Cervical Mucus
Cervical Mucus is 90% water. Depending on the water content which varies during the menstrual cycle the mucus functions as a barrier or a transport medium to spermatozoa. Cervical mucus also contains electrolytes (calcium, sodium and potassium), organic components such as glucose, amino acids and soluble proteins.
Cervical mucus contains trace elements including zinc, copper, iron, mangenese and selenium, the levels of which vary dependant on cyclical hormone variation during different phases of the menstrual cycle. Various enzymes have been identified in human cervical mucus. Glycerol is a natural ingredient of human cervical fluid. Studies have shown that the amount of glycerol in cervical fluid increases during sexual excitement. This increase in glycerol has been postulated to be responsible for the lubricating quality of this fertile cervical fluid and may be biologically relevant during the early phase of reproductive events.
After a menstrual period ends, the external os is blocked by mucus that is thick and acidic. This "infertile" mucus blocks spermatozoa from entering the uterus. For several days around the time of ovulation, "fertile" types of mucus are produced; they have a higher water content, and are less acidic and higher in electrolytes. These electrolytes cause the 'ferning' pattern that can be observed in drying mucus under low magnification; as the mucus dries, the salts crystallize, resembling the leaves of a fern.
Some methods of fertility awareness involve estimating a woman's periods of fertility and infertility by observing changes in her body. Among these changes are several involving the quality of her cervical mucus: the sensation it causes at the vulva, its elasticity (Spinnbarkeit), its transparency, and the presence of ferning.
Most methods of hormonal contraception work primarily by preventing ovulation, but their effectiveness is increased because they prevent the fertile types of cervical mucus from being produced. Conversely, methods of thinning the mucus may help to achieve pregnancy. One suggested method is to take guaifenesin in the few days before ovulation.
During pregnancy, the cervix is blocked by a special antibacterial mucosal plug, which prevents infection, somewhat similar to its state during the infertile portion of the menstrual cycle. The mucus plug comes out as the cervix dilates in labor or shortly before.
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