Here's what rhymes with endothelium.

Consider these alternatives

epithelium / helium vasodilation / operation capillaries / varies monocytes / rights choroid / avoid astrocytes / rights leukocytes / rights hepatocytes / rights hematopoietic / haemopoietic corneal / feel macrophages / native erythrocytes / rights pericytes / rights mucosal / social mesenchymal / final vasculature / neovasculature epidermal / internal mesodermal / internal keratinocytes / rights phagocytosis / diagnosis capillary / very xylem / asylum granulocytes / rights cambium / champion glial / colour