within the liver cells and are circulated through the blood vessels of all vertebrates.

Q.4. What is Pacemaker?

Sol. A Pacemaker is a small, medical device, which is placed in the chest region, which functions by controlling the abnormal heartbeat. The human heart consists of two nodal tissues – Sino-atrial node (SA node) and atrioventricular node (AV node). The SA nodes are called pacemakers.

Q.5. Define Cardiac cycle.

Sol: The cardiac cycle refers to the sequence of events that take place when the heart beats. A healthy human heart beats 72 times per minute which states that there are 72 cardiac cycles per minute.

Q.6. How many types of blood groups are there?

Sol: There are four major blood groups and are called the ABO Blood Group System. The types of blood groups are:

  1. Blood Group A
  2. Blood Group B
  3. Blood Group AB
  4. Blood Group O.

Q.7. What is Plasma?

Sol: Plasma is the liquid part of the blood, which is pale yellow in colour and alkaline in nature. About 55 per cent of total blood volume consists of plasma. It is generally composed of water, salts, lipids, proteins and hormones.

Q.8. What is Erythroblastosis Fetalis?

Sol: It is a type of disease, which occurs in the fetus. It is also called hemolytic disease. It is caused when a mother is Rh- and the father is Rh+. The infants born from these parents have this disease and the newborn baby is called the rhesus child.

Q.9. What is double blood circulation?

Sol: It is an efficient way of circulation. In double blood circulation, blood flows twice through the heart during one cycle of passage through the body. This type of circulatory system is seen in the majority of mammals.

Q.10. What is heart beat?

Sol: Rhythmic contraction of heart is known as heart beat. In this process, most of the muscles contract due to the stimulation of implusing nerves.

Q.11. What are Capillaries?

Sol. Capillaries are the largest network in the whole body, their walls are made of endothelium and are permeable for water and solutes.The thinnest blood vessels in the human body are called capillaries. The exchange of different substances between the blood and the body cells takes place through these capillaries.

Q.12. How many layers of tissues are present in the walls of arteries and veins?

Sol. There are three layers of tissues in the walls of arteries and veins:

  1. Tunica Externa.
  2. Tunica Media.
  3. Tunica Intima.

Q.13. What are blood vessels?

Sol. The tubular structures in which blood flows are called blood vessels. There are three main types of blood vessels:

  1. Arteries.
  2. Veins.
  3. Capillaries.

Q.14.What is ABO blood Group system?

Sol: The ABO blood group system is classified into four types of blood groups – A, B, AB, and O and is mainly based on the antigens and antibodies on red blood cells and in the plasma.

  1. Group A – contains antigen A and antibody B.
  2. Group B –contains antigen B and antibody A.
  3. Group AB –contains both A and B antigen and no antibodies (neither A nor B).
  4. Group O – contains neither A nor B antigen and both antibodies A and B.


Q.15. List out the primary functions of blood.

Sol: Blood is the fluid connective tissue and it is one of the most important components of the living system. The primary functions of blood are:

  1. Helps in homeostasis.
  2. Protect against pathogens
  3. Provides oxygen to the cells.
  4. Helps in the clotting process.
  5. Transports hormones and nutrients.

Q.16. What is the importance of the circulatory system in humans?

Sol: In humans, the circulatory system functions by transporting nutrients, oxygen, waste products and other necessary substances through the body for proper functioning of different organ systems.

Q.17. What is heart failure?

Sol: Heart failure is also known as congestive heart failure. This is a condition in which the heart could not supply enough blood necessary to different parts of the body. Both heart failure and heart attack are two different conditions, which vary with the symptoms and causes.

Q.18. What are the components of blood?

Sol: The main components of blood are:

  1. Plasma
  2. Red blood cells (RBC)
  3. White blood cells (WBC)
  4. Blood Platelets

Q.19. What is the “lub dub” sound of a heartbeat?

Sol. The closing of the atrioventricular valve during the contraction of the ventricle produces a sound called “Lup”.

The closing of semilunar valves at the time of ventricular relaxation produces sound called “Dup”

Q.20. What is SAN and AVN?

