Chapter – 3E : Circulation | Chapter Solution Class 9

(c) Thrombocyte

Explanation: Thrombocytes, or platelets, are blood cells responsible for the coagulation process. They help form clots by releasing thromboplastin, initiating the clotting cascade to prevent blood loss from injuries.

(c) 4

Explanation: The ABO blood group system classifies human blood into four main groups: A, B, AB, and O, based on the presence or absence of antigens A and B on red blood cells.

(c) Deoxygenated

Explanation: The pulmonary artery carries deoxygenated blood from the right ventricle of the heart to the lungs. It is the only artery that transports deoxygenated blood.

(b) To carry oxygen

Explanation: Red blood cells contain haemoglobin, a protein that binds with oxygen in the lungs and transports it to body tissues.

(d) To pump blood

Explanation: The heart is a muscular organ whose main function is to pump blood through the circulatory system, supplying oxygen and nutrients to the body and removing waste products.

(a) Pure

Explanation: Arteries generally carry oxygenated (pure) blood from the heart to various parts of the body. The only exception is the pulmonary artery, which carries deoxygenated blood to the lungs.

(a) Plasma

Explanation: Plasma is the fluid portion of blood that remains after removing the blood cells (RBCs, WBCs, and platelets). It is mostly water but contains proteins, nutrients, hormones, and waste products.

capillaries

Explanation: The three main types of blood vessels are arteries, veins, and capillaries. Capillaries are the smallest vessels where exchange of gases and nutrients occurs between blood and tissues.

arterioles

Explanation: Capillaries branch out from arterioles, which are small branches of arteries. These fine capillaries form networks in tissues for exchange processes.

haemolymph

Explanation: Cockroaches have an open circulatory system with a colourless blood-like fluid called haemolymph. It lacks respiratory pigments like haemoglobin and does not transport oxygen.

urochrome

Explanation: Urochrome is a yellow pigment that results from the breakdown of haemoglobin. It is excreted in urine and gives urine its typical yellow color.

antibody

Explanation: Blood group AB has both A and B antigens on red cells and no antibodies in plasma. This makes it a universal recipient in transfusions, as it won’t react with any donor’s blood antigens.

False

Explanation: Plasma actually makes up about 55% of the blood volume. The remaining 45% consists of blood cells (RBCs, WBCs, and platelets).

True

Explanation: In open circulatory systems (like in arthropods), blood is not confined to capillaries or blood vessels. It flows freely through body cavities, so capillaries are absent.

True

Explanation: Lymph originates as tissue fluid, which is derived from blood plasma. It is eventually collected into lymphatic vessels and returned to the blood circulation.

True

Explanation: Eosinophils are a type of WBC that defends against parasites and participates in allergic responses. They also help in modulating inflammation.

True

Explanation: The right ventricle pumps deoxygenated blood into the pulmonary artery, which carries it to the lungs for oxygenation. This is a key step in pulmonary circulation.

Tissue fluid

Reason: Rest are cellular component of blood.

Prothrombin

Reason: Rest are the type of white blood cell.

Mitral valve

Reason: Rest are the part of the heart’s conduction system.

A body cavity filled with blood or haemolymph is called haemocoel.

Explanation: In organisms with an open circulatory system (like arthropods), blood does not flow through closed vessels but instead bathes organs directly in a cavity called the haemocoel.

Between left atrium and left ventricle.

Explanation: The mitral valve (also called bicuspid valve) ensures one-way blood flow from the left atrium to the left ventricle and prevents backflow.

Fibrinogen

Explanation: Fibrinogen is a soluble plasma protein that is converted into fibrin threads by thrombin during clotting, forming the mesh that stops bleeding.

Prawn

Explanation: Prawns, being arthropods, have an open circulatory system where blood flows through open spaces or sinuses instead of closed vessels.

White blood cells (WBCs)

Explanation: WBCs, especially neutrophils and lymphocytes, are key to the immune system, defending the body against infections and foreign invaders.

No

Explanation: Mature mammalian RBCs lack a nucleus to provide more space for haemoglobin, which improves their efficiency in oxygen transport.

Haemoglobin

Explanation: Haemoglobin is the iron-containing respiratory pigment in RBCs that binds with oxygen and transports it to body tissues.

To carry oxygen.

Explanation: Haemoglobin binds to oxygen in the lungs and carries it to tissues throughout the body, releasing it where needed for cellular respiration.

72 beats per minute

Explanation: The normal resting heart rate for a healthy adult is approximately 72 beats per minute, though it may vary slightly based on age and fitness.

Four

Explanation: The ABO blood group system includes four main groups: A, B, AB, and O, based on the antigens present on red blood cells.

