RBCs and WBCs: Variation in count, Platelets, Practice Problems and FAQs

Why is our blood red in colour? How is our body saved from the storm of pathogen attacks every day? How does the blood flow stop after a few seconds when we get injured and our lives are saved?

The answer to all these questions is hidden in a special fluid that our body possesses. 

Yes you are right!

It is blood.

Blood is like an ocean in which many ships and boats are floating. The fluid part of the ocean is blood plasma and the floating parts are blood cells or formed elements. 

The red colour of blood is due to the haemoglobin pigment which is present inside the RBCs. Pigment is nothing but a coloured protein with metal ions. Blood has three types of cells named RBCs, WBCs and platelets. 

RBCs are cells which help in gaseous transport (O2 and CO2) throughout the body. WBCs are the warriors to fight infections by pathogens. Platelets are fragments of cells which make blood clots over the injured parts thus stop the bleeding immediately. Let’s take a deep dive into the formed elements of blood. 

Table of Content

• Introduction to Formed Elements
• RBCs and its Fate
• WBCs
• Types of WBCs
• Platelets
• Practice Problems of RBCs and WBCs
• FAQs of RBCs and WBCs

Formed Elements

The formed elements of blood include blood cells or blood corpuscles which constitute about 45% of total blood. These are of three types as follows: 

• Erythrocytes or red blood cells (RBC)
• Leukocytes or white blood cells (WBC)
• Thrombocytes or blood platelets 

Erythrocytes or Red Blood Cells (RBC) and its Fate

Erythrocytes or red blood cells (RBC) are the most abundant type of blood cells. In adults, RBCs are formed in the red bone marrow. A unique feature of these cells is the presence of red coloured iron containing pigment known as haemoglobin in their cytoplasm. It is mainly involved in carbon dioxide and oxygen transport. Haemoglobin contains four Fe (iron) ions per molecule which can carry four O2 molecules. 

In every 100 ml of blood, a healthy individual has 12 - 16 gms of haemoglobin. 5 millions to 5.5 millions of RBCs are present per mm–3 of blood. RBC is of biconcave shape and devoid of nucleus and other cell organelles in most mammals.

Fate of RBC

RBCs have a short lifespan of about 120 days after which they get destroyed in a body organ named spleen. Thus the spleen is considered the graveyard of RBCs.

Functions of RBCs

RBCs perform the following functions:

• RBCs help in the transport of gases with the help of haemoglobin.
• Haemoglobin plays a role in maintaining the pH of blood.

Leukocytes or White Blood Cells (WBCs)

The leukocytes are nucleated cells having all cell organelles. These cells lack any pigment like haemoglobin thus they are colourless, hence called white blood cells. They are relatively lesser in number which averages 6000 - 8000 mm–3 of blood. These cells are short lived and have a lifespan of about 3 - 4 days. Leukocytes are generally involved in immune functions, keeping the body protected from foriegn pathogens.

Types of White Blood Cells

WBCs are of mainly two types as follows:

• Granulocytes 
• Agranulocytes 

Granulocytes

These leukocytes contain granules in their cytoplasm and have a lobed nucleus. They can be further divided into neutrophils, eosinophils, and basophils

Eosinophils

Eosinophils stands for ‘eosine loving’ or ‘acid loving’. This is because granules in eosinophils take up acidic stains like eosin stains. Hence, they appear red in colour when observed under a microscope. They have a bilobed nucleus. They contribute 2 - 3% of white blood cell count. They are associated with allergic responses. They attach to parasites and release enzymes that kill them. They help in dissolving blood clots also. 

Basophils

Basophil stands for ‘base loving’. This is because these cells take up basic blue stains. Hence they appear blue in colour when observed under a microscope. They have two - three lobed nucleus. Basophils are involved mainly in inflammatory reactions. They secrete histamine, heparin, serotonin etc. They contribute 0.5 - 1 % of white blood cell count.

Neutrophils

Neutrophils are the most abundant WBCs. 60 - 65% of total WBCs are neutrophils. They have a multilobed nucleus. Neutrophils act as phagocytic cells. They attack and destroy foreign organisms entering the body.