Sol. Both SAN and AVN are small, cardiac fibres present within the right atrium.

SAN – sinoatrial node is present near the opening of the superior vena cava in the top of the right atrium and sets the rate at which the heart contracts.

AVN – atrioventricular node is present near the tricuspid valve on the interatrial septum between the two atria. It is involved in transferring the electrical stimulation, initiated in the SAN, to the ventricles.

RBSE Biology Class 12: Long Answer Type Questions

Q.1. What is the circulatory system? What type of circulatory system do humans have?

Sol. A network of organs that allow the circulation of blood throughout the body is known as the circulatory system. The human circulatory system consists of a network of arteries, veins, and capillaries, with the heart pumping blood through it. Its primary role is to provide required nutrients, minerals, and hormones to various parts of the body. Apart from these functions, the circulatory system is also involved in collecting metabolic waste and other toxins from the cells and tissues to be purified or expelled from the body with the help of excretory organs.

Humans have a closed circulatory system. The blood is enclosed in the vessels and the heart while circulating. The blood travels through arteries and veins and carries important molecules throughout the body. The closed circulation, the blood is pumped through the vessels separate from the interstitial fluid of the body.

Q.2. Write the difference between the Open and Closed Circulatory System.

Sol: Difference between Open and Closed Circulatory System

Open Circulatory System Closed Circulatory System
It is present in lower organisms. It is present in higher organisms.
Blood flows through the open system. Blood flows through the closed system of blood vessels.
Blood flows between cells and tissues. Blood flows in closed vessels.
Blood pressure is low. Blood pressure is high.
Blood flow is very slow. Blood flow is rapid.
A capillary system is not found. A capillary system is found.
Tissues are surrounded by blood. Blood does not directly contact with tissues
Only nutrients are exchanged . Both gases and nutrients are exchanged
It comprises a dorsal blood vessel. It comprises both dorsal and ventral blood vessels.
Examples: Molluscs and Arthropods, etc. Example: Human, Rabbit, etc.

Q.3. What are the functions of blood?

Sol: Listed below are important functions of blood.

It is involved in:

  1. Transportation of oxygen.
  2. Prevents loss of blood.
  3. Transportation of hormones.
  4. Maintains body temperature.
  5. Transportation of haemoglobin.
  6. Transportation of carbon dioxide.
  7. Maintains homeostasis in the body.
  8. Protects our body from engulfing pathogens.
  9. Provides immunity by forming antibodies.
  10. Transportation of digested food from ileum to various parts of the body.
  11. Transportation of urea, uric acids and other excretory wastes to kidneys.

Q.4. What is the difference between Arteries and Veins?

Sol. Difference Between Arteries and Veins.

Arteries Veins
Light pink in colour. Blue or dark red in colour.
Carry blood away from the heart. Carry blood toward the heart.
Deeply situated exception – radial artery is superficial. Superficially situated.
Carry oxygenated blood. Carry deoxygenated blood.
Thick walled. Thin walled.
Blood flows with more pressure. Blood flows with less power.
Non collapsible. Collapsible.
Without valves. With valves.
They contain 15 percent of blood. They contain 64 percent of total blood.
Lumen is narrow. Lemen is broad.
They are divided to form arterioles. They are formed by the union of venules.
Blood flows with jerks. Blood flows smoothly.

Q.5. Write an account of human blood groups.

Sol: Blood is a fluid connective tissue and the most crucial component of the circulatory system. IIn human beings, blood varies from person to person on the basis of surface antigen on the red blood cells. The blood grouping system plays a very important role during blood transfusion. Karl Landsteiner, an Austrian scientist discovered the ABO blood group system in the year 1900.

According to his experiments, he classified blood into two main systems:

  1. ABO system

According to the ABO system, human blood is of four different types. This classification is based on the presence of natural antigens on the red blood cells, namely A and B. Similarly, there are two types of natural antibodies in the plasma cells.

There are four different blood groups.

Blood Groups Antigen Antibody
A Antigen A. Antibody B.
B Antigen B. Antibody A.
AB Antigen A and Antigen B. Absent.
0 Absent. Antibody A and Antibody B.

