Question

Given below is a diagram of a human blood smear. Study the diagram and answer the questions that follow

(i) Name the components numbered ‘1’ to ‘4’.
(ii) Mention two structural differences between the parts ‘1’ and ‘2’.
(iii) Name the soluble protein found in part ‘4’ which forms insoluble threads during the clotting of blood.
(iv) What is the average lifespan of the component numbered ‘1’?
(v) Component numbered ‘1’ do not have certain organelles but are very efficient in their function. Explain.

Answer 1

Blood:

1. Blood is the red-colored fluid that circulates throughout the body and transports oxygen and nutrients to all the organs.
2. The components of the blood are plasma and formed elements - erythrocytes (RBCs), leucocytes (WBCs), and thrombocytes (platelets).
3. It performs various functions such as transporting respiratory gases, maintaining the body's pH, immunity, etc.

Plasma:

1. Plasma is a straw-colored fluid that gives liquid nature to the blood and has no blood cells in it.
2. It occupies about 50-60% of the total blood.
3. The components of plasma include water, proteins, inorganic salts, glucose, hormones, urea, etc.

Red blood Corpuscles:

1. The red blood corpuscles (RBCs), also known as erythrocytes are the kind of cells that are present most abundant in the blood.
2. RBCs are red-colored, biconcave, and disc-shaped cells without nuclei and other cell organelles.
3. The reddish color of the RBCs is due to the presence of a respiratory, iron-pigment called hemoglobin.

White Blood Corpuscles:

1. The most active and motile constituents of the blood that provides immunity are known as the white blood corpuscles (WBCs) or leucocytes.
2. The WBCs have five types of cells namely - neutrophils, eosinophils, basophils, lymphocytes, and monocytes.
3. The granular leucocytes - neutrophils, eosinophils, and basophils have lobed nuclei and granules in the cytoplasm.
4. The agranular leucocytes - lymphocytes and monocytes do not have lobes and granules.

Platelets:

1. The platelets, also known as thrombocytes are the minute, oval, or round structures found in the blood.
2. They lack nuclei and can be found floating in the blood.

(i) Components 1 to 4:

1. The components labeled ‘1’ are red blood corpuscles (RBCs) as they are biconcave and disc-shaped.
2. The components labeled ‘2’ are white blood corpuscles WBCs) as they are in different shapes and have lobed nuclei and granular cytoplasm.
3. The components labeled ‘3’ are platelets as they are the minute structures of all.
4. The component labeled ‘4’ is the plasma as it is the liquid part without corpuscles.

(ii) Structural differences between 1 and 2:

1. RBCs (part 1) are the most abundant and help in gaseous exchange.
2. WBCs (part 2) play a vital role in immunity.
3. Their structural differences are shown below:

Red Blood Corpuscles	White Blood Corpuscles
RBCs are biconcave and disc-shaped.	WBCs are amoeboid in shape.
Absence of nucleus.	Presence of nucleus.

(iii) Soluble protein - Blood clotting:

1. The soluble protein found in the plasma is called fibrinogen.
2. Fibrinogen is converted into fibrin with the help of the enzyme thromboplastin released by platelets and Calcium ions.
3. Fibrin is the insoluble thread formed during blood coagulation.

(iv) Average lifespan of RBCs:

1. The RBCs or erythrocytes can live up to an average of 120 days or 4 months.

(v) Mature RBCs:

1. When RBCs mature, they become enucleated.
2. This helps them to carry more hemoglobin for oxygen transport.
3. Also, the erythrocytes lack other cell organelles such as the endoplasmic reticulum and mitochondria.
4. This increases the flexibility of RBCs and prevents cellular respiration in RBCs (using the oxygen by themselves).