erütrotsüüdid

Erythrocytes, also known as red blood cells, are the most common type of blood cell and the vertebrate’s primary means of delivering oxygen 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 flowing through the smaller blood vessels. The man-made drug that has been used to increase red blood cell count is erythropoietin. The shape of the red blood cell is a biconcave disc. This shape increases the surface area to volume ratio, allowing for efficient diffusion of oxygen and carbon dioxide. In mammals, mature erythrocytes lack a nucleus and most organelles, including mitochondria, to maximize the space available for hemoglobin. Hemoglobin is the protein responsible for oxygen transport and gives blood its red color. Red blood cells are produced in the bone marrow through a process called erythropoiesis. This process is regulated by the hormone erythropoietin, which is produced by the kidneys in response to low oxygen levels. The lifespan of a red blood cell is about 120 days. After their lifespan, they are removed from circulation by macrophages in the spleen and liver. The destruction of red blood cells releases hemoglobin, which is then broken down into bilirubin and other components. Conditions affecting red blood cells include anemia, which is a deficiency in red blood cells or hemoglobin, and polycythemia, which is an excess of red blood cells.