Mast cells are found in loose connective tissue.
Connective tissue serves to connect and support other tissues and organs.
It is found throughout the body in mucous membranes, around blood vessels and nerves, around body organs and in the dermal region of the skin. Scattered throughout this loose connective tissues are various cells, some being mast cells. Mast cells play an important role in the body's immune response. They contain several kinds of chemicals. One is heparin, which prevents blood from clotting in the blood vessels.