Basic Facts About Blood That You Should Know: Brief Yet Meaningful

You must have heard of various blood disorders, blood transfusion and many other conditions related to blood. But do you know what exactly blood is made up of? Are you aware of the various types of blood groups? Here are some basic facts about blood that you should know.

Be it managing medical conditions or blood disorders, whether it is about blood grouping, blood donation or other activities, having basic knowledge about blood can help to a great extent.


Basic Facts About Blood That You Should Know

Basic Facts about Blood That You Should Know: Brief Yet Meaningful

The average volume of blood is 4.7 liters to 5 liters in an adult human body. Normally, Blood represents 7% of the total body mass in a normal healthy person. However this may not be applicable for people living at higher altitudes, as they may have more volume of blood to supply more oxygen to the cells.

Functions of Blood


Here are the main functions of blood, which are the important basic facts you should know.

  • Blood is the fluid medium of transport.
  • Blood, most importantly transports oxygen to human cells. It also supplies nutrients to the cells. Blood supplies hormones and other substances produced in the body like enzymes to the cells of the organs and to other tissue cells also.
  • Blood collects carbon dioxide from the cells and transports it to the lungs and maintains the process of breathing. It also collects some toxic element and chemicals like various sulphides and methane as a metabolic waste from the system to dispose it off through urine, stool and sweat.
  • Blood also transfers heats to the skin to maintain a stable equilibrium and also helps to maintain normal temperature.

Circulation of Blood

Another important fact about blood you should know includes circulation of blood.

  • The right ventricle of the heart pumps blood to the lungs through the capillaries for oxygenation or purification. This blood contains the carbon dioxide (Co2) produced by the cells of the body.
  • Presence of excess carbon dioxide (Co2) turns the blood pH to more acidic.
  • The lungs purify the blood, which reaches the left ventricle of the heart.
  • The left ventricle pumps out the oxygenated or purified blood coming from the lungs though the main artery called aorta to other smaller arteries.
  • The arteries carries blood to organs and tissues
  • The veins returns blood to hearth capillaries.

Composition and Basic Function of Blood

Let us understand the composition of blood:

Red Blood Cell (Erythrocyte)

  • Originates from the same hemocytoblast stem cell.
  • Also known as RBC. Its normal value is 5 to 6 million/mm3. Life span of RBC is 120days.
  • The main component of the RBC is hemoglobin protein. RBCs carry oxygen & carbon dioxide.

White Blood Cell (Leukocytes)

  • Originates from the same hemocytoblast stem cell as the red cells and platelets.
  • Known as WBC. It comprises of basophil, eosinophil, neutrophil, monocyte, B- and T-cell lymphocyte.
  • All of these granular leukocytes have different functions and life span.
  • Mostly WBCs are responsible to fight infections caused by bacteria, virus, and pathogens. It also develops immunity to protect you from infections.


  • It is made up of 90% water. Consists of soluble protein, which mainly originates from liver i.e. albumin (produced from liver), fibrinogens, globulins.
  • Plasma proteins are responsible for maintaining the osmosis balance of blood and tissue fluids, assist the transportation of different vitamins, minerals, glucose, fat, other nutrients and drugs etc. it assists immune system and develop the defense mechanisms.
  • It acts as an adhesive for binding other blood corpuscles like platelets etc. Fibrinogen the protein also assist as a clotting substance to repair the tissue damages etc. Plasma also carries the respiratory gases mainly carbon dioxide.
  • It also carries the waste of metabolic exchanges like ammonia, urea etc.


  • Known as thrombocytes. Platelets are membrane-bound cell fragments.
  • A little less of 1% of whole blood consist of platelets. Originates from stem cells in the bone marrow.
  • Production rate is 200 billion per day with a circulating life of 8-10 days.
  • Platelets help to form clots around broken blood vessels and prevent excessive bleeding.

Blood Groups


Although blood looks same but there are different groups and types. There are four major blood groups determined by the presence or absence of two antigens i.e. A and B on the surface of red blood cells. In the same four major blood group determined by Rh factor, there are eight different common blood types. The Rh factor is a type of protein on the surface of red blood cells. Most people who have the Rh factor are Rh-positive. Those who do not have the Rh factor are Rh-negative.

This ABO blood group system used to be expressed as A Positive (+) or A Negative (-). The (+) / (-) shows the presence or absence of the Rh factor respectively. So, the ABO system with Rh factor as described below:

  • Blood Group A+ or A -: has only the A antigen on red cells (and B antibody in the plasma)
  • Blood Group B+ or B-: has only the B antigen on red cells (and A antibody in the plasma)
  • Blood Group AB+ or AB– : has both A and B antigens on red cells (but neither A nor B antibody in the plasma)
  • Blood Group O+ or O– :has neither A nor B antigens on red cells (but both A and B antibody are in the plasma)

Role of the Rh factor and Blood Group in Blood/Plasma Transfusion

Cross matching of blood before transfusion is much important to prevent incompatible transfusion between the donor and the recipient. Incompatible transfusion would cause immunological reactions, hemolysis, renal failure, shock, and can sometimes be fatal. Another important basic fact about blood is that blood transfusion can be done only within blood groups which are compatible with each other and hence proper testing needs to be done.


Common Blood Disorders

Disorders of the blood are many and are commonly found in many people. Some of the common blood disorders include anemia (reduced hemoglobin in blood), thrombocytopenia (reduced platelet count), thrombocytosis (increased platelet count) and bleeding disorders like hemophilia. Blood cancers like leukemia, lymphoma, and myeloma too are some of the serious blood disorders.