Osmotic pressure is the minimum pressure required to prevent the inward flow of water across a semipermeable membrane separating two solutions with different concentrations.

Transpiration pull is the force generated due to the evaporation of water from the leaves, which helps draw water upward through the xylem from the roots to the aerial parts of the plant.

Cohesive force is the attractive force between molecules of the same substance, such as the attraction between water molecules that helps maintain a continuous water column in plants.

Adhesive force is the attractive force between molecules of different substances, like water molecules and the walls of xylem vessels, aiding in the upward movement of water in plants.

Passive absorption is the uptake of water by plant roots without the use of metabolic energy, primarily driven by transpiration and osmotic gradients.

Active absorption is the process where plant roots absorb water and minerals from the soil using metabolic energy (ATP), often against a concentration gradient.

Blood is a fluid connective tissue composed of plasma and formed elements such as red blood cells, white blood cells, and platelets.

Blood is called a connective tissue because it originates from mesoderm and functions to connect different body systems by transporting gases, nutrients, hormones, and waste materials.

Open circulation is a type of circulatory system where blood is not confined to blood vessels but flows freely through open body cavities, bathing organs directly.

A double circuit heart refers to a heart where blood passes through it twice in one complete circulation — once for pulmonary circulation and once for systemic circulation.

Cardiac output is the volume of blood pumped by the heart in one minute, calculated as the product of heart rate and stroke volume.

The mitral valve is a two-flapped valve located between the left atrium and the left ventricle of the heart that regulates blood flow and prevents backflow.

Portal circulation is the pathway of blood flow from the digestive organs to the liver through the hepatic portal vein before it returns to the heart.

Blood is a fluid connective tissue that circulates in a closed system of blood vessels. It plays a vital role in the transportation of nutrients, oxygen, hormones, enzymes, and waste materials throughout the body. Blood in an adult human is about 5–6 litres and has a pH of 7.4.

Constituents of blood: Blood is composed of two main parts:

1. Plasma: Plasma is the pale straw-coloured, slightly alkaline, viscous fluid part of blood. It constitutes about 55% of total blood volume.

Plasma contains:

• 91–92% water
• 7% proteins (albumin, globulin, fibrinogen, prothrombin)
• 1% inorganic salts, glucose, amino acids, enzymes, hormones, gases, and wastes

Functions of plasma:

• Transports food, CO₂, excretory substances, and hormones
• Maintains water balance and body temperature
• Helps in blood clotting

2. Blood Corpuscles: They make up about 45% of the blood volume and are of three types:

(i) Red Blood Cells (RBCs): Red Blood Cells (RBCs) are circular, biconcave cells without a nucleus that contain haemoglobin. They carry oxygen from the lungs to tissues and carbon dioxide back to the lungs.

Function of RBC:

• Carry oxygen and carbon dioxide

(ii) White Blood Cells (WBCs): White Blood Cells (WBCs), also called leucocytes, are colourless, nucleated cells in blood that defend the body against infections.

Function of WBCs:

• Defend the body by killing pathogens

(iii) Platelets (Thrombocytes): Platelets, also known as thrombocytes, are small, disc-shaped, non-nucleated cell fragments found in blood. They are produced in the red bone marrow from large cells called megakaryocytes.

Function of Platelets:

• Help in blood clotting and vessel repair

The human heart has four chambers — two upper chambers called auricles (also known as atria) and two lower chambers called ventricles. The right and left auricles have different but equally important functions in the circulation of blood.

Right Auricle (Right Atrium):

• The right auricle receives deoxygenated blood from the body through two large veins — the superior vena cava and inferior vena cava. This blood is poor in oxygen and rich in carbon dioxide. After collecting the blood, the right auricle contracts and pushes it into the right ventricle through the tricuspid valve, which prevents backflow.

Left Auricle (Left Atrium):

• The left auricle, on the other hand, receives oxygenated blood from the lungs through four pulmonary veins. This oxygen-rich blood is essential for body tissues. When the left auricle contracts, it sends the blood into the left ventricle through the bicuspid (mitral) valve, ensuring one-way flow and proper circulation to the rest of the body.

Blood is a red-coloured, slightly alkaline, viscous connective tissue that circulates through blood vessels in a closed circulatory system. It plays a vital role in the transportation of essential substances like oxygen, nutrients, hormones, and waste products throughout the body. In a healthy adult, the average volume of blood is about 5 to 6 litres, and its pH is around 7.4.

The constituents of blood are divided into two main parts:

1. Plasma – the fluid portion that makes up about 55% of blood. It contains water, proteins (like albumin, globulin, fibrinogen), salts, glucose, amino acids, hormones, and gases.
2. Blood corpuscles – the cellular portion that makes up about 45% of blood and includes Red Blood Cells (RBCs), White Blood Cells (WBCs), and Platelets.

