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Class 10 SELINA Solutions Biology Chapter 8 - The Circulatory System

The Circulatory System Exercise Ex. 1

Solution D.1

(a) Circulatory system: The circulatory system is responsible for transport of various substances in human beings and is composed of the heart, arteries, veins and blood capillaries.


(b) Blood: Blood is the circulating fluid contained in the heart and in the blood vessels such as arteries, veins and capillaries of the circulatory system.


(c) Heart: Heart is the muscular pumping organ which pushes the blood around the body and has different chambers such as right atrium, left atrium, right ventricle, left ventricle to prevent the mixing of oxygenated blood and carbon dioxide rich blood.


(d) Diapedesis: Diapedesis is the squeezing of leucocytes through the wall of capillaries into the tissues.


(e) Phagocytosis: Phagocytosis is the process in which most WBCs and particularly the neutrophils engulf particle-like solid substances, especially bacteria.


(f) Rh factor: Rh factor is an inherited antigen often found on the blood cells. Some individuals have these antigens and are thus Rh positive (Rh+) while others who do not have this antigen are Rh negative (Rh-)

Solution D.2

(a) Differences between systole and diastole:



1. The contraction of cardiac (heart) chambers is called systole.

1. The relaxation of cardiac (heart) chambers is called diastole.

2. Blood is pumped out of the cardiac chambers.

2. Blood is received in the cardiac chambers.

3. The valves are closed to prevent backflow.

3. The valves are opened to allow entry of blood.


(b) Differences between arteriole and venule:



1. The smallest or final branch of an artery is called an arteriole.

1. The smallest united branch of capillaries is called a venule.

2. They are highly muscular.

2. They are less muscular.

3. Arteriole breaks up into capillaries.

3. They unite to form larger veins.


(c) Differences between universal donor and universal recipient:

Universal donor

Universal recipient

1. It can donate blood to any ABO blood group. 

1. It can receive blood from any ABO blood group. 

2. The universal donor is Type O. 

2. The universal donor is Type AB. 

3. It lacks antigen A and antigen B on their red blood cells.

3. It contains both types of antigens on their red blood cells. 


(d) Differences between arteries and veins:



1. An artery is a vessel which carries blood away from the heart towards any organ.

1. A vein is a vessel which conveys the blood away from an organ towards the heart.

2. Artery has thick muscular walls.

2. Vein has thin muscular walls.

3. It has a narrow lumen. 

3. It has a broad lumen.

4. There are no valves. 

4. Thin pocket-shaped valves are present in the veins.


(e) Differences between haemoglobin and chlorophyll:



1. It is a respiratory pigment that transports oxygen from the lungs across the body parts.

1. It is a light-capturing pigment which facilitates light absorption during photosynthesis.

2. It is red in colour.

2. It is green in colour.

3. The central ion is iron.

3. The central ion is magnesium.

4. It is found in human blood.

4. It is found in green plants and algae.


Solution D.3

(a) The left ventricle pumps blood to the farthest points in the body such as the feet, the toes and the brain against the gravity while the right ventricle pumps the blood only up to the lungs. Therefore, the left ventricle has thicker walls than the right ventricle.


(b) The right ventricle pumps blood to the lungs for oxygenation whereas the right auricle receives the blood from vena cavae and passes it to the right ventricle. Therefore, walls of the right ventricle are thicker than those of the right auricle.


(c) The mechanism of blood clotting involves the presence of calcium and other clotting factors. Thrombokinase activates an enzyme called prothrombin activator. The enzyme prothrombin activator then converts plasma protein prothrombin into thrombin. Thrombin is the enzyme which in turn converts fibrinogen into fibrin. Polymerized fibrin together with platelets forms a clot at the wound site. The prothrombin is a plasma protein synthesized in the liver. Vitamin K is essential for the synthesis of prothrombin. Hence, Vitamin K is essential for the process of blood clotting. 

Solution D.4

(a) Tonsils: Tonsils are lymph glands located on the sides of the neck. They tend to localize the infection and prevent it from spreading it in the body as a whole.


(b) Spleen: The spleen is a large lymphatic organ. The spleen acts as a blood reservoir in case of emergency such as haemorrhage, stress or poisoning. It produces lymphocytes and destroys worn out RBCs.


(c) Hepatic portal vein: The hepatic portal vein is a blood vessel that carries blood from the gastrointestinal tract, gallbladder, pancreas and spleen to the liver. This blood contains nutrients and toxins extracted from digested contents.


(d) Basophils: They are a type of granular WBCs which release chemicals called histamine for inflammation which dilate blood vessels.


(e) S.A.N.: The sinoatrial node is a group of cells located in the wall of the right atrium of the heart. The action potential required for the rhythmic contractile activity of the heart is generated at the SA node. When the impulse is initiated, it results in the atrial systole.

