Facts about Human Blood

Human blood is an especially important fluid without which no human can survive. It carries oxygen as well as nutrients to the whole body.

Fact #1

Blood is made in the bone marrow.

Fact #2

Red blood cells, Platelets, White blood cells, and Plasma are the four main components of human blood.

components of blood

Fact #3 Plasma 

It is the liquid part of the blood which is made of water, salts, and proteins. It also consists of hormones, glucose, proteins, gases, electrolytes, and nutrients. It is yellow in color. Over half of our blood is plasma and 90% of blood plasma is water.

  Fact #4

The solid part of our blood contains red blood cells (erythrocytes), white blood cells(leukocytes), and platelets. They all flow in plasma.

Fact #5 Platelets form a clot in times of bleeding.

They prevent unwanted loss of blood at times of bleeding occurring due to a cut or bruise. While blood clotting is meant for good, it can become dangerous. If blood clots in blood vessels of heart, one can experience a heart attack. Similarly, blood clots in the brain can lead to stroke.

Fact #6 White blood cells protect against infections.

WBC’s form the defensive system of our body. They are responsible for fighting viruses, bacteria and other infectious diseases. They also fight cancer cells and other unwanted material that enter the human body. Blood consists of a special type of white blood cell known as a granulocyte. These cells roll along blood vessel walls and hunt for bacteria. If they find any harmful bacteria, granulocytes will destroy these bacteria by engulfing them.

Fact #7 Facts about Red Blood Cells

Red Blood Cells are the cells that are responsible for the red color of our blood. RBC’s carry oxygen to tissues and removes CO2 out of the body. Red blood cells survive in the circulatory system for no more than 120 days. They do not multiply through cell division because they do not have nuclei, which is a must for the cell to multiply. In every second around 2 million red blood cells are produced in the bone marrow to replace the same amount of dead cells.

Fact #8 Hemoglobin

Oxygen is inhaled by the tissues of the lungs and passed to the red blood cells (RBC). Each of the red blood cells contains a molecule called hemoglobin. Hemoglobin is an iron-rich protein that binds with oxygen and gives a red color to our blood.

Hemoglobin is made up of four protein chains that each bind an additional ring-shaped chemical structure called heme.

Our red blood cells are red because of the heme groups in hemoglobin.

Fact #9 Why human blood is Red?

The answer is Haemoglobin. The true color of human blood is bright red. It appears red because of an iron-rich pigment known as hemoglobin which helps in the transport of Oxygen. 

Fact #10

Nearly 7% of the bodyweight of a human is made up of blood. 

Fact #11 Blood Donation facts

  • Every year, around 1.3 million pints or units of donated blood is wasted because the shelf life of blood is 42 days.
  • There is a type of fatal blood disease whose only cure is to donate blood. The disease is known as hemochromatosis, which is actually a genetic deviation where too much iron gets absorbed in the gut causing a toxic iron buildup in organs.
  • Donated red blood cells cannot be stored for more than 42 days. Donated platelets cannot be stored for more than 5 days. Donated blood plasma can be stored for 1 year in frozen condition. Platelets, red blood cells and blood plasma can be separately donated instead of donating blood as a whole. This type of donation is known as Apheresis.

Fact #12 

The only place where blood cannot be found in the human body is the cornea (eye) because the cornea is capable of directly extracting oxygen from the air.

Fact # 13

The average volume of blood present in an adult male body is 5.6 liters while an adult female body contains 4.5 liters of blood on an average.

Fact # 14

Though we are familiar with common blood types A, B, AB and O, which is a part of simplified ABO system, there are actually around 30 different recognized blood groups or blood types.

Fact #15

The filtration of the blood is done by our kidneys. This organ filters more than 400 gallons of blood in one day.


In the year 1936 the world’s first blood bank was opened in Chicago. Matured human blood cells have varying life cycles. Red blood cells circulate in the body for about 4 months, platelets for about 9 days, and white blood cells range from a few hours to several days.

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