Difference between Red Blood Cells and White Blood Cells

Blood is an important component of the human body. There are two important types of blood cells present in the blood: Red Blood Cells (RBC) and White Blood Cells (WBC).

Understanding the difference between RBC and WBC helps us learn more about how blood transports oxygen and how humans defend against various pathogens. In this article we will learn more about what RBC is, what is WBC and the difference between RBC and WBC.

What is Red Blood Cells

Red blood cells (RBCs) also called erythrocytes, are the most abundant cells in the blood. It occupies 40-45% of the total volume of blood.

RBCs responsible for oxygen transport throughout the body. Red blood cells are round with a flattish, indented center. Red blood cells contain a protein called hemoglobin, which are responsible for carrying oxygen.

Hemoglobin is mainly composed of iron, which combines with the oxygen, which gives it reddish color to the blood.

Red blood cells develop in your bone marrow and release in the blood stream after they become fully mature which is around 7 days. Typical lifetime for the RBCs is about 120 days.

What is White Blood Cells

White blood cells are also known as leukocytes which are responsible for protecting your body from infection.

White blood cells are made in the bone marrow. They are commonly stored in your blood and lymph tissues.

There are many types of white blood cells. Each type of cell has a different role in your immune system. The main types of WBCs are neutrophils, monocytes, eosinophils, basophils, and lymphocytes.

WBCs make up about 1% of the total blood volume. A person with normal white blood cell count has between 4500 to 11000 white blood cells per microliter of blood.

Difference between Red Blood Cells and White Blood Cells

RBC	WBC
Definition
Hemoglobin-containing blood cells that transport oxygen.	Blood cells that defend the body against infection and foreign substances
Scientific name
Erythrocytes	Leukocytes
Colour
Red (haemoglobin)	Colourless
Shape
Biconcave disc	Irregular / round
Nucleus
Absent at maturity	Present (large and central in lymphocytes)
Diameter
6-8 µm	12-17 µm typical
Thickness
~2 µm (at the rim)	~5-15 µm
Surface area
~135 µm²	Varies by type
Surface antigens
ABO and Rh blood group antigens	HLA / MHC antigens
Count per mm³
4.5-5.9 million (men); 4.1-5.1 million (women)	4,000-11,000; average ~7,000-8,000
Count per liter
4.5-5.9 × 10¹²	4.0-11.0 × 10⁹
Ratio in blood
~600-700	1
Total cells
~25 trillion	~50 billion
Share of blood
~36-50%	~1% (<1%)
Main function
Transport of O₂ and CO₂	Immunity; produce antibodies and fight microbes
Movement
Passive (carried by blood flow)	Active (amoeboid; can leave capillaries)
Circulates in
Cardiovascular system	Cardiovascular and lymphatic systems
Site of production
Red bone marrow	Red bone marrow, lymph nodes, spleen
Formation process
Erythropoiesis	Leukopoiesis
Production rate
~2 million per second	~100 billion per day
Lifespan
~120 days	~12-20 days average (hours for neutrophils)
Site of destruction
Spleen and liver	Spleen, liver, lymph nodes, tissues
Low count condition
Anaemia (<4 million/µL)	Leukopenia (<4,000/µL)
High count condition
Polycythemia (>6 million/µL)	Leukocytosis (>11,000/µL)