Chapter – 3E : Circulation | Chapter Solution Class 9

(c) Thrombocyte

Explanation: Thrombocytes, also called platelets, are specialized blood cells that help in clotting. They gather at the site of a wound and form a plug to stop bleeding. This process is crucial for preventing excessive blood loss during injury.

(d) 4

Explanation: There are four main human blood groups—A, B, AB, and O—based on the presence or absence of specific antigens on the surface of red blood cells. This classification is crucial for blood transfusions and organ donation.

(b) Deoxygenated

Explanation: Unlike other arteries, the pulmonary artery carries deoxygenated blood from the right ventricle of the heart to the lungs for oxygenation. This is a unique exception in the circulatory system.

(b) To carry O₂

Explanation: Red blood cells (RBCs) contain hemoglobin, which binds to oxygen in the lungs and transports it to various tissues and organs of the body. They play a vital role in maintaining life by supplying oxygen.

d) To pump blood

Explanation: The primary function of the heart is to pump blood throughout the body. It acts as a muscular pump that maintains continuous circulation of blood through two main circuits—systemic circulation (to the body) and pulmonary circulation (to the lungs). This ensures oxygen, nutrients, and hormones are delivered to tissues, while waste products like CO₂ are carried away for excretion.

(b) Pure

Explanation: Arteries generally carry oxygen-rich blood (except the pulmonary artery). This oxygenated or “pure” blood is pumped from the heart to different parts of the body, delivering oxygen to tissues.

(a) Plasma

Explanation: Plasma is the liquid component of blood that remains after removing blood cells (RBCs, WBCs, and platelets). It contains water, salts, proteins, and nutrients, and is essential for transporting substances throughout the body.

Capillary

Explanation: Capillaries are tiny blood vessels that connect arteries and veins. They help in the exchange of oxygen, nutrients, and waste between blood and tissues. Thus, arteries, veins, and capillaries together form a complete network of blood circulation.

Arterioles

Explanation: Arterioles are small branches of arteries that lead to capillaries. They play a key role in regulating blood flow and blood pressure before the blood enters capillaries for nutrient exchange.

Haemolymph

Explanation: In cockroaches and other insects, blood is not red as it lacks hemoglobin. It is a colorless or slightly greenish fluid known as haemolymph, which transports nutrients but not oxygen, as insects breathe through tracheae.

Urochrome

Explanation: Urochrome is a pigment that results from the breakdown of hemoglobin in the liver. It gives urine its characteristic yellow color depending on the concentration.

Antibody

Explanation: People with AB blood group have both A and B antigens on red blood cells but no antibodies in their plasma. This makes them universal recipients for blood transfusion, as their plasma won’t attack donor RBCs.

False

Explanation: Plasma makes up about 55% of blood volume. The rest consists of the formed elements—red blood cells, white blood cells, and platelets.

True

Explanation: In open circulatory systems (as found in insects), blood is not confined to vessels and flows freely in body cavities. Therefore, capillaries are absent.

True

Explanation: Lymph is formed when fluid leaks out of blood capillaries into tissues. It is later collected by lymph vessels and returned to the bloodstream, helping in immunity and waste removal.

True

Explanation: Eosinophils are white blood cells involved in defense against parasitic infections and play a role in allergic reactions by releasing histamines.

True

Explanation: This is a key step in pulmonary circulation. The right ventricle pumps deoxygenated blood to the lungs via the pulmonary artery for oxygenation.

Tissue fluid

Explanation: RBCs, WBCs, and platelets are cellular components of blood, whereas tissue fluid is a non-cellular fluid outside the blood vessels.

Prothrombin

Explanation: Neutrophil, Eosinophil, and Basophil are types of white blood cells (granulocytes), while Prothrombin is a clotting protein, not a cell.

Mitral valve

Explanation: SA Node, AV Node, and Purkinje fibres are part of the heart’s conduction system, whereas the Mitral valve is a structural valve, not part of the conduction system.

A haemocoel is a body cavity filled with blood or hemolymph, found in organisms with an open circulatory system.