Solution D.5

Double circulation is a process during which blood passes twice through the heart during one complete cycle. The flow of blood in the heart consists of two phases-

1. The short pulmonary (lung) circulation

2. The long systemic (general body) circulation

Difference between pulmonary and systemic circulation:

Pulmonary circulation

Systemic circulation

1. It involves circulation of blood between the heart and the lungs.

1. It involves circulation of blood between the heart and the body organs (except lungs).

2. It carries deoxygenated blood to the lungs to receive oxygen.

2. It carries oxygenated blood to the body organs.

3. It returns oxygenated blood back to the heart.

3. It returns deoxygenated blood back to the heart.


Solution A.1

(a) lymphocytes and monocytes

Solution A.2

(b) phagocytosis

Solution A.3

(d) Heart itself

Solution A.4

(c) artery

Solution A.5

(b) chest pain due to inadequate supply of oxygen to the heart muscle

Solution A.6

(d) destroy pathogens

Solution A.7

(a) closure of tricuspid and bicuspid valves

(b) rushing of blood through valves producing turbulence

(c) closure of atrioventricular and semilunar valves

Solution B.1

(a) Blood platelets and blood coagulation

(b) Neutrophils and phagocytosis

(c) Erythrocytes and transportation of gases

(d) Lymphocytes and Produce antibodies

(e) Bone marrow and destruction of old and weak RBC's/production of RBCs and WBCs.

Solution B.2

(a) Red Blood Cells

(b) Blood Platelets

Solution B.3

(a) Hepatic portal vein

(b) Blood Capillaries

(c) Pulmonary artery

(d) White blood cells

(e) Venules

(f) Portal vein

(g) Atrial systole

(h) Tricuspid valve

(i) Atrial systole

(j) Pericardial fluid

Solution B.4

(a) The blood vessel that begins and ends in capillaries is the hepatic portal vein.

(b) A blood vessel which has small lumen and thick wall is artery.

(c) The valve which prevents the back flow of blood in the veins and lymph vessels is semilunar valve.

(d) An anticoagulant present in the blood is heparin.

Solution B.5

(a) Lubb: Atrio-ventricular valve:: Dup: Semilunar valves

(b) Coronary artery: Heart::Hepatic artery: Liver

Solution B.6

A matured mammalian erythrocyte lacks a nucleus and mitochondria. The lack of a nucleus increases the surface area-volume ratio of RBCs, thus increasing the area for oxygen absorption. Also, the lack of a nucleus reduces the size of the cell, making it easy to flow through the blood vessels and more cells can be accommodated in a small area.

The lack of mitochondria implies that the cell does not use any oxygen absorbed for respiration, thus increasing the efficiency of the cell to transport oxygen as all the oxygen absorbed is transported without any loss.

Solution C.1

Structural Differences between White Blood Cells and Red Blood Cells:

White Blood Cells Red Blood Cells
1. White blood cells are amoeboid. Red blood cells are minute biconcave disc-like structures.
2. They are nucleated cells. They anucleated cells.
3. Haemoglobin is absent in red blood cells. Haemoglobin is present in red blood cells.

Solution C.2

During blood transfusion it is necessary to know the blood groups before transfusion because it is important that the blood groups of the donor and the recipient are compatible. In case of an incompatible blood transfusion, the recipient develops antibodies that attack the antigens present on the RBCs of the donor causing the blood cells to clump together which may result in death.

Solution C.3

(a) Differences between antibodies and antibiotics based on their source:



They are produced by lymphocytes in response to the entry of pathogens in the bloodstream. 

They are the medicines extracted from some bacteria and fungi. Antibiotics destroy or inhibit the growth of pathogens.

(b) Differences between serum and vaccine based on their composition:



The plasma from which the protein fibrinogen has been removed is called serum. 

Vaccine is killed or living weakened germs which are introduced in the body to stimulate the production of antibodies against pathogens for a particular disease.

(c) Differences between erythrocytes and leucocytes based on their function:



They function in the transport of oxygen throughout the body and in the removal of carbon dioxide from the body.

They help in the defense of the body against disease-causing pathogens.

(d) Differences between tricuspid valve and bicuspid valve based on their location:

Tricuspid valve  

Bicuspid valve  

It is located between the right atrium and right ventricle of the heart.

It is located between the left atrium and left ventricle of the heart.


Solution C.4

People have a common belief that the heart is located on the left side of the chest because the narrow end of the roughly triangular heart is pointed to the left side and during its working the contraction of the heart is more powerful on the left side which can be felt.

Solution C.5

Column A

Column B

(a) SA node


(b) Defective hemoglobin in RBC

Sickle cell anemia

(c) Muscle fibres located in the heart

Purkinje fibres

(d) The liquid squeezed out of blood during clotting


(e) Never tires, keep on contracting and relaxing

Cardiac muscles

(f) Cardiac cycle

0.85 sec

(g) Liquid part of the blood without corpuscles



Solution D.7

The functions of blood plasma are:

(a) Transports of digested food from the alimentary canal to tissues.

