What are red blood cells?

Red blood cells, also known as erythrocytes, are the most common type of blood cell in the human body. They are responsible for carrying oxygen from the lungs to the body's tissues, where it is used to produce energy. Red blood cells are produced in the bone marrow, the spongy tissue inside the bones. They are small, round cells with a biconcave shape, which means they are slightly flattened and indented in the middle. This shape allows them to carry more oxygen and easily pass through the small blood vessels in the body. Red blood cells are made up of hemoglobin, a protein that binds to oxygen and carries it throughout the body. They also contain a small amount of iron, which is essential for carrying oxygen. Red blood cells have a lifespan of about 120 days. After this time, they are no longer able to function properly and are removed from the circulation by the spleen and liver. To maintain a healthy supply of red blood cells, the body constantly produces new ones to replace the old ones. This process is regulated by the hormone erythropoietin, which is produced by the kidneys. Red blood cells are an essential part of the body's circulatory system and play a crucial role in maintaining good health.