The topic of blood can be seen on four levels which are mutually related.
- Composition: As an organ, blood possesses unique properties and performs several important functions in the human body. It consists of liquid plasma, red and white blood cells and platelets. Changed properties of blood signal a disease, for example changed number of blood cells. That is why doctors do blood tests.
- Transfer of substances: Blood (red blood cells) transfers respiratory gases in the human body, plasma contains inputs and products of metabolism and hormones, which have a regulatory function.
- Protection of the body: White blood cells and antibodies in plasma recognise and destroy antigens and foreign proteins that get into the body. Platelets ensure blood clotting and healing of harmed veins to prevent bleeding to death after injuries.
- Blood types: Human blood has group properties. It is important to be aware of the blood types when saving human life by transfusion and considering possible complications in childbirth. Division of blood into types based on AB0 system and rhesus factor is best-known. Group properties of blood are inherited based on simple rules. Knowing them makes prediction of blood type before a child is born easier or helps in eliminating of paternity.
The main aim of this unit is to assist students in receiving a complete picture of knowledge about blood by means of practical tasks and situations, blood transfusion being the central motive of the topic. For safe transfusion medical staff has to handle blood in a sterile way. They use plastic aids made of polymers, separator and other equipment. It is also necessary to ensure that blood could be stored for some time in such a way that blood cells would remain alive. The cell damage caused by growing ice crystals during freezing can be prevented by addition of some polymers.