A mixture of sulfated glycosaminoglycans released from mast cells lying beneath the vascular endothelium. Pharmaceutical heparins are extracted from pig intestinal mucosa or bovine lung both of which are sources for mast cells. Pharmaceutical, unfractionated (standard) heparins have molecular weights that vary between 3,000 to 35,000 daltons. Heparins have no direct anticoagulant effect but act through Antithrombin.
