Components of Blood and their Functions

What Is Blood?

Blood is an essential fluid in the human body that carries out some essential functions for survival. It comprises different elements that work together and help transfer oxygen and nutrition, remove wastes, and provide immunity to diseases. The knowledge about blood components is, therefore, very important in understanding its role in health and disease.

Major Components of Blood

The major four parts include plasma, RBCs, WBCs, and platelets. All these components have certain specified purposes and features to make one complete circulatory system.

Plasma — Composition and Functions

Plasma is considered to be the liquid fraction combined with the cellular fractions in blood and is composed of about 55%. It provides a medium for carrying many substances.

Composition Of Plasma

• Water is 90-92%

• Proteins include albumins, globulins, fibrinogen

• Nutrients like glucose, amino acids, lipids

• Electrolytes like sodium, potassium, calcium, and magnesium

• Waste products such as urea, creatinine

• Hormones and enzymes

Functions Of Plasma

• Transport medium for nutrients and waste

• Holds the blood pressure and volume

• Critical proteins for blood clotting and immune response

Red Blood Cells (RBCs)

Red blood cells form the majority of blood cells. They are oval, and their main role is to assist in oxygen and carbon dioxide transport.

Structure of RBCs

• Biconcave disc shape

• Mature RBCs have no or almost nonexistent presence of a nucleus.

• Contains respiratory pigment in the form of haemoglobin.

Functions Of RBCs

• Carry oxygen from lungs to tissues

• Carry carbon dioxide from tissues to lungs

RBC Lifespan And Production

• Erythropoiesis occurs in the bone marrow.

• Life expectancy of about 120 days.

• Decomposition and recycling in the spleen and liver.

White Blood Cells (WBCs)

White blood cells are an integral part of your immunity system. They comprise the defence of our body against different infections and alien invaders.

Types Of WBCs

WBCs are divided into:

Neutrophils

• First responders to bacterial infection and inflammation.

• The pathogen is ingested and digested in a process called phagocytosis.

Lymphocytes

• T cells directly attack infected or cancerous cells of the body.

• B cells produce antibodies that target specific pathogens.

Monocytes

• They differentiate into macrophages and dendritic cells in tissues.

• Their main role includes the phagocytosis and presentation of antigens to T cells.

Eosinophils

• The cells fight infections caused by parasites and allergic reactions.

• It releases enzymes that will destroy parasites.

• However, these enzymes are controlled during an inflammatory response.

Basophils

• Releases histamine during allergic reactions and asthma.

• It is involved in inflammatory responses and parasitic infections.

Functions Of WBCs

• Immune response and defence against pathogens.

• Phagocytosis and antibody production.

• Allergic reactions and inflammatory responses.

WBC Count And Clinical Significance

• Normal Ranges: Adults: 4,000 to 11,000 cells per microliter of blood

• Children: Varies with age, generally higher than for adults.

High WBC Count (Leukocytosis)

• Can indicate infections, inflammation, stress, leukaemia, tissue damage, or certain medications.

• Symptoms may include fever, fatigue, weight loss, or easy bruising.

Low WBC Count (Leukopenia)

• Can indicate bone marrow disorders, autoimmune diseases, severe infections, certain medications, or malnutrition.

• Symptoms may include increased susceptibility to infections, fever, chills, or sweating.

Platelets

Small, disc-shaped cell fragments and platelets play a very significant role in blood clotting and wound healing.

Structure Of Platelets

• Small, disc-shaped cell fragments

• Origin from megakaryocytes in the bone marrow

Function Of Platelets

• Blood coagulation or hemostasis

• Maintenance of vascular integrity and wound healing.

Platelet Count And Disorders

• Normal ranges

• Conditions like thrombocytopenia, thrombocytosis, etc.

Blood 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 and their functions

• Functions of blood

• Process of blood formation in bone marrow

Practice Questions for NEET

Q1. Globulins contained in human blood plasma are primarily involved in:

1. osmotic balance of body fluids

2. oxygen transport in the blood

3. clotting of blood

4. defence mechanisms of body

Correct answer: 4) defence mechanisms of body

Explanation:

The blood plasma consists of 8-10% of water soluble proteins. Fibrinogen is involved in clotting of blood; globulins are involved in defence mechanisms and immunity whereas albumins maintain osmotic balance.

Hence, the correct answer is option 4) defence mechanisms of body .

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:

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. Which of the following changes (a-d) usually tend to occur in the plain dwellers when they move to high altitudes (3,500 m or more)?

1. Increase in red blood cell size

2. Increase in red blood cell production

3. Increased breathing rate

4. Increase in thrombocyte count

Correct answer: 2) Increase in red blood cell production

Explanation:

When plain dwellers move to high altitudes (3,500 m or more), they typically experience an increase in red blood cell production to cope with lower oxygen levels. Additionally, their breathing rate increases to compensate for the reduced oxygen availability. However, there is no evidence to suggest that red blood cell size or thrombocyte count changes significantly in response to high altitudes.

Hence the correct answer is Option 2) Increase in red blood cell production

Also Read:

• MCQs on Composition of Blood

• Body Fluids and Circulation

• Facts about Blood

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