According to this system, Blood group O is called the universal donor and Blood group AB is called the universal recipient or acceptor.

  1. Genetics of ABO system.

In 1925 Burn Stein, first explained that the ABO groups in humans are hereditary characters and are controlled by genes. Hence, it is an example of multiple gene inheritance. Based on his observations, here is the explanation of heredity of the ABO system.

Genes Nature
LA or IA Dominant.
LB or IB Dominant.
LO or IO Recessive.
Genotype Blood groups
Parents Blood group Possibilities of Blood groups in children. Impossibilities of Blood groups in children.
A X B A, O B, AB.
B X A A, B, AB, O None.
A x AB A, B, AB O.
A X O A, O B,
B X B B, O A, AB.
B X A B A, B, AB O
B X O B, O A , AB.
A B X A B A, B, AB O
O X O O A, B, AB.

Q.6. What is double blood circulation? What is its significance to the human body?

Sol: Double blood circulation is an efficient way of circulation, in which the blood flows twice through the heart during one cycle of passage through the body. This type of circulatory system is seen in the majority of mammals.

Double circulation supports a strict separation of both oxygenated and deoxygenated blood. Therefore, this circulation ensures that the body always has a dedicated supply of oxygen and it also improves body efficiency. This is also one of the reasons why mammals can maintain their body temperatures. Apart from the double circulation, a third portal system also exists to improve circulation efficiency.

Double circulation is the most effective circulation where blood flows in two pathways:

  1. Systematic pathway – oxygenated blood travels from the left side of the heart to all other body parts wherein exchange of nutrients, gases etc occurs, carrying the deoxygenated blood back again to the right side of the heart.
  2. Pulmonary pathway – carries deoxygenated blood from the right side of the heart to the lungs where gaseous exchange occurs in the lungs making the blood oxygenated.

Significance of double blood circulation:

  1. Oxygenated and deoxygenated blood never mixes in the heart and blood vessels and always remains separate.
  2. The blood can be pumped to the rest of the body at a higher pressure.
  3. To complete a cycle, blood has to pass through the heart for two times:
  • At first, the impure blood reaches the lungs through the right ventricle and auricle.
  • Later, the pure blood from the lungs through the pulmonary veins comes to the left auricles, then to the left ventricles, from there a single aorta goes to different parts of the body.

Q.7. What is the difference between Blood and Lymph?

Sol. Difference Between Blood and Lymph.

Blood Lymph
Red in colour. Colourless.
It contains Red Blood Corpuscles It doesn’t contain Red Blood Corpuscles
It has comparatively less number of white blood corpuscles. It has comparatively more number of white blood corpuscles.
It contains more proteins. It contains very few proteins.
It contains more nutritious substances and oxygen. It contains less nutritious substances and oxygen.
It is a fluid connective tissue. It is a filtered blood.
Clotting factors are present. Clotting factors are absent
Platelets are present. Platelets are absent.

Q.8. Explain the Rh system.

Sol: Rh system:

Landsteiner and Weiner in 1940 discovered the Rh factor in Rhesus monkeys. Rh antigen is found on the surface of red blood cells.

Such individuals are called Rh-positive (Rh+) and those without this antigen are called Rh-negative (Rh-) . Rh antigen is also called an Rh factor. It is controlled by a dominant gene.

If Rh+ blood is transfused to the Th person then it produces agglutinin. It is called Isoimmunization.

According to it, human blood is of two types:

Group Antigen Antibody Percentage
Rh+ Present Absent 85 to 98 percent
Rh- Absent Absent 2 to 15 percent

Erythroblastosis Fetalis

  • It is a type of disease, which occurs in the fetus. It is also called hemolytic disease. It is caused when a mother is Rh- and the father is Rh+.
  • Rh antigens of the fetus do not get exposed to the Rh-ve blood of the mother in the first pregnancy as the two types of blood are well separated by the placenta. But, during the delivery time of the first child, there are possibilities of exposure of the maternal blood in small amounts to the Rh+ blood from the fetus.
  • In such cases, the mother starts preparing against Rh antigen in her blood.
  • In case of her next pregnancies, the Rh antibodies from the mother (Rh-ve) can pass into the blood of the foetus (Rh+) and destroy the foetal RBCs. This could be fatal to the fetus or could cause severe anaemia and jaundice to the baby. This condition is called Erythroblastosis Fetalis.
Husband Wife Child
Rh+ Rh+ Rh+
Rh- Rh- Rh-
Rh- Rh+ Rh+
Rh+ Rh- Rh+

