The walls of the blood vessels consist of a series of layers, the tunica intima, tunica media, and tunica adventitia. These layers vary in thickness and are not always present in blood vessels. A relationship does exist between the structure of the blood vessel wall and its function.
The Structure of Blood
The fluid between blood cells in the plasma. It is mostly water and also contains other substances such as glucose, oxygen, and carbon dioxide, waste products such as urea, hormones, mineral salts and plasma proteins such as antibodies. Mineral salts and plasma proteins are continuously present in the blood while other substances move from one part of the body to another. In addition to this, blood also takes heat from warmer to cooler parts of the body.
The remainder of the tissue contains blood cells and platelets. Most of the cells are red blood cells that contain hemoglobin while the remaining are while blood cells, or leucocytes whose job is to fight against diseases. Leucocytes are classified as phagocytes which engulf foreign material adn lymphocytes which produce antibodies.