Explanation:

In animals like arthropods and mollusks, blood flows freely within this cavity instead of being confined to blood vessels. It surrounds organs and helps in nutrient and gas exchange.

The mitral valve is present between the left atrium and left ventricle of the heart.

Explanation:

It ensures unidirectional blood flow from the left atrium to the left ventricle and prevents backflow during ventricular contraction.

Fibrinogen

Explanation:

Fibrinogen is a plasma protein that converts into fibrin threads during clotting. These threads form a mesh that traps blood cells and seals wounds.

Earthworm

Explanation:

In open circulation, blood is not confined to vessels; it bathes organs directly. However, note: Earthworms actually have closed circulation. A correct example of open circulation is cockroach.

Connective tissue

Explanation:

Though fluid, blood connects different parts of the body by transporting nutrients, gases, and waste—hence classified as a connective tissue.

No

Explanation:

Mature red blood cells in mammals are enucleated (lack a nucleus). This adaptation allows more space for hemoglobin, improving oxygen-carrying efficiency.

Hemoglobin

Explanation:

Hemoglobin is an iron-containing pigment in RBCs that binds with oxygen and transports it to body tissues.

To carry oxygen from lungs to tissues

Explanation:

Hemoglobin binds with oxygen in the lungs and releases it in the tissues where it’s needed for cellular respiration.

To pump blood throughout the body

Explanation:

The heart acts as a muscular pump, ensuring circulation of oxygenated and deoxygenated blood via arteries and veins, maintaining life processes.

Four (A, B, AB, O)

Explanation:

Based on the presence or absence of antigens A and B on RBCs, human blood is categorized into four main groups: A, B, AB, and O.

The minimum pressure required to stop the inward flow of water across a semipermeable membrane due to osmosis is called osmotic pressure.

Example: Root cells absorb water from soil due to osmotic pressure.

The suction force developed due to water evaporation from leaves which helps in upward movement of water through xylem is called transpiration pull.

Example: Seen in tall trees where water rises from roots to leaves.

The force of attraction between similar water molecules that holds them together is called cohesive force.

Example: Water column in xylem remains unbroken due to cohesion.

The force of attraction between water molecules and the walls of xylem vessels is called adhesive force.

Example: Water sticks to xylem walls during upward movement.

The process of water absorption in plants that occurs due to transpiration pull and does not require metabolic energy is called passive absorption.

Example: It occurs mainly in tall plants during daytime.

The water absorption that takes place using metabolic energy (ATP) against the concentration gradient is called active absorption.

Example: Occurs when soil water is less and root cells absorb it actively.

Blood is a fluid connective tissue.

Example: It connects various organs by transporting nutrients, gases, and waste materials.

Because it connects different parts of the body by transporting oxygen, hormones, nutrients, and wastes, blood is called a connective tissue.

Example: RBCs, WBCs, and plasma serve different functions in transport and immunity.

A circulatory system in which blood is not confined within vessels and bathes organs directly is called open circulation.

Example: Found in cockroach, prawns, and other arthropods.

A heart that allows two separate circuits for oxygenated and deoxygenated blood flow is called a double circuit heart.

Example: Found in humans — pulmonary and systemic circulation.

The volume of blood pumped by each ventricle per minute is called cardiac output.

Example: In humans, it is about 5–6 liters per minute at rest.

A valve that separates the left auricle and left ventricle of the heart, preventing backflow of blood, is called mitral valve.

Example: Also known as bicuspid valve.

The circulation in which blood from one organ passes through another organ before returning to the heart is called portal circulation.

Example: Hepatic portal vein carries blood from intestines to liver.

Blood is a fluid connective tissue that circulates throughout the body, transporting nutrients, gases, hormones, and waste.

Constituents:

1. Plasma – 55% of blood; straw-colored fluid containing water, proteins, hormones, nutrients, and waste.
2. RBCs (Erythrocytes) – Carry oxygen using hemoglobin.
3. WBCs (Leukocytes) – Defend the body against pathogens.
4. Platelets (Thrombocytes) – Help in blood clotting.