This can be avoided by injecting anti-Rh antibodies into the mother’s blood immediately after the delivery of the first child. A baby suffering from this disease is called “Rhesus baby”.

Generally, they are born before the gestation period and have blood deficiency. Complete blood transmission of the newborn can be done to save the life of the child. A newborn can also be saved by injecting mother’s Rh-antibody just before 72 hours or 3 days before the delivery.

Q.9. Brief out the structure and functions of the human heart.

Sol: The human heart is divided into four chambers, namely two ventricles and two atria. The ventricles are the chambers that pump blood and atrium are the chambers that receive the blood. Among which, the right atrium and ventricle make up the “right portion of the heart”, and the left atrium and ventricle make up the “left portion of the heart.” The right side of our heart pumps deoxygenated blood into our lungs and the left side of our heart pumps oxygenated or oxygen-rich blood from our lungs to different parts of our body.

On an average, our heartbeats 70 to 72 times per minute, 100,000 times per day, 3,600,000 times per year, and 2.5 billion times in a complete lifetime.

The important functions of human heart are:

  1. The heart is the main organ in the circulatory system.
  2. The primary function of the heart is to pump blood throughout the body.
  3. It also helps to maintain adequate blood pressure throughout the body.
  4. The structure is primarily responsible for delivering the circulation of blood and transportation of nutrients in all parts of the body.
  5. It also functions by removing carbon dioxide and wastes from the blood.

Q.10. Draw a neat labelled diagram of the human heart.

Sol: Structure of the human heart

Q.11. What are blood vessels? Explain its types with the neat labelled diagram.

Sol. Blood Vessels

In organisms with closed circulatory systems, the blood flows within vessels of varying sizes. All vertebrates, including humans, possess this type of circulation. The external structure of the heart has many blood vessels that form a network, with other major vessels emerging from within the structure.

A blood vessel helps in transporting oxygen and nutrients in the cells and also ensures that waste products and carbon dioxide is thrown away from the cell. It also plays a vital role in controlling blood pressure.

Types of Blood Vessels

The human body comprises four main blood vessels:


It supplies deoxygenated blood to the heart via inferior and superior vena cava, and it eventually drains into the right atrium. They have much slighter walls compared to arteries.


They are tiny, tube-like blood vessels, which form a network between the arteries to veins. Capillaries are involved in transporting nutrients and oxygen to tissues and removing waste products. It allows the switching of chemicals and water between the tissues and blood.


They are muscular-walled flexible and strong tubes, which are mainly involved in supplying oxygenated blood away from the heart to all other parts of the body. Aorta is the largest of the arteries, and it branches off into various smaller arteries throughout the body. These blood vessels eventually branch into smaller branches called arterioles.


Valves are flaps of fibrous tissues located in the cardiac chambers between the veins. They ensure that the blood flows in a single direction (unidirectional). Flaps also prevent the blood from flowing backwards.

Q.12. Explain the internal structure of Heart.

Sol. Internal Structure of Heart

The internal structure of the heart is rather intricate with several chambers and valves that control the flow of blood.

Chambers of the Heart

Humans heart consists of four chambers:

  1. Left atrium.
  2. Right atrium.
  3. Left ventricle.
  4. Right ventricle.

Atria are the blood-receiving chambers that are fed by the large veins. They are thin, have less muscular walls and smaller than ventricles.

Ventricles are responsible for pumping and pushing blood out to the circulation. They are larger and more muscular chambers and are connected to larger arteries that deliver blood for circulation.

The right ventricle and right atrium are smaller than the left chambers. The heart wall consists of a small number of muscles compared to the left portion, and the size difference is based on their functions. The blood arising from the right side flows through the pulmonary circulation, while blood originating from the left chambers is pumped throughout the body.

