A prostaglandin is any member of a group of lipid compounds that are derived enzymatically from fatty acids and have important functions in the animal body. Every prostaglandin contains 20 carbon atoms, including a 5-carbon ring. They are mediators and have a variety of strong physiological effects, such as regulating the contraction and relaxation of smooth muscle tissue.[1] Prostaglandins are not hormones, but autocrine or paracrine, which are locally acting messenger molecules. They differ from hormones in that they are not produced at a discrete site but in many places throughout the human body. Also, their target cells are present in the immediate vicinity of the site of their secretion (of which there are many).This pathway was inferred from Homo sapiens pathway [http://www.wikipathways.org/index.php?title=Pathway:WP98&oldid=20887 WP98(r20887)] with a 83% conversion rate.b37PMID: 12962548 relationship with Annexin 2PMID: 7615804, PMID: 3292559PMID: 147434410785607PubMedGene knockout mice in the study of parturition.J Soc Gynecol Investig2000Gross GImamura TMuglia LJprostaglandin metabolic pathwayPW:0000156Pathway Ontology