BLOOD

BLOOD

Our blood is red because of the substance, haemoglobin, which is contained in our red blood cells (red corpuscles).The function of these specialised cells is to carry oxygen from our lungs to wherever it is needed in the body. They are formed in our bone marrow and the haemoglobin in them

, which is made of iron and protein, becomes redder as it picks up oxygen. It loses this colour as it deposits oxygen in other cells and picks up carbon dioxide to carry back to the lungs, which is why some of the blood vessels in our hands and arms appear blue through our skin.

As well as carrying oxygen and carbon dioxide, the blood carries nutrients to the cells, so that they can perform their functions, and for cell repair and growth. Waste products are carried back to the liver for removal. As well as the red cells, our blood also carries white blood cells, which help to fight off disease. All of the heart cells and nutrients are carried in a pale yellow, thick liquid which is called plasma. The other materials carried in the plasma include a substance called fibrinogen, which helps the blood to clot when we cut ourselves.