CBSE Class 11 Biology Chapter 20: Body Fluids and Circulation NCERT Solutions

The formed elements of blood are the cellular components suspended in the plasma. These include:

1. Erythrocytes (Red Blood Cells - RBCs): These are the most numerous blood cells. Their primary function is to transport oxygen from the lungs to all tissues of the body and carbon dioxide from the tissues back to the lungs. This is facilitated by the presence of the red pigment, hemoglobin, within them. RBCs are produced in the bone marrow.
2. Leukocytes (White Blood Cells - WBCs): These are colorless cells that are part of the body's immune system. They defend the body against infections and diseases. WBCs are broadly classified into two main categories:
   • Granulocytes: These have granules in their cytoplasm.
     • Neutrophils: They are phagocytic, meaning they engulf and destroy bacteria and other foreign particles, thus protecting the body against infections.
     • Eosinophils: They are involved in combating parasitic infections and are also associated with allergic reactions.
     • Basophiles: These cells release histamine and heparin, contributing to inflammatory responses and regulating blood clotting.
   • Agranulocytes: These lack prominent granules in their cytoplasm.
     • Lymphocytes: They are central to the immune system, producing antibodies and mediating cellular immunity against pathogens.
     • Monocytes: These are large phagocytic cells that engulf pathogens, cellular debris, and foreign material in the bloodstream and tissues.
3. Platelets (Thrombocytes): These are small, irregular cell fragments. Their primary function is to initiate blood clotting (coagulation) by releasing factors that help form a plug at the site of injury, thereby preventing excessive blood loss.

Plasma, the liquid matrix of blood, constitutes about 55% of the total blood volume and contains about 6.8% proteins. These plasma proteins are vital for several physiological functions. The major plasma proteins and their importance are:

• Fibrinogens: Synthesized by the liver, these proteins are essential for blood coagulation. They form fibrin threads that create the meshwork of a blood clot, stopping bleeding.
• Globulins: This group includes antibodies (immunoglobulins) which are crucial for the body's immune defense system, protecting against infections. Other globulins also play roles in transporting hormones, lipids, and metals.
• Albumins: These are the most abundant plasma proteins, also synthesized by the liver. Albumins are primarily responsible for maintaining the osmotic pressure of the blood, which helps to keep water within the blood vessels and regulate fluid distribution between the blood and tissues.

In summary, plasma proteins are indispensable for blood clotting, immune responses, and maintaining fluid and electrolyte balance within the circulatory system.

Here is the correct matching of Column I with Column II:

1. Eosinophils - Resist Infections (specifically parasites and involved in allergic reactions)
2. RBC - Gas transport (primarily oxygen)
3. AB Group - Universal Recipient (can receive blood from any group)
4. Platelets - Coagulation (initiate blood clotting)
5. Systole - Contraction of Heart (the phase of the cardiac cycle when the heart muscle contracts)

Blood is classified as a specialized type of connective tissue for two primary reasons:

1. Origin: Like other connective tissues, blood originates from the mesoderm, the middle germ layer in embryonic development.
2. Structure and Function: Blood consists of cells (red blood cells, white blood cells, and platelets) that are dispersed within an extracellular matrix called plasma. This plasma contains dissolved proteins, salts, nutrients, and waste products. This structure, with cells embedded in an extracellular matrix, is characteristic of connective tissues. Furthermore, blood connects different parts of the body by transporting essential substances like oxygen, nutrients, hormones, and antibodies to various tissues and organs, and by removing waste products like carbon dioxide and metabolic wastes. This connecting and transporting role is a hallmark of connective tissues.