Two important functions of blood are:

1. Transportation – It carries oxygen from the lungs to tissues and removes carbon dioxide from tissues to the lungs. It also transports nutrients, hormones, and waste materials.
2. Protection and clotting – WBCs protect the body from infections, and platelets help in clotting blood at the site of injury, preventing excess blood loss.

Functions of RBC (Red Blood Cells):

1. RBCs carry oxygen from the lungs to all body tissues with the help of haemoglobin.
2. They also transport carbon dioxide from the tissues back to the lungs.
3. RBCs help maintain the acid-base balance (pH) of the blood.
4. They carry blood group antigens and Rh factor on their surface.

Functions of WBC (White Blood Cells):

1. WBCs protect the body by fighting against infections and destroying pathogens.
2. Neutrophils act as the first line of defense and destroy microbes.
3. Lymphocytes (B and T cells) help in building immunity.
4. Eosinophils and basophils are involved in allergic responses.
5. Monocytes remove dead cells and microbes through phagocytosis.

The major blood groups of man are A, B, AB, and O, as classified under the ABO blood group system. This system was discovered by Karl Landsteiner and is based on the presence or absence of specific antigens on the surface of red blood cells and antibodies in the plasma.

The basis of such grouping lies in the antigen-antibody reaction:

• Blood group A has A antigen on RBCs and anti-B antibody in plasma.
• Blood group B has B antigen on RBCs and anti-A antibody in plasma.
• Blood group AB has both A and B antigens on RBCs and no antibodies in plasma.
• Blood group O has no antigens on RBCs but has both anti-A and anti-B antibodies in plasma.

This classification is crucial for safe blood transfusions, as mismatched blood groups can lead to dangerous agglutination (clumping) of blood.

Blood clotting is the process by which flowing blood is converted into a solid clot to prevent excessive bleeding at the site of injury. It is a protective mechanism of the body.

Mechanism of Clotting:

1. Injury to a blood vessel causes platelets to break and release a chemical called thromboplastin.
2. Thromboplastin, in the presence of calcium ions (Ca²⁺), converts prothrombin (a plasma protein) into thrombin.
3. Thrombin then acts on another plasma protein fibrinogen, converting it into fibrin.
4. Fibrin forms a mesh-like network at the wound, trapping blood cells and forming a clot.

This clot seals the wound, stops further bleeding, and prevents the entry of microbes.

Single circuit heart is found in animals like fish, where the blood passes through the heart only once in a complete circulation. In this type, blood flows from the heart to the gills for oxygenation and then directly to the rest of the body, without returning to the heart in between.

Path of circulation in single circuit heart:

Heart → Gills → Body → Heart

Double circuit heart is found in mammals and birds, including humans. In this type, blood passes through the heart twice during one complete circulation — once for oxygenation and once for distribution to the body. It consists of two separate circulations:

1. Pulmonary circulation – Carries deoxygenated blood from the right ventricle to the lungs through the pulmonary artery, and brings back oxygenated blood to the left atrium through the pulmonary veins.
   Path: Right ventricle → Pulmonary artery → Lungs → Pulmonary vein → Left atrium
2. Systemic circulation – Carries oxygenated blood from the left ventricle to the entire body through the aorta, and returns deoxygenated blood to the right atrium via the superior and inferior vena cava.
   Path: Left ventricle → Aorta → Body → Vena cava → Right atrium

This type of circulation maintains efficient separation of oxygenated and deoxygenated blood.

The course of circulation of blood through the human heart involves two main pathways: pulmonary circulation and systemic circulation, together forming a double circulation system. Blood passes twice through the heart during one complete circulation — once through the right side and once through the left side.

1. Pulmonary Circulation (Right Side of the Heart):

• Deoxygenated blood from the body returns to the right atrium through the superior and inferior vena cava.
• The right atrium contracts and sends the blood into the right ventricle through the tricuspid valve.
• The right ventricle then contracts and pumps the blood into the pulmonary artery, which carries it to the lungs.
• In the lungs, blood releases carbon dioxide and absorbs oxygen.

2. Systemic Circulation (Left Side of the Heart):

• Oxygenated blood from the lungs returns to the left atrium through four pulmonary veins.
• The left atrium contracts and pushes the blood into the left ventricle through the bicuspid (mitral) valve.
• The left ventricle then contracts and pumps the blood into the aorta, which distributes it to all parts of the body through arteries.
• After supplying oxygen and collecting waste products, the blood becomes deoxygenated and returns to the heart via veins, completing the cycle.