Serum-separating tube Serum-separating tube Serum-separating tubes, also known as serum separator tubes or SSTs, are used in medical clinical chemistry tests requiring blood serum. SSTs are sometimes called "marble-top tubes," "tiger-tops," or "gold-topped tubes", referring to the stoppers which are either gold, red with a gold ring on top, or marbled red and grey. Marble-top tubes are also referred to as "tiger-tops" in some clinics. SPS tubes have a paler colour, sometimes leading confusion; these are known as "yellow tops" not "gold". Trademarked versions include Covidien "Corvac" tubes. They contain a special gel that separates blood cells from serum, as well as
Mucus mucus has a threefold higher potential to limit agent penetration than purified mucus. Mucus Mucus ( ) is a polymer. It is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It is a viscous colloid containing inorganic salts, antiseptic enzymes (such as lysozymes), immunoglobulins, and glycoproteins such as lactoferrin and mucins, which are produced by goblet cells in the mucous membranes and submucosal glands. Mucus serves to protect epithelial cells (that line the