Composition of Blood: Function and Types

Blood is a fluid connective tissue with alkaline fluid with a pH of 7.3 that keeps circulating through the entire body. Blood is never stationary and keeps moving from the heart to the rest of the body and vice-versa.

Coronary circulation is dependent on the blood which circulates throughout the body performing different functions. There are four main components of blood: plasma, red blood cells, white blood cells, and platelets. Each blood component has its function. Example: White blood cells function by removing foreign elements from the body. They are the body’s defense mechanism.

In this article, we will study about Components of blood, Types of blood cells, Functions of blood, Blood vessels and their types, Disorders of blood, and Blood groups.

What is Blood?

Blood is a specialized body fluid that consists of plasma, platelets, and red and white blood cells that circulate through the body. It supplies essential substances, like oxygen, and hormones, to cells and organs, and removes waste from the same. Blood is 7% of the human body weight, and has an average density of around 1060 kg/m³.

It has a thick texture and its color varies from bright red to dark red based on where it is drawn from. A normal human has around 5-6 l of blood in his/her body.

Components of Blood

If a sample of blood is studied under the centrifuge machine, it splits into the following components- RBCs, WBCs, Plasma, and Platelets. Blood contains the component haemoglobin which is responsible for its red color. The components of blood by percentage are as follows:

Blood	Percentage
Red Blood Cells (Erythrocytes)	45%
White Blood Cells (Leukocytes)	1%
Platelets (Thrombocytes)	0.1%
Plasma	55%

To know more please refer to the article ‘Plasma And Formed Elements‘.

Types of Blood Cells

The components of blood consist of plasma and formed elements. The formed elements include Red blood cells, White blood cells, and Platelets.

Red Blood Cells

• Red blood cells are also known as Erythrocytes.
• They have a biconcave type of shape.
• The shape is flat towards the center and round at the periphery.
• This shape results in a large surface area.
• It makes them great at absorbing oxygen.
• Red blood cells contain a respiratory pigment called Haemoglobin.
• Haemoglobin contains iron and globin protein.
• It combines easily with oxygen to form oxyhaemoglobin.
• Oxyhaemoglobin transports oxygen throughout the body.

White Blood Cells

• White platelets (Leukocytes) account for 1% of our blood, and they are vital.
• They are responsible for the immunity of the body against sickness and infection.
• Like red blood cells, they are also produced from the bone marrow.
• They act as the body’s defense system.
• They keep circulating in the blood.

Types of White Blood Cells

White blood cells, are responsible for the immune system. They defend the body against infections and foreign invaders. White blood cells can be broadly classified as:

• Granulocytes
• Agranulocytes

Agranulocytes

These are the white blood cells that lack granules in their cell’s cytoplasm. Agranulocytes are further divided into two types:

Monocytes

Monocytes are large, phagocytic cells. They get converted to macrophages or dendritic cells after reaching tissues. Macrophages engulf and digest pathogens and cellular debris. The dendritic cells are responsible for triggering an immune response.

Lymphocytes

Lymphocytes are a diverse group of white blood cells. They are responsible for adaptive immunity. There are two types of lymphocytes:

• B Cells: B cells produce antibodies, that target specific pathogens. When activated, B cells can differentiate into plasma cells, to release antibodies into the bloodstream to fight against invaders.
• T Cells: T cells help B cells produce antibodies, that directly attack infected cells, and regulate the immune response. There are different types of T cells, such as Helper T cells, Cytotoxic T cells, and Regulatory T cells.

Granulocytes

These white blood cells contain granules in the cell cytoplasm. Granulocytes are further divided into three types:

Neutrophils

Neutrophils are identified by the presence of a multilobed nucleus. They migrate to sites of infection, where they perform phagocytosis. These are the most abundant kind of granulocytes and help the body in fighting againt bacterial and fungal infections.

Basophils

They get activated by allergic reactions and inflammation. They release Histamine and other chemicals that contribute to the body’s response to allergens. They are very less in number in the blood.

Eosinophils

Eosinophils have a bilobed nucleus and get stained by acidic dye. These help in fighting against parasitic infections as they release chemical toxins which damage the outer membrane of parasites.

Functions of Blood

Following is a list of functions of the blood:

• It transports gases providing oxygen to cells and tissues giving fundamental supplements to cells, like amino acids, unsaturated fats, and glucose.
• Blood helps in eliminating waste materials, like carbon dioxide, and urea.
• Blood carries hormones from their point of synthesis (such as endocrine glands) to their designated organs or tissues, facilitating the regulation of a variety of processes within the body.
• By transferring heat, blood aids in the regulation of body temperature. It transfers extra heat from working muscles to colder body parts.
• The platelets in blood empower the thickening, or coagulation, of blood.
• Homeostasis is also maintained for the proper functioning of the cells.

