Blood: composition and functions

In short: Blood consists of liquid plasma and blood cells. It transports oxygen, nutrients and hormones, protects against pathogens and seals wounds.

In more detail: About 55 percent of blood is plasma, 45 percent cells.

In detail

• Red blood cells (erythrocytes): Transport oxygen with the pigment haemoglobin.
• White blood cells (leukocytes): Immune defence (immunsystem-grundlagen).
• Platelets (thrombocytes): Clotting after injury.
• Plasma: Water, proteins, salts, hormones, nutrients.
• Blood groups: A, B, AB, O and the rhesus factor; important in transfusions.
• Formation: In the bone marrow.
• Blood donation: About 500 ml; the body replaces the volume within a few days to weeks.
• Iron deficiency: Can lead to anaemia and tiredness (herz-und-kreislauf).