Q.13. Explain the three layers of the heart wall.

Sol. The heart wall is made up of 3 layers, namely:

  1. Epicardium – This is the outermost layer of the heart. It is composed of a thin layer of membrane that protects and lubricates the outer section.
  2. Myocardium – This is a layer of muscle tissue that constitutes the middle layer wall of the heart. It is mainly responsible for the heart’s “pumping” action.
  3. Endocardium – It is the innermost layer of the heart wall, which lines the inner heart chambers and covers the heart valves. It functions by preventing blood from sticking, and thereby avoiding the formation of fatal blood clots.

Q.14. What is Rheumatic heart disease

Sol: Rheumatic heart disease is a chronic heart condition, caused by rheumatic fever. This is a very common heart disease in children and is more prevalent in developing countries, especially in areas of poverty.

Acute rheumatic fever is an inflammatory disease that primarily affects joints, heart, and central nervous system. Heart valve damage is the most common result of rheumatic fever. Pericardium and endocardium may be damaged due to the inflammation caused by rheumatic disease.


Heart valve problems are a result of rheumatic fever and it’s symptoms include:

  1. Chest pain.
  2. Giddiness.
  3. Excess fatigue.
  4. Swollen ankles.
  5. Heart missing a beat.
  6. Thumping sensation in the chest.


Treatment depends on the severity of the disease. Treatment for rheumatic heart disease generally includes:

  1. Antibiotics to prevent rheumatic fever.
  2. Surgery which involves repairing of heart valves.
  3. Medicines for blood thinning to prevent heart stroke.


Rheumatic fever generally starts with strep throat and develops into a fever. This development can be prevented by taking antibiotics or penicillin.

Q.15. Explain the external structure of Heart.

Sol. External Structure of Heart

One of the very first structures which can be observed when the external structure of the heart is viewed is the pericardium.


The human heart is situated to the left of the chest and is enclosed within a fluid-filled cavity described as the pericardial cavity. The walls and lining of the pericardial cavity are made up of a membrane known as the pericardium.

The pericardium is a fibre membrane found as an external covering around the heart. It protects the heart by producing a serous fluid, which serves to lubricate the heart and prevent friction between the surrounding organs. Apart from the lubrication, the pericardium also helps by holding the heart in its position and by maintaining a hollow space for the heart to expand itself when it is full. The pericardium has two exclusive layers:

  1. Visceral Layer: It directly covers the outside of the heart.
  2. Parietal Layer: It forms a sac around the outer region of the heart that contains the fluid in the pericardial cavity.

Structure of the Heart Wall

The heart wall is made up of 3 layers, namely:

  1. Epicardium – Epicardium is the outermost layer of the heart. It is composed of a thin-layered membrane that serves to lubricate and protect the outer section.
  2. Myocardium – This is a layer of muscle tissue, and it constitutes the middle layer wall of the heart. It contributes to the thickness and is responsible for the pumping action.
  3. Endocardium – It is the innermost layer that lines the inner heart chambers and covers the heart valves. Furthermore, it prevents the blood from sticking to the inner walls, thereby preventing potentially fatal blood clots.

Q.16. What is hemostasis?

Sol: The process of forming a clot or thrombus in order to prevent excess loss of blood from the body is called blood clotting. During the injury or a wound, a gel-like mass is formed by the platelets and fibrin in the blood, which present the flow of blood from the wound site. Coagulation of blood is a lengthy process occurring within a few minutes where numerous coagulation factors come into play. The mechanism which helps the body to prevent the blood loss is called hemostasis.

Hemostatic mechanism proceeds in the following series of steps:

  1. Changes in blood vessel cells
  2. Blood clot formation
  3. Platelet plug formation

Q.17. What is heart disease?

Sol. A heart is a muscular organ that pumps blood through the circulatory system by expansion and contraction. Any condition that affects the heart or it’s function results in heart diseases. Medically, heart disease is called cardiovascular disease.

