eritrosites

Erythrocytes, also known as 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 flowing throughout the body. The antonym is a leukocyte, or white blood cell, which is part of the immune system.

The shape of erythrocytes in mammals is a biconcave disc. They lack cell organelles, including a nucleus. This anucleated state allows more space for hemoglobin, the protein that carries oxygen. Erythrocytes are produced in the red bone marrow. The lifespan of an erythrocyte is about 120 days. After this time, they are removed from circulation by macrophages, primarily in the spleen and liver.

The color of erythrocytes comes from hemoglobin, which contains iron. When hemoglobin binds to oxygen, it becomes bright red. When it releases oxygen, it becomes darker red. The number of erythrocytes in the blood is a significant indicator of health. Conditions like anemia are characterized by a deficiency in erythrocytes or hemoglobin, leading to reduced oxygen-carrying capacity. Conversely, polycythemia refers to an excess of red blood cells. Erythrocytes play a crucial role in maintaining the body's oxygen supply and are essential for cellular respiration and overall metabolic function.