The three main types of blood cells produced by bone marrow are: Red blood cells: Red blood cells are responsible for carrying oxygen to tissues throughout the body. They are made up of haemoglobin, a protein that binds oxygen. White blood cells: White blood cells fight infection. There are many different types of white blood cells, each with a specific function. Platelets: Platelets help to stop b leeding. They are small, cell-like fragments that clump together to form a plug at the site of a bleeding wound.