Agranulocytes

These leukocytes lack granules in the cytoplasm. They have a large, non lobed, round or oval nucleus. They are of two types as follows:

• Monocytes
• Lymphocytes

Monocytes

They are the largest blood cells. The notable feature of monocytes is that the shape of its nucleus resembles a horseshoe. They form 6 - 8% of the total WBCs. Monocytes play a role in the first line of defence of the body. They become large as they reach the tissues and are named as macrophages.

Lymphocytes

Lymphocytes make up about 20 - 45% of total WBCs. They have a very large, rounded nucleus when compared to other WBCs. Lymphocytes can be of two types: B lymphocytes and T lymphocytes. Both T and B lymphocytes are involved in the immune responses in the body.

Thrombocytes or BloodPlatelets

Platelets are round, disc-like bodies which are the smallest formed elements of the blood. They are colourless just like leukocytes. Blood normally contains 1,500,00 - 3,500,00 platelets mm–3. Platelets release a number of substances which are involved in blood clotting. Reduction in the platelets can lead to clotting disorders. It can further lead to excessive loss of blood from the body.

Practice Problems of RBCs and WBCs

Q.1 Largest WBCs in peripheral blood is ____________.

(a) Neutrophil

(b) Lymphocyte

(c) Monocyte

(d) Eosinophil

Solution: Monocytes are the largest blood cells. The notable feature of monocytes is that the shape of its nucleus resembles a horseshoe. Monocytes play a role in the first line of defence of the body. They become large as they reach the tissues and are named as macrophages.

Q2. Each haemoglobin molecule carries ___________ number of O2 molecules. 

(a) 2 

(b) 4 

(c) 1 

(d) 8

Solution: Red blood cells contain red coloured iron containing pigment known as haemoglobin in their cytoplasm that is involved in oxygen and carbon dioxide transport. Haemoglobin contains four Fe (iron) ions per molecule which can carry four O2 molecules.

Q3. DNA is not present in ______________. 

(a) an ovum

(b) hair root cell

(c) a mature spermatozoa

(d) mature RBCs

Solution: While the RBCs get matured they lose most of their cell organelles to provide space for haemoglobin to accumulate inside it. Since these cells also stop mitotic division, they do not contain any DNA.

Q4. The most active phagocytic WBCs are ______________.

(a) lymphocytes and macrophages

(b) neutrophils and eosinophils

(c) neutrophils and monocytes

(d) eosinophils and lymphocytes

Solution : Neutrophils and monocytes are the most active phagocytic cells of white blood cells which destroy foreign organisms entering the body.

 FAQs of RBCs and WBCs

Question 1. What are the differences between RBCs and WBCs?

Answer. The major differences between WBCs and RBCs are as follows: 

• Red blood cells lack a nucleus on maturity. WBCs are characterised by the presence of a large central nucleus. 
• RBCs contain haemoglobin because of this they appear red in colour. WBCs are colourless, as they do not have any pigment.
• RBCs help in gaseous transport around the body whereas WBCs helps in immunity and fighting pathogens

Question 2. Write down the main functions of WBCs, RBCs and platelets?

Answer. The functions of blood cells are as follows:

• Red blood cells or erythrocytes mainly help in the transportation of gases.
• White blood cells or leukocytes are responsible for keeping us free of disease and healthy by providing immunity and fighting infections.
•  Platelets or thrombocytes are responsible for clotting our blood to stop the blood flow, whenever we have a cut or open wound.

Question 3. What will be the effect on our body if there is no platelet?

Answer. The function of platelets, also known as thrombocytes, is clotting the blood. If there are no platelets in the blood, a clot will not be formed. This can lead to continuous bleeding which can result in severe blood loss and death of the individual.

Question 4. What happens to the dead RBCs?

Answer. Worn out or old RBCs are removed from the circulation after about 120 days by the help of macrophages in the spleen and liver. The haemoglobin is broken down into heme and globin. The globin protein is broken down to smaller units called amino acids, which may be recycled or metabolised.

Other Related Topics

Other Related Topic Of Biology

• Disorders of circulatory system
• Blood and plasma