The different types of heart disease:

  1. Angina.
  2. Aneurysm.
  3. Atherosclerosis.
  4. High blood pressure.
  5. Valvular heart disease.
  6. Ischemic Heart Disease.
  7. Rheumatic heart disease.
  8. Inflammatory heart disease.
  9. Hypertensive heart diseases.
  10. Cerebrovascular heart disease.

Q.18. What is the difference between Red Blood Cells and White Blood Cells?

Sol: Difference between Red Blood Cells and White Blood Cells are:

Red Blood Cells (RBC’s) White Blood Cells (WBC’s)
Are biconcave disc shaped cells. Are irregular shaped cells.
Size varies from 6 – 8 µm in diameter. Size varies from 12 – 17 µm in diameter.
Life -span is about 120 days. Life -span is about 4-30 days, which depends upon the body.
Nucleus is absent at maturity. Presence of a large central nucleus.
Produced in the red bone marrow Produced in the red bone marrow, lymph nodes and spleen, etc.
These cells are red in colour, due to the presence of haemoglobin – Red colour pigment. These cells are colourless, due to the absence of pigment.
They are about 5 million/ mm³ of blood. They are about 7000–8000/mm³ of blood.
Low count of RBCS results in Anaemia. Low count of WBC’S results in Leukopenia.
The process of formation of RBC is known as erythropoiesis. The process of formation of WBC is known as leukopoiesis.
Functions by transporting respiratory gases to different parts of the human body. Functions by producing antibodies to fight against diseases causing microbes.
These cells make up around 36-50% of human blood. These cells make up around 1% of the human blood.
Only one kind of RBCs are found in the blood. Different types of WBCs are found in the blood such as neutrophils, B lymphocytes, T lymphocytes, monocytes, basophils, eosinophils.

Q.19. What is Pulse rate and Heart rate?


Pulse rate

A Pulse rate is generally defined as the number of heartbeats per minute. The resting pulse rate for an average adult ranges between 60 and 80 beats per minute.

A pulse rate is the number of times your arteries create a noticeable “pulse” due to an increase in blood pressure as a result of your heart contracting.

Heart rate

The speed at which the human heart beats is termed as the heart rate.

A heart rate is the number of times your heart beats in the span of a minute. The heartbeat of an average individual ranges from 60 to a 100 beats per minute at resting.

Q.20. What is Blood? Explain the different Types of Blood Cells.

Sol. Blood is a fluid connective tissue that consists of different types of blood cells and plasma. It circulates throughout our body delivering oxygen and nutrients to various cells and tissues. It makes up 8% of our body weight. An average adult possesses around 5-6 litres of blood.

Types of Blood Cells

Red blood cells (Erythrocytes)

RBCs are the biconcave cells; also known as erythrocytes. RBCs contain the iron-rich protein called haemoglobin, which gives blood its red colour. RBCs are the most copious blood cells produced in bone marrow. Their main function is to transport oxygen from and to various tissues and organs.

White blood cells (Leucocytes)

Leucocytes are the colourless blood cells. They are colourless because it is devoid of haemoglobin. They are further classified as granulocytes and agranulocytes. WBCs mainly contribute to immunity and defence mechanism.There are five different types of White blood cells and are classified mainly based on the presence and absence of granules.

  1. Granulocytes

They are leukocytes, with the presence of granules in their cytoplasm. The granulated cells include- eosinophil, basophil, and neutrophil.

  1. Agranulocytes

They are leukocytes, with the absence of granules in their cytoplasm. Agranulocytes are further classified into monocytes and lymphocytes.

Blood Platelets (Thrombocytes )

A tiny disc-shaped cell that helps in regulating blood flow during any damage, thereby aiding in fast recovery through clotting of blood. Thrombocytes are specialized blood cells produced from bone marrow. These blood cells function by clotting and coagulation of blood during a cut or wound.

We, at BYJU’S, aim to deliver students with all the necessary support and allow them to prove their abilities by performing best in their examination. Important Questions for RBSE Class 12 Biology Chapter- 24- Blood circulatory system of Humans are prepared under the guidance of RBSE syllabus for Class 12, with proper structure and after thorough research on the particular topics.

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