Where are red blood cell in human body?

Red blood cells (erythrocytes) circulate throughout the human body within the blood vessels. They are the most abundant type of blood cell, accounting for approximately 45% of the total blood volume. Red blood cells are produced in the bone marrow, which is a soft, gelatinous tissue found inside the bones. The bone marrow continuously produces new red blood cells to replace the ones that are worn out.

Within the blood vessels, red blood cells carry oxygen from the lungs to all the tissues and organs in the body. They also transport carbon dioxide, a waste product of metabolism, back to the lungs for exhalation. Red blood cells are packed with a protein called hemoglobin, which binds to oxygen and carbon dioxide, enabling their transportation throughout the body.

The lifespan of a red blood cell is approximately 120 days. After this time, old red blood cells are removed from the bloodstream by the spleen and liver and broken down into their components, which can then be recycled.