Punasolu

Punasolu is the Finnish term for the red blood cell (RBC). In humans and most vertebrates, punasolu is a small, flexible cell responsible for oxygen transport in the bloodstream. Mature punasolu in mammals lacks a nucleus and organelles, maximizing space for hemoglobin.

Punasolu contain hemoglobin, a protein complex with four globin chains and four heme groups containing iron. Each hemoglobin molecule can bind up to four oxygen molecules and releases them to tissues. It also picks up carbon dioxide from tissues for exhalation. The biconcave disk shape and membrane properties enable efficient gas exchange and flexible flow through narrow capillaries.

Development and lifespan: Erythropoiesis occurs in bone marrow, stimulated by erythropoietin from renal cells in response to hypoxia. Maturation removes the nucleus. In humans, punasolu live about 120 days and are cleared by macrophages in the spleen and liver; iron is recycled to form new RBCs.

Clinical aspects: Abnormalities include anemia (low RBC count or hemoglobin) and polycythemia (high RBC count). Disorders of hemoglobin, such as sickle cell disease and thalassemias, affect oxygen transport. Routine tests measure hemoglobin concentration, hematocrit, and red blood cell count. Punasolu transfusions and iron management are common medical interventions.

In other vertebrates, punasolu can be nucleated and vary in size and color; however, the core role of oxygen transport is conserved.