| − | '''Mucus''' is a slippery, viscous, water-based [[fluid]] produced by specialized mucous [[membrane]]s. Mucous membranes line the [[respiratory]], [[digestive]], and [[reproductive]] tracts. Mucus contains [[hydrophilic]] [[protein]]s, [[immunoglobulin]]s, [[enzyme]]s, and [[shed cell]]s, and serves a variety of functions in different circumstances. For example, mucus in the nose and respiratory tract serves to trap dust and other contaminants before they reach the [[lung]]s; in the gut it lubricates the lining; in the female reproductive tract, [[cervical]] mucus changes its properties during the [[menstrual cycle]] so as to promote or retard the passage of [[sperm]]. | + | '''Mucus''' is a [[slippery]], [[viscous]], water-based [[fluid]] produced by specialized [[mucous]] [[membrane]]s. Mucous membranes line the [[respiratory]], [[digestive]], and [[reproductive]] tracts. Mucus contains [[hydrophilic]] [[protein]]s, [[immunoglobulin]]s, [[enzyme]]s, and [[shed cell]]s, and serves a variety of functions in different circumstances. For example, mucus in the [[nose]] and [[respiratory tract]] serves to trap [[dust]] and other contaminants before they reach the [[lung]]s; in the [[gut]] it [[lubricate]]s the lining; in the [[female reproductive system]] tract, [[cervical]] mucus changes its properties during the [[menstrual cycle]] so as to promote or retard the passage of [[sperm]]. |