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In the US even though sildenafil is available only by prescription from a doctor, it was advertised directly to consumers on TV (famously being endorsed by former United States Senator Bob Dole and football star Pelé ). Numerous sites on the Internet offer Viagra for sale after an "online consultation", often a simple web questionnaire.   The Viagra name has become so well known, many fake aphrodisiacs now call themselves " herbal viagra " or are presented as blue tablets imitating the shape and colour of Pfizer's product. Viagra is also informally known as "vitamin V", "the blue pill", or "blue diamond", as well as various other nicknames.
Two additional semilunar valves sit at the exit of each of the ventricles. The pulmonary valve is located at the base of the pulmonary artery . This has three cusps which are not attached to any papillary muscles. When the ventricle relaxes blood flows back into the ventricle from the artery and this flow of blood fills the pocket-like valve, pressing against the cusps which close to seal the valve. The semilunar aortic valve is at the base of the aorta and also is not attached to papillary muscles. This too has three cusps which close with the pressure of the blood flowing back from the aorta.