develops_from simple squamous epithelium mesoderm endothelium CALOHA:TS-0278 GAID:520 A layer of epithelium that lines the heart, blood vessels (endothelium, vascular), lymph vessels (endothelium, lymphatic), and the serous cavities of the body[MESH]. Simple squamous epithelium which lines blood and lymphatic vessels and the heart[FMA] uberon galen:Endothelium EFO:0002548 UMLS:C0014257 BTO:0000393 FMA:63916 The term 'endothelium' has been either restricted to the continuous cell layer of the vertebrates, as we are assuming here, or applied to all the cells able to adhere to the luminal surface of the vascular basement membrane (Casley-Smith 1980) MESH:D004727 UBERON:0001986 endothelial meso-epithelium