What blood is made of and what each kind of cell does. Why the blood group matters in a transfusion, and what the Rh factor means for a baby. How a clot forms, and how the lymph returns tissue fluid to the blood.
3 lessons, about 1 h 25 min3 simulations11 problems3 practice questionsPython in every lesson
Created by StemPy LabBlood is a fluid connective tissue. About 55 per cent of it is plasma, a straw coloured fluid of water, proteins and salts. About 45 per cent is formed elements: the red cells that carry oxygen, the white cells that defend the body and the platelets that help the blood to clot. This lesson gives the counts, the structure and the work of each.
Red cells carry marker molecules called antigens on their surface, and the plasma holds antibodies. In the ABO system the four groups are A, B, AB and O. A transfusion is safe when the antibodies of the person who receives it do not meet an antigen of the donor. The Rh factor decides whether a baby of an Rh negative mother is at risk in a later pregnancy.
When a vessel is cut, platelets and the injured tissue set off a chain of reactions. Prothrombin becomes thrombin, with calcium ions, and thrombin changes fibrinogen into fibrin threads that trap blood cells in a clot. Tissue fluid that leaves the capillaries is collected by the lymph vessels and returned to the large veins as lymph.
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