(b) Transports excretory materials from tissues to excretory organs.

(c) Distributes hormones from the glands to their target site.

(d) Distributes heat in the body to maintain the body temperature.

Solution D.6

Blood clotting or coagulation occurs in a series of the following steps:

(a) The injured tissue cells and the platelets disintegrate at the site of wound to release thromboplastin.

(b) The thromboplastin with the help of calcium ions converts inactive prothrombin into active thrombin.

(c) Thrombin in the presence of calcium ions converts soluble fibrinogen into insoluble fibrin which forms a mesh or network at the site of wound.

(d) The blood cells trapped in this network shrink and squeeze out the plasma to leave behind a solid mass known as the clot.

Solution D.8

The functions of the blood are:

(a) Transport of digested food from the alimentary canal to tissues. These substances are simple sugars like glucose, amino acids, vitamins, mineral salts, etc.

(b) Transport of oxygen in the form of an unstable compound 'oxyhaemoglobin' from the lungs to the tissues.

(c) Transport of carbon dioxide from the tissues to the lungs.

(d) Transport of excretory materials from the tissues to the liver, kidney or the skin for elimination.

(e) Distribution of hormones from glands to the target sites.

(f) Distribution of heat to keep the body temperature uniform.

(Any five)

Solution D.9

(a) The left ventricle pumps blood to the farthest points in the body such as the feet, the toes and the brain against the gravity while the right ventricle pumps the blood only up to the lungs. Therefore, the left ventricle has thicker walls than the right ventricle.

(b) The right ventricle pumps blood to the lungs for oxygenation whereas the right auricle receives the blood from vena cavae and passes it to the right ventricle. Therefore, walls of the right ventricle are thicker than those of the right auricle.

Solution D.11

Blood flows twice in the heart before it completes one full cycle. This process of blood circulation in the human body is called double circulation.


The expansion or relaxation phase of the atria is called a diastole.

Solution E.1

(a) 1 → Red Blood Cell (RBC),

2 → White Blood Cell (WBC),

3 → Blood Platelet

4 → Blood Plasma.

(b) The red blood cells are minute biconcave disc-like structures whereas the white blood cells are amoeboid.

(c) Function of part 1 (RBC): Transport of respiratory gases to the tissues and from the tissues, transport of nutrients from the alimentary canal to the tissues.

Function of part 2 (WBC): WBCs play major role in defense mechanism and immunity of the body.

Function of part 3 (Blood Platelet): Blood platelets are the initiator of blood clotting.

(d) The average life span of a red blood cell (RBC) is about 120 days.

(e) Thromboplastin

Solution E.2

(a) The structure 3 represents the heart. It forms the centre of double circulation and is located between the liver and the head (as per the diagram). Also the blood circulation (indicated by 1) begins from heart to lungs.


Aorta 5
Hepatic portal vein 7
Pulmonary artery 1
Superior vena cava 9
Renal vein 8
Stomach 10

Solution E.7

(a) Tissue Fluid

(b) Red blood cells

(c) Lymph

(d) The lymph supplies nutrition and oxygen to those parts where blood cannot reach. The lymph drains away excess tissue fluids and metabolites and returns proteins to the blood from tissue spaces.

Solution E.3

(a) A- Artery, B-Vein, C-Capillary

(b) 1 - External layer made of connective tissue

2 - Lumen

3 - Middle layer of smooth muscles and elastic fibres

4 - Endothelium

(c) An artery has thick muscular walls and a narrow lumen. It does not have any valve. A vein on the other hand has thin muscular walls and a wider lumen. It has valves to prevent backflow of blood.

(d) A (Artery)- Oxygenated blood, B (Vein)- Deoxygenated blood

(e) At the capillary level the actual exchange of gases takes place.

Solution E.4

(a) Atrial Diastole and Ventricular Systole

(b) Ventricular muscles are contracting during this phase because the valves between the two ventricles and pulmonary artery and aorta are open while the atrio-ventricular valves are closed.




Pulmonary Artery




Pulmonary Vein


Left Atrium


Bicuspid Valve


Right Ventricle

(d) Part 1 (Pulmonary artery) → Deoxygenated blood

Part 2 (Aorta) → Oxygenated Blood

(e) Two i.e., bicuspid and tricuspid valves are closed in this phase.

Solution E.5

a.  1 - Red blood cell

b. Diapedesis




They lack a nucleus.

They have a nucleus.

They are biconcave and disc-shaped.

They are spherical and have different sizes.


d. The process which occurs in B and C is phagocytosis. In this process, the WBCs engulf the foreign particles and destroy them, thus preventing the occurrence of disease.

Solution E.6


1 - Arteriole

2 - Artery

3 - Venule

4 - Capillaries

5 - Vein


b. Such an arrangement can be observed in the lungs.

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