Types of Blood Cells and Their Functions

What Is Blood?

Blood is one of the most important fluids in the human body, made up of plasma and cellular components that include the different types of blood cells. Due to the highly specialised nature of various blood cells to do certain functions to ensure health and immunity throughout the life of an individual, it becomes very important to understand blood cell type.

Composition Of Blood

Blood consists of 55% plasma and 45% blood cells by volume.

Plasma

Plasma is a yellowish fluid mainly consisting of water (90%), proteins/enzymes (albumin, globulins, fibrinogen), different electrolytes (sodium, potassium, calcium), hormones, and waste products.

Blood Cells (Formed Elements)

Cellular elements are required for various physiological activities. This includes red blood cells (RBCs), white blood cells (WBCs) and platelets.

Red Blood Cells (RBCs)

Red Blood Cells (RBCs) carry oxygen from the lungs to tissues and carbon dioxide from tissues to be exhaled out from the lungs.

Structure and Morphology

• Biconcave discs are enucleated, making them flexible and increasing their surface area for efficient gas exchange.

• Contains haemoglobin molecules that reversibly bind oxygen.

Functions

• To transport oxygen bound to haemoglobin from the lungs to tissues.

• Helps to carry carbon dioxide from tissues to the lungs for excretion.

Lifespan And Production

• About 120 days in their lifetime.

• Produced constantly within the bone marrow through the process of erythropoiesis, a process under the control of the hormone erythropoietin.

Disorders Related To RBCs

• Anaemia is low count of RBCs and haemoglobin. Hence, low oxygen-carrying capacity.

• Polycythemia refers to abnormally high counts of RBCs, which may result in blood clots.

White Blood Cells (WBCs)

The White Blood Cells (WBCs) give protection to the body against a variety of disease-causing organisms and foreign products through immune responses.

Classification of WBCs

White blood cells are classified are:

Granulocytes

• Neutrophils are the most abundant, phagocytic cells that engulf and destroy bacteria and fungi.

• Eosinophils fight against multicellular parasites and contribute to allergic responses by releasing histamines.

• Basophils release histamine and other chemicals during inflammation and allergic reactions.

Agranulocytes

• Lymphocytes have a primary role in adaptive immunity.

• B cells take part in the production of antibodies.

• T cells help in the production of cells which directly attack the infected or abnormal cells.

• Natural Killer NK cells recognise and thus kill infected or cancerous cells.

• Monocytes go on to become macrophages in tissues, ingestion of foreign invaders and debris.

Disorders Related To WBCs

• Leukaemia is cancer of WBCs, an uncontrolled proliferation of blood cells which are abnormal.

• Lymphoma is cancer arising due to lymphocytes, affects the lymph nodes and other lymphatic tissues.

Platelets (Thrombocytes)

Platelets play a very crucial role in blood clotting, preventing excessive bleeding

Structure

• Small, disk-shaped portions of cells

• No nucleus

Functions

• Implicated in blood clotting or hemostasis

• Prevents the loss of blood

Lifespan And Production

• About 120 days in their lifetime.

• Produced constantly within the bone marrow through the process of erythropoiesis, a process under the control of the hormone erythropoietin.

Disorders Related To RBCs

• Anaemia is low count of RBCs and haemoglobin; hence, low oxygen-carrying capacity.

• Polycythemia refers to abnormally high counts of RBCs, which may result in blood clots.

Blood Cell Formation (Hematopoiesis)

Most of the blood cells forming occur in the bone marrow.

Stem Cells And Differentiation

• Hematopoietic stem cells give rise to diverse blood cell lineages through differentiation.

• This is tightly regulated via cytokines and growth factors.

Role of Bone Marrow

• Provides an inductive microenvironment for hematopoiesis.

• It contains particular stromal cells demonstrated to measure the maintenance, self-renewal, and differentiation fate of stem cells.

Clinical Significance And Diagnostic Tests

Common blood tests are:

• Complete Blood Count (CBC) is the quantitative and qualitative assay of the blood cells.

• Blood Smear is the examination of blood cells under a microscope to assess morphology and detect morphological abnormalities.

• The interpretation of CBC results will help diagnose anaemia, infections, leukaemia, and other blood disorders.

• Blood smear analysis allows for gaining more information about cell morphology and certain aberrations.

Types of Blood Cells NEET MCQs (With Answers & Explanations)

This is an important topic and carries significant weightage in NEET exam. Types of questions asked from this topic are:

• Types of blood cells (RBCs , WBCs, Platelets)

• Blood cell formation

Practice Questions for NEET

Q1. Which instrument is used to determine the red cell count?

1. Haemocytometer

2. Haemoglobinometer

3. Electrocardiogram

4. Sphygmomanometer

Correct answer: 1) Haemocytometer

Explanation:

Red cell count measures the number of red blood cells in a given volume of blood. It is typically carried out using a device called a hemocytometer. A hemocytometer is a specialized microscope slide with a grid pattern etched onto its surface. By diluting a small volume of blood and placing it on the hemocytometer, the red blood cells can be counted under a microscope, allowing for the determination of the red cell count.

Explanation for incorrect options :

Option (2)The Haemoglobinometer is incorrect because it is a device used to measure the concentration of haemoglobin in the blood, not the red cell count.

Option (3) Electrocardiogram (ECG) is a diagnostic tool used to record the electrical activity of the heart, and it is not directly involved in determining red cell count.

Option (4) Sphygmomanometer is a device used to measure blood pressure, and it is not used for red cell count assessment.

Hence, the correct answer is option 1) Haemocytometer.

Q2. There is no DNA in:

1. Mature RBCs

2. Mature spermatozoan

3. Hair Root

4. An enucleated ovum

Correct answer: 1) Mature RBCs

Explanation:

As we learnt in

RBCs are formed in the red bone marrow in adults. RBCs lack nuclei in most mammals and are biconcave in shape.

- wherein

They have a red-coloured, iron-containing complex protein called haemoglobin, hence the colour and name of these cells. A healthy individual has 12-16 gms of haemoglobin in every 100 ml of blood.

Mature RBCs are devoid of nucleus and DNA is absent.

Hence, the correct answer is option 1) mature RBCs.

Q3. Assertion: Eosinophils play a role in the destruction of parasitic forms.

Reason: Eosinophils can bind to parasitic forms and induce their destruction by releasing lysosomal enzymes from their surface.

1. The assertion is true, and the reason is false.

2. The assertion is false, and the reason is true.

3. Both the assertion and reason are true and are correctly related.

4. The assertion is true, but the reason does not provide a valid explanation.

Correct answer: 3) Both the assertion and reason are true and are correctly related.

Explanation:

The assertion states that eosinophils contribute to the destruction of parasitic forms, which is true. Eosinophils are a type of white blood cell that plays a role in the immune response against parasitic infections.

The reason is that eosinophils can attach themselves to parasitic forms and initiate their destruction by releasing lysosomal enzymes from their surface. This is also true. Eosinophils have specific surface receptors that allow them to bind to parasites. Upon attachment, they release toxic granules containing enzymes, such as major basic proteins, eosinophil peroxidase, and eosinophil-derived neurotoxin, which can damage and kill the parasites.

Hence, the correct answer is option 3) Both the assertion and reason are true and are correctly related.

Also Read-

• MCQs on Composition of Blood

• Cardiac Cycle

• Facts about Blood

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