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A Brief Review on The Study of Blood and Its Different Components

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A Brief Review on The Study of Blood and Its Different Components

What is Hematology?

  • Hematology is the study of the blood.  Blood is a fluid that is necessary for the maintenance of life. Without it we would all be dead.  We need blood to maintain good health. Blood carries nutrients and oxygen to the cells of the body and removes carbon dioxide and waste materials from the body.

Red Blood Cells and Platelets in an Artery

  • Blood travels through the body through  the following:
    • Arteries: delivers oxygenated blood to the organs
    • Veins
    • Capillaries

What are the components of blood?

The major components of blood are:


  • These are small fragments of cells.
  • They developed from megakaryocytes.
  • They help the blood to clot when there is an injury, by adhering to the lining of the injured blood vessel.


Plasma is the yellowish fluid in which the blood cells are suspended. Approximately 55% of the blood is composed of plasma. Plasma is said to be about 90% water, 8% protein and 2% other solutes. Plasma functions to carry the platelets, red blood cells and white blood cells. It brings nourishment to cells and removes waste materials. The plasma carries a lot of protein that is used to regulate bleeding and clotting.

Red Blood Cells

Red blood cells, also called erythrocytes, are large cells that have no nuclei, and are known by their red color. They are the most abundant component of the blood accounting for about 40-50% of the total blood volume. They are biconcave disk with the center flattened. You can say they look more like a donut.

RBC functions to transport oxygen from the lungs to the tissue of the body and get rid of carbon dioxide. RBCs are produced in the bone marrow. They contain hemoglobin which is an iron-rich protein. Hemoglobin functions to carry oxygen from the lungs to the tissues of the body and return carbon dioxide to the lungs.

The reason why the blood is red is because of the large number of red blood cells which get the color from hemoglobin. RBC lives for about 4 months, approximately 120days. Our body continues to produce RBC each day.

White Blood Cells

White blood cells (WBC) also called leukocytes are the body’s defense cells. They protect our body from infections. They are much less than RBC but are very important in protecting the body.

The Different Types of WBCs

There are various types of WBCs which have their own role in protecting the body. They are:

  • Neutrophils
  • Eosinophils
  • Lymphocytes
  • Monocytes
  • Basophils


  • Most abundant WBCs (40-70%).
  • They are the first to appear at an injured site.
  • They are the acute inflammatory response cells.
  • They ingest bacteria.
  • They have a nucleus that consists of 2- 5 lobes.
  • They have a life span of about 6-10hrs, thus the bone marrow produce them daily.


  • 1-6% of WBCs.
  • They have a bilobed nucleus.
  • They functions in allergic responses, and defense against parasitic worm infestation.



  • These cells make up <1% of leukocytes.
  • They have  pale bilobate nucleus hidden by densely basophilic granules.
  • They secrete histamine and heparin.
  • Histamine is a vasodilator; therefore it will increase blood flow through the dilation of blood vessels.
  • Heparin is an anticoagulant thus it helps with the movement of other WBCs and in so doing prevent the blood from clotting.


  • 2-10% of leukocytes.
  • They are large cells with kidney-shaped nucleus.
  • They develop into macrophages, which digests  bacteria and cell debris.

In the upcoming article we will discuss the blood production in a human body.

About The Author

Leslie Samuel

Leslie Samuel is the creator of Interactive Biology. His mission is to use this site to Make Biology fun for people all over the world.

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