vörösvértestekkel

Vörösvértestekkel, known scientifically as erythrocytes or red blood cells, are the most common type of blood cell and the vertebrate's primary means of delivering oxygen (O2) to the body tissues—via blood flow through the circulatory system. They take up oxygen in the lungs or gills and release it into tissues while squeezing through the body's capillaries. The term erythrocyte originates from Greek, meaning "red" and "hollow vessel". In humans, mature red blood cells are biconcave discs and are about 7–8 micrometers (μm) in diameter. They lack a nucleus and most organelles, including mitochondria, to maximize the space available for hemoglobin. Hemoglobin is the iron-containing protein responsible for oxygen transport. A typical human body contains about 25 trillion red blood cells. They are produced in the bone marrow through a process called erythropoiesis, which is stimulated by the hormone erythropoietin. Red blood cells have a lifespan of approximately 120 days in humans, after which they are removed from circulation by macrophages in the spleen and liver. The breakdown products of hemoglobin are then recycled. Variations in red blood cell count or hemoglobin levels can indicate various health conditions, such as anemia or polycythemia.