Blood

Blood is not the simple red liquid it appears to be. It is classified as a special type of connective tissue, because like other connective tissues it links different parts of the body and is built around a matrix in which its cells are suspended.

What makes blood distinctive is that its matrix is fluid rather than solid. This fluid part is called plasma. Floating within the plasma are the cellular components, known as the formed elements.

So, at the broadest level, blood has two constituents:

• Plasma — the fluid matrix. …