Blood Vessels and their Types

A blood vessels is a fine tube like structure that helps in the circulation of blood across the body. There are three different types of blood vessels in the body namely Artery, Vein and Capillaries. Below is some information on each of them:

1. Artery: This blood vessel is highly muscular and has thick walls. Its main function is to carry oxygenated blood from the heart to the rest of the body. Aorta is the biggest artery.
2. Vein: This blood vessel is thinner as compared to an artery. Its primary function is to carry deoxygenated blood from the body towards the heart. Superior and Inferior Vena Cava is the largest vein that enters the right atrium of the heart.
3. Capillary: This is the tiniest blood vessel with a very small diameter and it helps in connecting arteries with veins. The capillaries have very thin walls which helps in the exchanges of nutrients and gases between the vessels and the blood.

Disorders of Blood

Blood is responsible or performing major functions in the body. Any disorder in composition of blood or its function can result in severe harm to the body. Some of the blood disorders are:

Disorder	Causes	Symptoms	Treatments
Anemia	Lack of red blood cells or hemoglobin, often due to iron deficiency, vitamin B12 deficiency, or chronic diseases.	Fatigue, weakness, pale or yellowish skin, irregular heartbeats, shortness of breath, dizziness or lightheadedness.	Iron supplements, vitamin B12 injections, dietary changes, and treatment of underlying conditions.
Hemophilia	Genetic mutation leading to a deficiency in one of the blood clotting factors.	Excessive bleeding from cuts or injuries, many large or deep bruises, unusual bleeding after vaccinations, pain, swelling, or tightness in joints.	Regular injections of the clotting factor, physical therapy, and in severe cases, prophylactic treatment.
Leukemia	Cancer of the body’s blood-forming tissues, including the bone marrow and the lymphatic system.	Fever or chills, persistent fatigue, weakness, frequent or severe infections, losing weight without trying, swollen lymph nodes, enlarged liver or spleen.	Chemotherapy, radiation therapy, stem cell transplant, and targeted therapy.
Lymphoma	A type of cancer that affects the lymphatic system.	Swollen lymph nodes, fatigue, fever, night sweats, weight loss, itchy skin.	Chemotherapy, radiation therapy, stem cell transplant, immunotherapy.
Thalassemia	Genetic disorder causing the body to make an abnormal form of hemoglobin, resulting in excessive destruction of red blood cells.	Fatigue, weakness, pale or yellowish skin, facial bone deformities, slow growth, abdominal swelling.	Blood transfusions, chelation therapy to remove excess iron from the body, folic acid supplements, bone marrow transplant.
Sickle Cell Disease	Genetic disorder that leads to the production of abnormal hemoglobin. Red blood cells become rigid and shaped like sickles or crescent moons.	Episodes of pain, swelling of hands and feet, frequent infections, delayed growth or puberty, vision problems.	Pain management, hydroxyurea, blood transfusions, and in some cases, a stem cell transplant.
Polycythemia Vera	A type of blood cancer that causes the bone marrow to make too many red blood cells.	Headaches, dizziness, itchiness, especially after a warm bath or shower, redness of the skin, shortness of breath, bleeding or bruising easily.	Phlebotomy to remove excess blood, low-dose aspirin, hydroxyurea, and interferon alfa.
Deep Vein Thrombosis (DVT)	A blood clot in a deep vein, usually in the legs.	Swelling, pain, red or discolored skin on the leg, a feeling of warmth in the affected leg.	Blood thinners, clot busters for severe cases, filters inserted into a large vein, compression stockings.

Blood Groups

People can have one of four primary blood groups. Every one of these groups can be Rh-positive or Rh- negative, shaping eight fundamental classifications. Individuals with group O blood can give to essentially any blood classification and individuals with AB⁺ blood group can normally receive blood from any group. To know more, please refer to the article ‘Body fluids and Circulation‘.

Conclusion: Blood – Components, Functions, Groups and Disorders

Blood is a connective tissue. It is a specialised fluid that circulates throughout the body. The components of blood are: plasma, red blood cells, white blood cells, and platelets. The main function of blood is transporting oxygen, nutrients, carbon dioxide and other waste materials to different body parts.

FAQs on Blood Components, Functions, Groups and Disorders

What are the solid components of blood?

The solid components of the blood consist of the formed elements- red blood cells, white blood cells and platelets. The liquid part is the plasma.

What are the functions of blood components?

Some of the functions of blood components are as follows-

• Helps in the removal of wastes like carbon dioxide
• Circulates oxygen throughout the body
• Helps in clotting of blood

What blood disorder causes bleeding?

Hemophilia is a blood disorder in which the blood lacks certain clotting factors. As a result, if the person gets injured, there is high risk of extreme blood loss.

State the different types of white blood cells found in the blood.

The different types of white blood cells found in the body are granulocytes and agranulocytes. Agranulocytes are further divided into monocytes and lymphocytes. Granulocytes are classified into Eosinophils, Neutrophils and Basophils.

Which blood group is most common?

The Blood group ‘O’ is seen most commonly in humans. The other blood groups are A, B and AB.

What are the 3 types of blood cells?

The 3 types of blood cells are: Red Blood Cells (erythrocytes), White Blood Cells (leukocytes) and Platelets (which help in clotting).