composed primarily of bodily fluid material sebum material A bodily fluid material which is composed primarily of sebum, an oily bodily fluid secreted from the sebaceous glads that is made of fat (lipids) and the debris of dead fat-producing cells. In the glands, sebum is produced within specialized cells and is released as these cells burst. Sebum acts to protect and waterproof hair and skin, and keep them from becoming dry, brittle and cracked. It can also inhibit the growth of microorganisms on skin. ENVO bodily fluid classes differ from UBERON's treatment of bodily fluids. UBERON refers to the substance itself ("S"). We assert that UBERON's classes are the primary compositional component of the terms in ENVO ("S material"). Use of the ENVO terms is typically recommended when you wish to indicate that there may be other materials intermixed with S. sebum